# The 4th Conference of the Polish Society on Relativity

Sep 24 – 28, 2017
Kazimierz Dolny, Poland
Europe/Warsaw timezone

## Towards a theory of nonlinear gravitational waves: a systematic approach to nonlinear gravitational perturbations in vacuum

Sep 26, 2017, 12:40 PM
20m
Kazimierz Dolny, Poland

#### Kazimierz Dolny, Poland

Dom Pracy Twórczej SDP ul. Małachowskiego 17 24-120 Kazimierz Dolny
Oral presentation (preferred)

### Speaker

Andrzej Rostworowski

### Description

I will present a systematic and robust approach to nonlinear gravitational perturbations of vacuum spacetimes. In particular, I will show that the system of perturbative Einstein equations reduces at each perturbation order to two (for each gravitational mode in $3+1$ dimensions on which our study is focused) scalar wave equations, and then we show how the metric perturbations can be explicitly obtained, once the solutions to these scalar wave equations are known. These results show that the concept of polarization of a gravitational wave does make sense also beyond the linear approximation and provides a basis for a theory of nonlinear gravitational waves. The talk is based on a recent preprint http://arxiv.org/abs/1705.02258.