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SUMMARY:Sneaking up on lattice chiral fermions - Simon Catterall\, Syracus
 e University
DTSTART:20250403T120000Z
DTEND:20250403T130000Z
UID:TALK229987@talks.cam.ac.uk
CONTACT:122734
DESCRIPTION:I will show how staggered or Kaehler-Dirac fermions suffer fro
 m a gravitational anomaly that can be computed exactly on a finite lattice
 .  The anomaly breaks an exact onsite $U(1)$ symmetry to $Z_4$.  This cont
 radicts the usual folklore that anomalies can only arise in systems with a
 n infinite number of degrees of freedom.  It also evades the Nielsen-Ninom
 iya theorem since the $U(1)$ symmetry in question is not generated by $\\g
 amma_5$. Furthermore\, a mod 2  't Hooft anomaly arises if we attempt to g
 auge this residual $Z_4$ symmetry which can only be cancelled if the syste
 m contains even numbers of flavors of staggered field. While the theory is
  not invariant under the usual chiral symmetry at non-zero lattice spacing
 \, the naive continuum limit of the minimal anomaly free model in four dim
 ensions nevertheless possesses the symmetries and matter representations o
 f the Pati-Salam GUT - a chiral gauge theory containing the Standard Model
 . These conclusions are based on path integral methods but a Hamiltonian a
 nalysis is also possible and I will comment also on that.
LOCATION:Potter Room (B1.19)
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