The apparent Universe

Abstract

We exploit the parallel between dynamical black holes and cosmological spacetimes to describe the evolution of Friedmann-Lemaître-RobertsonWalker universes from the point of view of an observer in terms of the dynamics of the apparent horizon. Using the Hayward-Kodama formalism of dynamical black holes, we clarify the role of the Clausius relation to derive the Friedmann equations for a universe, in the spirit of Jacobson's work on the thermodynamics of spacetime. We also show how dynamics at the horizon naturally leads to the quantum-mechanical process of Hawking radiation. We comment on the connection of this work with recent ideas to consider our observable Universe as a Bose-Einstein condensate and on the corresponding role of vacuum energy.

Thermodynamics of universe with a varying dark energy component

“…(2) to obtain this equation [51,68,[71][72][73]. It is useful to note here that for the FRW universe supported by a fluid with ρ = −p = constant (ω = −1),Ḣ = 0 and therefore this equation covers the result of de-Sitter spacetime (T = − H 2π ) [50,51].…”

“…It is useful to note here that for the FRW universe supported by a fluid with ρ = −p = constant (ω = −1),Ḣ = 0 and therefore this equation covers the result of de-Sitter spacetime (T = − H 2π ) [50,51]. In cosmological setups, some authors use various definition of temperature and get the corresponding Einstein equations (Friedmann equations) on the apparent horizon [51,52,68,[71][72][73][74]. In order to avoid the negative temperature, authors in [52], have defined T = H 2π ≃ |κ| 2π and used the first law of thermodynamics (in the T dS A = −dQ form) to get the Friedmann equations.…”

“…Indeed, authors argued that the extra minus sign in the first law of thermodynamics is the result of universe expansion leading to decrease the energy of confined fluid together with increase the size of the universe and thus S A . Therefore, by using original definition of temperature (2) and thus (7), called the Hayward-Kodama temperature [51,68,72,73], together with the T dS A = dQ form of the first law of thermodynamics we can cover the Friedmann equation. Moreover, it seems that W = 1 2 h ab T ab , where T ab is the energy momentum tensor of fluid which spreads over the cosmos, plays the role of pressure in the dynamics spacetimes and thus the FRW universe [51,68,[71][72][73][74][75].…”

Corpuscular consideration of eternal inflation

“…In fact, some phenomena, like Hawking radiation, the Bekenstein entropy, or, the information paradox, can only be fully understood in this quantum picture [9][10][11][12][13][14][15] (cf. also [16][17][18][19][20][21][22][23][24][25][26][27] for recent progress).…”

Quantum portrait of a black hole with Pöschl-Teller potential

“…Both proposals state that the classical description of gravity breaks down at the horizon, not just at the singularity, as has been the standard point of view. The quantum Nportrait may also shed light upon the species problem [8], whereas extending the idea of quantum compositeness to other gravitational backgrounds has far-reaching consequences for cosmology [9,10], for earlier ideas see, e.g., [11]. For relates studies, see [12][13][14].…”