Challenging theories of gravitation: dark matter, compact objects and gravitational waves
Details

Call:
IDPASC Portugal  PHD Programme 2016

Academic Year:
2016 / 2017

Domains:
General Relativity  Astrophysics

Supervisor:
Vitor Cardoso

CoSupervisor:
Leonardo Gualtieri

Institution:
Instituto Superior Técnico

Host Institution:
Instituto Superior Técnico

Abstract:
On September 14, 2015 the two LIGO interferometers have detected for the first time the gravitational wave signal emitted during the coalescence of a binary black hole system. This detection provides the first direct evidence of the existence of black holes and of the existence of BH binaries. It also allows to test, for the first time, gravity in the strongfield regime and close to horizons. This proposal aims at studying how possible modifications of general relativity would affect the gravitational wave signal emitted by astrophysical sources, in order to constrain such modifications. I shall consider some of the simplest and most interesting modifications of GR: (i) scalartensor theories, in which the tensor field which mediates gravity is (nonminimally) coupled to a scalar field, and (ii) theories in which the EinsteinHilbert action includes higherorder curvature invariants coupled to scalar fields, such as EinsteinDilatonGaussBonnet gravity and Chern Simons gravity. The main stronggravity astrophysical processes I want to study are:  the socalled "spontaneous scalarization" phenomena, which are nontrivial scalar field configurations associated to neutron stars, in the context of scalartensor theories; I have studied this process in my master thesis, focussing on the case of massive scalar fields; next step is the modeling of the gravitational wave signal, and the study of its detectabilityl  the excitation of the quasinormal modes of oscillations of black holes in quadratic gravity theories; these modes are excited in the final part of a binary black hole coalescence (as predicted by numerical simulations, and confirmed in the LIGO detection), and carry the imprint of the underlying gravity theory in the strongfield, highcurvature regime.
Thesis Student

Student:
Lorenzo Annulli

Status:
Concluded

Started At:
January 01, 2017

Ended At:
July 20, 2021