Relativistický seminář
Ústavu teoretické fyziky

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

12. prosince 2023
Static metric with a ring source in toroidal coordinates
doc. Tomáš Ledvinka
(seminář v angličtině)

In 1975, in a short paper named "A toroidal solution of the vacuum Einstein field equations", Kip S. Thorne suggested that an external field of gravitating toroidal source requires introducing cuts and identifications in order to be expressed in Weyl coordinates with their attractively simple form of field equations. Since then only 10 papers seem to have this result in their references and only one actually uses Thorne's result. Among others, I will show how these cuts and identifications necessarily arise from the analytic properties of transformations leading to Weyl metric, what coordinates should be used to get smooth metric, and how one can find metric of this spacetime numerically.

19. prosince 2023
Measuring the temperature of quantum fields: Unruh and Hawking effects
Tales Rick Perche
Perimeter Institute for Theoretical Physics / University of Waterloo
(seminář v angličtině)

In this talk we will show that if the field is in a state that satisfies the KMS condition with inverse temperature beta with respect to a detector's local notion of time evolution, reasonable assumptions ensure that the probe thermalizes to the temperature 1/beta; in the limit of long interaction times. This is true regardless of the field operator that the detector couples to. Our method also imposes bounds on the size of the system with respect to its proper acceleration and spacetime curvature in order to accurately probe the KMS temperature of the field. We then comment on applications to the case of detectors probing the Unruh and Hawking temperatures.

Jiří Bičák                                                                                                  Oldřich Semerák