Cosmological constant

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Vacuum Fluctuations ◽  
Present Epoch ◽  
Modify Gravity ◽  
Expansion Of The Universe ◽  
The Universe

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.

New Limits on a Cosmological Constant from Statistics of Gravitational Lensing

1999 ◽  
Vol 510 (1) ◽  
pp. 42-53 ◽  
Author(s):  
Masashi Chiba ◽  
Yuzuru Yoshii
Keyword(s):  
Cosmological Constant ◽  
Gravitational Lensing

scholarly journals Neutral signature gauged supergravity solutions

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
J. Gutowski ◽  
W. A. Sabra
Keyword(s):  
Cosmological Constant ◽  
Geometric Structure ◽  
Base Space ◽  
Killing Spinor ◽  
Positive Cosmological Constant ◽  
3 Dimensional

Abstract We classify all supersymmetric solutions of minimal D = 4 gauged supergravity with (2) signature and a positive cosmological constant which admit exactly one Killing spinor. This classification produces a geometric structure which is more general than that found for previous classifications of N = 2 supersymmetric solutions of this theory. We illustrate how the N = 2 solutions which consist of a fibration over a 3-dimensional Lorentzian Gauduchon-Tod base space can be written in terms of this more generic geometric structure.

scholarly journals Bootstrapped Newtonian Cosmology and the Cosmological Constant Problem

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 358
Author(s):  
Roberto Casadio ◽  
Andrea Giusti
Keyword(s):  
Black Holes ◽  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Quantum Physics ◽  
Gravitational Interaction ◽  
Newtonian Gravity ◽  
Cosmological Constant Problem ◽  
Newtonian Cosmology ◽  
Natural Solution ◽  
The Impact

Bootstrapped Newtonian gravity was developed with the purpose of estimating the impact of quantum physics in the nonlinear regime of the gravitational interaction, akin to corpuscular models of black holes and inflation. In this work, we set the ground for extending the bootstrapped Newtonian picture to cosmological spaces. We further discuss how such models of quantum cosmology can lead to a natural solution to the cosmological constant problem.

scholarly journals Constraining the Swiss-Cheese IR-Fixed Point Cosmology with Cosmic Expansion

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 263
Author(s):  
Ayan Mitra ◽  
Vasilios Zarikas ◽  
Alfio Bonanno ◽  
Michael Good ◽  
Ertan Güdekli
Keyword(s):  
Fixed Point ◽  
Cosmological Constant ◽  
Cosmic Acceleration ◽  
Fine Tuning ◽  
Clusters Of Galaxies ◽  
Swiss Cheese ◽  
Coincidence Problem ◽  
Cosmological Expansion ◽  
Cosmic Evolution ◽  
Previous Assumption

A recent work proposed that the recent cosmic passage to a cosmic acceleration era is the result of the existence of small anti-gravity sources in each galaxy and clusters of galaxies. In particular, a Swiss-cheese cosmology model, which relativistically integrates the contribution of all these anti-gravity sources on a galactic scale has been constructed assuming the presence of an infrared fixed point for a scale dependent cosmological constant. The derived cosmological expansion provides an explanation for both the fine tuning and the coincidence problem. The present work relaxes the previous assumption on the running of the cosmological constant and allows for a generic scaling around the infrared fixed point. Our analysis reveals that, in order to produce a cosmic evolution consistent with the best ΛCDM model, the IR-running of the cosmological constant is consistent with the presence of an IR-fixed point.

scholarly journals Corners of gravity: the case of gravity as a constrained BF theory

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Remigiusz Durka ◽  
Jerzy Kowalski-Glikman
Keyword(s):  
Cosmological Constant ◽  
Boundary Structure ◽  
Schwarzschild Solution ◽  
Bf Theory ◽  
Theory Of Gravity

Abstract Following recent works on corner charges we investigate the boundary structure in the case of the theory of gravity formulated as a constrained BF theory. This allows us not only to introduce the cosmological constant, but also explore the influence of the topological terms present in the action of this theory. Established formulas for charges resemble previously obtained ones, but we show that they are affected by the presence of the cosmological constant and topological terms. As an example we discuss the charges in the case of the AdS-Schwarzschild solution and we find that the charges give correct values.

scholarly journals MEASUREMENTS AND INFORMATION IN SPIN FOAM MODELS

2012 ◽  
Vol 27 (28) ◽  
pp. 1250164
Author(s):  
J. MANUEL GARCÍA-ISLAS
Keyword(s):  
Information Theory ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Shannon Entropy ◽  
Three Dimensional ◽  
Spin Network ◽  
Spin Foam Models ◽  
Foam Model ◽  
Spin Foam Model ◽  
Spin Foam

In the three-dimensional spin foam model of quantum gravity with a cosmological constant, there exists a set of observables associated with spin network graphs. A set of probabilities is calculated from these observables, and hence the associated Shannon entropy can be defined. We present the Shannon entropy associated with these observables and find some interesting bounded inequalities. The problem relates measurements, entropy and information theory in a simple way which we explain.

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