Holography and the generalized second law of thermodynamics in (2+1)-dimensional cosmology

The Fischler-Susskind entropy bound has been studied in (2 + 1)-dimensional universes with negative cosmological constant. As in all contracting universes, that bound is not satisfied. Furthermore, we found that the Fischler-Susskind bound is not compatible with a generalized second law of thermodynamics in (2 + 1)-dimensional cosmology, neither the classical nor the quantum version. On the other hand, the Hubble entropy bound has been constructed in (2 + 1)-dimensional cosmology and it is shown compatible with the generalized second law of thermodynamics. (C) 2000 Published by Elsevier Science B.V. All rights reserved.