Dr. Taran Driver, PULSE institute and SLAC National Accelerator Laboratory and Linac Coherent Light Source

Probing Correlated Multi-Electron Dynamics on the Attosecond Timescale

The interaction of light with matter is a fundamental process for probing and engineering the quantum properties of a molecule or material. This interaction is mediated by electrons, and understanding the many-body dynamics of electronic systems in the first moments following light-driven excitation is a frontier challenge. The characteristic timescale for this electron motion is set by the splitting of the relevant energy levels, which results in motion on the attosecond (10-18 s) timescale. It is now possible to generate pulses of light lasting on the order of one hundred attoseconds, both on the tabletop in the laboratory and at large free-electron laser facilities. I will present recent work using attosecond x-ray pulses to probe the ultrafast dynamics of multi-electron systems. We measured the photoemission delay in the core-level ionization of a molecule. This is the delay between the arrival of a photon and the emission of an electron in photoionization, which was long considered an instantaneous process. In fact, this delay reveals strong modulations due to electron correlation. We also time-resolved the response of an aromatic molecule, para-aminophenol, to impulsive photoionization. By accessing the dynamics within the first femtosecond following the removal of an electron, we observed the interplay between the sub-femtosecond decay of shake-up states and coherent charge density oscillation on the few-femtosecond timescale. I will also touch on future directions which will harness these new methods to develop ultrafast probes of electron motion and exotic light-engineered states in quantum materials.

Prof. Lina Necib, Department of Physics, MIT

Mapping out the Dark Matter in the Milky Way

In this talk, I will explore the interfacing of simulations, observations, and machine learning techniques to construct a detailed map of Dark Matter in the Milky Way, focusing on the Galactic Center/Halo and dwarf galaxies. For the Galactic Halo, I will present a recent work that reveals a decline in the stellar circular velocity, inducing tensions with established estimates of the Milky Way’s mass and Dark Matter content. I will discuss how the underestimated systematic errors in such a common methodology necessitates a revised approach that combines theory, observations, and machine learning. In dwarf galaxies, I will present a novel Graph Neural Network methodology that facilitates the accurate extraction of Dark Matter density profiles, validated against realistic simulations. I will conclude with a discussion on the future trajectory of astroparticle physics, emphasizing the need for the integration of astrophysical probes with experimental Dark Matter research, potentially leading to a better understanding of the nature of Dark Matter.

Prof. Philip Mannheim, Department of Physics, University of Connecticut

Why there are dark matter, dark energy, and quantum gravity problems, and what we can do about them

We trace the origin of the dark matter, dark energy and quantum gravity problems to the extrapolation of the standard Newton-Einstein wisdom to beyond its solar system origins. We show that this same solar system wisdom can be obtained from the conformal gravity theory, with its extrapolation leading to a resolution of all of the dark matter, dark energy and quantum gravity problems.

Prof. Vernon Cormier, Department of Physics, University of Connecticut

Physics of Earth’s Core

Among the terrestrial planets, Earth has the largest magnetic field, driven by convective motion in an electrically conducing iron rich liquid outer core.  This field has been sustained since nearly the time of Earth’s formation, preventing loss of water and atmospheric erosion by the solar wind.  Research to understand the evolution and dynamics of the core includes measurements and modeling of its gravitational and magnetic fields, the propagation of elastic waves sampling its interior, and the theories of condensed matter physics.  Outstanding problems include the unknown light element composition of the outer and inner cores, the crystalline lattice structure of the solid inner core and that of iron at 360 GPa and 6000 deg. K, gravitational and electromagnetic coupling between Earth’s mantle and solid inner core, the low shear modulus and Poisson’s ratio of the inner core, and the possibility of the inner core being in a superionic state.

Dr. Yu He, Yale University

Electronic pseudogap from fluctuations in low dimensional materials

Most metal-to-insulator and metal-to-superconductor transitions are so dramatic that certain symmetries are also concurrently broken, and an energy gap opens in lockstep with this process. But there are electronic systems that develop energy gaps without any broken symmetry, most notably the “pseudogap” in cuprate superconductors. In this talk, I will show two examples of electronic pseudogap in unexpected places: the heavily hole-doped cuprates [1], and an excitonic insulator candidate Ta2NiSe5 [2]. The former is supposedly a good metal where mean-field BCS is thought to apply, and the latter is a structural symmetry-breaking system with strong electron-phonon coupling. Via angle-resolved photoemission spectroscopy and x-ray scattering, we show the electronic gap to persist well above the transition temperature in both systems. With insights from controlled numerical calculations, we show that fluctuation is an important factor when describing the properties of low dimensional material systems. Finally, I will discuss a few new directions in the study of fluctuations.

[1] Phys Rev X 11, 031068 (2021); Nat Mater 22, 671 (2023)

[2] Phys Rev Research 5, 043089 (2023); Nat Commun 14, 7512 (2023)

Adam Riess- Bloomberg Distinguished Professor and 2011 co-winner of the Nobel Prize in Physics, Johns Hopkins University

In 1929 Edwin Hubble discovered that our Universe is expanding. Eighty years later, the Space Telescope that bears his name is being used to study an even more surprising phenomenon: that the expansion is speeding up. The origin of this effect is not known, but is broadly attributed to a type of “dark energy” first posited to exist by Albert Einstein and now dominating the mass-energy budget of the Universe. Professor Riess will describe how his team discovered the acceleration of the Universe and why understanding the nature of dark energy presents one of the greatest remaining challenges in astrophysics and cosmology. He will also discuss recent evidence that the Universe continues to defy our best efforts to predict its behavior.

Adam Riess is a Bloomberg Distinguished Professor, the Thomas J. Barber Professor in Space Studies at the Krieger School of Arts and Sciences, a distinguished astronomer at the Space Telescope Science Institute and a member of the National Academy of Sciences.

He received his bachelor’s degree in physics from the Massachusetts Institute of Technology in 1992 and his PhD from Harvard University in 1996. His research involves measurements of the cosmological framework with supernovae (exploding stars) and Cepheids (pulsating stars). Currently, he leads the SHOES Team in efforts to improve the measurement of the Hubble Constant and the Higher-z Team to find and measure the most distant type Ia supernovae known to probe the origin of cosmic acceleration.

In 2011, he was named a co-winner of the Nobel Prize in Physics and was awarded the Albert Einstein Medal for his leadership in the High-z Supernova Search Team’s discovery that the expansion rate of the universe is accelerating, a phenomenon widely attributed to a mysterious, unexplained “dark energy” filling the universe. The discovery was named by Science magazine in 1998 as “the Breakthrough Discovery of the Year.”

His accomplishments have been recognized with a number of other awards, including a MacArthur Fellowship in 2008, the Gruber Foundation Cosmology Prize in 2007 (shared), and the Shaw Prize in Astronomy in 2006.

Reception at 3:00pm in the Gant Science Light Court

Madisyn Brooks, UConn

Title and abstract TBA

Prof. Andrew Puckett, Department of Physics, University of Connecticut

Precision studies of proton and neutron structure via medium-energy electron scattering

Electron scattering has been one of the most important tools for precisely probing the femtoscopic structure of strongly interacting matter ever since Hofstadter’s pioneering measurements of electron-proton scattering and electron-nucleus scattering at Stanford in the 1950s revealed the non-point-like nature of the proton and provided a first direct measurement of the proton’s size, leading to the Nobel Prize in Physics in 1961. The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) in Newport News, Virginia, is the world’s leading facility for the precision three-dimensional imaging of the nucleon’s quark-gluon structure in both coordinate and momentum space. CEBAF uses superconducting radio-frequency acceleration technology to deliver electron beams of unparalleled quality in terms of energy, intensity, duty-cycle, and polarization. Experimentalists use these high-quality electron beams together with state-of-the-art target and detector technologies and high-performance data acquisition and computing capabilities to map the internal structure of strongly interacting matter with unprecedented precision and kinematic reach. In this talk, I will give a brief overview of the physics of electron scattering and its utility as a precision probe of nuclear structure, followed by a detailed overview of UConn’s role and Ph.D. research opportunities at JLab with the Puckett group.