Colloquium

Host: Emine Altuntas

Title: "What’s the matter with dark matter?"

Abstract: Astrophysical observations give overwhelming evidence for the existence of dark matter. Several theoretical particles have been proposed as dark matter candidates, including weakly interacting massive particles (WIMPs), axions, and, more recently, their much lighter counterparts. However, there has yet to be a definitive detection of dark matter. For years, one group, the DAMA collaboration, has asserted that they observe a dark matter-induced annual modulation signal in their NaI(Tl)-based detectors. Their observations are inconsistent with those from other direct detection dark matter experiments under most assumptions of dark matter. In this talk, I will describe how I came to work on this topic and the debate's current status, the worldwide experimental effort to test this extraordinary claim, and our progress toward resolving the current stalemate in the field.

Host: Joe Tischler

Title: "Structuring Light with Metamaterials"

Abstract: To manipulate and tailor light,we need materials. Judiciously designed metamaterials and metasurfaces can be utilized to structureand sculptlight and achieve unconventional light-matter interaction with unprecedented functionalities. The extreme properties of such metamaterialsprovide novel opportunities in optics andphotonics. One category of extreme metastructures is materials that function asanalog computing machines when waves interact with them, providing the capability to perform mathematical operations, solve equations (such asintegraland differential equations), invert matrices, and conduct vector-matrix multiplicationwith the near speed of light. Another class of extreme platform for light-matter interaction is four-dimensional (4D) metamaterials, in which the material parameters can rapidly vary with time in addition to their variation in space while waves are propagating in them. These 4D material structures provide additional degrees of freedom for light-matter interaction. The third category includes materials with near-zero refractive indices. Such near-zero-index structures provide unprecedented mechanisms for light-matter interaction with unconventional features and exciting properties. In this talk, I will give an overview of some of the phenomenawe haveintroduced and exploredwithmetastructures, including analog computing with waves, 4Doptics, and,if time permits,near-zero-index photonics. I will discuss their salient features and forecast future possibilities.

Host: Sean Matt

Title: "25 years of science with Chandra"

Abstract: Chandra is one of NASA's "great observatories" and was launched in 1999. In this talk, I will review Chandra's history and instruments and show highlights from an absolutely astonishing 25 years of science observations. A "30 ft orbiting X-ray telescope" was first proposed by Riccardo Giacconi in the 1960's, and today's Chandra grew out of that idea. I will describe the mirrors, instruments, and technologies in Chandra and show how it was put together and launched into orbit. Chandra has looked at a vast range of objects in the last 25 years, and I will highlight and explain just a few of them: Quasars, jets, SMBH, galaxy clusters, SNR, stars, star forming regions, planets, and comets. I will show some example of how we deal with the challenges of operating a aging observatory. Unfortunately, Chandra's funding environment is uncertain; I will provide an update on NASA's current funding promises and plans.

Host: Michael Strauss

Title: "Searching for Naturalness: The Quest for Vector-Like Quarks"

Abstract: Despite its remarkable success in describing the subatomic world, the Standard Model leaves many unanswered questions (dark matter, matter-antimatter asymmetry, quantum gravity...). One of the most pressing issues facing particle physics today is the so-called "hierarchy problem." According to the Standard Model, quantum mechanical corrections from virtual top quarks should cause the mass of the Higgs boson to blow up to a value near the Planck scale, some 16 orders of magnitude larger than the observed value of 125 GeV. This discrepancy suggests either an extremely unlikely cancellation between unrelated parameters or the existence of some physics mechanism that naturally keeps the Higgs boson mass well below the Planck scale. A wide range of beyond-the-Standard-Model theories have been proposed to solve the hierarchy problem, with a common feature in many being the prediction of new particles called vector-like quarks. In this talk, I will explain what vector-like quarks are, why they are interesting, and how we search for them using the ATLAS experiment at CERN.

Host: Sean Matt/Mukremin Kilic

Title: "Studying Low-Mass Stars in the Era of Surveys: Data, Models, and Surprises"

Abstract: Stellar ages are notoriously difficult to measure accurately for main-sequence low-mass stars, which limits our ability to address questions ranging from the evolutionary state of exoplanets to the chemical history of our Galaxy. Gyrochronology, which uses stellar rotation as a proxy for age, is a promising solution to this quandary. Unfortunately, however, empirical and theoretical models of the age-rotation relation have been hampered by a lack of rotational measurements for large numbers of low-mass stars with a wide range of well-known ages. We are still far from being able to describe fully the evolution of rotation for low-mass stars, or from being able to use rotation measurements to estimate accurately the ages of isolated field stars. I will summarize recent ground-based and space-based work to characterize the rotational behavior of G, K, and M dwarfs in open clusters ranging in age from 125 Myr (the Pleiades) to 3 Gyr (Ruprecht 147), and then compare these data to each other and to models for stellar spin-down to appraise our current understanding of the age-rotation relation. I will also touch on an on-going survey targeting newly (re)discovered single-aged stellar populations to address the broader age-rotation-activity relation.

Host: Bruno Uchoa

Title: "Measurement-induced Criticality"

Abstract: While many-body quantum physics has traditionally focused on the properties of cold matter in thermal equilibrium, emerging noisy intermediate scale quantum (NISQ) platforms allow access to far-from-equilibrium dynamics with local space and time control over interactions. In this new era of “interactive quantum dynamics”, a key challenge is to identify universal features of non-equilibrium quantum dynamics, transport and many-body entanglement. In this talk, I will discuss new types of non-equilibrium quantum phases of matter and phase transitions, with an emphasis on emergent classical statistical mechanics descriptions of quantum entanglement dynamics. In particular, I will focus on the recently discovered “entanglement phase transitions” that occur in monitored quantum systems, and separate phases characterized by the amount of quantum information that can be extracted from measurements. I will also highlight emerging connections between quantum entanglement, quantum communication theory and classical statistical physics.

Host: Howie Baer

Title: "Cosmological Moduli and Dark Matter"

Abstract: In this talk, we discuss some of the implications of cosmological moduli on the production of dark matter. Moduli fields are parameterizations of additional compact dimensions, and are generic in string theory. If such moduli fields are present after an inflationary phase, they are expected to dominate the energy density of the universe until they decay and thus can drastically alter the expected abundance for many dark matter candidates. We investigate this effect on two dark matter candidates in particular, Weakly Interacting Massive Particles (WIMPs) and axions. Additionally, we discuss the impact of a modulus-dominated universe on dark matter substructure formation for both dark matter candidates as well as results for models which possess both WIMPs and axions. Finally, we present upcoming results which suggest that the rapid decay of the modulus is possible through non-perturbative field dynamics with the axion field - which may also help evade the problems of dark radiation production in Large Volume Scenario models.

Host: Michael Strauss

Title: "How to do particle physics in a climate emergency?"

Abstract: The pursuit of particle physics, or any kind of discovery-driven research, requires a stable and prosperous society. Today, our society is increasingly threatened by global climate change. Human-influenced climate change has already impacted weather patterns, and global warming will only increase unless deep reductions in emissions of CO2 and other greenhouse gases are achieved. Current and future activities in particle physics need to be considered in this context, either on the moral ground that we have a responsibility to leave a habitable planet to future generations, or on the more practical ground that, because of their scale, particle physics projects and activities will be under scrutiny for their impact on the climate. I will discuss several contexts in which particle physics has an impact on greenhouse gas emissions, and how our field can contribute to a more sustainable future.

Host: Sean Matt

Title: "The Royal Road, Redux: Eclipses and Transits in the Era of Gaia and TESS"

Abstract: In his 1946 inauguration of the lectureship that now bears his name, Henry Norris Russell described eclipses as a "royal road" that "repays its followers richly." I begin by summarizing results from a number of rare, but astrophysically important eclipsing binary stars, that have paid richly in our understanding of the effects of magnetism on the physical structure of low-mass stars and brown dwarfs. Next, I describe how eclipsing binary stars can serve as independent, empirical benchmarks for trigonometric parallaxes---with an accuracy of 200 micro-arcseconds or better that does not degrade with distance---and show an application of such a test to the parallaxes of the ongoing Gaia mission. I then describe a "pseudo-interferometry" approach by which the Gaia parallaxes, together with observations of granulation "flicker" in light curves from NASA's TESS mission, permit the radii and masses of stars and planets to be measured with an accuracy of better than 5%, in an entirely empirical fashion. Finally, returning to Henry Norris Russell's famous H-R diagram as an example, I conclude with some remarks on the role of data visualization in scientific discovery, and describe new efforts to quantify neurodiverse visuo-cognitive capabilities (such as in autism) in order to teach humans and machines to make unexpected discoveries in data through visualization.

Host: Doerte Blume

Title: "Quantum optical mega-networks in biological architectures, and the computational capacity of life "

Abstract: In this talk I will present an overview of our work analyzing mega-networks of tryptophan in biological architectures with numerical simulations and steady-state ultraviolet spectroscopy, providing opportunities for measurement, readout, and control of light-matter interactions in large protein aggregates, cellular organelles, and neuronal bundles. I will then, based on these insights and fundamental physical considerations, consider the computational limits of living systems. As time permits, the implications for information processing in aneural organisms like the humble slime mold and for the development of artificial intelligence(s) will also be discussed.