Seminář se koná v úterý ve 13:10 v posluchárně ÚTF MFF UK
v 10. patře katedrové budovy v Tróji, V Holešovičkách 2, Praha 8
On one hand, the formalism developed in thermodynamics of spacetime allows a derivation of Einstein equations from the proportionality of entropy to the area. On the other hand, low energy quantum gravity effects imply a modified entropy formula with an additional term logarithmic in the area. Combining both concepts, I will introduce the derivation of quantum modified gravitational dynamics from the modified entropy and discuss its main features. Moreover, I will show its physical implications on a simple cosmological model and show that it suggests the replacement of the Big Bang singularity by a regular bounce.
Cosmological observations represent a powerful tool to test gravity at large scales. In particular, a possible way to do it is by introducing a couple of phenomenological functions that can be measured and which completely characterise deviations from general relativity. Their observational values can be used to constrain the parameter space of modified gravity theories and, eventually, rule out some of them. This possibility will be discussed for two classes of scalar-tensor theories, Horndeski and beyond Horndeski gravity, using the formalism of the effective field theory of dark energy. Particular emphasis will be given to the subclasses of these theories which predict a non-vanishing gravitational slip.
Jiří Bičák Oldřich Semerák