I will show how Kaehler-Dirac fermions suffer from an anomaly in a U(1) symmetry that can be computed exactly on a finite lattice contradicting the usual folklore. This anomaly is connected to an ambiguity in the path integral measure for a reduced lattice Kaehler fermion that is an analog of the measure problem for chiral lattice fermions. In the Kaehler case it can be explicitly solved using a mirror fermion construction.
To gap the mirror fermions requires all 't Hooft anomalies vanish which then determines the fermion content.
We show that the minimal anomaly free theory has a continuum limit that corresponds to the Pati-Salam GUT - a chiral gauge theory containing the Standard Model. Because of the close connection between the lattice Kaehler fermion and staggered fermions this suggests an alternative approach to at least a class of lattice chiral gauge theory.
To gap the mirror fermions requires all 't Hooft anomalies vanish which then determines the fermion content.
We show that the minimal anomaly free theory has a continuum limit that corresponds to the Pati-Salam GUT - a chiral gauge theory containing the Standard Model. Because of the close connection between the lattice Kaehler fermion and staggered fermions this suggests an alternative approach to at least a class of lattice chiral gauge theory.