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We study the effect of self-gravity on entropy by directly solving the 4D semi-classical Einstein equation. In particular, we focus on whether the Bekenstein-Hawking formula holds when self-gravity is extremely strong. As an example, we consider a simple spherically symmetric static configuration consisting of many quanta and construct a self-consistent non-perturbative solution for ħ in which the entropy exactly follows the area law for many local degrees of freedom of any kind. This can be a candidate for black holes in quantum theory. It represents a compact dense configuration with near-Planckian curvatures, and the interior typically behaves like a local thermal state due to particle creation inside. Here, the information content is stored in the interior bulk, and the self-gravity plays an essential role in changing the entropy from the volume law to the area law. We finally discuss implications to black holes in quantum gravity and a speculative view of entropy as a gravitational charge. [ABSTRACT FROM AUTHOR]

The motivation behind this study is to enumerate the leading order corrections to the thermodynamics of BTZ black hole (named after three scientists; Banados, Teitelboim, and Zanelli). We first analyze the effect of quantum corrections (motivated from string theory and loop quantum gravity) on various thermodynamic variables for uncharged and stationary BTZ black hole. We, later on, endow charges and rotations to the same black hole and rederive all the expressions once again. The comparative analysis is done between the corrected and uncorrected thermodynamics via plots. [ABSTRACT FROM AUTHOR]

We use data from M87* central black hole shadow, as well as from the S2 star observations, in order to extract constraints on Barrow entropy. The latter is a modified entropy arising from quantum-gravitational effects on the black hole horizon, quantified by the new parameter Δ . Such a change in entropy leads to a change in temperature, as well as to the properties of the black hole and its shadow. We investigate the photon sphere and the shadow of a black hole with Barrow entropy, and assuming a simple model for infalling and radiating gas we estimate the corresponding intensity. Furthermore, we use the radius in order to extract the real part of the quasinormal modes, and for completeness we investigate the spherical accretion of matter onto the black hole, focusing on isothermal and polytropic test fluids. We extract the allowed parameter region, and by applying a Monte-Carlo-Markov Chains analysis we find that Δ ≃ 0.0036 − 0.0145 + 0.0792 . Hence, our results place the upper bound Δ ≲ 0.0828 at 1 σ , a constraint that is less strong than the Big Bang Nucleosynthesis one, but significantly stronger than the late-time cosmological constraints. [ABSTRACT FROM AUTHOR]

We study microscopic entropy of the near-extremal rotating black hole in four-dimensional (4D) 풩 = 2 supergravity with four charges set pairwise equal from AdS2/CFT1 correspondence. This correspondence is realized in terms of asymptotic symmetries of the AdS2 geometry and a two-dimensional near-horizon effective quantum theory of residual fields from a dimensional reduction proposed by Robinson and Wilczek. We compute the relevant central charge and derive the microscopic entropy of this near-extremal black hole by Cardy formula. Our results can be extended to more general near-extremal rotating black holes in 4D supergravity. They further support the notion that black hole entropy is generally controlled by near-horizon conformal symmetry. [ABSTRACT FROM AUTHOR]

In 1996, Rovelli suggested a connection between black hole entropy and the area spectrum. Using this formalism and a theorem we prove in this paper, we briefly show the procedure to calculate the quantum corrections to the Bekenstein-Hawking entropy. One can do this by two steps. First, one can calculate the 'naive' black hole degeneracy without the projection constraint (in case of the $$U(1)$$ symmetry reduced framework) or the $$SU(2)$$ invariant subspace constraint (in case of the fully $$SU(2)$$ framework). Second, then one can impose the projection constraint or the $$SU(2)$$ invariant subspace constraint, obtaining logarithmic corrections to the Bekenstein-Hawking entropy. In this paper, we focus on the first step and show that we obtain infinite relations between the area spectrum and the naive black hole degeneracy. Promoting the naive black hole degeneracy into its approximation, we obtain the full solution to the infinite relations. [ABSTRACT FROM AUTHOR]

The entropie gravity scenario recently proposed by Erik Verlinde reproduced Newton's law of purely classical gravity yet the key assumptions of this approach all have quan-tum mechanical origins. As is typical for emergent phenomena in physics, the underlying, more fundamental physics often reveals itself as corrections to the leading classical be-havior. So one naturally wonders: where is h hiding in entropie gravity? To address this question, we first revisit the idea of holographic screen as well as entropy and its vari-ation law in order to obtain a self-consistent approach to the problem. Next we argue that since the concept of minimal length has been invoked in the Bekenstein entropie derivation, the generalized uncertainty principle (GUP), which is a direct consequence of the minimal length, should be taken into consideration in the entropie interpretation of gravity. Indeed based on GUP it has been demonstrated that the black hole Bekenstein entropy area law must be modified not only in the strong but also in the weak gravity regime where in the weak gravity limit the GUP modified entropy exhibits a logarithmic correction. When applying it to the entropie interpretation, we demonstrate that the resulting gravity force law does include sub-leading order correction terms that depend on h. Such deviation from the classical Newton's law may serve as a probe to the validity of entropie gravity. [ABSTRACT FROM AUTHOR]

We investigate the entropy counting for black hole horizons in loop quantum gravity (LQG). We argue that the space of 3D closed polyhedra is the classical counterpart of the space of SU(2) intertwiners at the quantum level. Then computing the entropy for the boundary horizon amounts to calculating the density of polyhedra or the number of intertwiners at fixed total area. Following the previous work (Bianchi 2011 Class. Quantum Grav. 28 114006) we dub these the classical and quantum polymer models for isolated horizons in LQG. We provide exact micro-canonical calculations for both models and we show that the classical counting of polyhedra accounts for most of the features of the intertwiner counting (leading order entropy and log-correction), thus providing us with a simpler model to further investigate correlations and dynamics. To illustrate this, we also produce an exact formula for the dimension of the intertwiner space as a density of 'almost-closed polyhedra' [ABSTRACT FROM AUTHOR]

In this paper, we calculate the heat flux passing through the horizon TS|rh and the difference of energy between the Einstein and Mailer prescription within the region M, in which is the region between outer horizon H+ and inner horizon H-, for the modified GHS solution, KLOPP solution and CLH solution. The formula EEinstein=Møller|M --∑∂M TS is obeyed for the mGHS solution and the KLOPP solution, but not for the CLH solution. Also, we suggest a RN-like stringy dyonic black hole solution, which comes from the KLOPP solution under a dual transformation, and its thermodynamical properties are the same as the KLOPP solution. [ABSTRACT FROM AUTHOR]

The well-known area relation of the black hole entropy can be modified from the inclusion of quantum effects, motivated from the loop quantum gravity. Applying this modified entropy-area relation to brane cosmology, we derive the modified cosmological equations governing the evolution of the universe on the brane. We adopt the viewpoint that interprets gravity as an entropic force caused by the changes in the information when a material body moves away from the holographic screen. [ABSTRACT FROM AUTHOR]

It has been shown recently that information is lost in the Hawking radiation of the linear dilaton black holes in various theories when applying the tunneling formalism of Parikh and Wilczek without considering quantum gravity effects. In this paper, we recalculate the emission probability by taking into account the log-area correction to the Bekenstein-Hawking entropy and the statistical correlation between quanta emitted. The crucial role of the quantum gravity effects on the information leakage and black hole remnant is highlighted. The entropy conservation of the linear dilaton black holes is discussed in detail. We also model the remnant as an extreme linear dilaton black hole with a pointlike horizon in order to show that such a remnant cannot radiate and its temperature becomes zero. In summary, we show that the information can also leak out of the linear dilaton black holes together with preserving unitarity in quantum mechanics. [ABSTRACT FROM AUTHOR]

Entropy plays a crucial role in the characterization of information and entanglement, but it is not a scalar quantity and for many systems it is different for different relativistic observers. We discuss two examples: entropy of a single qubit and renormalized entropy as given by a uniformly accelerated observer. Loop quantum gravity predicts the Bekenstein–Hawking term for black hole entropy and the logarithmic correction to it. The latter originates in the entanglement between the pieces of spin networks that describe black hole horizon. Entanglement between gravity and matter may restore the unitarity in the black hole evaporation process. If the collapsing matter is assumed to be initially in a pure state, then entropy of the Hawking radiation is exactly the created entanglement between matter and gravity. [ABSTRACT FROM AUTHOR]

The search for a quantum theory of gravity has followed two parallel but different paths. One aims at arriving at the final theory starting from a priori assumptions as to its form and building it from the ground up. The other tries to infer as much as possible about the unknown theory from the existing ones and use our current knowledge to constrain the possibilities for the quantum theory of gravity. Probably the biggest success of the second path has been the results of black hole thermodynamics. The subject of this essay is a new, highly promising such result, the application of quasinormal modes in quantum gravity. [ABSTRACT FROM AUTHOR]

Using the quasilocal properties alone we show that the area spectrum of a black hole horizon must be discrete, independent of any specific quantum theory of gravity. The area spectrum is found to be half-integer spaced with values 8πγℓ²pj where j∈N/2. We argue that if microstate counting is carried out for quantum states residing on the horizon only, correction of exp(-A/4ℓ²p) over the Bekenstein-Hawking area law must arise in black hole entropy. [ABSTRACT FROM AUTHOR]

It is argued that, using the black hole area entropy law together with the Boltzmann-Gibbs statistical mechanics and the quasinormal modes of the black holes, it is possible to determine univocally the lowest possible value for the spin j in the context of the Loop Quantum Gravity theory which is j m i n = 1. Consequently, the value of Immirzi parameter is given by γ = ln ⁡ 3 / (2 π 2). In this paper, we have shown that if we use Tsallis microcanonical entropy rather than Boltzmann-Gibbs framework then the minimum value of the label j depends on the nonextensive q -parameter and may have values other than j m i n = 1. [ABSTRACT FROM AUTHOR]

Critical gravity is a quadratic curvature gravity in four dimensions which is ghost-free around the AdS background. Constructing a Vaidya-type exact solution, we show that the area of a black hole defined by a future outer trapping horizon can shrink by injecting a charged null fluid with positive energy density, so that a black hole is no more a one-way membrane even under the null energy condition. In addition, the solution shows that the Wald-Kodama dynamical entropy of a black hole is negative and can decrease. These properties expose the pathological aspects of critical gravity at the non-perturbative level. [ABSTRACT FROM AUTHOR]

Most calculations of black hole entropy in loop quantum gravity indicate a term proportional to the area eigenvalue A with a correction involving the logarithm of A. This violates the additivity of the entropy. An entropy proportional to A, with a correction term involving the logarithm of the classical area k, which is consistent with the additivity of entropy, is derived in both U(1) and SU(2) formulations. [ABSTRACT FROM AUTHOR]