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Events on Friday, March 4th, 2022

Theory Seminar (High Energy/Cosmology)
Corrections to the LARGE-Volume Scenario
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Daniel Junghans, Harvard University
Abstract: We argue that de Sitter vacua in the LARGE-volume scenario of type IIB string theory are vulnerable to various unsuppressed curvature, warping and g_s corrections. We discuss how these corrections affect the moduli vevs, the vacuum energy and the moduli masses. Our analysis reveals that the corrections are parametrically larger in the relevant expressions than one might have guessed from their suppression in the off-shell potential. Some corrections appear without any parametric suppression at all, which makes them particularly dangerous for candidate de Sitter vacua. Other types of corrections can in principle be made small for appropriate parameter choices. However, we show in an explicit model that this is never possible for all corrections at the same time when the vacuum energy is positive.
Host: George Wojcik
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Physics Department Colloquium
Extreme Plasma Astrophysics
Time: 3:30 pm - 4:30 pm
Place: 2103 Chamberlin Hall
Speaker: Dmitri Uzdensky, University of Colorado
Abstract: Physical conditions in plasma environments of exotic relativistic objects like neutron stars and black holes can be extreme and very different from those in more familiar, traditional heliospheric and laboratory plasmas. The richer physics of these extreme astrophysical plasmas includes the effects of special and general relativity, pair-plasma composition, strong interaction between plasma particles and high-energy photons, and, in the most extreme cases, QED effects like pair production and annihilation. Understanding how these “exotic” physical effects modify fundamental collective plasma processes — such as waves, instabilities, magnetic reconnection, shocks, turbulence — is the scope of Extreme Plasma Astrophysics — an challenging and exciting frontier of modern physics. I will review the recent rapid progress in exploring this frontier, motivated by spectacular astrophysical discoveries and enabled by recent computational advances like the development of novel kinetic plasma codes incorporating radiation and pair-creation effects, in combination with vigorous, concerted theoretical efforts. Examples include new breakthroughs in our understanding of radiative relativistic magnetic reconnection and turbulence, with applications to accreting black holes and neutron star magnetospheres. I will also outline the key future directions of this burgeoning field, including for laboratory studies.
Host: Stas Boldyrev & Cary Forest
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