Publikace ÚTF

We investigate quasilocal horizons in inhomogeneous cosmological models,
specifcally concentrating on the notion of a trapping horizon defned by
Hayward as a hypersurface foliated by marginally trapped surfaces. We
calculate and analyse these quasilocally defned horizons in two dynamical
spacetimes used as inhomogeneous cosmological models with perfect fluid
source of non-zero pressure. In the spherically symmetric Lemaître spacetime
we discover that the horizons (future and past) are both null hypersurfaces
provided that the Misner–Sharp mass is constant along the horizons. Under
the same assumption we come to the conclusion that the matter on the
horizons is of special character—a perfect fluid with negative pressure. We
also fnd out that they have locally the same geometry as the horizons in the
Lemaître–Tolman–Bondi spacetime. We then study the Szekeres–Szafron
spacetime with no symmetries, particularly its subfamily with β,z = 0, and we
fnd conditions on the horizon existence in a general spacetime as well as in
certain special cases.