Quasilocal thermodynamics of de Sitter space*

Shortly after the discovery of black hole thermodynamics Gibbons and Hawking found that gravitational systems with cosmological horizons have temperature and entropy and obey a first law, according to which the cosmological horizon area is reduced by addition of matter Killing energy. There is no boundary in de Sitter space at which the temperature or energy of the ensemble can be defined, therefore the statistical foundation of their approach deserves further study. When an asymptotic boundary is absent, finite size boundaries may be employed to specify quasilocal data and define the sensemble. In this presentation we see how introducing an artificial "York boundary" in the static patch of de Sitter space helps understanding its thermodynamics, with the focus being on entropy derivation and interpretation of the first law. Additionally quantization of de Sitter space in a 2-dimensional dilaton gravity theory with timelike boundaries is briefly discussed.