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SUMMARY:Matt Reece (Harvard)
DTSTART:20240305T150000Z
DTEND:20240305T160000Z
DTSTAMP:20260423T035617Z
UID:SymSem/58
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/SymSem/58/">
 Instanton Number as a Symmetry</a>\nby Matt Reece (Harvard) as part of Sym
 metry Seminar\n\n\nAbstract\nGauge theories in d dimensions have a (d-5)-f
 orm generalized global symmetry whose conserved charge is instanton number
 . In quantum gravity\, we expect such symmetries to always be gauged or ex
 plicitly broken. I will discuss examples of how both can happen: gauging v
 ia Chern-Simons terms or (in 4d) massless fermions\, and explicit breaking
  via magnetic monopoles (in both abelian and nonabelian gauge theories). I
 n the case d=4\, instanton number symmetry is a “(-1)-form U(1) symmetry
 \,” a somewhat degenerate case. I will discuss several closely analogous
  properties of the cases d=4 and d>4\, to argue that we should take the no
 tion of (-1)-form symmetry seriously. I will comment on some implications 
 of this perspective for the Strong CP problem. This talk will draw on mult
 iple papers\, including https://arxiv.org/abs/2012.00009 with Ben Heidenre
 ich\, Jake McNamara\, Miguel Montero\, Tom Rudelius\, and Irene Valenzuela
 \; https://arxiv.org/abs/2105.09950 with JiJi Fan\, Katie Fraser\, and Joh
 n Stout\; https://arxiv.org/abs/2402.00117 with Daniel Aloni\, Eduardo Gar
 cía-Valdecasas\, and Motoo Suzuki\; and other work in progress.\n
LOCATION:https://researchseminars.org/talk/SymSem/58/
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