Happening @ Michigan https://events.umich.edu/group/3806/rss RSS Feed for Happening @ Michigan Events at the University of Michigan. HET Seminar | What's Done Cannot Be Undone: Non-Invertible Symmetries (March 29, 2024 3:00pm) https://events.umich.edu/event/116879 116879-21838139@events.umich.edu Event Begins: Friday, March 29, 2024 3:00pm
Location: West Hall
Organized By: HET Seminars

In massless QED, we find that the classical U(1) chiral symmetry is not completely broken by the Adler-Bell-Jackiw anomaly. Rather, it is resurrected as a generalized global symmetry labeled by the rational numbers. Intuitively, this new global symmetry in QED is a composition of the naive axial rotation and a fractional quantum Hall state. The conserved symmetry operators do not obey a group multiplication law, but a non-invertible fusion algebra. We further generalize our construction to QCD, and show that the neutral pion decay can be derived from a matching condition of the non-invertible global symmetry.

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Lecture / Discussion Tue, 27 Feb 2024 09:38:16 -0500 2024-03-29T15:00:00-04:00 2024-03-29T16:00:00-04:00 West Hall HET Seminars Lecture / Discussion West Hall
HET Seminar | Recent developments in N=4 Yang-Mills Amplitudes (April 5, 2024 3:00pm) https://events.umich.edu/event/111198 111198-21842585@events.umich.edu Event Begins: Friday, April 5, 2024 3:00pm
Location:
Organized By: HET Seminars

The most important experimental probes of fundamental physics involve
the scattering of elementary particles. Over the years we have seen
significant progress in understanding the properties of scattering
amplitudes and in our ability to carry out new computations both for
theoretical and phenomenological purposes. I will overview some recent
developments in N=4 Yang-Mills amplitudes.

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Lecture / Discussion Sun, 25 Feb 2024 21:01:54 -0500 2024-04-05T15:00:00-04:00 2024-04-05T16:00:00-04:00 HET Seminars Lecture / Discussion
HET Seminar | On Causality Conditions in de Sitter Spacetime (April 12, 2024 3:00pm) https://events.umich.edu/event/117228 117228-21838851@events.umich.edu Event Begins: Friday, April 12, 2024 3:00pm
Location: West Hall
Organized By: HET Seminars

Causality conditions provide powerful constraints on low energy theories. In this talk, I will discuss how standard causality conditions of AdS and flat spacetimes can be extended to de Sitter spacetime. In particular, I will consider the Shapiro time delay experienced by a particle in a black hole or shockwave background and discuss how "fastest null geodesics" can be defined using spatial shifts on the boundary of de Sitter and the relevance of the "stretching" of the de Sitter Penrose diagram. I will discuss a few illustrative examples.

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Lecture / Discussion Thu, 28 Mar 2024 10:59:25 -0400 2024-04-12T15:00:00-04:00 2024-04-12T16:00:00-04:00 West Hall HET Seminars Lecture / Discussion West Hall