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Quantum gravity places entirely new challenges on the formulation of a consistent theory as well as on an extraction of potentially observable effects. Quantum corrections due to the gravitational field are commonly expected to be tiny…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Martin Bojowald

We consider further consequences of recently [1] revealed role of cosmological constant \Lambda as of a physical constant, along with the gravitational one to define the gravity i.e. the General Relativity and its low-energy limit. We now…

General Physics · Physics 2019-03-13 V. G. Gurzadyan , A. Stepanian

We consider cosmological consequences of a conformal-invariant unified theory which is dynamically equivalent to general relativity and is given in a space with the geometry of similarity. We show that the conformal-invariant theory offers…

General Relativity and Quantum Cosmology · Physics 2007-05-23 D. Behnke , D. Blaschke , V. Pervushin , D. Proskurin , A. Zakharov

After a short history of the $\Lambda$-term it is explained why the (effective) cosmological constant is expected to obtain contributions from short-distance physics, corresponding to an energy at least as large as the Fermi scale. The…

Astrophysics · Physics 2007-05-23 Norbert Straumann

In a quest to explain the small value of the today's cosmological constant, following the approach introduced in [1], we show that the theoretical value of cosmological constant is consistent with its observational value. In more detail, we…

General Relativity and Quantum Cosmology · Physics 2015-10-08 T. Rostami , S. Jalalzadeh

Unimodular relativity is a theory of gravity and space-time with a fixed absolute space-time volume element, the modulus, which we suppose is proportional to the number of microscopic modules in that volume element. In general relativity an…

General Relativity and Quantum Cosmology · Physics 2009-10-31 David R. Finkelstein , Andrei A. Galiautdinov , James E. Baugh

We show that it is possible to solve the cosmological constant (CC) problem in a discrete quantum gravity theory based on Regge calculus by using the effective action approach and a special path-integral measure. The effective cosmological…

General Relativity and Quantum Cosmology · Physics 2015-06-15 Aleksandar Mikovic , Marko Vojinovic

We propose "conformal supersymmetry breaking" models, which tightly relate the conformal breaking scale (i.e. R-symmetry breaking scale) and the supersymmetry breaking scale. The both scales are originated from the constant term in the…

High Energy Physics - Theory · Physics 2008-11-26 M. Ibe , Y. Nakayama , T. T. Yanagida

We show that the cosmological constant appears as a Lagrange multiplier if nature is described by a canonical noncommutative spacetime. It is thus an arbitrary parameter unrelated to the action and thus to vacuum fluctuations. The…

High Energy Physics - Theory · Physics 2008-11-26 Xavier Calmet

We construct a model of conformal gravity with Higgs field. This model has a positive Newton's constant and exhibits a novel symmetry breaking mechanism of gauge symmetries. A possible application to cosmology is briefly mentioned.

General Relativity and Quantum Cosmology · Physics 2015-05-27 Ichiro Oda

The evolution of cosmological large-scale perturbations is described in terms of the concordant model based on the recent discovery of cosmic vacuum. It is demonstrated that the process is robustly controlled by a few epoch-independent…

Astrophysics · Physics 2016-08-30 Arthur D. Chernin

It is argued in a recent letter Phys. Rev. Lett. 123, 131302(2019) that the effect of a large cosmological constant can be naturally hidden in Planck scale curvature fluctuations. We point out that there are problems with the author's…

General Relativity and Quantum Cosmology · Physics 2019-11-26 Qingdi Wang , William G. Unruh

We reconcile seemingly conflicting statements in the literature about the behavior of cosmological solutions in modified theories of gravity where the Einstein-Hilbert Lagrangian for gravity is modified by the addition of a function of the…

Astrophysics · Physics 2008-11-26 Ignacy Sawicki , Wayne Hu

We address issues on the origin of gravity and the cosmological constant problem based on a recent understanding about the correspondence between noncommutative field theory and gravity. We suggest that the cosmological constant problem can…

High Energy Physics - Theory · Physics 2008-03-28 Hyun Seok Yang

In a recent paper (Vigoureux et al. Int. J. Theor. Phys. 47:928, 2007) it has been suggested that the velocity of light and the expansion of the universe are two aspects of one single concept connecting space and time in the expanding…

Cosmology and Nongalactic Astrophysics · Physics 2011-03-22 David Viennot , Jean-Marie Vigoureux

In the present article, which is the first part of a work in three parts, we build an equation of quantum gravity. This equation is tensorial, is equivalent to general relativity in vacuum, but differs completely from general relativity…

General Physics · Physics 2007-11-25 Christophe Real

It was recently suggested that the cosmological constant problem as viewed in a non-perturbative framework is intimately connected to the choice of time and a physical Hamiltonian. We develop this idea further by calculating the…

General Relativity and Quantum Cosmology · Physics 2018-04-05 Syed Moeez Hassan

Unimodular gravity addresses the old cosmological constant (CC) problem, explaining why such constant is not at least as large as the largest particle mass scale, but classically it is indistinguishable from ordinary gravity. Conversely,…

High Energy Physics - Theory · Physics 2024-08-05 Alberto Salvio

It is necessary to make assumptions in order to derive models to be used for cosmological predictions and comparison with observational data. In particular, in standard cosmology the spatial curvature is assumed to be constant and zero (or…

General Relativity and Quantum Cosmology · Physics 2019-05-14 A. A. Coley

We present an unconventional approach for addressing the old cosmological constant (CC) problem in a class of F(R,G) models of modified gravity. For a CC of arbitrary size and sign the corresponding cosmological evolution follows an…

High Energy Physics - Theory · Physics 2010-05-12 Florian Bauer , Joan Sola , Hrvoje Stefancic