Colloquium Calendar

Title: Beyond Academia, Still Physics: Medical Physics and My Path into the Profession

Abstract: 

Physics as a profession is not just limited to academia or a laboratory setting. One profession of note is medical physics, where the physicist works alongside physicians and other healthcare workers to develop, implement and oversee the use of technologies for the diagnosis and treatment of disease. To ensure the safe and effective use of these technologies, medical physicists must take on roles spanning numerous fields including physics, engineering, metrology, medicine, safety, computer science, research, education, and management. This presentation will provide a general introduction to the field of medical physics by highlighting the roles a medical physicist performs. While not intended to be exhaustive, this introduction will detail the knowledge and its application necessary to perform the duties of a medical physicist. The presentation will conclude with my experience entering the profession, additionally providing an overview of the educational, clinical, and certification pathways required to become a medical physicist.

Title: The Renaissance of Stellar Intensity Interferometry and Recent Advances with VERITAS

Abstract: 

Seventy years ago, Robert Hanbury Brown devised an ingenious technique to measure stellar sizes.  Quite distinct from the more common Michelson (or amplitude) interferometry, stellar intensity interferometry (SII) is insensitive to atmospheric turbulence that renders Michelson interferometry impossible at visual wavelengths. I will give a brief introduction of the history of SII and the controversy it generated over the nature of quantum mechanics. I will discuss the recent renaissance of SII with modern electronics and large Cherenkov telescope arrays. I will then introduce the Very Energetic Radiation Imaging Telescope Array System (VERITAS) SII system and novel results in imaging the shape of the photosphere of the rapid rotator gamma Cassiopeia and the complete geometry of the binary star alpha Virginis. I will discuss the implementations for understanding fundamental stellar properties and give an outlook for this new area of astronomy.

Title: Cosmic Shear Systematics in the LSST Era

Abstract: 

In the next decade, the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will collect data for billions of galaxies across the sky, mapping the underlying web-like structure of the universe evolving over cosmic time. In this new data-rich era, cosmological inference will no longer be limited by statistical uncertainty; instead, significant sources of biases are expected to arise from incomplete and/or incorrect characterization of the systematics induced by astrophysical processes, methodologies, and technological realities. I will introduce the main observational probes for large-scale structure cosmology with LSST with a focus on weak gravitational lensing (or cosmic shear) and recent work on diagnosing systematic effects. I will also briefly discuss new work on using synthetic source injection techniques for characterizing cross-redshift effects for improved cosmic shear analysis.

Title: Diving deep into galaxy winds and their engines

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Some galaxies host powerful multi-phase outflows of material that regulate galaxy growth and pollute the circumgalactic gas with heavy elements and dust. These outflows are powered by nuclear activity, either due to star formation, supermassive black hole accretion, or a combination of both depending on the source, and they are thought to play a key role in shaping galaxies during their formative epoch. Their underlying physics, however, are not settled.  I will discuss observations of the cooler phases of the winds in three nearby galaxies, primarily from ALMA and JWST. I will then shift to look at the starburst at the base of the wind in these objects, presenting observations of the massive young stellar clusters that are the engine of the star formation activity and the wind and discussing the feedback mechanisms behind super star cluster formation.

Title: What's new with neutrinos?

Abstract: 

Experiments over the past 30 years have firmly established that neutrinos are weird. They definitely have mass, but are (at least) a million times lighter than any other particles. There are (at least) three different neutrinos, and there is very large mixing between the neutrinos and their charged lepton partners. This leads to the phenomenon of oscillation, where the "flavor" of a neutrino can change as it travels. The masses of the three neutrinos might be "inverted", which would be different from the quarks and charged leptons. This weirdness begs an important question: Why? Present-day experiments have done a reasonable job of measuring most of the parameters of neutrino mixing, assuming that the standard, three-flavor picture is correct and complete. The Deep Underground Neutrino Experiment (DUNE) is currently under construction, and will be a big leap forward in our ability to test the validity of the standard neutrino oscillation model, and to search for new physics in neutrino oscillations. In this talk, I will describe the current state of neutrino oscillations and how DUNE will advance it.

Title: Ultrafast Spin Dynamics in Quantum Materials and Strong Light-Matter Interactions in Nanocavities

Abstract: 

Light offers powerful routes to create hybrid quantum states and transform magnetic order. This talk explores these possibilities through two studies: optically induced magnetization in chiral helimagnets and strong exciton-plasmon coupling in a single quantum dot nanocavity. First, we demonstrate how ultrafast optical excitation transforms magnetic order and spin dynamics in a single-crystalline chiral helimagnet using time-resolved magneto-optical Kerr spectroscopy. At low temperatures and without an applied magnetic field, optical excitation induces a magnetization response that develops over tens of picoseconds. Under an applied magnetic field, laser excitation drives magnetization precession about its equilibrium orientation, revealing an anomalous dependence of the precession dynamics on magnetic field within specific magnetization phases.

Second, we investigate room-temperature plexciton formation in a single MAPbBr3 perovskite quantum dot confined within a plasmonic nanocavity formed between a gold AFM tip and a gold substrate. Femtosecond excitation through two-photon absorption produces distinct upper and lower polariton branches with Rabi splitting energies up to 250 meV. Tuning the tip-sample distance and excitation polarization enables control over the coupled optical response, providing a tunable platform for nanoscale quantum optics. Together, these studies highlight complementary approaches to controlling light–matter coupling and spin dynamics, with potential applications in quantum photonics and ultrafast information technologies.

Title: From TeV Halos to PeVatrons: Exploring the Highest-Energy Gamma Rays in the Galaxy with HAWC

Abstract: 

High-energy gamma rays provide a unique window into the most extreme particle accelerators in the Universe. In particular, observations at tens to hundreds of TeV allow us to probe the origin and propagation of Galactic cosmic rays and to identify sources capable of accelerating particles to PeV energies.

The High Altitude Water Cherenkov (HAWC) Observatory is a wide-field gamma-ray and cosmic-ray detector located at an altitude of 4,100 meters in central Mexico. Operating continuously for more than a decade, HAWC surveys a large fraction of the sky each day and is particularly well suited for studying extended sources, diffuse emission, transient phenomena, and the highest-energy gamma-ray sources in our Galaxy.

I will present recent results from HAWC on Galactic particle accelerators, including pulsar wind nebulae, TeV halos, extended gamma-ray sources, and the search for Galactic PeVatrons. I will discuss what these observations are teaching us about the maximum energies achieved by Galactic accelerators, the transport of cosmic rays through their surrounding environments, and the relative roles of hadronic and leptonic processes in producing the highest-energy gamma rays. I will also highlight recent improvements in HAWC analysis and reconstruction that are extending the observatory’s sensitivity and scientific reach.

Title: Planet Formation and Evolution Through a Statistical Lens

Abstract: 

As exoplanet science moves towards bigger, noisier datasets, smaller signals, and more complicated physical models, statistical inference is becoming more and more essential. In this talk, I’ll give a tour of my group’s work applying cutting-edge statistical methods in order to: 1) push the limits of exoplanet detection methods-- particularly radial velocity and astrometric methods-- expanding our understanding of what types of planets can exist; 2) look for patterns across populations of planets, informing theories about how planets form and evolve; and 3) maximize the utility of future data, particularly from the Gaia observatory. I will also discuss my work on open-source software, highlighting the widely-used Bayesian orbit-fitting package orbitize! and the summer school Code/Astro.

Title:Particle Physics: From Theory to Experiment and Back Again

Abstract: 

The discovery of the Higgs boson, predicted nearly fifty years earlier, led to the completion of the Standard Model (SM) of particle physics,  a quantum field theory in which all massive elementary particles acquire mass via the interaction with the Higgs field. This theory includes  all the forces observed in nature other than gravity and leads to an explanation of all the observed phenomena in terrestrial laboratories.  The Higgs discovery is part of a two-way road between theory and experiment which started a century ago and has led to the development of the SM. There are many reasons to believe that this theory is not complete, in part due to the need for new ingredients, such as Dark Matter and Dark Energy, to explain astrophysical and cosmological observations. The Higgs may be a bridge to new physics: additional Higgs-like states, connections to the origin of the matter-antimatter asymmetry, or links to the Dark Matter that makes up most of the matter in the Universe. I will also discuss how current and future experiments, from the LHC to underground Dark Matter detectors, may reveal what lies beyond the Standard Model.

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