Séminaire de Physique Théorique

Ghost condensation and horizon entropy
Shinji Mukohyama (Université de Kyoto, Japon)
Thursday 10 November 2016 15:30 -  Tours -  Salle 1180 (Bât E2)

Résumé :
Ghost condensation is the simplest realization of an analogue of Higgs mechanism in gravity and provides a theoretically consistent way to modify gravity in the infrared. After reviewing the basic idea of ghost condensation and its phenomenologies, we revisit some issues with horizon thermodynamics. In the setup of ghost condensation model the generalized second law of black hole thermodynamics can be respected under a radiatively stable assumption that couplings between the field responsible for ghost condensate and matter fields such as those in the Standard Model are suppressed by the Planck scale. Since not only black holes but also cosmology are expected to play important roles towards our better understanding of gravity, we consider a cosmological setup to test the theory of ghost condensation. In particular we shall show that the de Sitter entropy bound proposed by Arkani-Hamed, et al. is satisfied if ghost inflation happened in the early epoch of our universe and if there remains a tiny positive cosmological constant in the future infinity. We then propose a notion of cosmological Page time after inflation.

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