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
In the first part of my talk I will discuss the variational principle for general relativity and some associated subtle facts. In particular, I will try to arrive at the correct action principle for general relativity in presence of null boundaries. Possible generalization to Lovelock theories will also be presented. In the second part of my talk, I will discuss the thermodynamics of null surfaces. In particular, I will show that three different projections of gravitational momentum related to an arbitrary null surface in the space time leads to three different equations, all of which have thermodynamic interpretations.
In this talk, I will discuss the problem which arises by the existence of zero cover measures in the classical limit of the consistent histories approach of quantum theory. I will analyze the time-of-arrival of a (semi-) classical free particle in an infinite square well and I will show how we end up with contrary inferences.
A notable class of torsionful but curvatureless gravitational theories of gravity, known as teleparallel theories of gravity (or teleparallel gravity in brief), arise from assuming that both the non-metricity and the curvature of the affine connection are zero. Teleparallel theories of gravity have a long history of analysis, including Einstein himself who believed that the space of distant parallelism, (also called ``absolute parallelism'' or ``tele-parallelism'' by others) was the most promising candidate to unify gravitation and electromagnetism. Intriguingly, there exists a subclass of teleparallel theories of gravity that are dynamically equivalent to general relativity.
In teleparallel gravity and its generalizations, a frame basis replaces the metric as the central object of study, although the metric can still be constructed from the frame basis. Consequently, the concept of an isometry as a symmetry of the metric may no longer act as a symmetry of a solution to a given teleparallel gravity theory. However, for any teleparallel gravity solution, the set of symmetries are related to the set of invariants and studying the set of invariants will provide information about the symmetries. In this talk, I will discuss the equivalence algorithm for teleparallel gravity, which provides a set of invariants that uniquely characterizes (locally) a teleparallel gravity solution, and use this set of invariants to determine the group of symmetries for the space.
Jiří Bičák Oldřich Semerák