| Popis: |
This thesis investigates the implications of gravitational waves (GWs) for particle physics and cosmology. We first give an overview of the current state of general relativity and quantum field theory. We also emphasize where GWs may come into play to shed new light on unsolved problems in physics. First, we make use of GWs to constrain the scale of non-commutative space-time. Assuming such quantum fuzziness, we compute the equations of motion of a binary black hole and the associated generation of GWs. Compared to general relativity, leading non-commutative effects produce a post-Newtonian correction of order (v/c)^4. Using the recent GW150914 signal, we find that the scale of non-commutativity is bounded to be below or at the order of the Planck scale. This represents an improvement of ~15 orders of magnitude compared to previous constraints. Second, we study the production of GWs from cosmological phase transitions. We consider two unrelated extensions of the standard model: a non-linear realization of the electroweak gauge group and a model with hidden scale invariance. In the first case, the Higgs vacuum configuration is altered by a cubic coupling giving the possibility to have a strong and prolonged electroweak first-order transition. In our second model, the electroweak transition cannot proceed until it is triggered by a first-order QCD chiral symmetry breaking around 130 MeV. We compute that the stochastic GW background produced during these two phase transitions is expected to be in the detection range of pulsar timing arrays. Finally, we investigate the backreaction of particle production on false vacuum decay. We present a formalism which makes use of the reduced density matrix of the system to quantify the impact of these particles on the decay rate of a scalar field in flat space-time. We then apply this method to a toy model potential and we exhibit different scenarios with either significant or negligible backreaction. |
