Colloquia / Seminars

Fall 2024

M, Sept 16

Towards the three-hadron S matrix from QCD

Andrew Jakura, College of William and Mary

Accessing the hadron spectrum from Quantum ChromoDynamics (QCD) poses several challenges given its non-perturbative nature and the fact that most states couple to multi-particle decay modes. Although challenging, advances in both theoretical and numerical techniques have allowed us to determine few-body systems directly from QCD. A synergistic approach between lattice QCD and scattering theory offers a systematic pathway to numerically compute properties such as the hadron spectrum from first principles. I will present an overview of this program and discuss developments in determining three-hadron scattering processes using lattice QCD. These techniques allow us to push the boundaries of resolving the few-body problem in spectroscopy from first-principles.

M, Oct 14

From dust to dust: Using infrared surveys to reveal the explosive life cycles of stars and their remnants

Kishalay De, MIT

Multiplicity is ubiquitous in stars and the remnants they leave behind. While eruptive mass transfer has profound impacts on their long term evolution, the resulting processes are commonly enshrouded in dust produced by mass outflows, preventing direct observational constraints at optical/X-ray/UV bands. In pursuit of a complete census of the role of accretion outbursts in stellar and black hole evolution, I will present the WISE Transients Project — a new effort aimed at a complete census of the variable mid-infrared sky using 15 years of data from the NEOWISE survey. With systematic selection from millions of new infrared variables, I will highlight recent and ongoing work revealing i) a missed population of dusty stellar mergers in our Galactic backyard, ii) new insights into the fiery fates of close planetary worlds, iii) the birth of black holes from dusty eruptions of stripped stars and iv) eruptive pre-supernova mass loss revealed in the dusty aftermath of nearby supernovae. I will end with an overview of the exciting upcoming decade of ground-based infrared surveys that is poised to finally reveal a complete roadmap from stellar birth to the stellar graveyard.

M, Oct 21

Title: Identifying the Origin of Exoplanetary Diversity

Joey Rodriguez, Michigan State

Abstract: Nearly thirty years after the Nobel-prize-winning discovery of the exoplanet 51 Pegasi b, astronomers have discovered thousands of planets outside the solar system, and the field of exoplanetary astronomy has shifted from purely being driven by discovery to performing demographic analysis, and detailed characterization of properties like mass, radius, and atmospheric composition. However, even today, basic questions remain, like “why do some systems end up looking like the Solar System with orderly co-planar architectures, with small planets close-in, and giant planets orbiting far from their stars, while others, like the so-called Hot Jupiters, are dramatically different?” My team and I are tackling this question from both sides: understanding the evolutionary origins of hot Jupiters and understanding the properties of compact multi-planet systems. Using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and Kepler/K2 missions, we are working to find keystone planetary systems around bright stars (those well suited for atmospheric observations) that can help address specific questions about planet formation and evolution. I will review our efforts to discover and characterize hundreds of hot Jupiters while investigating the compact architectures of small rocky planets. Finally, uncertainty in planetary orbital solutions for hundreds of planets have accumulated since their initial detection to the extent that they are not accessible with the James Webb Space Telescope (JWST) to study their atmospheres. I will also discuss how we are addressing this problem on a large scale to make hundreds of planets accessible for JWST.

M, Nov. 4

TBA

Paulo Bedaque, University of Maryland 

TBA

M, Nov. 11

Modern CT Theory: Insight and Beyond

Ge Wang, Rensselaer Polytechnic Institute

Over the past century, computed tomography (CT) has experienced rapid advancements, grounded in integral geometry, linear algebra, and numerical optimization, each marked by sophisticated mathematical nuances. Today, CT is the most widely used medical imaging modality, with approximately 300 million scans performed annually worldwide for screening, diagnosis, and therapeutic guidance across a broad spectrum of diseases. In this talk, I will provide a heuristic overview of CT theory, spanning from classical Fourier slice theorems to modern algorithms for cone-beam spiral CT image reconstruction. Then, I will delve into cutting-edge topics such as interior tomography, robot-based CT, and stationary CT, with an emphasis on generative AI-based image reconstruction.

M, Nov. 18

Spectrum Management at the National Radio Astronomy Observatory: Protecting the Spectrum for Radio Frequency Observations

Chris De Pree, National Radio Astronomy Observatory

The National Radio Astronomy Observatory (NRAO) was founded in 1956, and the National Radio Quiet Zone (NRQZ) was established just two years later.  In the past 70 years, the NRAO has designed, built and dedicated many of the world’s preeminent radio telescopes, including the 140 Foot Telescope (Green Bank; 1965), the Jansky Very Large Array (VLA; 1980), the Very Long Baseline Array (VLBA; 1993), the Green Bank Telescope (GBT; 2000), and the Atacama Large Millimeter Array (ALMS; 2013).  These telescopes have been involved in many groundbreaking astronomical discoveries, most recently the imaging of the event horizons around the black holes at the center of M87 and our own Milky Way.  All of these were designed to operate at remote sites, far from sources of radio frequency interference (RFI) that were common at the time that they were dedicated. The modern era has brought with it an explosion in the number of devices that emit radio waves, from kitchen appliances to consumer devices to electronics in the cars that we drive.  Even these sources of RFI are potentially manageable at remote sites. Satellite constellations in Low Earth Orbit (LEO) have changed the balance significantly. Satellites like those in the Starlink network mean that even the most remote radio astronomy sites now have a large number of radio transmitters about them at all times. I will describe current NRAO efforts to better understand and alleviate these new challenges to radio astronomy observations.

M, Nov. 25

TBA

Jessie Shelton, University of Illinois Urbana-Champaign

TBA

M, Dec. 2

TBA

Nick Stone, University of Wisconsin

TBA

Spring 2025

M, Feb. 24

TBD

Alan Stern, Southwest Research Institute

M, Mar. 3

TBD

M, Mar. 17

TBD

M, Mar. 24

TBD

M, Mar. 31

TBD

M, Apr. 7

TBD

M, Apr. 14

TBD

M, Apr. 21

TBD

M, Apr. 28

TBD