Beyond the Standard Theories of Fundamental Interactions. The status quo of fundamental physics i... more Beyond the Standard Theories of Fundamental Interactions. The status quo of fundamental physics is the Standard Model (SM) of particle physics and General Relativity (GR). While both theories separately are able to describe a wide range of phenomena in their respective domain to high accuracy, there are problems which arise solely when the two are coupled. Examples include the cosmological constant problem, baryogenesis or the absence of a suitable dark matter (DM) candidate in the SM. In this thesis, several solutions are presented and discussed. One is Bimetric Gravity, a modification of GR which breaks the assumption that one single, massless spin-2 object acts as its force carrier. Original results are presented on the phenomenology of the massive graviton, where we analyse the modified propagation of gravitational waves and set competitive bounds on the graviton mass. Furthermore, the cosmological history of the model is investigated, incorporating data from baryon acoustic osc...
We consider the possible existence of a SM-neutral and light dark sector coupled to the visible s... more We consider the possible existence of a SM-neutral and light dark sector coupled to the visible sector through irrelevant portal interactions. Scenarios of this kind are motivated by dark matter and arise in various extensions of the Standard Model. We characterize the dark dynamics in terms of one ultraviolet scale Λuv, at which the exchange of heavy mediator fields generates the portal operators, and by one infrared scale ΛIR, setting the mass gap. At energies ΛIR « E « Λuv the dark sector behaves like a conformal field theory and its phenomenology can be studied model independently. We derive the constraints set on this scenario by high- and low-energy laboratory experiments and by astrophysical observations. Our results are conservative and serve as a minimum requirement that must be fulfilled by the broad class of models satisfying our assumptions, of which we give several examples. The experimental constraints are derived in a manner consistent with the validity of the effecti...
Beyond the Standard Theories of Fundamental Interactions. The status quo of fundamental physics i... more Beyond the Standard Theories of Fundamental Interactions. The status quo of fundamental physics is the Standard Model (SM) of particle physics and General Relativity (GR). While both theories separately are able to describe a wide range of phenomena in their respective domain to high accuracy, there are problems which arise solely when the two are coupled. Examples include the cosmological constant problem, baryogenesis or the absence of a suitable dark matter (DM) candidate in the SM. In this thesis, several solutions are presented and discussed. One is Bimetric Gravity, a modification of GR which breaks the assumption that one single, massless spin-2 object acts as its force carrier. Original results are presented on the phenomenology of the massive graviton, where we analyse the modified propagation of gravitational waves and set competitive bounds on the graviton mass. Furthermore, the cosmological history of the model is investigated, incorporating data from baryon acoustic osc...
We consider the possible existence of a SM-neutral and light dark sector coupled to the visible s... more We consider the possible existence of a SM-neutral and light dark sector coupled to the visible sector through irrelevant portal interactions. Scenarios of this kind are motivated by dark matter and arise in various extensions of the Standard Model. We characterize the dark dynamics in terms of one ultraviolet scale Λuv, at which the exchange of heavy mediator fields generates the portal operators, and by one infrared scale ΛIR, setting the mass gap. At energies ΛIR « E « Λuv the dark sector behaves like a conformal field theory and its phenomenology can be studied model independently. We derive the constraints set on this scenario by high- and low-energy laboratory experiments and by astrophysical observations. Our results are conservative and serve as a minimum requirement that must be fulfilled by the broad class of models satisfying our assumptions, of which we give several examples. The experimental constraints are derived in a manner consistent with the validity of the effecti...
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