Strong gravity effects from populations of binary black holes

August 2016

Andrea Maselli, Stefania Marassi, Valeria Ferrari, Kostas D. Kokkotas, Raffaella Schneider

Gravitational waves represent a powerful tool to investigate gravity in extreme conditions, which involve the most compact objects of our Universe, as neutron stars and black holes. Searching for possible signatures of strong gravity effects is a crucial ingredient, provided by alternative theories to compare against General Relativity. Black hole coalescences represent the ideal candidates for such tests, as they constitute the primary target to be detected by terrestrial interferometers.

In our study we focus on the gravitational wave background emitted by a population of binary black holes, which are too distant to be resolved as individual sources. We investigate how modified theories of gravity alter the expected signal. Employing a pure phenomenological and agnostic parametrization, we identify the parameter space which lead to relevant changes, and therefore to signatures potentially observable by current detectors. We show the constraints that advanced LIGO may be able to set in the near future on alternative theories, significantly improving the current bounds coming from electromagnetic observations.

Phys. Rev. Lett. 117, 091102 (2016), arXiv:1606.04996