HEP Theory Journal Club

Dynamical Chern-Simons gravity: Anomalies, gravitational axions, and neutrinos

Heliudson Bernardo

Brown University

Motivated by the interplay between the scalar-gravitational Pontryagin term in dynamical Chern-Simons (dCS) gravity and the baryon-lepton (B-L) number symmetry in the Standard Model (SM), I will revisit some aspects of the dCS classical and quantum symmetries. It has been argued that dCS gravity can be reduced to Einstein gravity after "rotating away" the gravitational-Pontryagin coupling into the phase of the Weinberg operator -- analogous to the rotation of the axion zero-mode into the quark mass matrix. I will show that this is not the case, precisely because of the B-L chiral gravitational anomaly. Then I will introduce a minimal extension of the SM where the coupling of the dCS scalar with right-handed neutrinos induces both the scalar-Pontryagin coupling and an axion-like phase in the dimension-five Weinberg operator at low energies.