The first colloquium of spring 2026 will be a Town Hall to discuss the department’s achievements and goals, followed by a Q&A with faculty, staff, and students.

Note: Because of weather UT is following remote operations for February 2. This colloquium has been moved to Zoom.

Nature violates parity symmetry. Discovered almost 70 years ago, this phenomenon implies that the universe is “left handed.” Although we have a very successful theory, the Standard Model of Particle Physics, which agrees with scores of experimental tests, it includes parity violation in an ad hoc way. There are hints that the Standard Model should break down at very high energies, restoring parity symmetry. There are viable conjectures for how that might come about, and much of High Energy Physics tries to reach the energy scales where this breakdown might occur.

This talk describes a different approach, trading very high energy interactions for extremely precise measurements at lower energies. The MOLLER experiment at Jefferson Lab will measure parity violation in electron-electron scattering for which the Standard Model makes a precise prediction. Disagreement between experiment and theory at this level would indicate “new physics” at energies beyond the reach of current high energy collider facilities. After introducing the key concepts, I will describe the challenges of making this ultra precise measurement and the timeline for executing the experiment.

Below the geographic South Pole, the IceCube project has transformed one cubic kilometer of natural Antarctic ice into a neutrino detector. IceCube detects more than 100,000 neutrinos per year in the one to a million GeV energy range. Among those, we have isolated high-energy neutrinos originating beyond our Galaxy, with a flux that exceeds the extragalactic high-energy gamma-ray flux observed by astronomers in a similar energy range. With a decade of data, we have identified their first sources, which point to supermassive black holes at the centers of active galaxies powering the cosmic ray accelerators that produce high-energy neutrinos. Machine learning techniques eventually revealed that our own Milky Way emits neutrinos but, interestingly, it is not a prominent feature in the neutrino sky as it is in all wavelengths of light. We will also review the study of the neutrinos themselves, emphasizing oscillation measurements.

Magnons and phonons are collective excitations in crystals that often behave as independent quasiparticles when their mutual coupling is weak. When magnetoelastic coupling becomes strong, interactions between spin and lattice degrees of freedom can open gaps at band crossings and give rise to hybridized excitations known as magnon-polarons. Because such hybridized modes appear only when energy matching, symmetry compatibility, and microscopic coupling all align, their presence and momentum dependence provide a particularly sensitive probe of the underlying spin–lattice interactions.

In this talk, I will use the olivine-type silicate Co₂SiO₄ to illustrate how this physics plays out in a real material. I will begin by presenting inelastic neutron-scattering measurements that reveal a rich set of hybridized excitations involving magnons, phonons, and spin–orbit excitons. To understand these observations, I will introduce an effective spin Hamiltonian that captures the main features of the magnetic excitations and discuss density functional theory calculations that reproduce the phonon spectrum. Building on these microscopic descriptions, a symmetry analysis of the magnon and phonon modes reveals which excitations can hybridize and where in momentum space such coupling is allowed. This framework naturally leads to a minimal hybridization model that explains the observed avoided crossings and mode mixing, providing a unified picture of the hybridized excitation spectrum in Co₂SiO₄.

More broadly, this work establishes olivine-type oxides as a clean setting for studying magnetoelastic coupling and illustrates how combining dynamical measurements with symmetry-based modeling can reveal microscopic interactions that are difficult to access otherwise.

The magnetic moment of muon can be characterized by its gyro-magnetic factor $g$, which is numerically close to 2. Fermilab announced a new experimental result for muon $g-2$ on June 3, 2025.
The new result is consistent with the previous BNL measurement, but with about 4 times higher precision. For the Standard Model prediction, the recent theoretical muon $g-2$ white paper was released on May 27, 2025. The new theory result is consistent with the new experimental result, but is about 3 sigma larger than the previous theory white paper result, released on June 8, 2020. Two hadronic contributions, HVP (hadronic vacuum polarization) and HLbL (hadronic light-by-light), are the dominant sources of the theoretical uncertainty. The change in the central value is largely due to the many advances in lattice QCD calculations of these hadronic contributions, particularly the HVP contribution. In this talk, I will describe the theoretical determination of muon $g-2$ with focus on the lattice QCD calculations of the hadronic contributions.

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There will be no physics colloquium during spring break.

There will be no physics colloquium on March 16, 2026.

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The department will celebrate our students, faculty, and staff at the 2026 Honors Day celebration on May 4.