This week's seminars
Maths HEP Lunchtime Seminars: Global anomaly cancellation in 6d supergravity
25 January 2019 13:00 in CM101
Anomalies put strong constraints on 6d supergravity, making it an interesting setup to study the question of string universality, i.e. whether every consistent effective gravity theory can be obtained from string theory. Global anomalies, i.e. anomalies of symmetries disconnected from the identity, are still poorly understood, in particular in the context of 6d supergravity. In the present talk, I will report on work with Greg Moore where we took the first steps toward a systematic study of global anomaly cancellation in 6d supergravity. The cancellation of local and global anomalies in 6d supergravity require a version of the Green-Schwarz mechanism and a significant part of this work involves defining the Green-Schwarz terms in backgrounds of arbitrary topology. The very existence of the Green-Schwarz term provide constraints, some of which are new. Moreover, the Green-Schwarz mechanism is generally unable to cancel all global anomalies, leading to further residual constraints from anomaly cancellation. I will also explain that these constraints are naturally satisfied in 6d F-theory vacua.