Gravitational-wave signatures from compact binaries beyond general relativity and the standard model of particle physics

The central topic of this thesis project is the numerical simulation of compact binary systems in the framework of Einstein's theory of general relativity and modification of this theory. These simulations target the theoretical prediction of gravitational-wave signals generated by these binaries with particular focus on possible signatures of sources beyond the standard model of particle physics and/or general relativity. These signatures are to be used in ongoing data analysis with the existing network of ground-based gravitational-wave detectors (LIGO, Virgo, KAGRA) as well as future ground or space based observatories such as LISA or the Einstein Telescope. A particular type of physical systems targeted are so-called boson stars, a hypothesised class of compact stellar objects composed of bosonic matter (e.g. scalar or vector fields). Their modelling will employ stand-alone codes for the modelling of single boson-star spacetimes as well as full numerical simulations in 3+1 space-time dimensions using the GRChombo and Lean codes. We target to specific physical configurations. First, the inspiral and merger of boson-star binaries in scalar-tensor theory of gravity where an effect called spontaneous secularisation will likely result in prominent gravitational-wave emission that differs strongly from the signals expected in general relativity. The second class of binaries are thin-wall boson stars whose merger will likely result in characteristic features in the gravitational-wave emission different from the more common mergers of compact objects with more homogeneous mass distributions.