#### Alladi Ramakrishnan Hall

#### Gauge theories on black hole spacetimes

#### Karan Fernandes

##### CMI, Chennai

*My talk will consider constrained field theories on fixed black*

hole spacetimes, which may either be asymptotically flat or possess a

cosmological horizon. I will demonstrate that non-vanishing gauge

parameters at the horizons lead to additional contributions in the

constraints of gauge theories from these surfaces (unlike spacetimes with

spatial boundaries). By applying the Dirac-Bergmann formalism on the

Maxwell field, the Gauss law constraint will be shown to involve surface

contributions from the horizons. The physical implication of this result on

charges at the horizon will be discussed. Since our result follows from the

Gauss law constraint, it has further implications on the gauge fixed

theory. I will consider fixing null components of gauge fields at the

horizons in scalar electrodynamics, as an example of an interacting theory,

within the Hamiltonian BRST formalism. I will derive the surface terms in

the BRST invariant action which results from this choice. It will also be

shown that horizons provide surface corrections to the ghost number charge

and the electromagnetic dressing of gauge invariant fields. I will conclude

with an overview of these results and discuss some future directions.

Done