Speaker
Description
Gravitational entropy and the cosmological “no-hair” conjecture
Gravitational entropy [1] and the “no-hair” conjectures [2, 3] are seemingly contradictory: the growth of the first one is associated with the growth of inhomogeneity [4, 5, 6], while the second one argues that the dark energy dominated Universe will asymptotically approach a homogeneous and isotropic de Sitter state[7, 8].
In my talk I will present the analysis of both of these conjectures within the silent universes [9, 10]. Irrotational silent universes belong to a class of systems where each worldline evolves independently of other worldlines - there is no communication between the worldlines, i.e. no pressure gradients, no energy flux, no gravitational radiation. In my talk I will discuss properties and evolution of the irrotational silent universe. I will focus on the gravitational entropy and future asymptotic state of the silent universe dominated by dark energy [11]. Finally, I will comment on the gravitational entropy of gravitational waves.
References
[1] T. Clifton, G. F. R. Ellis, and R. Tavakol, “A gravitational entropy proposal,” Classical and Quantum Gravity, vol. 30, p. 125009, 2013.
[2] G. Götz, “On the cosmological ’no-hair’ conjecture,” Physics Letters A, vol. 128, no. 3, pp. 129 – 132, 1988.
[3] L. G. Jensen and J. A. Stein-Schabes, “Is inflation natural?,” Phys. Rev. D, vol. 35, pp. 1146–1150, 1987.
[4] K. Bolejko and W. R. Stoeger, “Intermediate homogenization of the Universe and the problem of gravitational entropy,” Phys. Rev. D, vol. 88, no. 6, p. 063529, 2013.
[5] R. A. Sussman and J. Larena, “Gravitational entropies in LTB dust models,” Classical and Quantum Gravity, vol. 31, p. 075021, 2014.
[6] R. A. Sussman , “Gravitational entropy of cosmic expansion,” Astronomische Nachrichten, vol. 335, p. 587, 2014.
[7] R. M. Wald, “Asymptotic behavior of homogeneous cosmological models in the presence of a positive cosmological constant,” Phys. Rev. D, vol. 28, pp. 2118–2120, 1983.
[8] T. Pacher and J. A. Stein-Schabes, “On the Locality of the No Hair Conjecture and the Measure of the Universe,” Annalen der Physik, vol. 503, pp. 518–526, 1991.
[9] M. Bruni, S. Matarrese, and O. Pantano, “Dynamics of silent universes,” Astroph. J., vol. 445, pp. 958–977, 1995.
[10] H. van Elst, C. Uggla, W. M. Lesame, G. F. R. Ellis, and R. Maartens, “Integrability of irrotational silent cosmological models,” Classical and Quantum Gravity, vol. 14, pp. 1151–1162, 1997.
[11] K. Bolejko, In preparation, 2017.
