3/1Atomic, Molecular, And Optical Physics Seminar
Atomic, Molecular, And Optical Physics SeminarMonday, March 1st, 202104:00 PM - 05:00 PMStorrs Campusonline
Molecules in quantum motion ---
Understanding electrons, nuclei, and their interactions
In order to fully understand the chemical physics of molecular systems, we need to simulate both the electronic and vibrational motion quantum mechanically. However, simulations of quantum many-body systems, such as molecules, scale exponentially with system size. I will explain how to tame this ‘curse of dimensionality’ by combining methods from the traditionally disjoint fields of electronic structure and nuclear dynamics. This combination has enabled the simulation of complex systems with unprecedented accuracy and speed. I will demonstrate how these methods make it possible to solve a diverse set of problems, ranging from characterizing hydrated protons on a molecular quantum level to the interaction of molecules with extremely short and intense light pulses on attosecond time scales. I will demonstrate how these simulations provide new insight into complex fundamental physical processes.
Astronomy SeminarWednesday, March 3rd, 202111:00 AM - 11:30 AMStorrs Campusonline
Early Science with the Large Millimeter Telescope: Constraining the Gas Fraction of a Compact Quiescent Galaxy at z = 1.883
We present constraints on the dust continuum flux and inferred gas content of a gravitationally lensed massive quiescent galaxy at z=1.883 +/- 0.001 using AzTEC 1.1mm imaging with the Large Millimeter Telescope. MRG-S0851 appears to be a prototypical massive compact quiescent galaxy but has evidence that it experienced a centrally concentrated rejuvenation event in the last 100 Myr. This galaxy is undetected in the AzTEC image but we calculate an upper limit on the millimeter flux and use this to estimate the H_2 mass limit via an empirically calibrated relation that assumes a constant molecular gas-to-dust ratio of 150.
We constrain the 3 sigma upper limit of the H_2 fraction from the dust continuum in MRG-S0851 to be M_(H_2)/M_* < 6.8%. MRG-S0851 has a low gas fraction limit with a moderately low sSFR owing to the recent rejuvenation episode, which together results in a relatively short depletion time of
Astronomy SeminarWednesday, March 3rd, 202111:30 AM - 12:00 PMStorrs Campusonline
Investigating Populations across the Gravitational-Wave Mass Spectrum: Statistical Tools and Implications for Astrophysics
Merging compact object binaries comprising of pairs of black holes, neutron stars or a neutron star and a black hole are energetic sources of gravitational-wave (GW) and electromagnetic (EM) radiation. Current and future gravitational-wave observatories such as LIGO-Virgo-KAGRA, LISA and NANOGrav will help uncover a diverse population of these binaries across the mass spectrum. While the LIGO-Virgo-KAGRA observatories probe compact objects roughly from 1 to 100 times a solar mass, observatories such as LISA and NANOGrav are predicted to probe supermassive binaries in the million to billion solar mass regimes. On the other hand, telescopes around the world will aid in detecting binaries that contain neutron stars by observing an associated electromagnetic counterpart called a kilonova. Investigating the properties of these binary populations will shed light on some long-standing problems in astrophysics such as stellar and galaxy evolution and nuclear equation of state. In this talk, I will present an attempt to create a Bayesian framework that can simultaneously use information from GW and EM surveys to place constraints on the kilonova population. I will also briefly introduce a method to model the mass distribution of binaries detectable by LIGO-Virgo-KAGRA, using Gaussian processes. Finally, I will also present some investigations into modeling the effects of circum-binary gas and eccentricity on the expected gravitational-wave sources from merging supermassive black hole binaries detectable by observatories like NANOGrav.
3/3Atomic, Molecular, And Optical Physics Seminar
Atomic, Molecular, And Optical Physics SeminarWednesday, March 3rd, 202104:00 PM - 05:00 PMStorrs Campusonline
Mapping the real-time movies of chemical bonds
Valence electrons play a crucial role in the formation of chemical bonds within a molecular system and determine its charge and electron transfer properties. In the static regime, these properties are defined by the electron density distribution of the equilibrium geometry. However, when out of equilibrium, ultrafast electronic rearrangements within the order of a few femtoseconds together a significant alteration of the chemical bonds can occur. I will address in this talk our undergoing investigations for mapping these ultrafast changes through X-ray photoelectron spectroscopy that have been critical in retransforming the well-established concepts of chemical shifts. I will additionally illustrate our developments for the selective manipulation of chemical bonding through X-ray free electron laser pulses.
3/5Graduate Student Seminar
Graduate Student SeminarFriday, March 5th, 202112:15 PM - 01:15 PMStorrs Campusonline
Earth’s Core: formation, structure, and the geodynamo
Earth’s magnetic field has been sustained for more than 3 b.y. by convection of a
liquid-iron alloy situated between a silicate outer mantle and a solid iron inner core in its center. Its magnetic field is characterized by a rich spectrum of secular and
spatial variations, having correlations with the elastic structures of the lowermost
mantle and an oscillating inner core, driven by lateral variations in convective and
conductive heat transport and Lorentz forces. In this talk, I will review current
research on the structure andevolution of Earth’s core and its magnetic fieldContact Information: Prof. V. Kharchenko More
3/5Prof. Philip Mannheim (Physics Colloquium)
Prof. Philip Mannheim (Physics Colloquium)Friday, March 5th, 202103:30 PM - 04:30 PMStorrs Campusremote
University of Connecticut
Physics Department Colloquium Series
Title: Quantum mechanics off the beaten track
Abstract: We discuss some non-conventional options for quantum theory.
We show that not only do Hamiltonians not need
to be Hermitian to have real eigenvalues, they do not even need to be
diagonalizable or possess a complete spectrum of energy eigenstates. We
discuss how to formulate quantum mechanics in such cases.
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. Following
work by Bender and Mannheim [Phys. Rev. Lett. 100, 110402 (2008)] we show
how these issues are relevant to the construction of a consistent theory
of quantum gravity in four spacetime dimensions. In this theory there is no observable graviton.Contact Information: Prof. Philip Mannheim More
Astronomy SeminarWednesday, March 10th, 202111:00 AM - 12:00 PMStorrs Campusonline
Sharpening our view of the atomic ISM throughout the Local Group
Encoded in the atomic ISM is physics crucial to the baryonic cycle, including the formation of molecular clouds and the origin of interstellar turbulence from stellar feedback. Nearby galaxies provide an important top-down view on how these processes act over a wide range of ISM environments, however, existing extragalactic observations of the 21-cm HI line have limited resolution - both spatial and spectral - that provides a coarse view of the intricate atomic gas structure that has long been studied within the Milky Way. I will present the first results from an on-going Local Group 21-cm HI VLA survey that aims to bridge between our Galactic and extragalactic views of the atomic ISM. These new observations combine high sensitivity with a fine spectral resolution to reveal complex HI spectra that were unresolved in previous observations. I will show that (i) HI spectra trace multiple velocity components along most lines-of-sight, and (ii) linking individual HI components with molecular gas tracers reveals a strong correlation between the molecular and atomic ISM kinematics throughout the star formation process. These results from our continuing HI survey provide important insights into the role of atomic gas in the baryonic cycle while providing a galaxy-scale perspective for Milky Way ISM studies. With upcoming high-resolution molecular and ionized ISM surveys, the future is bright for bridging between Galactic and extragalactic studies. With upcoming high-resolution molecular and ionized ISM surveys, the future is bright for bridging between Galactic and extragalactic studies using the Local Group's ISM.
3/18PhD Dissertation Defense
PhD Dissertation DefenseThursday, March 18th, 202101:00 PM - 03:00 PMStorrs CampusVideo meeting
Paschen-line Star Formation and Dust Attenuation with HST and JWST
Star formation rates (SFRs) are one of the most critical quantities in understanding galaxy evolution. There exist many different methods of measuring extragalactic SFRs, commonly using emission-line luminosities. Recombination lines of hydrogen are especially useful as SFR tracers due to their insensitivity to nuisance parameters like metallicity, density, and temperature in the interstellar medium. Paschen emission offers a ‘gold standard’ tracer of recent (< 10 Myr) star formation with its relative insensitivity to interstellar dust attenuation compared to more common Balmer and UV continuum SFRs, while maintaining the benefits of hydrogen recombination lines. We use Paschen (1282 nm) observations from the Hubble Space Telescope (HST) G141 grism to study star formation and dust attenuation properties of 32 low redshift (z < 0.3) galaxies in the CANDELS Lyman Emission at Reionization (CLEAR) survey. We find evidence suggesting that Pa is revealing star formation otherwise ‘hidden’ within gas optically thick to shorter wavelengths, and we use Pa/H. We also find evidence to support the claim that lower mass galaxies exhibit burstier star formation histories. We will also discuss future observations of Paschen-line star formation with the James Webb Space Telescope (JWST).
Webex link: https://uconn-cmr.webex.com/join/jot16106Contact Information: Prof. J. Trump More
3/26Professor Jorge Moreno (Physics Colloquium)
Professor Jorge Moreno (Physics Colloquium)Friday, March 26th, 202103:30 PM - 04:30 PMStorrs CampusremoteProfessor Jorge Moreno, Pomona College
Physics Department Colloquium
Title and abstract forthcomingContact Information: Prof. Daniel Angles-Alcazar More