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We have critically compared different approaches to the cosmological constant problem, which is at the edge of elementary particle physics and cosmology. This problem is deeply connected with the difficulties formulating a theory of quantum…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Stefan Nobbenhuis

We study a symmetry, schematically Energy -> - Energy, which suppresses matter contributions to the cosmological constant. The requisite negative energy fluctuations are identified with a "ghost" copy of the Standard Model. Gravity…

High Energy Physics - Theory · Physics 2009-11-11 David E. Kaplan , Raman Sundrum

Cosmological perturbations in an expanding universe back-react on the space-time in which they propagate. Calculations to lowest non-vanishing order in perturbation theory indicate that super-Hubble-scale fluctuations act as a negative and…

High Energy Physics - Theory · Physics 2007-05-23 Robert H. Brandenberger , C. S. Lam

As we showed in a preceding arXiv:gr-qc Einstein equations, conveniently written, provide the more orthodox and simple description of cosmological models with a time dependent speed of light $c$. We derive here the concomitant dependence of…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Ll. Bel

The paper aims to provide an explanation for the tiny value of the cosmological constant and the low vacuum energy density to represent the dark energy. To accomplish this, we will search for a fundamental principle of symmetry in…

General Relativity and Quantum Cosmology · Physics 2016-11-14 Cláudio Nassif

Possible analogies between vacuum state and quantum fluid provide a model to study vacuum energy density induced by thermal corrections, space-time curvature, boundary conditions and quantum back-reaction. We find that vacuum energy density…

High Energy Physics - Theory · Physics 2012-06-19 J. A. Sanchez-Monroy , C. J. Quimbay

The fundamental constants of electromagnetism, gravity and quantum mechanics can be related empirically by the numerical approximation $\ln(V_e/V_P)\approx \alpha^{-1}$, where $\alpha$ is the low energy value of the electromagnetic fine…

General Physics · Physics 2018-01-31 L. Eaves

We investigate anisotropic fluid cosmology in a situation where the spacetime metric back-reacts in a local, time-dependent way to the presence of inhomogeneities. We derive exact solutions to the Einstein field equations describing…

General Relativity and Quantum Cosmology · Physics 2021-08-25 Mariano Cadoni , Andrea P. Sanna

The purpose of this study is to describe a perfect fluid matter distribution that leads to a constant curvature region, thanks to the effect of a non-minimal coupling. This distribution exhibits a density profile within the range found in…

General Relativity and Quantum Cosmology · Physics 2011-07-04 J. Páramos , O. Bertolami

Within conventional big bang cosmology, it has proven to be very difficult to understand why today's cosmological constant is so small. In this paper, we show that a cyclic model of the universe can naturally incorporate a dynamical…

Astrophysics · Physics 2009-09-01 Paul J. Steinhardt , Neil Turok

It is suggested that the exact value of the cosmological constant could be derived from first principles, based on entanglement of the Standard Model field vacuum with emergent holographic quantum geometry. For the observed value of the…

General Relativity and Quantum Cosmology · Physics 2018-04-03 Craig Hogan

We explore the interplay between three well-established physical principles: QCD confinement, the Third Law of Thermodynamics, and holography, and examine how their combined implications may shed light on several open problems in…

General Relativity and Quantum Cosmology · Physics 2025-07-31 Malak Ali , Ahmed Farag Ali

We analyze the spectrum of time observable in noncommutative cosmological model introduced in [5], defined by $(\rho, s=\frac 12)\,$ representation of the de Sitter group. We find that time has peculiar property: it is not self-adjoint, but…

High Energy Physics - Theory · Physics 2019-07-31 Maja Buric , Dusko Latas

The fundamental laws of physics are required to be invariant under local spatial scale change. In 3-dimensional space, this leads to a variation in Planck constant \hbar and speed of light c. They vary as \hbar ~ a^(1/2) and c ~ a^(-1/2), a…

General Physics · Physics 2013-02-28 Hoang K. Nguyen

We derive necessary density conditions for sampling and for interpolation in general reproducing kernel Hilbert spaces satisfying some natural conditions on the geometry of the space and the reproducing kernel. If the volume of shells is…

Functional Analysis · Mathematics 2018-04-03 Hartmut Führ , Karlheinz Gröchenig , Antti Haimi , Andreas Klotz , José Luis Romero

The standard formulation of the cosmological constant problem is based on one critical assumption---the spacetime is homogeneous and isotropic, which is true only on cosmological scales. However, this problem is caused by extremely small…

General Relativity and Quantum Cosmology · Physics 2020-08-05 Qingdi Wang

Starting from generic quantum effects at the Planck scale M_P, we find that the renormalization group running of the cosmological constant (CC) at low energies is possible if there is a smooth decoupling of all massive particles from M_P to…

High Energy Physics - Phenomenology · Physics 2009-11-10 Ilya L. Shapiro , Joan Sola

Suppose the usual description of spacetime as a 4-dimensional manifold with a Lorentzian metric breaks down at Planck energies. Can we still construct sensible theoretical models of the universe? Are they testable? Do they lead to a…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Fotini Markopoulou

A new perspective on the Cosmological Constant Problem (CCP) is proposed and discussed within the multiverse approach of Quantum Cosmology. It is assumed that each member of the ensemble of universes has a characteristic scale $a$ that can…

General Relativity and Quantum Cosmology · Physics 2020-09-09 Vesselin G. Gueorguiev , Andre Maeder

The current observations seem to suggest that the universe has a positive cosmological constant of the order of $H_0^2$ while the most natural value for the cosmological constant will be $L_P^{-2}$ where $L_P = (G\hbar/c^3)^{1/2}$ is the…

General Relativity and Quantum Cosmology · Physics 2009-11-07 T. Padmanabhan