Seminarium "Teoria cząstek elementarnych i kosmologia"

In this talk, I will present two specific modifications of gravity in which the number of degrees of freedom (d.o.f.) is minimized using a cosmological-scale violation of Lorentz invariance. I will focus on their construction, showing how different methods can be used to accomplish the same goal, i.e. keeping a low number of d.o.f. As a first example, I will describe a class of modified gravity theories that propagate only the usual two polarizations of gravitational waves and that have an Einstein frame. As a second example I will give a short overview of the minimal theory of massive gravity, a theory of massive gravity with only two d.o.f., and on its generalizations.