We investigate a possibility of realizing the entropic force into the cosmology. A main issue is how the holographic screen is implemented in the Newtonian cosmology. Contrary to the relativistic realization of Friedmann equations, we do not clarify the connection between Newtonian cosmology and entropic force because there is no way of implementing the holographic screen in the Newtonian cosmology.
We use the ideas of entropic gravity to derive the FRW cosmological model and show that for late time evolution we have an effective cosmological constant. By using the first law of thermodynamics and the modified entropy area relationship derived from the supersymmetric Wheeler-DeWitt equation of the Schwarzschild black hole, we obtain modifications to the Friedmann equations that in the late time regime gives an effective positive cosmological constant. Therefore, this simple model can account for the dark energy component of the universe by providing an entropic origin to the cosmological c…
In this study, we investigate the effects of the one and two-parameters deformed systems on the Friedmann equations of the Friedmann-Robertson-Walker (FRW) universe in the context of the entropic gravity approach. We give simplified forms for the deformed Unruh temperature and Einstein field equations for three different deformed systems. Based on these compact equations, we derive the Friedmann equations with the effective gravitational and cosmological constant.
We study the relation between entropy and Action Complexity (AC) for various examples of cosmological singularities in General Relativity. The complexity is defined with respect to the causal domain of dependence of the singular set, and the entropy is evaluated on the boundary of the same causal domain. We find that, contrary to the situation for black hole singularities, the complexity growth near the singularity is controlled by the dynamics of the entropy $S$, with a characteristic linear relation. This formula is found to apply to singularities with vanishing entropy as well as those with…
In this paper, we consider $(n+1)$-dimensional topological dilaton de Sitter black holes with power-Maxwell field as thermodynamic systems. The thermodynamic quantities corresponding to the black hole horizon and the cosmological horizon respectively are interrelated. So the total entropy of the space-time should be the sum of the entropies of the black hole horizon and the cosmological horizon plus a corrected term which is produced by the association of the two horizons. We analyze the entropic force produced by the corrected term at given temperatures, which is affected by parameters and di…
It is an old idea to realize Einstein's equations as a thermodynamical equation of state. Since then, there has been new conjectures to understand gravity from another point of view. In this way we can accept that the gravitational field is not an underlying one like an emergent force from other approaches based on the knowledge of relativity, quantum and black holes thermodynamics, and different statistical formalisms. One important question concerning this gravity/thermostatistics correspondence is whether the holographic screen could be well defined for a nonrelativistic case of a source ma…
Entropy applications in cosmology: spacetime thermodynamics, holographic dark energy, entropic gravity and beyond - a review
National Observatory of Athens（雅典国家天文台）；University of Science and Technology of China（中国科学技术大学）；Universidad Católica del Norte（北方天主教大学）；University of Lleida（莱里达大学）；University of Patras（帕特雷大学）；Perimeter Institute for Theoretical Physics（理论物理前沿研究所）；University of Waterloo（滑铁卢大学）
Inhomogeneous cosmological models such as the Stephani universes could, in principle, provide an explanation for the observed accelerated expansion of the Universe. Working with a concrete, popular model of the Stephani cosmology -- the Stephani-Dabrowski model, we found that it is entropically viable. We also comment on the energy conditions and the two-sheeted geometry of the spacetime. However, similar to the LTB models, despite satisfying the holographic principle, Stephani cosmology has difficulty satisfying all the constraints from observations.
In this paper, thermodynamic properties of the Reissner-Nordström-de Sitter (RN-dS) black hole have been studied on the basis of the correlation between the black hole and cosmological horizons. It is found that the RN-dS black hole experiences a phase transition, when its state parameters satisfy certain conditions. From the analysis of the interaction between two horizons in RN-dS spacetime, we get the numerical solution of the interaction between two horizons. It makes us to realize the force between the black hole and cosmological horizons, which can be regarded as a candidate to explain o…
We rediscuss the main Cosmological Problems as illusions originated from our ignorance of the hidden information holographically stored in {\it vacuo}. The Cosmological vacuum state is full of a large number of dynamical quantum hairs, dubbed {\it hairons}, which dominate the Cosmological Entropy. We elaborate on the Cosmological Constant (CC) problem, in both the dynamical and time-constant possibilities. We show that all dangerous quantum mixings between the CC and the Planck energy scales are exponentially suppressed as an entropic collective effect of the hairon environment. As a consequen…
In this study, we investigate the effect of the generalized uncertainty principle on the $Λ$CDM cosmological model. Using quantum corrected Unruh effect and Verlinde's entropic gravity idea, we find Planck-scale corrected Friedmann equations with a cosmological constant. These results modify the $Λ$CDM cosmology.
New modified cosmology from a new generalized entropy
Universidad de Lleida（莱里达大学）；National Observatory of Athens（雅典国家天文台）；University of Science and Technology of China（中国科学技术大学）；Universidad Católica del Norte（天主教主教大学）
It is well known that de Sitter(dS) black holes generally have a black hole horizon and a cosmological horizon, both of which have Hawking radiation. But the radiation temperature of the two horizons is generally different, so dS black holes do not meet the requirements of thermal equilibrium stability, which brings certain difficulties to the study of the thermodynamic characteristics of black holes. In this paper, dS black hole is regarded as a thermodynamic system, and the effective thermodynamic quantities of the system are obtained. The influence of various state parameters on the effecti…
We explore the cosmological implications of quantum entanglement between two causally disconnected universes in the multiverse. We first consider two causally separated de Sitter spaces with a state which is initially entangled. We derive the reduced density matrix of our universe and compute the spectrum of vacuum fluctuations. We then consider the same system with an initially non-entangled state. We find that scale dependent modulations may enter the spectrum for the case of initially non-entangled state due to quantum interference. This gives rise to the possibility that the existence of c…
We formulate the basic framework of thermodynamical entropic force cosmology which allows variation of the gravitational constant $G$ and the speed of light $c$. Three different approaches to the formulation of the field equations are presented. Some cosmological solutions for each framework are given and one of them is tested against combined observational data (supernovae, BAO, and CMB). From the fit of the data it is found that the Hawking temperature numerical coefficient $γ$ is two to four orders of magnitude less than usually assumed on the geometrical ground theoretical value of $O(1)$ …
In this study, we investigate the influences of fermionic $q$-deformation on the Einstein equations by taking into account of Verlinde's entropic gravity approach and Strominger's proposal on quantum black holes. According to Verlinde's proposal, gravity is interpreted as an entropic force. Moreover, Strominger's suggetion claims that extremal black holes obey deformed statistics instead of the standard Bose or Fermi statistics. Inspired by Verlinde's and Strominger's suggestions, we represent some thermostatistical functions of VPJC-type $q$-deformed fermion gas model for the high-temperature…
Holographic dark energy from a new two-parameter entropic functional
Universidad de Lleida（莱里达大学）；National Observatory of Athens（雅典国家天文台）；Universidad Católica del Norte（北天主教大学）；University of Science and Technology of China（中国科学技术大学）
A modified Born-Infeld gravitation theory with a $f\left(R\right)$ function being added to the determinant action is analyzed from a cosmological viewpoint. The corresponding accelerating dynamics are studied in a simplified conformal approach without matter. Three different structures for the auxiliary metric function are analyzed, with the aim to establish a deeper understanding of the role of this function in cosmology. After performing the analysis, it is seen that, by modifying the auxiliary metric function, a Big Rip singularity or either a Little Rip dark energy model may arise.
Signature change at high density has been obtained as a possible consequence of deformed space-time structures in models of loop quantum gravity. This article provides a conceptual discussion of implications for cosmological scenarios, based on an application of mathematical results for mixed-type partial differential equations (the Tricomi problem). While the effective equations from which signature change has been derived are shown to be locally regular and therefore reliable, the underlying theory of loop quantum gravity may face several global problems in its semiclassical solutions.
ACT-DR6 consistent inflation in generalised entropic cosmology and $f(Q)$ gravity
Shanghai Jiao Tong University（上海交通大学）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构）；Nagoya University（名古屋大学）；Institució Catalana de Recerca i Estudis Avançats (ICREA)（加泰罗尼亚研究与高等研究学院）
