String Theory Seminars
Gauge and Gravitational anomalies of Discrete ZN symmetries
by Dr. Tarun Sharma (Wits university, Johanneshberg,South Africa)
Monday, August 28, 2017 from to (Asia/Kolkata)
We will discuss the consistency conditions which a discrete ZN symmetry should satisfy in order that it is not violated by gauge and gravitational instantons. As examples, we enlist all ZN R-symmetries (N=2,3,4) in the minimally supersymmetric standard model (MSSM) that are free from gauge and gravitational anomalies. We show that there exists non-anomalous discrete symmetries that forbid Baryon number violation up to dimension 6 level (in superspace). We also observe that there exists no non-anomalous Z3 R-symmetry in the MSSM. Furthermore, we point out that in a theory with one Majorana spin 3/2 Gravitino, a large class of Z4 R-symmetries are violated in the presence of Eguchi-Hanson (EH) gravitational instanton. This is also in general true for higher ZN R-symmetries. We also notice that in 4 dimensional N=1 supergravity, the global U(1) R-symmetry is always violated by the EH instanton irrespective of the matter content of the theory.