Prof. Moshe Gai, Department of Physics, University of Connecticut

Concepts of Stellar Evolution

Star are born, they evolve to a mature midlife and sooner or later die, some in an amazing last display. We will discuss how star reveal the stages of Stellar Evolution and what makes them tick. We will also seek feedback on the need for such a graduate class at UConn.

Prof. Matthew Guthrie, University of Connecticut;

A New Era for Connecticut’s Oldest Planetarium: Historic Roots to Modern Revival

The UConn Planetarium, built in 1954, has long been a central resource for astronomy education and outreach at the University of Connecticut. In this talk, I will present an overview of the planetarium’s historical roots at UConn, its significance in the community, and the extensive renovations we have completed to bring this important facility back to life. After years of disuse, the planetarium has been fully upgraded with modern technology and will officially reopen on November 1st, immediately following this colloquium.

Our efforts to restore the planetarium are guided by the legacy of Dr. Cynthia Peterson, UConn’s first woman physics faculty member and a pioneer in science education. The planetarium now officially bears her name as the Cynthia Wyeth Peterson Memorial Planetarium, in honor of her decades of dedication to astronomy outreach. Following my presentation, Nora Berrah and Celeste Peterson will speak about Dr. Peterson’s life and achievements - how her contributions to UConn and the wider scientific community continue to resonate today.

Prof. Anh-Thu Le, Department of Physics, University of Connecticut

Following electron-nuclear dynamics with ultrafast intense lasers

Recent progress in laser technology has led to new coherent light sources that can be used to investigate ultrafast processes in matter. To take advantage of these new light sources, different experimental techniques have been developed to reveal the inner-workings of coupled electron-nuclear dynamics in molecules. Concurrently, theoretical and computational tools have also been developed to understand and decode hidden information from experimental measurements. In this talk, I will present our group’s recent progress in understanding intense laser-atom/molecule interactions by using some of the most promising techniques such as laser-induced electron diffraction, high-harmonic generation spectroscopy, and attosecond transient absorption spectroscopy. I will also address the challenges and opportunities in this field for practical realization of molecular “movies” with atomic resolution in space and time that can provide new insights into fundamental chemical reactions.

Dr. Jakob den Brok, Harvard Smithsonian Center for Astrophysics

Title and abstract TBA

Prof. Philip Mannheim, University of Connecticut

The Accelerating Universe

I will describe some of the background that led to the award of the Nobel prize to Dr. Adam Riess, who will be our 2024 Katzenstein speaker on November 15.

Prof. Luca Argenti, University of Central Florida

ASTRA: A Transition-Density-Matrix Approach to Time-Resolved Molecular Ionization

Attosecond science, which investigates the time-resolved correlated motion of electrons in atoms, molecules, and solids, is rapidly advancing toward larger molecular systems and more complex processes, such as multiple ionization and molecular fragmentation. Theoretical methods capable of addressing both multiple excitations and photofragment entanglement are essential to capture these phenomena. Among the most promising theoretical approaches are ab initio wave-function-based close-coupling (CC) methods, increasingly adopted by the AMO community.

Despite significant progress from codes like XCHEM [1,2], tRecX [3], RMT [4], and UKRmol+ [5], scaling remains a major challenge – whether in handling ionic correlation, accounting for many atoms, or for distant fragments. To address these limitations, we developed ASTRA [6] (AttoSecond TRAnsitions), an ab initio CC molecular ionization code based on high-order transition density matrices between correlated ionic states of arbitrary multiplicity [7], and hybrid Gaussian-B-spline integrals [5,9]. ASTRA integrates multiple state-of-the-art codes, such as DALTON [8], a general-purpose quantum chemistry code, LUCIA [7], a large-scale CI code, and GBTOlib [5], a hybrid integral library suited for slow photoelectrons and comparatively small molecules.

ASTRA has successfully reproduced total and partial photoionization cross sections, photoemission asymmetry parameters, and molecular-frame photoelectron angular distributions for molecules such as N ₂ , CO, H ₂ CO, and Pyrazine, showing excellent agreement with existing benchmarks. Currently, ASTRA is being applied to study attosecond transient absorption spectra of CO and O ₂ , as well as sequential XUV-pump IR-probe ionization of C ₂ H ₄ . Its formalism naturally extends to molecular double ionization and can efficiently model electron exchange between multiple disjoint molecular fragments − relevant for describing ionization in weakly bound clusters like (H ₂ O) _n .

Looking ahead, continued integration with tools tailored to high-energy photoemission, non-adiabatic nuclear dynamics, and strong fields ionization will be critical for addressing emerging challenges in ultrafast many-body dynamics. Free-electron lasers enable time-resolved studies of core ionization, while table-top attosecond pump-probe experiments are targeting increasingly larger molecules, monitoring both electron dynamics and nuclear rearrangements throughout chemical reactions with intense probe pulses [10]. To reproduce these complex experiments, we are collaborating with NIST to replace GBTOlib with a more efficient hybrid library capable of handling larger molecules and higher orbital angular momenta. We are also pairing ASTRA with surface-hopping methods [11], where multiphoton ionization is typically not available. Additionally, to track the asymptotic evolution of weakly coupled photofragments under strong light fields − without incurring prohibitive computational costs − we are considering integrating separate optimized propagators for each fragment, which will open the door for us to simulate strong-field multichannel molecular-ionization processes.

[1] M. Klinker et al., J. Phys. Chem. Lett. 9, 756 (2018).

[2] V. J. Borràs et al., Science Advances 9, eade3855 (2023).

[3] A. Scrinzi, Comput. Phys. Commun. 270, 108146 (2022).

[4] A. C. Brown et al., Comput. Phys. Commun. 250, 107062 (2020).

[5] Z. Masin et al., Comp. Phys. Commun. 249, 107092 (2020).

[6] J. M. Randazzo et al., Phys. Rev. Res. 5, 043115 (2023).

[7] J. Olsen et al., J. Chem. Phys. 89, 2185 (1988); ibid. 104, 8007 (1996).

[8] K. Aidas et al., Comp. Mol. Sci. 4, 269 (2014).

[9] H. Gharibnejad et al., Comp. Phys. Commun. 263, 107889 (2021).

[10] F. Vismarra et al., Nature Chemistry (2024).

[11] L. Fransén et al., J. Phys. Chem. A 128, 1457 (2024).

Dr. Shafique Adam, Washington University in St. Louis

A narrow magic window for ultraflat bands and emergent heavy fermions near the magic angle in twisted bilayer graphene

The notion of a single “magic angle” in twisted bilayer graphene has evolved into a fascinating array of magic angles and ranges each describing different facets of the material’s behavior.  While the original continuum model predicted a nominal magic angle, its simplicity ignored the intricate interplay of different physical phenomena.  For example, lattice relaxation [1] near the magic angle shifts its value upward, only to be counteracted by pseudomagnetic fields.  Including a symmetry allowed relaxation parameter changes this magic angle to a magic range.  Yet another magic angle emerges from the coupling to phonons when the Fermi velocity equals the phonon sound velocity.  Building upon this rich tapestry of magical effects, we will discuss our recent work on the convergence of lattice relaxation and Hartree interaction near the magic angle [2]. We unveil a previously unreported Lifshitz transition to a Fermi surface topology that supports a “heavy fermion” pocket and an ultraflat band pinned to the Fermi energy. Analytical and numerical insights shed light on the narrow “magic angle range” where the “heavy fermion” is stable and make predictions for its experimental observation.  We believe that the bands presented here are accurate  at high temperature and provide a good starting point to understand the myriad of complex behavior observed in this system.

[1] “Analytical Model for Atomic Relaxation in Twisted Moiré Materials” by MMA Ezzi, GN Pallewela, C De Beule, EJ Mele, and S Adam, arXiv:2401.00498 (2024)

[2] “A self-consistent Hartree theory for lattice-relaxed magic-angle twisted bilayer graphene” by MMA Ezzi, L Peng, Z Liu, JHZ Chao, GN Pallewela, D Foo, and S Adam arXiv:2404.17638 (2024)

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.

Madisyn Brooks, UConn

Title and abstract TBA

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

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)

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.

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.