# YTF 11

Dec 19 – 20, 2018
Centre for Particle Theory, Durham
Europe/London timezone

## Semiclassical gravity in the far field of stars and black holes

Dec 20, 2018, 11:25 AM
20m
CM107 (Department of Mathematical Sciences)

### Speaker

Jake Percival (University of Sheffield)

### Description

In semiclassical gravity, the expectation value of the stress-energy operator $\left\langle T_{\mu\nu}\right\rangle$ is an infinite quantity. To avoid having to renormalize it, one can calculate the difference in $\left\langle T_{\mu\nu}\right\rangle$ between a pair of quantum states in such a manner that the divergent parts cancel. However, another technique explored more recently is to take the difference in $\left\langle T_{\mu\nu}\right\rangle$ between two different spacetimes, while in the same quantum state. I will summarize prior work on this method and detail how we have applied it to calculate the difference $\Delta\left\langle T_{\mu\nu}\right\rangle$ between the spacetimes of a non-Newtonian star and a Schwarzschild black hole.

### Primary author

Jake Percival (University of Sheffield)