Statistical mechanics of gravitons in a box and the black hole entropy

Viaggiu, Stefano

doi:10.1016/j.physa.2017.01.052

Cited by 15 publications

(61 citation statements)

References 48 publications

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“…In [13,14] we have advanced a physical mechanism, mimicking solid state physics, capable, thanks to Planckian fluctuations, to change the equation of state of a radiation field into an effective one with a γ− linear equation of state. This has been firstly applied in order to explain the logarithmic corrections [13] to the semi-classical Bekenstein-Hawking entropy [15,16] and further applied in [1] in order to depict the cosmological constant. To start with, we consider the free energy F (0) (V, N, T ) of a radiation field with N excitations in a proper volume V at the temperature T and with energy E (0) in the continuum limit, given, as well known, by:…”

Section: Continuum Limit For a General Equation Of Statementioning

confidence: 99%

The physical origin of the cosmological constant: continuum limit and the analogy with the Casimir effect

Viaggiu

2019

Phys. Scr.

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In this paper we continue the investigations in [1] concerning the origin of the cosmological constant. First of all, we generalise the results in [1,2] by considering a continuum approximation for a radiation field in a cosmological background. In this way, we clearly show that the bare cosmological constant is obtained with wanishing temperature T and that the specific heat C is zero at the decoherence scale L D . Moreover, we address the issue to fix the parameters present in our model. In particular, we push forward the analogy between our expression for Λ L at a given proper scale L and the one extrapolated by the Casimir effect. As a consequence, we can fix the decoherence scale L D at which we have the crossover to classicality to be of the order of ∼ 10 −5 meters. This implies that the actual observed value of the cosmological constant is fixed (frozen) at this new physical scale.

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Section: Continuum Limit For a General Equation Of Statementioning

confidence: 99%

The physical origin of the cosmological constant: continuum limit and the analogy with the Casimir effect

Viaggiu

2019

Phys. Scr.

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“…where a L (t) denotes the effective volume scale factor in (20) at the scale L with L the areal radius of the spatial average surface S. The relevant generalized Buchert equations at microscopic Planckian scales for irrotational fluids are:…”

Section: Dynamical Evolution With R =mentioning

confidence: 99%

“…See also[20,21,22] for an application of my proposal to the black hole case and[23] in a more general context and[24] for an earlier proposal also in terms of massless excitations within the apparent horizon.…”

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confidence: 99%

The Cosmological Constant From Planckian Fluctuations and the Averaging Procedure

Viaggiu

2019

Found Phys

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In this paper I continue the investigation in [1,2] concerning my proposal on the nature of the cosmological constant. In particular, I study both mathematically and physically the quantum Planckian context and I provide, in order to depict quantum fluctuations and in absence of a complete quantum gravity theory, a semiclassical solution where an effective inhomogeneous metric at Planckian scales or above is averaged. In such a framework, a generalization of the well known Buchert formalism [3] is obtained with the foliation in terms of the mean value s(t) of the time operatort in a maximally localizing state {s} of a quantum spacetime [4,5,6,7] and in a cosmological context [8]. As a result, after introducing a decoherence length scale L D where quantum fluctuations are averaged on, a classical de Sitter universe emerges with a small cosmological constant depending on L D and frozen in a true vacuum state (lowest energy), provided that the kinematical backreaction is negligible at that scale L D . Finally, I analyse the case with a non-vanishing initial spatial curvature R showing that, for a reasonable large class of models, spatial curvature and kinematical backreation Q are suppressed by the dynamical evolution of the spacetime. * viaggiu@axp.mat.uniroma2.it and s.viaggiu@unimarconi.it 1

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“…In any case, the physical origin of Λ, its smallness and the role of the vacuum energy in the dynamic of the universe are yet fundamental unsolved problems. Recentely, I have proposed [1,2,3,4] a way to depict the black hole entropy in terms of trapped gravitons [1,2] together with the logarithmic entropy corrections [3]. The treatment has been extended in [4] to any massless excitation.…”

Section: Introductionmentioning

confidence: 99%

On a physical description and origin of the cosmological constant

Viaggiu¹

2018

Class. Quantum Grav.

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In this paper we use and extend the results present in [1,2,3,4] and in particular in [4] to obtain a statistical description of the cosmological constant in a cosmological de Sitter universe in terms of massless excitations with Planckian effects. First of all, we show that at a classical level, the cosmological constant Λ > 0 can be obtained only for T → 0. Similarly to the black hole case, when quantum effects are taken into account, a representation for Λ is possible in terms of massless excitations, provided that quantum corrections to the Misner-Sharp mass are considered. Moreover, thanks to quantum fluctuations, an effective cosmological constant arises depending on the physical scale under consideration, thus representing a possible solution to the cosmological constant problem without introducing a quintessence field. The smalness of the actual value for Λ can be due to the existence of a quantum decoherence scale above the Planck length such that the spacetime evolves as a pure de Sitter universe with a small averaged cosmological constant frozen in the lowest energy state. Number(s): 95.36.+x, 04.60.Bc, PACS

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Statistical mechanics of gravitons in a box and the black hole entropy

Cited by 15 publications

References 48 publications

The physical origin of the cosmological constant: continuum limit and the analogy with the Casimir effect

The physical origin of the cosmological constant: continuum limit and the analogy with the Casimir effect

The Cosmological Constant From Planckian Fluctuations and the Averaging Procedure

On a physical description and origin of the cosmological constant

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