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Events on Friday, February 7th, 2020

Theory Seminar (High Energy/Cosmology)
Einstein’s Microscope: Uncovering Small-Scale Dark Matter Structures with Novel Gravitational Lensing Probes
Time: 1:30 pm
Place: 5280 Chamberlin
Speaker: Liang Dai, Institute for Advanced Study
Abstract: The physical nature of the astrophysical dark matter (DM) is a fundamental question in cosmology. The clustering structure of DM on sub-galactic scales is key to distinguishing between various viable DM models which all make successful predictions about the large-scale structure and galaxy formation, but empirical tests have been fundamentally hindered by the lack of electromagnetic tracers of sub-galactic structures. In this talk, I aim to introduce novel and practical gravitational-lensing based methods which can be employed to push forward this research frontier. I will first discuss the new phenomenon of extremely magnified cosmological sources as deep imaging of strong lensing clusters has recently started to uncover, and explain how this phenomenon can be exploited as a sensitive probe of compact halo objects, non-luminous DM subhalos smaller than those who host dwarf galaxies, and even (sub-)planetary mass DM minihalos as expected in the axion DM scenario. The full scientific potential of these new ideas will be realized as forthcoming photometric surveys will greatly expand the catalog of highly magnified lensed galaxies and deep follow-up observations with space-borne or ground-based optical/infrared telescopes will enable detailed studies of their lensed appearances. I will also discuss the exciting prospect to exploit lensing of alternative extragalactic sources such as fast radio bursts and gravitational waves from merging black holes to probe small-scale DM lenses. In particular, I will explain how one can extract unique information by observing wave diffraction of gravitational waves, which would be typically infeasible with electromagnetic sources.
Host: Dan Chung
Presentation: dai_lensing_talk.pdf
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Physics Department Colloquium
Is This Even a Plasma? Physics of Strongly Coupled Plasmas
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Scott Baalrud, University of Iowa
Abstract: Plasma is often described as an ionized gas. However, a rapidly growing field of research is concerned with strongly coupled states of plasma that are more akin to ionized liquids, solids, or supercritical fluids. Strongly coupled plasmas are found in nature, including the interior of giant planets, the core of stars, and even in lightning bolts. The recent surge of interest has been driven by the advent of high-intensity lasers capable of ionizing, heating and compressing materials to tens of thousands of degrees at near solid density or several times compressed. These dense plasmas are not well described by either the methods of condensed matter theory (which deals with lower temperatures) or plasma theory (which deals with lower densities). Unique properties of this warm dense state of matter arise due to the combined influence of strong correlations amongst ions and Fermi degeneracy of electrons. This talk will present a new approach to kinetic theory that has made it practical to describe the dynamical transport properties of dense strongly coupled plasmas. It will also show how we have used simulations enabled by state-of-the-art high-performance computing to validate this theory.
Host: John Sarff
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