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Prof. P. Mannheim, Department of Physics, University of Connecticut, "Quantum mechanics off the beaten track", Graduate Student Seminar12:15pm
9/13
All Events »Prof. P. Mannheim, Department of Physics, University of Connecticut, "Quantum mechanics off the beaten track", Graduate Student Seminar
Friday, September 13th, 2019
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. P. Mannheim, Department of Physics, University of Connecticut
Quantum mechanics off the beaten track
We discuss some non-conventional options for quantum theory. We show that
it is not always possible to write the momentum operator as the familiar derivative operator \(-id/dx\) where x is real, and discuss what one should then do. We show that basis states do not need to be normalizable to be complete, and even if normalizable do not have to obey the standard Dirac
completeness relation \(\sum |n>
Prof. B. Spivak, Department of Physics, University of Washington, " Anomalous metals", Condensed Matter Physics Seminar2:00pm
9/10
Prof. B. Spivak, Department of Physics, University of Washington, " Anomalous metals", Condensed Matter Physics Seminar
Tuesday, September 10th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS-119
Prof. B. Spivak, Department of Physics, University of Washington
Anomalous metals
The observation of metallic ground states in a variety of two-dimensional electronic systems poses a fundamental challenge for the theory of electron fluids. I will analyze evidence for the existence of a regime, which we call the "anomalous metal regime," in diverse 2D superconducting systems driven through a quantum superconductor to metal transition by tuning physical parameters such as the magnetic field, the gate voltage in the case of systems with a MOSFET geometry, or the degree of disorder. The principal phenomenological observation is that in the anomalous metal, as a function of decreasing temperature, the resistivity first drops as if the system were approaching a superconducting ground state, but then saturates at low temperatures to a value that can be orders of magnitude smaller than the Drude value. The anomalous metal also shows a giant positive magneto-resistance. This behavior is observed in a broad range of parameters. I will exhibit, by theoretical solution of a model of superconducting grains embedded in a metallic matrix, that as a matter of principle such anomalous metallic behavior can occur in the neighborhood of a quantum superconductor-metal transition. However, I will also argue that the robustness and ubiquitous nature of the observed phenomena are difficult to reconcile with any existing theoretical treatment and speculate about the character of a more fundamental theoretical framework. Prof. N. Berrah, Department of Physics, University of Connecticut, "Towards Making Molecular Movies", Graduate Student Seminar12:15pm
9/6
Prof. N. Berrah, Department of Physics, University of Connecticut, "Towards Making Molecular Movies", Graduate Student Seminar
Friday, September 6th, 2019
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. N. Berrah, Department of Physics, University of Connecticut
Towards Making Molecular Movies
In the past decade, improved laser technology from the Infrared to the X-ray regime has allowed scientists to advance the frontiers of time-resolved ultrafast science. Table-top ultrafast lasers as well as Free Electron Lasers (FELs) science have been identified as one of the highest priority for funding agencies.
We have pursued photo-induced molecular dynamics research with complementary table-top as
well as XUV and X-ray FELs with the ultimate goal of making molecular movies. These movies
follow the electronic and nuclear dynamics induced by the absorption of photons by molecules that occur because of the coupling between the electronic and nuclear motion in the molecules. This coupling first leads to attosecond electron excitation within the molecules, followed by nuclear motion in the femtosecond range, eventually resulting in the formation and breaking of chemical bonds on the picosecond timescale. Research highlights will be presented.
Dr. Molly Gallagher, Department of Physics,University of Connecticut, "Mapping Extragalactic Dense Molecular Gas: Ties to Environment and Star Formation ", Astronomy Seminar2:00pm
9/4
Dr. Molly Gallagher, Department of Physics,University of Connecticut, "Mapping Extragalactic Dense Molecular Gas: Ties to Environment and Star Formation ", Astronomy Seminar
Wednesday, September 4th, 2019
02:00 PM - 03:00 PM
Storrs Campus GS-119
Dr. Molly Gallagher, Department of Physics,University of Connecticut
Mapping Extragalactic Dense Molecular Gas: Ties to Environment and Star Formation
Gas density plays an important role in galactic evolution via its connection to star formation. Yet because dense gas is difficult to observe, we are only beginning to explore how interstellar gas density and its relationship to the star formation rate depend on galactic environment. We will explore how gas density, star formation rate, and galactic environment interact on scales ranging from Galactic scale down to the scale of individual molecular clouds. This work relies on new dense gas observations of nearby spiral galaxies from the Atacama Large Millimeter/submillimeter Array (ALMA). Prof. V. Kharchenko, Department of Physics, University of Connecticut, "Non-equilibrium Processes in Atomic Science, Astrophysics, and Biology", Graduate Student Seminar12:15pm
8/30
Prof. V. Kharchenko, Department of Physics, University of Connecticut, "Non-equilibrium Processes in Atomic Science, Astrophysics, and Biology", Graduate Student Seminar
Friday, August 30th, 2019
12:15 PM - 01:15 PM
Storrs Campus GS-119
Prof. V. Kharchenko, Department of Physics, University of Connecticut
Non-equilibrium Processes in Atomic Science, Astrophysics, and Biology
Non-equilibrium processes arise in transitions between different steady /equilibrium states. Experimental and theoretical investigations of these processes are most formidable tasks for researches in various scientific disciplines, including quantum mechanics, plasma physics, astrophysics, climate change, and biology. Examples of theoretical analysis of non-equilibrium processes in atomic physics, astrophysics, and biology will be discussed and current research projects will be described.
Dr. Jan M Rost, Max Planck Institute for the Physics of Complex Systems, Dresden, Germany, Atomic, Molecular, and Optical Physics Seminar2:00pm
8/21
Dr. Jan M Rost, Max Planck Institute for the Physics of Complex Systems, Dresden, Germany, Atomic, Molecular, and Optical Physics Seminar
Wednesday, August 21st, 2019
02:00 PM - 03:00 PM
Storrs Campus GS-119
Dr. Jan M Rost,
Max Planck Institute for the Physics of Complex Systems,
Dresden, Germany
Sculpting electron dynamics through its environment
Interfacing an electron with a well-controlled environment can generate unusual dynamics, in particular if the electron is easily polarizable. The Rydberg Composite, a highly excited Rydberg electron whose spatial density encompasses many atoms or molecules on sites of a designed spatial lattice is one example. We will show that a 2D Composite with a two-dimensional lattice in form of an atomic monolayer has a particularly reach electron spectrum which features energy bands and exhibits regular as well as chaotic features depending on the ratio of lattice spacing and the wavelength of the Rydberg wave function. Possibilities for experimental realizations in the ultracold will be discussed.
The second part of the talk concerns noisy photo electron spectra as generated, e.g., by short and intense SASE free electron laser pulses. Learning the corresponding electron dynamics with a deep neural network by introducing synthetic Hamilton matrices, we can purify the spectrum as if it would have been created with a normal Gaussian pulse. Perspectives of this novel way to construct ultrafast electron dynamics from given noisy spectra will be discussed. Prof. Keith Horne, University of St. Andrews, "Echo Tomography of Black Hole Accretion Flows in Active Galactic Nuclei", Special Astronomy Seminar2:00pm
7/26
Prof. Keith Horne, University of St. Andrews, "Echo Tomography of Black Hole Accretion Flows in Active Galactic Nuclei", Special Astronomy Seminar
Friday, July 26th, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West P121
Prof. Keith Horne,
University of St. Andrews
Echo Tomography of Black Hole Accretion Flows in Active Galactic Nuclei
Echo Tomography uses light travel time delays to resolve micro-arcsecond structure of black hole accretion flows in active galactic nuclei. I will discuss methods used to map the temperature-radius profile of black hole accretion discs, and to construct velocity-delay maps that probe the geometry, kinematics and ionisation structure of the associated broad emission-line regions. In particular, I will present results from the 2014 STORM campaign using HST, Swift, and ground-based telescopes to monitor spectral variations in the Seyfert galaxy NGC 5548. I will discuss anomalous behaviour observed during the campaign, and present a determination of the inclination and temperature-radius profile of its accretion disc and velocity-delay maps exhibiting evidence for an inclined Keplerian flow extending from 2 to 20 light days. Tilting the inner disc to align with black hole spin may help to address several features we are seeing in the reverberation mapping studies.
Dissertation Defense, Niraj Ghimire- Density Matrix Renormalization Group studies of interacting dipoles in a zigzag chain- Ph. D. defense11:00am
6/26
Dissertation Defense, Niraj Ghimire- Density Matrix Renormalization Group studies of interacting dipoles in a zigzag chain- Ph. D. defense
Wednesday, June 26th, 2019
11:00 AM - 01:00 PM
Storrs Campus Gant West Room 103-A
Dissertation Defense
Niraj Ghimire
Physics Department
University of Connecticut
"Density Matrix Renormalization Group studies of interacting dipoles in a zigzag chain"
The goal of my research is to simulate quantum mechanics, which is known to be a very challenging problem even for the most advanced supercomputers of today. The system I have chosen consists of molecular dipoles in a quasi-one-dimensional optical lattice. For the first part of the talk, I will discuss the situation where the dipoles are polarized in the plane of the lattice at half-filling and double occupancy is not allowed on any lattice sites. The dipoles can hop around between sites and the interactions between them can be attractive or repulsive, with the hopping and interaction allowed up to second neighbors. I am particularly interested in the zero-temperature quantum phases induced by geometrical frustration, a situation where not all the interactions are satisfied. By mapping the dipoles in this lattice to a spin-1/2 model and by using the numerical approximation method known as density matrix renormalization group (DMRG), I have studied this system and produced a complex phase diagram.
For the second part of the talk, I will discuss the situation where a dipole is trapped in each lattice site such that the dipole moment vector can be oriented in any direction. The dipoles interact with one another via dipole-dipole potential and also interact with the external field, but they do not hop around between lattice sites. I will talk about some results for this classical model. Then I will explain how I have mapped it to a spin-2 model (which is quantum mechanical) and explain some results obtained using DMRG.
Major Advisor: Dr. Susanne Yelin
Wednesday, June 26, 2019
11:00 AM
Gant Science Complex
GW-103A
Dr. Ryan C. Hickox, Department of Physics and Astronomy, Dartmouth College, "Black Holes Near and Far: Environments and Evolution of Active Galactic Nuclei ", Sigma Pi Sigma Colloquium4:00pm
5/3
Dr. Ryan C. Hickox, Department of Physics and Astronomy, Dartmouth College, "Black Holes Near and Far: Environments and Evolution of Active Galactic Nuclei ", Sigma Pi Sigma Colloquium
Friday, May 3rd, 2019
04:00 PM - 05:00 PM
Storrs Campus GW-38
Dr. Ryan C. Hickox,
Department of Physics and Astronomy, Dartmouth College
Black Holes Near and Far: Environments and Evolution of Active Galactic Nuclei
Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies, and astronomers have now spectacularly obtained the first image of one in the nearby galaxy M87. Yet SMBHs are not just fascinating objects in their own right; they also have a key role to play in the cosmic evolution of their host galaxies and large-scale structures, as they grow and radiate energy in the form of active galactic nuclei (AGN). I will give an overview of recent breakthroughs in our understanding of AGN, exploring the smallest scales around the SMBH to the huge surrounding dark matter halos, and tracing the growth of SMBHs from the early Universe to the present epoch. I will conclude with a look forward at exciting prospects in AGN science with upcoming and proposed future observatories.
Coffee will be served prior to the talk, at 3:00 p.m., In Room GW-103 Dr. Jim Zickefoose, Senior Research Scientist, Mirion Technologies, "Applying a physics degree to positions in industry", Graduate Student Seminar12:15pm
5/3
Dr. Jim Zickefoose, Senior Research Scientist, Mirion Technologies, "Applying a physics degree to positions in industry", Graduate Student Seminar
Friday, May 3rd, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Dr. Jim Zickefoose,
Senior Research Scientist, Mirion Technologies
Applying a physics degree to positions in industry
I received my PhD from the University of Connecticut 9 years ago and since that time have been working in industry as a physicist for Canberra Inc. (now Mirion Technologies). There were a number of skills I gained during my studies as a PhD student that helped me obtain my job in industry as well as progress up the technical ladder. I will briefly discuss my primary PhD research topic, experimental nuclear astrophysics, identifying some of the skills obtained during my research that are vital in industry. Mirion is involved in the detection, quantification, remediation of nuclear radiation on a number of levels, most notable in the development of High Purity Germanium (HPGe) detectors. I will provide an overview of Mirion's core interests and describe how my current and previous roles there have contributed to those interests. As is true with any sector you will choose to work in, there are benefits and drawbacks to working there. I will discuss a number of aspects that are in my opinion assets of industrial work as well as number of points of frustration that I have found in industry. Finally, I have been involved in the hiring of a number of incoming physicist personnel at Mirion. I will discuss some key points to consider when searching for, applying to, interviewing for, and accepting positions in industry. Atomic, Molecular, and Optical Physics Seminar2:15pm
5/2
Atomic, Molecular, and Optical Physics Seminar
Thursday, May 2nd, 2019
02:15 PM - 03:15 PM
Storrs Campus Physics Building, P121
Dr. Ryan Carollo,
Department of Physics and Astronomy, Bates College
Blowing Bubbles... in Space!
Bose-Einstein condensates (BECs) can be used as sensitive probes or tests of delicate physics. However, gravitational sag equivalent to 100 nanokelvin per micron can adversely affect sensitive measurements or delicate potentials. NASA and JPL have solved this problem by installing a BEC machine (the Cold Atom Laboratory - CAL) on the International Space Station. We're using it to blow bubbles - fully-connected, quasi-2-dimensional shells of weakly-trapped condensate - and study them in a shape that can't be achieved on Earth. Astronomy Seminar12:15pm
5/1
Astronomy Seminar
Wednesday, May 1st, 2019
12:15 PM - 01:15 PM
Storrs Campus Gant West P121
Dr. Erin Cox, UConn Counseling & Mental Health Services
Career Development Series
In this semester's "Career Development Series" we will have a special session focusing on Mental Health. We will have a presentation from Dr. Erin Cox. Dr. Erin Cox is the Assistant Director/Director of Outreach at UConn's Counseling & Mental Health Services (CMHS). With over nine years in university counseling, she has expertise in supporting students with a wide variety of mental health concerns that can impact academic performance. In this workshop, Dr. Cox will provide tips on managing stress, and an overview of services available at CMHS.
Prof. Gerald Dunne, Department of Physics, University of Connecticut, "Resurgent Extrapolation: Squeezing Non-Perturbative Information from Perturbation Theory", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
4/29
Prof. Gerald Dunne, Department of Physics, University of Connecticut, "Resurgent Extrapolation: Squeezing Non-Perturbative Information from Perturbation Theory", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, April 29th, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Prof. Gerald Dunne, Department of Physics, University of Connecticut
Resurgent Extrapolation: Squeezing Non-Perturbative Information from Perturbation Theory
Extrapolation is an important problem in physics: how to use asymptotic data in one parametric regime to learn about the behavior of a physical function in another parametric regime. For example: extending weak coupling expansions to strong coupling, or high temperature expansions to low temperature, or vice versa. I present new methods from "resurgent asymptotics" that dramatically improve standard numerical procedures for performing such an extrapolation: Borel summation, Pad'e approximants and conformal mapping. I illustrate the method with the concrete example of one of the Painlev'e equations, a class of nonlinear equations with many applications in physics. Starting solely with a finite number of asymptotic coefficients, we obtain a high precision extrapolation of the function throughout the complex plane, even across a phase transition. The precision far exceeds that of state-of-the-art numerical integration methods. Prof. Tracy Webb, Department of Physics, McGill University, "The Growth of the Most Massive Galaxies in the Highest Density Regions: Evidence for In-Situ Star Formation in Brightest Cluster Galaxies", Physics Colloquium (Prof. Tracy Webb, McGill)3:30pm
4/26
Prof. Tracy Webb, Department of Physics, McGill University, "The Growth of the Most Massive Galaxies in the Highest Density Regions: Evidence for In-Situ Star Formation in Brightest Cluster Galaxies", Physics Colloquium (Prof. Tracy Webb, McGill)
Friday, April 26th, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Tracy Webb, Department of Physics, McGill University
The Growth of the Most Massive Galaxies in the Highest Density Regions: Evidence for In-Situ Star Formation in Brightest Cluster Galaxies
The most massive galaxies in the local universe reside at the centres of galaxy clusters. These so-called Brightest Cluster Galaxies (BCGs) exhibit, as a class, highly uniform properties and are distinct from the general galaxy population. This suggests formation processes which are themselves distinct from those which dominate in massive galaxies outside of cluster cores. The mass growth of BCGs is likely linked to the overall physics of hierarchical structure formation on galaxy cluster scales, including the fundamental processes of gas cooling, star formation, energy feedback and galaxy mergers, at the centers of giant dark matter halos. In this talk I will present new results from the largest study of high-redshift BCGs conducted to date, drawn from the SpARCS optical/NIR cluster survey. Using archival infrared data we show the star formation rate within BCGs increases to z~2, and can add as much mass to the BCG population as the previous standard model of growth by dry mergers. At low redshifts, and in X-ray/SZ selected clusters, the rare examples of star forming BCGs appear to be fed by large-scale cooling flows. However, the first of the SpARCS systems we have studied in detail, SpARCS1049, has revealed a very different phenomenon -- a train-wreck of a galaxy merger at the center of the cluster. This is the first example of such a process in high-redshift cluster cores and may represent a new phase of BCG evolution, previously unaccounted for.
Coffee and tea will be served prior to the talk, at 3:00 p.m., In Room GW-103 Dr. Drew Chieda, ASML, "Physics Ph.D.'s in Private Sector Careers", Graduate Student Seminar12:15pm
4/26
Dr. Drew Chieda, ASML, "Physics Ph.D.'s in Private Sector Careers", Graduate Student Seminar
Friday, April 26th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Dr. Drew Chieda, ASML
Physics Ph.D.'s in Private Sector Careers
Careers outside academia are a less common choice for Ph.D. physicists. Drew Chieda (Ph.D. 2012) took the less common path and is currently employed by ASML where he provides technical oversight into the development of semiconductor lithography tools.
This talk will be an open discussion forum where Drew will share his experiences and motivations to transition into the private sector. He will review some of what ASML does and why it's interesting work (for him), where some of his friends and former students are employed, how his Ph.D. skills fit into a commercial environment, and some interesting data from the American Institute of Physics.
Please come with questions! Dr. Sarah Wellons, CIERA Postdoctoral Fellow, Northwestern University, "Wild and Crazy Kids: Simulating Galaxy Formation in the Early Universe", Astronomy Seminar12:15pm
4/24
Dr. Sarah Wellons, CIERA Postdoctoral Fellow, Northwestern University, "Wild and Crazy Kids: Simulating Galaxy Formation in the Early Universe", Astronomy Seminar
Wednesday, April 24th, 2019
12:15 PM - 01:15 PM
Storrs Campus Gant West P121
Dr. Sarah Wellons,
CIERA Postdoctoral Fellow,
Northwestern University
Wild and Crazy Kids: Simulating Galaxy Formation in the Early Universe
As techniques have improved over the last decade, observations have peered deep into the Universe's history and begun to glimpse galaxies which formed in the first few billion years after the Big Bang. Evidence is mounting that galaxies in the early Universe appear and behave very differently from those nearby - for example, the most massive galaxies are extremely compact, and star-forming disks appear to have strange clumpy morphologies. In this talk, I will discuss galaxy formation at z > 2 from a theoretical perspective, presenting results drawn from both large-volume cosmological simulations (which allow us to compare and predict the statistical properties of galaxy populations) and high-resolution zoom-in simulations (which allow us to drill down on the physics governing individual systems). I will focus in particular on massive compact galaxies, whose varied formation and evolution present a case study on how galaxy populations evolve over time, and on massive disks, which are independently predicted by both simulation approaches to be very rapidly rotating at high redshift. The advents of JWST, LSST, and WFIRST over the next decade will provide us an unprecedented view of this dynamic and exciting time in the Universe's history. I will conclude by discussing future prospects for how high-z galaxy theory and simulation can anticipate and meet the challenges that these new observations will inevitably bring. Prof. Jordy de Vries, University of Massachusetts Amherst, "Neutrinoless double beta decay in effective field theory", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
4/22
Prof. Jordy de Vries, University of Massachusetts Amherst, "Neutrinoless double beta decay in effective field theory", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, April 22nd, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Prof. Jordy de Vries, University of
Massachusetts Amherst
Neutrinoless double beta decay in effective field theory
Next-generation neutrinoless double-beta decay (0nu2beta) experiments aim to discover lepton number violation in order to shed light on the nature of neutrino masses. A non-zero signal would have profound implications by demonstrating the existence of elementary Majorana particles and possibly pointing towards a solution of matter-antimatter asymmetry in the universe. However, the interpretation of the experimental signal (or lack thereof) requires care as complicated hadronic and nuclear input is required to connect the experimental data to a fundamental description of lepton-number violation. In this talk, I use effective field theories to connect 0nu2beta measurements to the fundamental lepton-number-violating source. In particular, I will argue that interpretation in terms of a light Majorana neutrino mass is more complicated than normally considered, and a new leading contributions must be included. Women in Physics Colloquium3:30pm
4/19
Women in Physics Colloquium
Friday, April 19th, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Women in Physics Colloquium Prof. George Gibson, High-Intensity Laser Physics Group, Department of Physics, University of Connecticut, "Exploring EXTREME Nonlinear Physics and Quantum Molecular Dynamics with High-Intensity Laser Pulses ", Graduate Student Seminar12:15pm
4/19
Prof. George Gibson, High-Intensity Laser Physics Group, Department of Physics, University of Connecticut, "Exploring EXTREME Nonlinear Physics and Quantum Molecular Dynamics with High-Intensity Laser Pulses ", Graduate Student Seminar
Friday, April 19th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Prof. George Gibson, High-Intensity Laser Physics Group,
Department of Physics, University of Connecticut
Exploring EXTREME Nonlinear Physics and Quantum Molecular Dynamics with High-Intensity Laser Pulses
Ultrafast laser systems can now produce ultrashort (attosecond) pulses of light with extremely high intensity (\(10^{22}\) W/cm\(^2\)), as recognized by the 2018 Nobel Prize in Physics. This has opened up a new world in nonlinear physics and may even test the nonlinear polarizability of the vacuum, itself. More immediate applications may include direct imaging of molecular orbitals and ultrafast atomic scale dynamics. Dr. Yu-Sheng Liu, Tsung-Dao Lee Institute, Shanghai , "First Principle Calculation of PDFs from LaMET", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
4/15
Dr. Yu-Sheng Liu, Tsung-Dao Lee Institute, Shanghai , "First Principle Calculation of PDFs from LaMET", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, April 15th, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. Yu-Sheng Liu, Tsung-Dao Lee Institute, Shanghai
First Principle Calculation of PDFs from LaMET
Parton distribution functions (PDFs) are important
quantities describing the probability densities of constituents of hadrons and serve as key inputs in high energy experiments. PDFs, with their nonperturbative nature and intrinsic Minkowski time dependence, can only obtain from phenomenological global fits for decades. A breakthrough came with the Large Momentum Effective Theory (LaMET), which allows us to extract PDFs on the lattice. In this talk, I will introduce the framework of LaMET, then give a lattice simulation example to demonstrate how it works.
Edward Pollack Distinguished Lecture , Pollack Distinguished Lecture3:30pm
4/12
Edward Pollack Distinguished Lecture , Pollack Distinguished Lecture
Friday, April 12th, 2019
03:30 PM - 05:00 PM
Storrs Campus GW-38 (formerly PB-38)
Edward Pollack Distinguished Lecture
Attosecond Pulses Generated in Gases and Solids
P.B. Corkum
Joint Attosecond Science Lab
University of Ottawa and National Research Council of Canada
Abstract: Attosecond pulses are generated by electron wave packets that are extracted from a quantum system by an intense light pulse and travel through the continuum under the influence of the electric field of the light. Portions of each electron wave packet are forced to re-collide with its parent ion after the field reverses direction. Upon re-collision, the electron and ion can recombine, emitting soft X-ray radiation that can be in the form of attosecond pulses. This highly nonlinear process occurs in atoms, molecules and solids and offers unique measurement opportunities -- for measuring the attosecond pulse itself; the orbital(s) from which it emerged; and the band structure of material in which the wave packets moved.
Bio: Dr. Corkum is a fellow of the Royal Societies of Canada and London; a foreign member of the US, the Austrian and the Russian Academy of Science. In 2013, he was awarded Saudi Arabia's King Faisal Prize for science and Israel's Harvey Prize for physics. In 2014 he was named "Thompson Reuters Citation Laureate for work that is of Nobel class and likely to earn the Nobel someday". In 2018 he received the SPIE Gold medal and the IOP's Newton Medal, both societies' highest awards.
Friday, April 12, 2019
3:30 p.m.
Gant Science Complex
Physics, Room GW-38
Refreshments will be served prior to the talk at 2:30 outside of the lecture hall Prof. Menka Jain, Department of Physics, University of Connecticut, "Interests in Multiferroics and Other Functional Materials", Graduate Student Seminar12:15pm
4/12
Prof. Menka Jain, Department of Physics, University of Connecticut, "Interests in Multiferroics and Other Functional Materials", Graduate Student Seminar
Friday, April 12th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Prof. Menka Jain,
Department of Physics, University of Connecticut
Interests in Multiferroics and Other Functional Materials
A multiferroic combines any two or more of the primary ferroic orderings (ferroelectric, ferroeleastic, ferromagnetic) in the same phase, such as the ferroelectric-ferroelastics that form the basis of piezoelectric transducers. The term "magnetoelectric multiferroics" is used for materials that combine ferroelectricity with ferromagnetism or, more loosely, with any kind of magnetism. One of the most appealing aspects of such multiferroics is their so-called magnetoelectric coupling. Even though first experimental observation of magnetoelectric multiferroicity was done in 1960s; today's renaissance of these material was enabled by a combination of theoretical and experimental factors. This includes the availability of modern synthesis techniques--particularly thin-film allowing good control over crystallinity and chemical stoichiometry in samples. In my talk, I will discuss some of the basic properties of ferroics/multiferroics and my group's research work on a few other function and multifunctional materials. Prof. Carlos Trallero, Department of Physics, University of Connecticut, "Your job most likely won't be in academia: Transferring your skills to industry", Graduate Student Seminar12:15pm
4/5
Prof. Carlos Trallero, Department of Physics, University of Connecticut, "Your job most likely won't be in academia: Transferring your skills to industry", Graduate Student Seminar
Friday, April 5th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Prof. Carlos Trallero,
Department of Physics, University of Connecticut
Your job most likely won't be in academia: Transferring your skills to industry
Statistically Ph.D. and M.Sc. in physics are more likely to obtain a job in industry. I will present some of examples of very successful transfers to industry jobs and some of the skills that you will gain working in the lab that will help you with the transition. Prof. Ben Heidenreich, University of Massachusetts Amherst, "Quantum gravity and the swampland", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
4/1
Prof. Ben Heidenreich, University of Massachusetts Amherst, "Quantum gravity and the swampland", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, April 1st, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Prof. Ben Heidenreich, University of Massachusetts Amherst
Quantum gravity and the swampland
I review the "swampland" approach to extracting testable predictions from quantum gravity, with a particular focus on the Weak Gravity Conjecture as a well developed example. Prof. Beth Parks, Department of Physics & Astronomy, Colgate University, "Air Quality Measurements in Uganda ", Physics Colloquium (Prof. Beth Parks, Colgate University)3:30pm
3/29
Prof. Beth Parks, Department of Physics & Astronomy, Colgate University, "Air Quality Measurements in Uganda ", Physics Colloquium (Prof. Beth Parks, Colgate University)
Friday, March 29th, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Beth Parks, Department of Physics & Astronomy, Colgate University
Air Quality Measurements in Uganda
During the 2015-16 academic year, I was a Fulbright scholar at Mbarara University of Science and Technology in Uganda, where I initiated a program to monitor PM10 concentrations in three distinct environments: an urban center (Kampala), a small city (Mbarara) and a village location (Rubindi), both in the wet season and the dry season. These measurements are still underway through the PhD project of a Ugandan student I am supervising. These concentrations were measured using co-located gravimetric (filter-based) collectors and real-time optical instruments.
The results show that particulate levels are high in all three locations, with average PM10 levels measured gravimetrically of 157 mg/m3 in Kampala; 124 mg/m3 in Mbarara; and 188 mg/m3 in Rubindi. (WHO guidelines for maximum PM10 levels are 20 mg/m3; US EPA levels are somewhat more lenient.) Ongoing work involves correlating the different measurement techniques, as well as analysing the particulates to determine the sources. Prof. Boris Sinkovic, Department of Physics, University of Connecticut, "Topological Insulators, New Paradigm for Quantum Electronics", Graduate Student Seminar12:15pm
3/29
Prof. Boris Sinkovic, Department of Physics, University of Connecticut, "Topological Insulators, New Paradigm for Quantum Electronics", Graduate Student Seminar
Friday, March 29th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Prof. Boris Sinkovic,
Department of Physics, University of Connecticut
Topological Insulators, New Paradigm for Quantum Electronics
Recent discovery of topological insulators (TI) and realization that they present new states of matter has generated much excitement in the condensed matter physics community and beyond. TI are insulators in the bulk but their boundaries support gapless spin-chiral state with extraordinary properties and relativistic momentum dispersion. Because of the time reversal symmetry, the electrons at the boundaries cannot back-scattered by non-magnetic impurities and their spin-coherence is preserved over very long distances, which is of great technological interest in spintronics and quantum computing. In particular, magnetic TI are predicted to exhibit opening of the energy gap at the Dirac point and give rise to massive Dirac fermions, leading to the experimental realizations of quantum anomalous Hall effect (QAHE). On the other hand the superconducting TI are proposed to induce new collective particle, Majorana fermions that have a potential to be a platform for quantum computing. In this talk I will present our group's attempts to induce the magnetism and superconductivity in TI, and the challenges to overcome. The studies combine growth of atomically thin films of TI and momentum resolving spectroscopy of Dirac states by angle-resolved photoemission (ARPES) technique, performed at our UCONN lab and at the Brookhaven National Lab. The talk has been rescheduled for April 22, RESCHEDULED: Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
3/18
The talk has been rescheduled for April 22, RESCHEDULED: Particle, Astrophysics, and Nuclear Physics Seminar
Monday, March 18th, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
The talk has been rescheduled for April 22
Prof. Jordy de Vries, University of
Massachusetts Amherst
Neutrinoless double beta decay in effective field theory
Next-generation neutrinoless double-beta decay (0nu2beta) experiments aim to discover lepton number violation in order to shed light on the nature of neutrino masses. A non-zero signal would have profound implications by demonstrating the existence of elementary Majorana particles and possibly pointing towards a solution of matter-antimatter asymmetry in the universe. However, the interpretation of the experimental signal (or lack thereof) requires care as complicated hadronic and nuclear input is required to connect the experimental data to a fundamental description of lepton-number violation. In this talk, I use effective field theories to connect 0nu2beta measurements to the fundamental lepton-number-violating source. In particular, I will argue that interpretation in terms of a light Majorana neutrino mass is more complicated than normally considered, and a new leading contributions must be included. Dr. Andrew Millis, Center for Computational Quantum Physics, The Flatiron Institute and Department of Physics, Columbia University, "Meeting Dirac's Challenge: From Quantum Entanglement to Materials Theory", Charles Reynolds Distinguished Lecture3:30pm
3/15
Dr. Andrew Millis, Center for Computational Quantum Physics, The Flatiron Institute and Department of Physics, Columbia University, "Meeting Dirac's Challenge: From Quantum Entanglement to Materials Theory", Charles Reynolds Distinguished Lecture
Friday, March 15th, 2019
03:30 PM - 04:30 PM
Storrs Campus GW 38, Physics Building
Dr. Andrew Millis, Center for Computational Quantum Physics, The Flatiron Institute and Department of Physics, Columbia University
Meeting Dirac's Challenge:
From Quantum Entanglement to Materials Theory
About 90 years ago, P. A. M. Dirac established the foundations of many-body quantum mechanics. Summarizing, he wrote ``The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.'' Meeting Dirac's challenge, in other words developing approximate practical methods of determining the properties of interacting many-electron systems, so as to predict e.g. which materials will be novel magnets or high transition temperature superconductors, is one of the grand challenges of modern science. Recent progress has been enabled by remarkable developments in ideas, algorithms and computational power. The interplay between theoretical materials science and research into the fundamental phenomenon of quantum mechanical entanglement, has been crucial to progress in both fields. In this talk I will give an overview of modern quantum many-body theory, outlining the difficulties, describing some recent successes, and presenting a vision for the future.
Friday, March 15, 2019
3:30 p.m.
Gant Science Complex
Physics, Room GW-38
Refreshments will be served prior to the talk at 2:30 in room GW-103 Prof. Alan Wuosmaa, Department of Physics, University of Connecticut, "The Structure of "Exotic" Nuclei", Graduate Student Seminar12:15pm
3/15
Prof. Alan Wuosmaa, Department of Physics, University of Connecticut, "The Structure of "Exotic" Nuclei", Graduate Student Seminar
Friday, March 15th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Prof. Alan Wuosmaa, Department of Physics, University of Connecticut
The Structure of "Exotic" Nuclei
Atoms you can't dig out of the ground, and why you should care about them.
Nuclear physicists developed a basic understanding of the properties of atomic nuclei many decades ago, and that understanding has evolved to the point where the structure of stable or near-stable nuclei is reasonably well understood through a combination of modeling, theory and experiment. The theories used to explain stable and near-stable radioactive nuclei, however, are not well tested for nuclei that possess a large imbalance in the numbers of protons and neutrons that makes them behave very differently than stable nuclei. Such unstable nuclei are not typically present on Earth, however play a very significant role in violent astrophysical events that are responsible for the formation of many of the elements that are found in nature. I will describe some of the characteristics that make such nuclei "exotic," and present some new experimental methods that are being used to provide data that can help understand the properties of these systems that can be used to guide new, modern theories of nuclear structure. Dr. Adam Summers, Department of Physics, Kansas State University, "Ultrafast, Strong-Field Investigation of Nanosystems", Atomic, Molecular, and Optical Physics Seminar1:30pm
3/14
Dr. Adam Summers, Department of Physics, Kansas State University, "Ultrafast, Strong-Field Investigation of Nanosystems", Atomic, Molecular, and Optical Physics Seminar
Thursday, March 14th, 2019
01:30 PM - 02:30 PM
Storrs Campus Physics Building, P103A
Dr. Adam Summers, Department of Physics, Kansas State University
Ultrafast, Strong-Field Investigation of Nanosystems
Here I present work investigating the evolution of various nanosystems in extremely intense, ultrafast laser pulses. We study the dynamical processes initiated in these nanosystems over five order of magnitude of peak laser intensity, from 10^10 W/cm2 to 10^15 W/cm2. Specific processes include: thermal evolution and damage of nanowires under irradiation of a train of intense pulses, photoelectron reqscattering on the surface of nanoparticles, plasmonic enhancements of photoionization and the ultrafast formation of nanoplasmas from nanoparticles. Multimodal Spectroscopies of Correlated Materials" Dr Ilya Drozdov, Brookhaven National Laboratory , Condensed Matter Physics Seminar2:00pm
3/13
Multimodal Spectroscopies of Correlated Materials" Dr Ilya Drozdov, Brookhaven National Laboratory , Condensed Matter Physics Seminar
Wednesday, March 13th, 2019
02:00 PM - 03:00 PM
Storrs Campus GW103A
Multimodal Spectroscopies of Correlated Materials"
Dr Ilya Drozdov,
Brookhaven National Laboratory
In this talk Ilya will present the ongoing work, plans and past results on spectroscopy of correlated oxides. Ilya is a part of the BNL team building a unique capability mergin ARPES, local spectroscopy and MBE growth at BNL. The talk will highlight the past work and present new directions. Dr. Catherine Kealhofer, Department of Physics, Williams College, "Generating and controlling ultrafast electron pulses for time-resolved electron diffraction", Atomic, Molecular, and Optical Physics Seminar3:30pm
3/11
Dr. Catherine Kealhofer, Department of Physics, Williams College, "Generating and controlling ultrafast electron pulses for time-resolved electron diffraction", Atomic, Molecular, and Optical Physics Seminar
Monday, March 11th, 2019
03:30 PM - 04:30 PM
Storrs Campus Physics Building, P121
Dr. Catherine Kealhofer,
Department of Physics,
Williams College
Generating and controlling ultrafast electron pulses for time-resolved electron diffraction
Ultrafast electron diffraction (UED) is a powerful technique that lets us measure the positions of atoms in a crystal as they evolve during chemical and physical transformations. These measurements can give insight into how materials work on a microscopic level as well as guide the design of devices that respond on fast timescales. For some time, the best-available time resolution in UED has hovered around 100 fs (1 fs =10-15 s), just shy of the 10 fs resolution required to see the fastest atomic motions. In my talk, I'll explain how ultrafast electron diffraction works and why it's challenging to break the 100-fs resolution barrier. I'll show experimental results on a recent technique that uses terahertz electromagnetic fields to compress electron pulses in time. This technique has the potential to improve the resolution of UED below 100 fs and maybe even below ~1 fs, into the regime of electronic dynamics. The talk will also introduce ultrafast electron sources based on laser-triggered electron emission from nanometrically sharp metal tips. Not only is the physics of ultrafast electron emission in this system very rich, but the extraordinarily small source size in comparison with typical ultrafast flat photocathode sources can dramatically improve the beam quality, leading to smaller probe sizes, higher quality diffraction patterns, and enabling new techniques like ultrafast electron holography. Prof. Stephen Pate, New Mexico State University, "Exploring the Axial Structure of the Nucleon", Physics Colloquium (Professor Stephen Pate, NMSU)3:30pm
3/8
Prof. Stephen Pate, New Mexico State University, "Exploring the Axial Structure of the Nucleon", Physics Colloquium (Professor Stephen Pate, NMSU)
Friday, March 8th, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Stephen Pate,
New Mexico State University
Exploring the Axial Structure of the Nucleon
Modern electron-scattering facilities, such as CEBAF at Jefferson Lab and MAMI at Mainz, have made possible a deep exploration of the electric and magnetic distributions in the nucleon, via measurement of the so-called "vector form factors" accessible via elastic electron scattering experiments. Our knowledge of the "axial form factor", on the other hand, has lagged behind because this sector, related to angular momentum, is suppressed in electron scattering and is more easily explored in elastic and quasi-elastic neutrino scattering. Of particular interest is the isolation of the strange quark contribution to the nucleon axial form factor, as this is related to the strange quark contribution to the nucleon spin, a quantity which has so far resisted a definitive determination. The MicroBooNE experiment at Fermilab is uniquely suited to explore the axial form factor through both neutral-current and charge-current neutrino interactions. I'll present an overview of the general MicroBooNE physics program and an in-depth look at our current status with respect to the axial form factor determination. Prof. Robin Cote, Department of Physics, University of Connecticut, "AMO Theory at UConn: Ultracold Physics", Graduate Student Seminar12:15pm
3/8
Prof. Robin Cote, Department of Physics, University of Connecticut, "AMO Theory at UConn: Ultracold Physics", Graduate Student Seminar
Friday, March 8th, 2019
12:15 PM - 01:15 PM
Storrs Campus P121
Prof. Robin Cote, Department of Physics, University of Connecticut
AMO Theory at UConn: Ultracold Physics
Whenever a new window of parameters open up in Science, new discoveries follow. Examples range from ultrafast physics with atto-second lasers probing the time scale of electrons' motion, or the Kepler space telescope which allows the discovery of thousands of exo-planets. Another such new regime arises from ultracold temperatures, where the slow motion of particles allow to probe new behaviors, such as Bose-Einstein condensation of atoms or molecules, degenerate Fermi gases, and much more. In this presentation, I will introduce what ultracold AMO physics is, and describe the current research in my group on ultracold Rydberg physics and ultracold chemistry, and their applications to quantum information science and astrophysics. Prof. Zohreh Davoudi, University of Maryland., "Towards analog and digital quantum simulations of strongly-interacting dynamics", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
3/4
Prof. Zohreh Davoudi, University of Maryland., "Towards analog and digital quantum simulations of strongly-interacting dynamics", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, March 4th, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Prof. Zohreh Davoudi, University of Maryland.
Towards analog and digital quantum simulations of strongly-interacting dynamics
According to Feynman, quantum computers will be the most suitable platforms to simulate nature. Although as of today, quantum computers with capability and reliability comparable or beyond those of classical computers do not exist, rapid progress in quantum technologies, and a vast growth in interest and resources in quantum information sciences, promise a future in which quantum computation may play an important role in addressing computationally-challenging problems in all areas of sciences and technology. Nuclear and high-energy physics are among the areas in which high-performance computing has been applied successfully to address a range of problems arising from the strong-interactions dynamics. However, our current approach has severe limitations when it comes to investigations of finite-density systems or real-time dynamics. It is believed that a quantum computational approach to such problems is superior to classical approaches, but it remains an open question how to reformulate problems accordingly to harness the quantum advantage on
near-term and future devices. This talk will report on some of the progress made in addressing this question in simple strongly-interacting models, with a focus on an ongoing work at the University of Maryland that leverages on the existing quantum hardware, in particular the ion-trap quantum simulator and quantum computer. Prof. Philip Mannheim, University of Connecticut, "Title: Is dark matter fact or fantasy -- clues from the data", Physics Colloquium (Prof. Philip Mannheim)3:30pm
3/1
Prof. Philip Mannheim, University of Connecticut, "Title: Is dark matter fact or fantasy -- clues from the data", Physics Colloquium (Prof. Philip Mannheim)
Friday, March 1st, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Philip Mannheim, University of Connecticut
Title: Is dark matter fact or fantasy -- clues from the data
Abstract: We discuss the arguments both in favor of and against dark matter. With the repeated failure of experiment to detect dark matter we discuss what could be done instead, and to this end look for clues in the data themselves. We identify a contribution to galactic rotation curves coming from the rest of the visible Universe, and suggest that dark matter is just an attempt to describe this global effect in terms of standard Newtonian gravity within galaxies. Dr. Vladimir Juricic, Nordic Institute for Theoretical Physics, "Interacting spin-1/2 and spin-3/2 nodal fermions: Quantum criticality and transport", Condensed Matter Physics Seminar2:30pm
3/1
Dr. Vladimir Juricic, Nordic Institute for Theoretical Physics, "Interacting spin-1/2 and spin-3/2 nodal fermions: Quantum criticality and transport", Condensed Matter Physics Seminar
Friday, March 1st, 2019
02:30 PM - 03:30 PM
Storrs Campus GW121
Dr. Vladimir Juricic,
Nordic Institute for Theoretical Physics
Interacting spin-1/2 and spin-3/2 nodal fermions: Quantum criticality and transport
Theoretical proposals and experimental realizations of the condensed matter systems, such as topological insulators, Weyl and Dirac semimetals, displaying emergent pseudorelativistic nodal quasiparticles, have triggered a surge of activity in understanding their stability against interactions and disorder. This also motivated exploration of their universal responses, such as optical conductivity.
I will first discuss the quantum critical theory of an interacting nodal Fermi liquid of quasirelativistic pseudospin-3/2 fermions featuring a noninteracting birefringent spectrum with two distinct Fermi velocities [1]. As I will show using perturbative field-theoretical renormalization group analysis, when such quasiparticles interact via either the long-range Coulomb interaction or its short range component (responsible for spontaneous symmetry breaking), in the quantum critical regime, in two dimensions, the system is, respectively, described by a marginal Fermi liquid (featuring interaction-driven log-corrections to observables) or a non-Fermi liquid of relativistic spin-1/2 fermions, and is always a marginal Fermi liquid in three dimensions. I will also discuss our conjecture that critical spin-1/2 excitations represent a superuniversal description of the entire family of interacting quasirelativistic fermions.
In the second part of the talk, I will consider the quantum transport close to a relativistic quantum critical point, separating two-dimensional massless Dirac fermions from a fully gapped insulator or superconductor. In particular, I will consider the scaling of optical conductivity in the (high-frequency) collisionless regime (ω ≫ T) [2]. Close to such a critical point, gapless fermionic and bosonic excitations are strongly coupled, which inside the critical regime leads to a universal suppression of the interband optical conductivity as well as of the Drude peak. These results are obtained by performing the leading order 1/Nf- and ϵ-expansions, where Nf counts the fermion flavor number and ϵ is the distance from the upper-critical three spatial dimensions in the problem.
[1] B. Roy, M. P. Kennett, K. Yang & V. J., PRL 121, 157602 (2018).
[2] B. Roy & V. J., PRL 121, 137601 (2018). Prof. Michael Lubell, CCNY, "Navigating the Maze. How Science and Technology Policy Shape America and the World", Physics Colloquium (Prof. Michael Lubell, CCNY)3:30pm
2/22
Prof. Michael Lubell, CCNY, "Navigating the Maze. How Science and Technology Policy Shape America and the World", Physics Colloquium (Prof. Michael Lubell, CCNY)
Friday, February 22nd, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Michael Lubell, CCNY
Navigating the Maze. How Science and Technology Policy Shape America and the World Dr. Elisa Chisari, Department of Physics, University of Oxford, "Cosmology with weak gravitational lensing: challenges and opportunities", Astronomy Seminar12:30pm
2/22
Dr. Elisa Chisari, Department of Physics, University of Oxford, "Cosmology with weak gravitational lensing: challenges and opportunities", Astronomy Seminar
Friday, February 22nd, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Elisa Chisari,
Department of Physics,
University of Oxford
Cosmology with weak gravitational lensing: challenges and opportunities
68% of the energy density of the Universe today is in the form of a mysterious "dark energy" component which seems to be driving its accelerated expansion. To elucidate the nature of this component, and to assess whether it is compatible with General Relativity, a next generation of experiments is at our doorstep. These experiments use weak distortions of galaxy shapes ("gravitational lensing") as one of their main probes, and will soon reach an unprecedented high-precision regime. In such regime, accurate modeling of the large-scale structure of the Universe becomes crucial to realize the goal of obtaining unbiased constraints on the cosmological model. I will describe efforts to build and test models of the large-scale structure using a combination of analytical theory, cosmological simulations and existing observational data sets. In particular, I will demonstrate that the incidence of galaxy formation on our interpretation of gravitational lensing observables is significant. Effects such as the impact of Active Galactic Nuclei feedback on the distribution of matter, or tidal correlations between the shapes of galaxies, are starting to play a role in our efforts to constrain cosmology. At the same time, I will show that these effects can also open up new windows into the Universe. Looking ahead to the next decade, I will describe the construction of a robust software pipeline for cosmological model predictions for the Large Synoptic Survey Telescope. Alexey Onufriev, Departments of Computer Science and Physics, Virginia Tech, "The nucleosome: from structure to function through physics", Condensed Matter Physics Seminar3:30pm
2/19
Alexey Onufriev, Departments of Computer Science and Physics, Virginia Tech, "The nucleosome: from structure to function through physics", Condensed Matter Physics Seminar
Tuesday, February 19th, 2019
03:30 PM - 04:30 PM
Storrs Campus BPB131
Alexey Onufriev, Departments of Computer Science and Physics, Virginia Tech
The nucleosome: from structure to function through physics
The nucleosome, a complex of 147 base-pairs of DNA with eight histone proteins, must protect its DNA, but, at the same time, allow on-demand access to it when needed by the cell. The exact mechanism of the control remain unclear.
We consider a series of physics-based models of the nucleosome, from the highly coarse-grained cylinders model, to fully atomistic, to multi-state atomistic.
One key conclusion is that at physiological conditions the nucleosome complex is close to the phase boundary separating it from the "unwrapped" states where the DNA is more accessible. A small drop in the positive charge (e.g. through acetylation of a lysine) of the globular histone core can significantly lower the DNA affinity to the core, and thus increase DNA accessibility. The findings suggest that charge-altering post-translational modifications in the histone core might be utilized by the cell to modulate accessibility to its DNA at the nucleosome level.
The multi-state atomistic model explores virtually all possible charge-altering post translational modifications (PTMs) in the globular histone core. The model reveals a rich and nuanced picture: the effect of PTMs varies greatly depending on location, including counter-intuitive trends such as decrease of DNA accessibility for some lysine acetylations in the core. A detailed connection to transcription regulation in-vivo is made. Dr. Alexander Khaetskii Department of Physics, University at Buffalo, SUNY and Department of Physics, UConn, Condensed Matter Physics Seminar2:00pm
2/19
Dr. Alexander Khaetskii Department of Physics, University at Buffalo, SUNY and Department of Physics, UConn, Condensed Matter Physics Seminar
Tuesday, February 19th, 2019
02:00 PM - 03:00 PM
Storrs Campus GW121
Dr. Alexander Khaetskii
Department of Physics, University at Buffalo, SUNY
and Department of Physics, UConn
Giant edge spin accumulation in a symmetric quantum well with two subbands
We have studied [1] the edge spin accumulation due to an electric current in a high mobility two-dimensional electron gas formed in a symmetric quantum well with two subbands. This study is strongly motivated by the recent experiment [2] which demonstrated the spin accumulation near the edges of a symmetric two-subband GaAs structure in contrast to no effect in a single-subband configuration. The intrinsic mechanism of the spin-orbit (SO) interaction we consider arises from the coupling between two subband states of opposite parities [3].
We have explained the experimental results. We obtain, in particular, a parametrically large magnitude of the edge spin density for a two-subband well as compared to the usual single-subband structure. Following the method developed in [4], we show that the presence of a gap in the system (i.e., the energy separation between the two subband bottoms) changes drastically the picture of the edge spin accumulation. The gap value governs the effective strength of the inter-subband SO interaction which provides a controllable crossover from the regime of weak spin accumulation to the regime of strong one by varying the Fermi energy (electron density) and/or energy gap. We estimate that by changing the gap from zero up to 1-2 K, the magnitude of the effect changes by three orders of magnitude. This opens up the possibility for the design of new spintronic devices.
[1]. A. Khaetskii and J. C. Egues, Europhysics Letters 118, 57006 (2017).
[2]. F. Hernandez et al., Phys. Rev. B 88, 161305(R) (2013).
[3]. E. Bernardes et al., Phys. Rev. Lett. 99, 076603 (2007).
[4]. A. Khaetskii, Phys. Rev. B 89, 195408 (2014). Dr. Adrian Price-Whelan, Department of Astrophysical Sciences, Princeton University, "The Milky Way as a benchmark: using surveys of our Galaxy to inform fundamental astrophysics", Astronomy Seminar12:30pm
2/15
Dr. Adrian Price-Whelan, Department of Astrophysical Sciences, Princeton University, "The Milky Way as a benchmark: using surveys of our Galaxy to inform fundamental astrophysics", Astronomy Seminar
Friday, February 15th, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Adrian Price-Whelan,
Department of Astrophysical Sciences, Princeton University
The Milky Way as a benchmark: using surveys of our Galaxy to inform fundamental astrophysics
The Milky Way is currently the only galaxy in which we can study the detailed kinematic and chemical properties of large numbers of stars. It therefore provides a unique laboratory to test predictions made by astrophysical models of dark matter and galaxy assembly. In this talk, I will focus on how the recent confluence of all-sky photometric, astrometric, and spectroscopic surveys of Milky Way stars has enabled new dynamical constraints on the nature of dark matter. However, these surveys have also presented challenges to many of the simplifying assumptions that have enabled these inferences, for example by revealing the imprints of time-dependence and disequilibrium in the kinematics of stars throughout the Galaxy. I will discuss ways in which we can generalize our dynamical models and improve our statistical inferences to make and test precise astrophysical predictions about dark matter and galaxy formation using stars in the Milky Way. Dr. Sarah Ballard, MIT Kavli Institute, "Lifetimes of Planetary Systems around Small Stars", Astronomy Seminar12:30pm
2/13
Dr. Sarah Ballard, MIT Kavli Institute, "Lifetimes of Planetary Systems around Small Stars", Astronomy Seminar
Wednesday, February 13th, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Sarah Ballard,
MIT Kavli Institute
Lifetimes of Planetary Systems around Small Stars
The Solar System furnishes our most familiar planetary architecture: many planets, orbiting nearly coplanar to one another. However, a typical system of planets in the Milky Way orbits a much smaller M dwarf star. Small stars present a very different blueprint in key ways, compared to the conditions that nourished evolution of life on Earth. Using ensemble studies of hundreds-to-thousands of exoplanets orbiting small stars, my research program investigates the links between planet formation from disks, orbital dynamics and stability of planetary systems, and the presence and observability of their atmospheres. These processes bear upon the potential for M dwarf systems to evolve and sustain life. Studies of exoplanets with the James Webb Space Telescope comprise the clear next step toward understanding the hospitability of the Milky Way to life. Our success hinges upon leveraging the many thousands of planet discoveries in hand to determine how to use this precious and limited resource. Prof. Lee Roberts, Boston University, "Searching for Physics Beyond the Standard Model with the World's Largest Penning Trap", Physics Colloquium (Prof. Lee Roberts, Boston University)3:30pm
2/8
Prof. Lee Roberts, Boston University, "Searching for Physics Beyond the Standard Model with the World's Largest Penning Trap", Physics Colloquium (Prof. Lee Roberts, Boston University)
Friday, February 8th, 2019
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Lee Roberts, Boston University
Searching for Physics Beyond the Standard Model with the World's Largest Penning Trap
Measurements of the magnetic moments of the electron and muon were intertwined with the development of the "modern physics" of the 20th century. For the muon, this trend continues, perhaps pointing to New Physics beyond the Standard Model (BSM). The magnetic moment is along the spin,
For leptons, the factor g is greater than the Dirac value of 2 because of radiative corrections, so g =2(1+ a), or equivalently a = (g-2)/2, where a is the magnetic anomaly. While the value of the muon anomaly is dominated by the lowest-order Schwinger term /2≃ 0.00116⋯, it is necessary to include higher order contributions from QED, as well as contributions from the strong interaction and electroweak gauge bosons, to compare with the experimental value. The SM value now has an uncertainty of 0.3 parts per million (ppm), and the experimental value has an uncertainty of ± 0.54 ppm. The experimental value is larger than the Standard Model value by ≃ 3.7 standard deviations, which could come from new, as yet undiscovered, BSM physics. To clarify this situation, a new experiment, E989 with the total error budget of ±0.14 ppm has been mounted at Fermilab and will soon begin the second data collection period. I will review the history of what we have already learned from previous (g-2) experiments, the physics reach of 989, and will report on its present status.
Friday, February 8, 2019
3:30 P.M.
Gant Science Complex, Physics, GW-38
Coffee and tea will be served prior to the talk, at 3:00 p.m., In Room P-103 Dr. Daniel Angles-Alcazar, Center for Computational Astrophysics, Flatiron Institute, "Multi-scale physical modeling in galaxy formation and evolution", Astronomy Seminar12:30pm
2/8
Dr. Daniel Angles-Alcazar, Center for Computational Astrophysics, Flatiron Institute, "Multi-scale physical modeling in galaxy formation and evolution", Astronomy Seminar
Friday, February 8th, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Daniel Angles-Alcazar,
Center for Computational Astrophysics, Flatiron Institute
Multi-scale physical modeling in galaxy formation and evolution
While observations across the electromagnetic spectrum are providing an increasingly detailed view of galaxy evolution across cosmic time, theoretical models face the challenge of understanding the multi-scale physical processes that connect stars and supermassive black holes to galaxies and their cosmological environment. I will show that cosmological hydrodynamic simulations are a crucial tool to interpret observations and improve our understanding of galaxy evolution, highlighting recent results on (1) the role of supernovae, stellar winds, and radiation from massive stars regulating galaxy growth, (2) the large-scale gas flows that connect galaxies and their surrounding circumgalactic medium, and (3) the co-evolution of galaxies and their central supermassive black holes. Looking forward, I will discuss the need for leveraging major advances in a variety of simulation methodologies and I will present novel techniques that will enable a more detailed understanding of the dominant physical processes operating over the full range of scales involved in galaxy evolution. Dr. Massimo Gaspari, Department of Astrophysical Sciences, Princeton University, "Raining on Galaxies and Black Holes: Unifying the Micro and Macro Properties of AGN Feeding and Feedback", Astronomy Seminar12:30pm
2/6
Dr. Massimo Gaspari, Department of Astrophysical Sciences, Princeton University, "Raining on Galaxies and Black Holes: Unifying the Micro and Macro Properties of AGN Feeding and Feedback", Astronomy Seminar
Wednesday, February 6th, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Massimo Gaspari,
Department of Astrophysical Sciences, Princeton University
Raining on Galaxies and Black Holes: Unifying the Micro and Macro Properties of AGN Feeding and Feedback
Feeding and feedback tied to supermassive black holes (SMBHs) play central role in the cosmic evolution of galaxies, groups, and clusters of galaxies. The self-regulated active galactic nucleus (AGN) cycle is matter of intense debate. I review key results of our numerical campaign to unveil how SMBHs are tightly coupled to the multiphase gaseous halos, linking the inner gravitational radius to the large Mpc scale and vice versa. Massively parallel magnetohydrodynamic simulations show the turbulent plasma halo radiatively cools via a top-down multiphase condensation rain of warm filaments and molecular clouds. The multiphase precipitation inherits the hot halo kinematics and thermodynamics, ultimately establishing a 'cosmic weather'. In the nuclear region, the recurrent collisions between the clouds and filaments promote angular momentum cancellation and boost the SMBH accretion rate through a mechanism known as Chaotic Cold Accretion (CCA). The CCA rapid variability triggers powerful AGN outflows, which quench the macro cooling flow and star formation, while preserving the atmospheres of galaxies, groups, and clusters in global thermal equilibrium throughout cosmic time. I highlight the key imprints of AGN feedback and feeding, such as bubbles, shocks, turbulence, and condensed structures, with a critical eye toward observational concordance, including the X-ray plasma, optical filaments, and radio molecular clouds. Ben Augenbraun, Harvard University, "Laser-cooled polyatomic molecules for improved precision measurements", Atomic, Molecular, and Optical Physics Seminar2:00pm
2/5
Ben Augenbraun, Harvard University, "Laser-cooled polyatomic molecules for improved precision measurements", Atomic, Molecular, and Optical Physics Seminar
Tuesday, February 5th, 2019
02:00 PM - 03:00 PM
Storrs Campus Gant West Building, GW121
Ben Augenbraun,
Harvard University
Laser-cooled polyatomic molecules for improved precision measurements
Ultracold molecules are a promising platform for applications in myriad fields, ranging from quantum simulation and chemistry to precision tests of fundamental physics. Recent work on the direct laser cooling of molecules has brought a number of diatomic molecules to the ultracold regime. These molecules are representative of a large, diverse class of molecules amenable to laser cooling. In this talk, we will focus on how polyatomic molecules (with three or more atoms) offer qualitatively new and powerful features, and the interesting physics of laser cooling polyatomic molecules will be described. We will discuss experimental work in the Doyle group on laser cooling CaF and SrOH molecules, and introduce a new experiment aimed at laser cooling of polyatomic molecules with high sensitivity to Beyond-the-Standard-Model physics, including YbOH and YbOCH3. Dr. Shea Garrison-Kimmel, Einstein Postdoctoral Fellow, TAPIR, Caltech, "Dark matter and galaxy formation in the Local Group", Astronomy Seminar12:30pm
2/1
Dr. Shea Garrison-Kimmel, Einstein Postdoctoral Fellow, TAPIR, Caltech, "Dark matter and galaxy formation in the Local Group", Astronomy Seminar
Friday, February 1st, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Shea Garrison-Kimmel,
Einstein Postdoctoral Fellow,
TAPIR, Caltech
Dark matter and galaxy formation in the Local Group
Simulations show that an expanding universe where luminous galaxies trace a massive underlying web of dark matter -- an unknown type of mass whose only strong interaction is via gravity -- reproduce a wide variety of large-scale observations spectacularly well. However, basic questions remain within the model, including the nature of dark matter and the small-scale physics important to galaxy formation. Our cosmic neighborhood, the Local Group (LG), is one of the best laboratories for answering these vital questions. Because the LG contains both our galaxy, the Milky Way, and a similarly-sized neighbor, Andromeda, it provides an unprecedented viewpoint on relatively high-mass galaxy evolution. Moreover, tiny and faint dwarf galaxies, which have historically presented "problems" within the model, are only observationally accessible within the LG. I demonstrate how zoom-in simulations yield insights into the formation of the Milky Way and Andromeda, and how they reveal these so-called small-scale problems that relate to the number and internal structure of dwarf galaxies in the LG. I culminate by presenting new simulations of the LG that incorporate well-motivated prescriptions for galaxy micro-physics (e.g. star formation and stellar feedback), then discuss how these micro-physics combine to successfully reproduce the dwarf galaxies around the Milky Way. However, these new simulations also highlight how the wide variety in the structure of the dwarf galaxies around Andromeda could present a new challenge to the model, pointing either to the standard model physics neglected in the simulations or new dark matter physics. Soroush Khosravi Dehaghi, Department of Physics, University of Connecticut, "Femtosecond Laser Transient Spectroscopy of Carotenoids and Carbon Nanotubes", PhD Defense2:30pm
1/23
Soroush Khosravi Dehaghi, Department of Physics, University of Connecticut, "Femtosecond Laser Transient Spectroscopy of Carotenoids and Carbon Nanotubes", PhD Defense
Wednesday, January 23rd, 2019
02:30 PM - 04:30 PM
Storrs Campus GW103A
Soroush Khosravi Dehaghi,
Department of Physics,
University of Connecticut
Femtosecond Laser Transient Spectroscopy of Carotenoids and Carbon Nanotubes
Carotenoids and semiconducting single-wall carbon nanotubes, which are both nanoscale carbon-based quantum mechanical systems, were studied using different optical spectroscopy techniques.
The lifetime of the S\(_2\) excited state of the carotenoids were estimated using a model-based lifetime analysis routine. It was found that the addition of a conjugated carbonyl group to the carotenoid has several crucial effects on the optical response due to the alteration of the delocalized conjugated \(\pi\) molecular orbital of the molecule. These effects include the shortening of the lifetimes of the excited states, the change in the decay mechanism from the S\(_2\) excited state to the S\(_1\) excited state, and the unresolved vibrational peaks in the steady-state absorption spectrum.
The decay of the E\(_{22}\) excited state of (6,5) semiconducting carbon nanotube dispersed in flavin mononucleotide with water was observed using transient grating spectroscopy. The lifetime of this excited state was estimated to be 450 ± 50 fs. A very strong single-frequency oscillatory component was observed in the transient grating decay profile. Dr. Chiara Mingarelli, Center for Computational Astrophysics, Flatiron Institute, "Probing supermassive black hole mergers with pulsar timing", Astronomy Seminar12:30pm
1/23
Dr. Chiara Mingarelli, Center for Computational Astrophysics, Flatiron Institute, "Probing supermassive black hole mergers with pulsar timing", Astronomy Seminar
Wednesday, January 23rd, 2019
12:30 PM - 01:30 PM
Storrs Campus Gant West 103B
Dr. Chiara Mingarelli,
Center for Computational Astrophysics, Flatiron Institute
Probing supermassive black hole mergers with pulsar timing
Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz regime. An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in this band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent limits which have emerged from international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers. Electric Form Factor of the Neutron from Asymmetry Measurements, Doctoral Dissertation Oral Defense of Richard Obrecht11:00am
1/4
Electric Form Factor of the Neutron from Asymmetry Measurements, Doctoral Dissertation Oral Defense of Richard Obrecht
Friday, January 4th, 2019
11:00 AM - 12:00 PM
Storrs Campus Gant West, P-121
Electric Form Factor of the Neutron from Asymmetry Measurements
Field of Study: Physics Dr. Marko Gacesa, BAER Institute / NASA Ames Research Center, "Photoassociation of ultracold molecular ions and controlling atom-ion charge exchange using magnetic Feshbach resonances", Atomic, Molecular, and Optical Physics Seminar4:00pm
12/10
Dr. Marko Gacesa, BAER Institute / NASA Ames Research Center, "Photoassociation of ultracold molecular ions and controlling atom-ion charge exchange using magnetic Feshbach resonances", Atomic, Molecular, and Optical Physics Seminar
Monday, December 10th, 2018
04:00 PM - 05:00 PM
Storrs Campus Physics Building, P121
Dr. Marko Gacesa,
BAER Institute / NASA Ames Research Center
Photoassociation of ultracold molecular ions and controlling atom-ion charge exchange using magnetic Feshbach resonances
Feshbach resonances offer a way to control the strength and sign of particle-particle interactions in ultracold atomic and molecular gases by tuning external magnetic or electric fields. This discovery led to a number of experimental applications in ultracold AMO physics, in particular in preparation and production of dense samples of ultracold molecules. Because of their importance, Feshbach resonances have been measured and characterized in numerous of neutral diatomic mixtures. A natural generalization of studies of neutral ultracold gases includes atom-ion mixtures, which remain much less investigated than neutral systems. Atom-ion interactions are, generally, more difficult to investigate due to their long-range nature and presence of the charge. Nevertheless, the same properties also offer a window to investigate different physical regimes than the ones accessible by the neutral systems.
In this talk, I will present recent results, obtained in collaboration with the group of Prof. Robin Cote, related to using external magnetic and electric fields in controlling charge-exchange in atom-ion collisions. Specifically, I will present our theoretical investigation of magnetic Feshbach resonances and their application to controlled charge transfer in \({}^{9,10}\)Be + \({}^{9,10}\)Be+, and \({}^{40}\)Ca+\({}^{43}\)Ca+ both of which are good model systems for heavier and more complex elements. I will also present the results of first theoretical study of photoassociative formation of cold molecular ions, where we estimated the production rates of NaCa+ molecular ions from trapped cold Na+ ions and Ca atoms. This study is based on experiments conducted in the group of Prof. W. Smith at UConn. Dr. Thomas Allison, Stony Brook University, "Ultrafast extreme ultraviolet photoemission without space charge", Condensed Matter Physics Seminar2:00pm
12/4
Dr. Thomas Allison, Stony Brook University, "Ultrafast extreme ultraviolet photoemission without space charge", Condensed Matter Physics Seminar
Tuesday, December 4th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. Thomas Allison,
Stony Brook University
Ultrafast extreme ultraviolet photoemission without space charge
Time- and Angle-resolved photoelectron spectroscopy from surfaces can be used to record the dynamics of electrons and holes in condensed matter on ultrafast time scales. However, ultrafast photoemission experiments using extreme-ultraviolet (XUV) light have previously been limited by either space-charge effects, low photon flux, or limited tuning range. In this article, we describe space-charge-free XUV photoelectron spectroscopy experiments with up to 5 nA of average sample current using a tunable cavity-enhanced high-harmonic source operating at 88 MHz repetition rate. The source delivers \(> 10^{11}\) photons/s in isolated harmonics to the sample over a broad photon energy range from 18 to 37 eV with a spot size of \(58 \times 100 \mu m^2\). From photoelectron spectroscopy data, we place conservative upper limits on the XUV pulse duration and photon energy bandwidth of 93 fs and 65 meV, respectively. The high photocurrent, lack of space charge distortions of the photoelectron spectra, and excellent isolation of individual harmonic orders allow us to observe laser-induced changes to the photoelectron spectrum at the \(10^{-4}\) level in minutes of integration time, enabling time-resolved XUV photoemission experiments in a qualitatively new regime. I will discuss demonstration experiments on Au (111) and progress towards electron dynamics in molecular films. Dr. Thomas Allison Stony Brook University, Atomic, Molecular, and Optical Physics Seminar4:00pm
12/3
Dr. Thomas Allison Stony Brook University, Atomic, Molecular, and Optical Physics Seminar
Monday, December 3rd, 2018
04:00 PM - 05:00 PM
Storrs Campus Physics Building, P121
Dr. Thomas Allison
Stony Brook University
Cavity-enhanced ultrafast spectroscopy: ultrafast meets ultrasensitive
Ultrafast optical spectroscopy methods, such as transient absorption spectroscopy and 2D spectroscopy, are widely used across many disciplines. However, these techniques are typically restricted to optically thick samples, such as solids and liquid solutions. Using a frequency comb laser and optical cavities, we present a technique for performing ultrafast optical spectroscopy with high sensitivity, enabling work in dilute gas-phase molecular beams. Resonantly enhancing the probe pulses, we demonstrate transient absorption measurements with a detection limit of \(\Delta OD = 2 \times 10^{−10}\) (\(1 \times 10^{-9} / \sqrt{Hz}\)). Resonantly enhancing the pump pulses allows us to produce a high excitation fraction at a high repetition rate, so that signals can be recorded from samples with optical densities as low as \(OD ≈ 10^{−8}\), or column densities \( < 10^{10}\) molecules∕cm\(^2\). In this talk, I will discuss initial demonstration experiments, methods for cavity-enhancing multidimensional spectroscopy signals using multiple frequency combs, and progress towards widely tunable cavity-enhanced ultrafast spectrometers operating from the ultraviolet to the infrared. Jonathan Kwolek, Department of Physics, University of Connecticut, "Studying Charge Exchange in a Hybrid Ion-neutral Trap", PhD Defense1:30pm
11/30
Jonathan Kwolek, Department of Physics, University of Connecticut, "Studying Charge Exchange in a Hybrid Ion-neutral Trap", PhD Defense
Friday, November 30th, 2018
01:30 PM - 03:30 PM
Storrs Campus GW121
Jonathan Kwolek,
Department of Physics,
University of Connecticut
Studying Charge Exchange in a Hybrid Ion-neutral Trap
Interactions between neutral and ionized atoms are medium-range, and the spiraling nature of these collisions can lead to long interaction times and large cross sections. The field of ion-neutral interactions is bolstered by methods from atomic physics, which allow us to accurately control and determine the quantum-states of the reactants. Atomic physics opens the door to studying these interactions over a large range of energies, in order to observe interesting effects from the ultracold to hot temperature regimes.
The hybrid-trap enables the concentric trapping of a sample of cold atoms and ions. The dissertation discusses our exploration into the controlled reactions in the Na+Ca^+ system, including measurements of sympathetic cooling and a charge-exchange rate which changes as a function of energy and atomic state. The quantum-state distributions of Na in our magneto-optical trap is also explored, as well as its agreement and subsequent deviation based on a predictive model. The measurements of reaction rates indicate a reaction-energy threshold in two different reaction channels, which can be corroborated by theoretical investigation. Dr. Daniel Angles-Alcazar, Center for Computational Astrophysics, Flatiron Institute, "The dual role of stellar feedback regulating galaxy evolution and the growth of supermassive black holes", Astronomy Seminar2:00pm
11/28
Dr. Daniel Angles-Alcazar, Center for Computational Astrophysics, Flatiron Institute, "The dual role of stellar feedback regulating galaxy evolution and the growth of supermassive black holes", Astronomy Seminar
Wednesday, November 28th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West 121
Dr. Daniel Angles-Alcazar,
Center for Computational Astrophysics, Flatiron Institute
The dual role of stellar feedback regulating galaxy evolution and the growth of supermassive black holes
Feedback from massive stars, including supernovae, stellar winds, and radiation, is believed to play a central role in galaxy evolution. In this talk, I will present recent progress in understanding the implications of stellar feedback using cosmological hydrodynamic simulations from the Feedback In Realistic Environments (FIRE) project. In these simulations, stellar feedback regulates star formation locally in galaxies while driving large-scale winds that connect galaxies with their surrounding circumgalactic medium. I will discuss the efficiency of winds evacuating gas from galaxies, the importance of wind re-accretion to galaxy mass assembly, and the surprising contribution of intergalactic transfer of material between galaxies via winds. Zooming into galactic nuclei, I will show that stellar feedback regulates the early growth of the central black hole in low mass galaxies by continuously evacuating the nuclear gas reservoir, which has important implications for the co-evolution of supermassive black holes and galaxies and the frequency and mass scale of massive black hole mergers. Dr. Nora Kling Department of Physics, University of Connecticut, "Ultrafast Nuclear Motion: Resolving Hydrogen Migration(s) in Time", Atomic, Molecular, and Optical Physics Seminar4:00pm
11/26
Dr. Nora Kling Department of Physics, University of Connecticut, "Ultrafast Nuclear Motion: Resolving Hydrogen Migration(s) in Time", Atomic, Molecular, and Optical Physics Seminar
Monday, November 26th, 2018
04:00 PM - 05:00 PM
Storrs Campus Physics Building, P121
Dr. Nora Kling
Department of Physics,
University of Connecticut
Ultrafast Nuclear Motion: Resolving Hydrogen Migration(s) in Time
Intramolecular hydrogen migration is a natural process that plays a crucial role in many biological, chemical, and physical phenomena, and is the object of current research efforts in fuel cells, proteomics, and combustion chemistry. Using ultrafast, intense lasers and sophisticated pump-probe ion imaging techniques, we can explore the rich dynamics of hydrogen migration reactions, including what timescale they occur on. In my talk, I will present two studies. The first study is on acetylene, a small hydrocarbon, where a hydrogen can migrate across the carbon atoms to form its vinylidene isomer [1,2]. The second study is on ethanol, a complex molecule where both single and double hydrogen migrations occur, and the timescale for each is individually determined [3]. These experimental results, in combination with state-of-the art quantum chemical trajectory calculations, give us new insight into the complex nuclear motions in complex polyatomic molecules.
[1] C. Burger et al. Faraday Discussions 194, 495 (2016).
[2] M. Kübel et al. Phys. Rev. Lett. 116, 193001 (2016).
[3] N. G. Kling et al. submitted for publication Dr. David Murphy, MIT, "Matrix Elements for Neutrinoless Double Beta Decay from Lattice QCD", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
11/26
Dr. David Murphy, MIT, "Matrix Elements for Neutrinoless Double Beta Decay from Lattice QCD", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, November 26th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. David Murphy, MIT
Matrix Elements for Neutrinoless Double Beta Decay from Lattice QCD
While neutrino oscillation experiments have demonstrated that neutrinos have small, nonzero masses, much remains unknown about their properties and decay modes. One potential decay mode --- neutrinoless double beta decay (\(0 \nu \beta \beta\)) --- is a particularly interesting target of experimental searches, since its observation would imply both the violation of lepton number conservation in nature as well as the existence of at least one Majorana neutrino, in addition to giving further constraints on the neutrino masses and mixing angles. Relating experimental constraints on \(0 \nu \beta \beta\) decay rates to the neutrino masses, however, requires theoretical input in the form of non-perturbative nuclear matrix elements which remain difficult to calculate reliably. In this talk we will discuss progress towards first-principles calculations of relevant nuclear matrix elements using lattice QCD and effective field theory techniques, assuming neutrinoless double beta decay mediated by a light Majorana neutrino. Professor Nadia Fomin, University of Tennessee, "Life and Death of the Free Neutron", Physics Colloquium3:30pm
11/16
Professor Nadia Fomin, University of Tennessee, "Life and Death of the Free Neutron", Physics Colloquium
Friday, November 16th, 2018
03:30 PM - 04:30 PM
Storrs Campus PB-38
Professor Nadia Fomin, University of Tennessee
Life and Death of the Free Neutron
Modern neutron sources provide extraordinary opportunities to study a wide variety of physics topics, including the physical system of the neutron itself. One of the processes under the microscope, neutron beta decay, is an archetype for all semi-leptonic charged-current weak processes. Precise measurements of the correlation parameters in neutron beta decay as well as the neutron lifetime itself are required for tests of the Standard Model and for searches of new physics. The state of the field will be presented and a program of current and future experiments and potential impacts explored. Dr. Turgut Yilmaz, Department of Physics, University of Connecticut, "Topological insulators and their interaction with magnetic impurities and superconductors", Condensed Matter Physics Seminar2:00pm
11/13
Dr. Turgut Yilmaz, Department of Physics, University of Connecticut, "Topological insulators and their interaction with magnetic impurities and superconductors", Condensed Matter Physics Seminar
Tuesday, November 13th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. Turgut Yilmaz, Department of Physics, University of Connecticut
Topological insulators and their interaction with magnetic impurities and superconductors
Topological properties of materials have recently attracted much attention in the condensed matter physics community due, in part to their possible applications in quantum electronic devices. In particular, topological insulators (TIs) that possess gapless surface states that are topologically protected and can lead to dissipationless quantum electronics. TI's surface state exhibit relativistic momentum dispersion with the Dirac point (DP) located at the time reversal invariant momenta point while the bulk bands are inverted and gapped [1]. Currently, two majority experimental efforts have concentrated on inducing the magnetic and superconducting properties in TI, which would lead to the experimental realizations of quantum anomalous Hall effect (QAHE) and Majorana fermions, respectively [2-3].
Magnetism can be induced in TIs by incorporating impurities into the bulk or on the surface of TIs. If there is a net out-of-plane magnetic moment, an energy gap opens at the DP due to broken time reversal symmetry, which would give rise to QAHE. On the other hand, the superconductivity in can be induced in TI through the proximity effect by growing TIs on the surface of a superconductor. Both, the gapped DP and the superconductivity can be probed by angle-resolve photoemission spectroscopy (ARPES). In this talk, I will present our photoemission studies on the search of broken time reversal symmetry in magnetic TIs and proximity induced superconductivity in TI/superconductor heterostructures. Also, the experimental setup to grow and study TIs at the Physics Department of the University of Connecticut will be presented.
[1] L. Fu, C. L. Kane, and E. J. Mele, Phys. Rev. Lett. 98, 106803 (2007).
[2] X.-L. Qi and S.-C. Zhang, Rev. Mod. Phys. 83, 1057 (2011).
[3] T. Yilmaz, et al., Appl. Surf. Sci. 407, 371 (2017). Prof. Serge M. Nakhmanson, Department of Materials Science and Engineering, and Institute of Materials Science, University of Connecticut, "Mesoscale simulations of ferroic functionalities with finite elements: MOOSE, Ferret and other animals", Physics Colloquium3:30pm
11/9
Prof. Serge M. Nakhmanson, Department of Materials Science and Engineering, and Institute of Materials Science, University of Connecticut, "Mesoscale simulations of ferroic functionalities with finite elements: MOOSE, Ferret and other animals", Physics Colloquium
Friday, November 9th, 2018
03:30 PM - 04:30 PM
Storrs Campus GW038
Prof. Serge M. Nakhmanson, Department of Materials Science and Engineering, and Institute of Materials Science, University of Connecticut
Mesoscale simulations of ferroic functionalities with finite elements: MOOSE, Ferret and other animals
Ferret is an open-source highly scalable real-space finite-element-method (FEM) based code for simulating transitional behavior of materials systems with coupled physical properties at mesoscale. This code is built on MOOSE, Multiphysics Object Oriented Simulation Environment, and is being developed by a team of collaborators at the University of Connecticut and Argonne National Laboratory. MOOSE allows efficient solving of coupled-physics problems, has a proven record of scaling of execution on up to 10K nodes, and is easily extendable to include new physics and couplings. Real-space FEM approach allows treatment of materials systems possessing complicated geometry and morphology, and evaluation of property dependencies on the system shape, size, microstructure and applied boundary conditions. In this presentation we provide an overview of computational approach utilized by the code, as well as its technical features and the associated software within its tool chain. We also highlight a variety of examples of the code applications, some of which are being pursued in collaboration with a number of different experimental groups. These applications include (a) evaluation of size- and microstructure-dependent elastic and electronic properties of semiconducting core-shell nanostructures; (b) investigation of transitional behavior and topological phases in ferroelectric films, islands, particles and particle-based ferroelectric/dielectic materials; and (c) understanding the workings of photoelectric and electro-optic effects in piezoelectric and ferroelectric materials and nanostructures.
SN acknowledges the efforts of his students John Mangeri, Krishna Chaitanya Pitike and Lukasz Kuna, and senior collaborators S. Pamir Alpay (UConn), and Olle G. Heinonen (ANL), all of whom made major contributions to the projects discussed in this presentation. Funding support from the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program is acknowledged. The SCGSR program is administered by the Oak Ridge Institute for Science and Education (ORISE) for the US Department of Energy. ORISE is managed by ORAU under contract number DE-SC0014664. US National Science Foundation (award number DMR 1309114) is also acknowledged for partial funding of some activities related to the development of the Ferret code. Dr. Chiara Mingarelli, Center for Computational Astrophysics, Flatiron Institute, "Pulsar Timing Arrays: The Next Window to Open on the Gravitational-Wave Universe", Astronomy Seminar2:00pm
11/7
Dr. Chiara Mingarelli, Center for Computational Astrophysics, Flatiron Institute, "Pulsar Timing Arrays: The Next Window to Open on the Gravitational-Wave Universe", Astronomy Seminar
Wednesday, November 7th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West 121
Dr. Chiara Mingarelli, Center for Computational Astrophysics, Flatiron Institute
Pulsar Timing Arrays: The Next Window to Open on the Gravitational-Wave Universe
Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz to microhertz regime. An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in the nanohertz band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent limits which have emerged from international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers. Adam Ginsburg, National Radio Astronomy Observatory, Socorro, New Mexico, "High mass star and cluster formation", Physics Colloquium3:30pm
11/2
Adam Ginsburg, National Radio Astronomy Observatory, Socorro, New Mexico, "High mass star and cluster formation", Physics Colloquium
Friday, November 2nd, 2018
03:30 PM - 04:30 PM
Storrs Campus GW-38
Adam Ginsburg, National Radio Astronomy Observatory, Socorro, New Mexico
High mass star and cluster formation
High mass stars are responsible for most of the photons, heavy elements, and energy in galaxies, thereby driving their evolution. They tend to form in dense environments and clusters, which means we can only observe their formation at relatively large distances. I will discuss observational programs, primarily with ALMA, that show how stars form differently in denser parts of galaxies. At higher densities, more stars form in clusters, more stars form in the vicinity of massive stars, and the stellar initial mass function (IMF) shifts to favor higher masses. ALMA data at high resolution show how the feedback from massive stars shapes their environments. The upcoming ALMA-IMF large program will extend this work, showing how the stellar IMF is shaped throughout our Galaxy. Dr. Aaron LaForge, Department of Physics, University of Connecticut, "Excitation dynamics in helium nanodroplets induced by XUV radiation", Atomic, Molecular, and Optical Physics Seminar2:00pm
11/1
Dr. Aaron LaForge, Department of Physics, University of Connecticut, "Excitation dynamics in helium nanodroplets induced by XUV radiation", Atomic, Molecular, and Optical Physics Seminar
Thursday, November 1st, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West Building (aka Physics Building), GW121
Dr. Aaron LaForge, Department of Physics, University of Connecticut
Excitation dynamics in helium nanodroplets induced by XUV radiation
As opposed to purely molecular systems where electron dynamics proceed only through intramolecular processes, weakly-bound complexes like helium nanodroplets offer an environment where local excitations can interact with neighboring molecules leading to new intermolecular relaxation mechanisms. Here, we present a systematic, time-resolved study of the excitation dynamics when helium nanodroplets are resonantly excited by XUV free electron laser radiation. At low pulse energy, a single atom is excited leading to the formation of a bubble state which relaxes to the droplet surface on a femtosecond timescale. At high pulse energy, a network of excited atoms is formed within a nanodroplets which then collectively autoionizes with high efficiency. Using the pump-probe technique, we were able to time resolve this process. John Donoghue, UMass Amherst, "A possible QFT pathway for UV complete quantum gravity", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
10/29
John Donoghue, UMass Amherst, "A possible QFT pathway for UV complete quantum gravity", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, October 29th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
John Donoghue, UMass Amherst
A possible QFT pathway for UV complete quantum gravity
This is a study of a renormalizable quantum field theory for gravity. It makes use of a gravitational sector which is weakly coupled at all scales, and a helper Yang Mills gauge theory which becomes strong at the Planck scale. While it has an unstable ghost in the propagator, and other unusual properties, unitarity is satisfied at the one loop level as determined by explicit calculation. Further
explorations will be discussed. Professor Rainer Weiss, Massachusetts Institute of Technology, 2017 Nobel Prize Winner, Member of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration, "Exploration of the Universe with Gravitational Waves", Katzenstein Distinguished Lecture4:00pm
10/26
Professor Rainer Weiss, Massachusetts Institute of Technology, 2017 Nobel Prize Winner, Member of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration, "Exploration of the Universe with Gravitational Waves", Katzenstein Distinguished Lecture
Friday, October 26th, 2018
04:00 PM - 05:00 PM
Storrs Campus GW-36
Professor Rainer Weiss, Massachusetts Institute of Technology, 2017 Nobel Prize Winner,
Member of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration
Exploration of the Universe with Gravitational Waves
The observations of gravitational waves from the merger of binary black holes and from a binary neutron star coalescence followed by a set of astronomical measurements is an example of investigating the universe by "multi-messenger" astronomy. Gravitational waves will allow us to observe phenomena we already know in new ways as well as to test General Relativity in the limit of strong gravitational interactions -- the dynamics of massive bodies traveling at relativistic speeds in a highly curved space-time. Since the gravitational waves are due to accelerating masses while electromagnetic waves are caused by accelerating charges, it is reasonable to expect new classes of sources to be detected by gravitational waves as well. The lecture will start with some basic concepts of gravitational waves. Briefly describe the instruments and the methods for data analysis that enable the measurement of gravitational wave strains of 10-21 and then present the results of recent runs. The lecture will end with a vision for the future of gravitational wave astrophysics and astronomy.
22nd Annual Katzenstein Distinguished Lecture
Refreshments will be served at 3:00 p.m. outside of GW-38 Dr. Yuya Tanizaki, RIKEN-BNL, "Constraints on possible dynamics of QCD by symmetry and anomaly", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
10/22
Dr. Yuya Tanizaki, RIKEN-BNL, "Constraints on possible dynamics of QCD by symmetry and anomaly", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, October 22nd, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. Yuya Tanizaki, RIKEN-BNL
Constraints on possible dynamics of QCD by symmetry and anomaly
Low-energy dynamics of Quantum Chromodynamics (QCD) is an important subject for nuclear and hadron physics, but it is a strongly coupled system and difficult to solve. In this situation, symmetry and also anomaly give us an important guide to make a solid conclusion on possible
behaviors of QCD. We will give a brief review on recent development of anomaly matching condition, starting from a simple quantum mechanical example. After that, we explain the newly found anomaly of QCD in chiral limit, and discuss the conclusion of anomaly matching. Prof. Roger Falcone, University of California, Berkeley and 2018 President of the American Physical Society, "Science at High Energy Density and Work of the American Physical Society", Physics Colloquium3:30pm
10/19
Prof. Roger Falcone, University of California, Berkeley and 2018 President of the American Physical Society, "Science at High Energy Density and Work of the American Physical Society", Physics Colloquium
Friday, October 19th, 2018
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Roger Falcone, University of California, Berkeley and 2018 President of the American Physical Society
Science at High Energy Density and Work of the American Physical Society
Materials taken to extreme densities and temperatures exhibit unique properties due to changes in electronic structure. I will describe experiments, done at facilities that use the world's highest energy lasers and x-ray lasers, to excite such materials and probe their properties. At the end if this talk I will focus on the work of the American Physical Society, in publishing, advocating for science, and reaching out to broader communities. Dr. Charlotte A. Mason, Harvard-Smithsonian Center for Astrophysics, "What Can Galaxies Tell Us About Reionization", Astronomy Seminar2:00pm
10/17
Dr. Charlotte A. Mason, Harvard-Smithsonian Center for Astrophysics, "What Can Galaxies Tell Us About Reionization", Astronomy Seminar
Wednesday, October 17th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West 121
Dr. Charlotte A. Mason, Harvard-Smithsonian Center for Astrophysics
What Can Galaxies Tell Us About Reionization
The reionization of intergalactic hydrogen in the universe's first billion years was likely driven by the first stars and galaxies. The timeline of reionization is currently uncertain but if it is accurately measured it can unveil the properties of 'first light' sources. Lyman alpha (Lyα) emission from galaxies can potentially probe the intergalactic medium (IGM) at high redshifts but requires modeling physics from pc to Gpc scales. I will introduce a new forward-modeling framework which combines cosmological IGM simulations with interstellar medium models to enable Bayesian inference of the IGM neutral hydrogen fraction from observations of Lyα from galaxies. I will present our new measurements of the neutral fraction at z~7 and z~8 and place them in the context of the reionization history. I will describe ongoing efforts with the HST survey GLASS to build larger spectroscopic samples of galaxies at z>6 to further measure the reionization timeline, and future prospects with JWST. Prof. J. Brad Marston, Physics Department, Brown University, "El Nino as a Topological Insulator: A Surprising Connection Between Climate and Quantum Physics", Physics Colloquium3:30pm
10/12
Prof. J. Brad Marston, Physics Department, Brown University, "El Nino as a Topological Insulator: A Surprising Connection Between Climate and Quantum Physics", Physics Colloquium
Friday, October 12th, 2018
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. J. Brad Marston, Physics Department, Brown University
El Nino as a Topological Insulator: A Surprising Connection Between
Climate and Quantum Physics
Symmetries and topology play central roles in our understanding of physics. Topology, for instance, explains the precise quantization of the
Hall effect and the protection of surface states in topological insulators
against scattering from disorder or bumps. However discrete symmetries and
topology have so far played little role in thinking about the fluid dynamics of oceans and atmospheres. In this talk I show that, as a consequence of the rotation of the Earth that breaks time reversal symmetry, equatorially trapped Kelvin and Yanai waves emerge as
topologically protected edge modes. Thus the oceans and atmosphere of Earth naturally share basic physics with topological insulators. As
equatorially trapped Kelvin waves in the Pacific ocean are an important component of El Nino Southern Oscillation and other climate processes,
these new results demonstrate that topology plays a surprising role in Earth's climate system. Dr. Jeff Powell, Department of Physics, University of Connecticut, "Photoelectron emission from metal and dielectric nanoparticles in intense laser fields", Condensed Matter Physics Seminar2:00pm
10/9
Dr. Jeff Powell, Department of Physics, University of Connecticut, "Photoelectron emission from metal and dielectric nanoparticles in intense laser fields", Condensed Matter Physics Seminar
Tuesday, October 9th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. Jeff Powell, Department of Physics, University of Connecticut
Photoelectron emission from metal and dielectric nanoparticles in intense laser fields
Nanoparticles provide a unique platform to study the mechanisms of light interactions with complex systems, in particular, the motion of electrons driven by strong fields and excitation of plasmonic resonances. Here I report on the systematic analysis of the photoelectron emission from single, isolated, gas-phase, spherical nanoparticles as a function of particle size, composition and laser intensity. Gold, silica (SiO2), and silica core/gold shell nanoparticles ranging in size from 5nm to 750nm were irradiated by 800nm, 25fs laser pulses at 0.2-20 TW/cm2 peak intensities. A high energy velocity-map imaging spectrometer was used to determine the cutoff photoelectron energy for each sample and intensity. Nanoparticle size and composition influence the electron cutoff energy, which provides insight into photoelectron trajectories and rescattering dynamics, both of which are affected by near-field enhancement and plasmonic excitation. In particular, I observe that photoelectrons emitted from gold nanoparticles are much more energetic than those from silica, which, in turn, are much faster than those from isolated atoms or molecules exposed to the same light pulses. This work reveals the complex interplay between the external optical field and the induced near-field of the nanoparticle. Prof. Dawn Meredith, Department of Physics, University of New Hampshire, "Instructor and student resources in the physics course for life science students", Physics Colloquium3:30pm
10/5
Prof. Dawn Meredith, Department of Physics, University of New Hampshire, "Instructor and student resources in the physics course for life science students", Physics Colloquium
Friday, October 5th, 2018
03:30 PM - 04:30 PM
Storrs Campus GW-38
Prof. Dawn Meredith, Department of Physics, University of New Hampshire
Instructor and student resources in the physics course for life science students
Over a decade ago, professionals in life science called for the education for the next generation of practitioners to be more interdisciplinary and quantitative. Physicists listened, and in the last decade we have learned a lot about the students and the potential of this course. I will share some insights about what makes this course different from the course for engineers, best practices and new curricula, and the soon-to-be-live Living Physics Portal that provides community and resources for instructors. In the second part of the talk, I'll discuss research that uncovers some productive cognitive resources that life science students bring to the physics classroom on which new understandings can be built.
Coffee and tea will be served prior to the talk, at 3:00 p.m., In Room GW-103 Prof. Steve Finkelstein, Department of Astronomy, University of Texas, Austin, "Understanding the Reionization of the Universe Now and with JWST", Physics Colloquium3:30pm
9/28
Prof. Steve Finkelstein, Department of Astronomy, University of Texas, Austin, "Understanding the Reionization of the Universe Now and with JWST", Physics Colloquium
Friday, September 28th, 2018
03:30 PM - 04:30 PM
Storrs Campus PB-38
Prof. Steve Finkelstein, Department of Astronomy, University of Texas, Austin
Understanding the Reionization of the Universe Now and with JWST
The universe just after the Big Bang was a dark place, while the remnant radiation from the Big Bang cooled, and gas began to pile into dark matter halos. After a few hundred million years, the as-yet unseen first galaxies began to form, and the ionizing radiation produced by their massive stars ionized the intergalactic medium, in a process known as reionization. The search for these first galaxies, and an understanding of the process of reionization, has been a major goal of extragalactic astronomy for decades. While it is commonly assumed that massive stars within star-forming galaxies provide the needed ionizing photons to reionize the intergalactic medium, the commonly assumed ionizing photon escape fractions in the range of 10-50% have thus far exceeded what has been observed (except in a few extreme cases). I will discuss the results of a new semi-empirical model, combining simulated galaxy escape fractions with observed rest-UV galaxy luminosity functions. We find that we can successfully match all observational constraints on reionization by 1) forming stars to physically-motivated halo mass limits; 2) allowing galaxies to be more efficient ionizing photon producers at higher redshift, and 3) allowing a (not strong) contribution from AGNs. This predicts that reionization is a smoother process than previous models, with a predicted volume-averaged ionized fraction of 20% at z=10. JWST will soon dramatically improve our view of the z~10 universe and validate whether significant star-formation is occurring in that epoch, and I will conclude by discussing a recently-approved JWST Early Release Science program which will begin to probe this epoch. Shany Danieli, Yale University, "Hunting low surface brightness galaxies with the Dragonfly Telephoto Array", Astronomy Seminar2:00pm
9/26
Shany Danieli, Yale University, "Hunting low surface brightness galaxies with the Dragonfly Telephoto Array", Astronomy Seminar
Wednesday, September 26th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West 121
Shany Danieli, Yale University
Hunting low surface brightness galaxies with the Dragonfly Telephoto Array
Dwarf galaxies are a significant component of the galaxy population. Their number density, among other properties, provides strong constraints on theories of galaxy formation, stellar feedback processes, and the distribution and nature of dark matter. However, their low central surface brightnesses makes them difficult to detect and study beyond the Local Group, leading to a biased view of the full galaxy population. To address this problem a new robotic telescope was developed and built, called the Dragonfly Telephoto Array, that is optimized to explore the universe at surface brightness levels below 30 mag/arcsec^2. In this talk I'll describe the technology behind the 1m f/0.4 refractor and present some early results in the dwarf galaxy regime. I will then present our strategy for finding these low surface brightness galaxies as part of the on-going Dragonfly Wide Field Survey that will cover 500 sq. deg. upon survey completion. We will use these data to empirically constrain the Luminosity Function of field galaxies down to the low mass end which is essential for understanding the nature of low-mass dark matter halos.
Shany Danieli is a Physics PhD student at Yale University, working with Prof. Pieter van Dokkum. She specializes in the formation and evolution of dwarf galaxies and Ultra Diffuse Galaxies, both in galaxy groups and in the field (isolated galaxies), using various observational tools such as the Dragonfly Telephoto Array and the Hubble Space Telescope. Prof. Gerald Dunne, Department of Physics, University of Connecticut, "Resurgence and Phase Transitions", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
9/24
Prof. Gerald Dunne, Department of Physics, University of Connecticut, "Resurgence and Phase Transitions", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, September 24th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Prof. Gerald Dunne, Department of Physics, University of Connecticut
Resurgence and Phase Transitions
Resurgence is a new approach to quantum field theory that combines perturbative and non-perturbative effects in a unified framework. I'll give an overview of the key ideas and discuss applications to phase transitions in physical problems. The main motivation is to find a new way to probe the QCD phase diagram. In this approach, a phase transition is interpreted as a change of dominant saddle in a path integral or partition function. Examples include the Ising model, chiral symmetry breaking in the Gross-Neveu model, the Thirring and Hubbard models, and the large N phase transition in 2d lattice gauge theory. Dr. Peter D Drummond FAA, Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Australia, "Testing quantum mechanics with modern technology", Physics Colloquium3:30pm
9/21
Dr. Peter D Drummond FAA, Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Australia, "Testing quantum mechanics with modern technology", Physics Colloquium
Friday, September 21st, 2018
03:30 PM - 04:30 PM
Storrs Campus Gant Science Complex, GW-38
Dr. Peter D Drummond FAA, Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Australia
Testing quantum mechanics with modern technology
Wendell Furry [1] and Sydney Coleman [5] were two of Harvard's most original quantum theorists. What can modern quantum technology contribute to their work? Experimentally tested simulations of opto-mechanics[4] and atom interferometers [3], with thermal noise and losses, will be used to analyse proposals for testing Furry's nonlocal decoherence, and Coleman's QFT tunnelling to the true vacuum. Both these ideas are fundamental to our understanding of the quantum universe. Nonlocal decoherence was proposed in Furry's response to Einstein's EPR paper. Today, this idea is becoming testable for massive objects at low temperatures. Entanglement decoherence and massive Schrodinger cats are testable [4] through an optomechanical memory, simulated using the positive-P representation, thus combining technology at Yale and JILA. Coleman's proposal of a false vacuum models fluctuations in the early universe, leading to large-scale structure in the microwave background. Coleman's ideas will be applied to construct a proposal for a laboratory model of the quantum fluctuations in the 'Big Bang', using a coupled BEC experiment in ultracold 41K, simulated with a Wigner phase-space representation [6].
[1] W. H. Furry, Phys. Rev. 49, 393 (1936).
[2] A. Einstein, B. Podolsky, and N. Rosen, Phys. Rev. 47, 777 (1935).
[3] M. Egorov et. al, Phys. Rev. A 84, 021605 (2011).
[4] S. Kiesewetter, R. Y. Teh, P. Drummond and M. Reid, Phys. Rev. Lett. 119, 023601 (2017).
[5] S. Coleman, Phys. Rev. D 15, 2929 (1977).
[6] O. Fialko et. al., J. Phys. B 50 024003 (2017).
Coffee and tea will be served prior to the talk, at 3:00 p.m., In Room GW-103 Jennifer Bergner, Harvard-Smithsonian Center for Astrophysics, Harvard University, "Chemical complexity during star and planet formation: new observational and laboratory insights", Astronomy Seminar2:00pm
9/19
Jennifer Bergner, Harvard-Smithsonian Center for Astrophysics, Harvard University, "Chemical complexity during star and planet formation: new observational and laboratory insights", Astronomy Seminar
Wednesday, September 19th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West 121
Jennifer Bergner, Harvard-Smithsonian Center for Astrophysics, Harvard University
Chemical complexity during star and planet formation: new observational and laboratory insights
Planets form by accreting material from a protoplanetary disk, meaning that the inventory of molecules in the disk sets what subsequent chemistry can occur on a newly formed planet. Constraining the organic chemistry in disks and their precursors is therefore key to origins of life studies. I will discuss recent progress in detecting and characterizing simple (HCN and C2H) and complex (CH3CN and HC3N) organic molecules in protoplanetary disks using ALMA, as well as implications for the chemistry at play. As we are sensitivity-limited in the level of molecular complexity that can be detected in disks, observations of organic molecules around low-mass protostars are providing important windows into the initial chemical conditions of disk and planet formation. To complement these observational
approaches, we use laboratory experiments to understand how reactions proceed under conditions of low temperature and low pressure. I will outline our recent work exploring new pathways to chemical complexity in laboratory analogs of
astrophysical ices.
About the speaker: Jennifer Bergner is a graduate student in (Astro)Chemistry at Harvard working with Prof. Karin Oberg at the Harvard-Smithsonian Center for Astrophysics. She is a National Science Foundation graduate research fellow and
specializes in laboratory astrochemistry, focused on the physics and chemistry of interstellar ice analogs. Dr. Shimshon Kallush, Physics and Optical Engineering Department, ORT Braude College, Karmiel, and The Fritz Haber Center for Molecular Dynamics, The Hebrew University, Jerusalem, Israel, "Molecular alignment in hot and cold regimes, and its relationship to quantum coherence", Atomic, Molecular, and Optical Physics Seminar4:00pm
9/17
Dr. Shimshon Kallush, Physics and Optical Engineering Department, ORT Braude College, Karmiel, and The Fritz Haber Center for Molecular Dynamics, The Hebrew University, Jerusalem, Israel, "Molecular alignment in hot and cold regimes, and its relationship to quantum coherence", Atomic, Molecular, and Optical Physics Seminar
Monday, September 17th, 2018
04:00 PM - 05:00 PM
Storrs Campus Physics Building, P121
Dr. Shimshon Kallush, Physics and Optical Engineering Department, ORT Braude College, Karmiel, and The Fritz Haber Center for Molecular Dynamics, The Hebrew University, Jerusalem, Israel
Molecular alignment in hot and cold regimes, and its relationship to quantum coherence
The phenomena of field-free instantaneous quantum revivals of molecular alignment and orientation driven by optical and/or terahertz fields will be introduced. A brief survey over a few applications of the phenomena will be presented within this context:
1. Ultracold photoassociation will be shown to intrinsically contain molecular alignment. Its characteristics and the feasibility to detect directional preferences for the photoassociated species will be discussed.
2. Rotational echoes of alignment under multiple pulses will be shown to lead to unique spatial-temporal structures of the refractive index. Several applications of this feature will be suggested.
3. The quantum picture of alignment raises questions that relate to the ability to embed quantum coherences into thermal quantum systems. The problem of quantification of coherences is defined and some results that predict the ability to induce field-driven coherences will be presented Dr. Ming Li, Department of Physics, University of Connecticut, "High Baryon Densities Achievable in the Fragmentation Regions of High Energy Heavy-Ion Collisions", Particle, Astrophysics, and Nuclear Physics Seminar2:00pm
9/17
Dr. Ming Li, Department of Physics, University of Connecticut, "High Baryon Densities Achievable in the Fragmentation Regions of High Energy Heavy-Ion Collisions", Particle, Astrophysics, and Nuclear Physics Seminar
Monday, September 17th, 2018
02:00 PM - 03:00 PM
Storrs Campus Gant West (Physics Building), P121
Dr. Ming Li, Department of Physics, University of Connecticut
High Baryon Densities Achievable in the Fragmentation Regions of High Energy Heavy-Ion Collisions
In high energy heavy-ion collisions, the two colliding nuclei pass through each other leaving behind an almost baryon-free central region. Most of the baryon charges are carried away by the receding nuclear remnants. During the collisions, a large amount of kinetic energy is deposited in the central region where a new form of matter called quark-gluon plasma is formed. At the same time, the colliding nuclei are highly compressed, resulting in very high baryon densities in the nuclear remnants. In this talk, I will explore the high baryon density achievable in the nuclear remnants and study the hydrodynamic evolution of the high baryon density matter.
This seminar was originally scheduled for September 10.