INFLATION, QUINTESSENCE PROBLEM AND VARYING SPEED OF LIGHT

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.

Heuristic determination of the cosmological constant

Modern Physics Letters A ◽

10.1142/s0217732321501145 ◽

2021 ◽

pp. 2150114

Author(s):

Manuel Urueña Palomo ◽

Fernando Pérez Lara

Keyword(s):

Field Theory ◽

Energy Density ◽

Cosmological Constant ◽

Accelerated Expansion ◽

Fundamental Constants ◽

Quantum Field ◽

Brute Force ◽

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

THE POINCARÉ CONJECTURE AND THE COSMOLOGICAL CONSTANT

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194511001280 ◽

2011 ◽

Vol 03 ◽

pp. 195-202

Author(s):

M. D. MAIA

Keyword(s):

Cosmological Constant ◽

Riemannian Geometry ◽

Extrinsic Curvature ◽

Space Time ◽

Local Change ◽

Accelerated Expansion ◽

Observable Effect ◽

Cosmological Constant Problem ◽

The concept of deformation of Riemannian geometry is reviewed, with applications to gravitation and cosmology. Starting with an analysis of the cosmological constant problem, it is shown that space-times are deformable in the sense of local change of shape. These deformations leave an observable signature in the space-time, characterized by a conserved tensor, associated with a tangent acceleration, defined by the extrinsic curvature of the space-time. In the applications to cosmology, we find that the accelerated expansion of the universe is the observable effect of the deformation, dispensing with the cosmological constant and its problems.

DELTA GRAVITY AND THE ACCELERATED EXPANSION OF THE UNIVERSE

International Journal of Modern Physics E ◽

10.1142/s0218301311040086 ◽

2011 ◽

Vol 20 (supp01) ◽

pp. 65-72

Author(s):

JORGE ALFARO

Keyword(s):

General Relativity ◽

Gravitational Field ◽

Cosmological Constant ◽

Equivalence Principle ◽

Equations Of Motion ◽

Accelerated Expansion ◽

Symmetric Tensors ◽

Test Particles ◽

We study a model of the gravitational field based on two symmetric tensors. The equations of motion of test particles are derived. We explain how the Equivalence principle is recovered. Outside matter, the predictions of the model coincide exactly with General Relativity, so all classical tests are satisfied. In Cosmology, we get accelerated expansion without a cosmological constant.

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

The Super-Stückelberg procedure and dS in pure supergravity

10.1098/rspa.2020.0035 ◽

2020 ◽

Vol 476 (2237) ◽

pp. 20200035 ◽

Cited By ~ 1

Author(s):

Silvia Nagy ◽

Antonio Padilla ◽

Ivonne Zavala

Keyword(s):

Cosmological Constant ◽

Vacuum Expectation ◽

Vacuum Expectation Value ◽

Accelerated Expansion ◽

Spontaneous Breaking ◽

De Sitter ◽

Expectation Value ◽

The Universe ◽

Natural Way

Understanding de Sitter space in supergravity—and string theory—has led to an intense amount of work for more than two decades, largely motivated by the discovery of the accelerated expansion of the Universe in 1998. In this paper, we consider a non-trivial generalization of unimodular gravity to minimal N = 1 supergravity, which allows for de Sitter solutions without the need of introducing any matter. We formulate a superspace version of the Stückelberg procedure, which restores diffeomorphism and local supersymmetry invariance. This introduces the goldstino associated with spontaneous breaking of supersymmetry in a natural way. The cosmological constant and gravitino mass are related to the vacuum expectation value of the components of a Lagrange multiplier imposing a super-unimodularity condition.

THE POINCARÉ CONJECTURE AND THE COSMOLOGICAL CONSTANT

International Journal of Modern Physics A ◽

10.1142/s0217751x11054279 ◽

2011 ◽

Vol 26 (22) ◽

pp. 3813-3820 ◽

Cited By ~ 4

Author(s):

M. D. MAIA

Keyword(s):

Cosmological Constant ◽

Riemannian Geometry ◽

Extrinsic Curvature ◽

Space Time ◽

Local Change ◽

Accelerated Expansion ◽

Observable Effect ◽

Cosmological Constant Problem ◽

The concept of deformation of Riemannian geometry is reviewed, with applications to gravitation and cosmology. Starting with an analysis of the cosmological constant problem, it is shown that space-times are deformable in the sense of local change of shape. These deformations leave an observable signature in the space-time, characterized by a conserved tensor, associated with a tangent acceleration, defined by the extrinsic curvature of the space-time. In the applications to cosmology, we find that the accelerated expansion of the universe is the observable effect of the deformation, dispensing with the cosmological constant and its problems.

Dark Energy and Cosmological Constant

Mapana Journal of Sciences ◽

10.12723/mjs.44.3 ◽

2018 ◽

Vol 17 (1) ◽

pp. 25-32

Author(s):

Louise Rebecca ◽

C Sivaram ◽

Kenath Arun

Keyword(s):

Dark Energy ◽

Cosmological Constant ◽

Mass Density ◽

Critical Density ◽

Accelerated Expansion ◽

Microwave Background ◽

Type Ia ◽

Ia Supernovae ◽

One of the unresolved problems in cosmology is that the measured mass density of the universe has revealed a value that was about 30% of the critical density. Since the universe is very nearly spatially flat, as is indicated by measurements of the cosmic microwave background, about 70% of the energy density of the universe was left unaccounted for. Another observation seems to be connected to this mystery. Generally one would expect the rate of expansion to slow down once the universe started expanding. The measurements of Type Ia supernovae have revealed that the expansion of the universe is actually accelerating. This accelerated expansion is attributed to the so-called dark energy (DE).Here we give a brief overview on the observational basis for DE hypothesis and how cosmological constant, initially proposed by Einstein to obtain a static universe, can play the role of dark energy.

Accelerated expansion induced by Dark Matter with two charges

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slab103 ◽

2021 ◽

Author(s):

Steen H Hansen

Keyword(s):

Dark Matter ◽

Cosmological Constant ◽

Accelerated Expansion ◽

Microwave Background ◽

Dynamic Variations ◽

Acceleration Of The Universe ◽

Internal Velocity ◽

The Universe ◽

Range Force

Abstract The accelerated expansion of the universe has been established through observations of supernovae, the growth of structure, and the cosmic microwave background. The most popular explanation is Einsteins cosmological constant, or dynamic variations hereof. A recent paper demonstrated that if dark matter particles are endowed with a repulsive force proportional to the internal velocity dispersion of galaxies, then the corresponding acceleration of the universe may follow that of a cosmological constant fairly closely. However, no such long-range force is known to exist. A concrete example of such a force is derived here, by equipping the dark matter particles with two new dark charges. This result lends support to the possibility that the current acceleration of the universe may be explained without the need for a cosmological constant.

Revolutionary Approach for Fusion of the Classic, Relativity and Quantum field Theories: Sayed’s Acceleration Equation and Probable Violation of E=mc2

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v19i.9048 ◽

2021 ◽

Vol 19 ◽

pp. 134-141

Author(s):

Sayed A. El-Mongy

Keyword(s):

Cosmological Constant ◽

Planck Scale ◽

Accelerated Expansion ◽

Vacuum Energy Density ◽

Quantum Field Theories ◽

Quantum Field ◽

Field Equations ◽

Atom Nucleus ◽

Expansion of the universe is a divine fact in the glorious Quran. The accelerated expansion of the universe is one of the physics mysteries and challenges. This article is a try to find an answer to this ambiguity. A simple fusion and merging of the Newton, Einstein and quantum field equations were carried out to clarify this topic. Innovative equations correlating the acceleration (As), cosmological constant (Ʌ), vacuum energy density (ρ) and distance (d) was deduced. It can be concluded that Sayed`s acceleration constant (As) is proportional to (Ʌ/ρ), (1/8mc2) and (1/πd2). The derivative equation reveals a probable violation of the mass-energy formula (E= mc2); the speed of light might be 12.5% more. This disparity may be due to antimatter contribution; neutrino-antineutrino, β-β+ annihilation and/or a predicted unrecognized very light particle in the atom nucleus. The Sayed`s acceleration constant (As) and (As/Ʌ) ratio were calculated and found to be 6.33825x10-8 m/s2 and 5.7620475x10+44 m3/s2 respectively. Using Sayed`s equations, the calculated acceleration in planck scale is matched with the declared 5.56081x1051 m/s2 value. The The calculated recession velocity at 1 Mpc was found to be 6.5192677 x 108 m/s .and the cosmological constant (Ʌ) is as measured;~1.1x10-52 m-2

Harnessing Dark Energy in Five-dimensional Brans-Dicke Universe

Communications in Physics ◽

10.15625/0868-3166/15782 ◽

2021 ◽

Vol 31 (3) ◽

Author(s):

Kangujam Priyokumar Singh ◽

Koijam Manihar Singh

Keyword(s):

Dark Energy ◽

Cosmological Constant ◽

Accelerated Expansion ◽

Fifth Dimension ◽

Big Rip ◽

New Type ◽

The Universe ◽

Accepted Form

In trying to explain the present accelerated expansion of the universe in the light of a five-dimensional Brans-Dicke theory, it is found that the fifth dimension itself here acts as a source of dark energy. It may be taken as a curvature-induced form of dark energy, in one case of which it behaves similar to that form of dark energy arising out of the cosmological constant which is the most commonly accepted form of dark energy. It is also found that this new type of dark energy is free from big rip singularity and may be taken as a viable form of dark energy which can explain some of physical mysteries of the universe.