Theory of gravity with the Dirac scalar field and the problem of cosmological constant

2012 ◽  
Vol 55 (7) ◽  
pp. 855-857 ◽  
Author(s):  
O. V. Babourova ◽  
K. N. Lipkin ◽  
B. N. Frolov
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Theory Of Gravity

scholarly journals Decaying Cosmological Constant and the Choice of a Conformal Frame

1999 ◽  
Vol 183 ◽  
pp. 310-310
Author(s):  
Yasunori Fujii
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Scalar Tensor Theory ◽  
Nonminimal Coupling ◽  
Tensor Theory ◽  
Theory Of Gravity ◽  
To Come ◽  
Hilbert Action

A solution of the cosomlogical constant problem seems to come from a version of the scalar-tensor theory of gravity, which is characterized by a “nonminimal coupling“ in place of the standard Einstein-Hilbert action, where ɸ is the scalar field while ξ a constant. One then encounters an inherent question never fully answered: How can one single out a right conformai frame?

scholarly journals Decrease of the effective cosmological constant in the Poincare gauge theory of gravity with a scalar field

2021 ◽  
Vol 2081 (1) ◽  
pp. 012015
Author(s):  
O V Babourova ◽  
B N Frolov
Keyword(s):  
Gauge Theory ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Big Bang ◽  
Cosmological Constant Problem ◽  
Effective Cosmological Constant ◽  
Theory Of Gravity ◽  
The Big Bang ◽  
Modern Era ◽  
Gauge Theory Of Gravity

Abstract Cosmological consequences of the Poincare gauge theory of gravity are considered. An effective cosmological constant depending from the Dirac scalar field is introduced. It is proved that at the super-early Universe, the effective cosmological constant decreases exponentially from a huge value at the Big Bang to its extremely small value in the modern era, while the scale factor sharply increases and demonstrates inflationary behavior. This fact solves the well-known “cosmological constant problem” also in the Poincare gauge theory of gravity.

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.

GALACTIC AND ASTROPHYSICAL SIZES FROM SCALAR-TENSOR THEORY OF GRAVITY

2004 ◽  
Vol 13 (02) ◽  
pp. 359-371 ◽  
Author(s):  
GIUSEPPE BASINI ◽  
MARCO RICCI ◽  
FULVIO BONGIORNO ◽  
SALVATORE CAPOZZIELLO
Keyword(s):  
Scalar Field ◽  
Spiral Galaxies ◽  
Weak Field ◽  
Newtonian Potential ◽  
Scalar Tensor Theory ◽  
Field Limit ◽  
Weak Field Limit ◽  
Tensor Theory ◽  
Flat Rotation Curves ◽  
Theory Of Gravity

We investigate the weak-field limit of scalar-tensor theory of gravity and show that results are directly depending on the coupling and self-interaction potential of the scalar field. In particular, corrections are derived for the Newtonian potential. We discuss astrophysical applications of the results, in particular the flat rotation curves of spiral galaxies.

scholarly journals Cosmological constant in chameleon Brans–Dicke theory

2019 ◽  
Vol 28 (01) ◽  
pp. 1950022 ◽  
Author(s):  
Yousef Bisabr
Keyword(s):  
Exact Solution ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Exact Solutions ◽  
Effective Mass ◽  
Potential Function ◽  
Power Law ◽  
Exponential Form ◽  
First Case ◽  
Different Types

We consider a generalized Brans–Dicke model in which the scalar field has a self-interacting potential function. The scalar field is also allowed to couple nonminimally with the matter part. We assume that it has a chameleon behavior in the sense that it acquires a density-dependent effective mass. We consider two different types of matter systems which couple with the chameleon, dust and vacuum. In the first case, we find a set of exact solutions when the potential has an exponential form. In the second case, we find a power-law exact solution for the scale factor. In this case, we will show that the vacuum density decays during expansion due to coupling with the chameleon.

SAVING THE MECHANISM OF A DECAYING COSMOLOGICAL CONSTANT

1989 ◽  
Vol 04 (06) ◽  
pp. 513-518 ◽  
Author(s):  
YASUNORI FUJII
Keyword(s):  
Scalar Field ◽  
Simple Model ◽  
Cosmological Constant ◽  
Gravitational Constant ◽  
Atomic Clock ◽  
Fifth Force

The mechanism of a decaying cosmological constant in terms of a scalar field has been criticized for its ensuing diminishment of the gravitational constant with time. Contrary to a naive view, however, the physical results can be made fully nontrivial, as demonstrated explicitly by a simple model in which the scalar field generates particle masses that increase with time, but in such a way that the gravitational constant stays constant asymptotically when time is measured by an atomic clock. The scalar field might also be an origin of the fifth force.

scholarly journals The Effect of a Positive Cosmological Constant on the Bounce of Loop Quantum Cosmology

Mathematics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 186
Author(s):  
Mercedes Martín-Benito ◽  
Rita B. Neves
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Quantum Cosmology ◽  
Quantum Dynamics ◽  
Solvable Model ◽  
Massless Scalar ◽  
Loop Quantum Cosmology ◽  
Massless Scalar Field ◽  
Positive Cosmological Constant ◽  
Semiclassical States

We provide an analytical solution to the quantum dynamics of a flat Friedmann-Lemaître- Robertson-Walker model with a massless scalar field in the presence of a small and positive cosmological constant, in the context of Loop Quantum Cosmology. We use a perturbative treatment with respect to the model without a cosmological constant, which is exactly solvable. Our solution is approximate, but it is precisely valid at the high curvature regime where quantum gravity corrections are important. We compute explicitly the evolution of the expectation value of the volume. For semiclassical states characterized by a Gaussian spectral profile, the introduction of a positive cosmological constant displaces the bounce of the solvable model to lower volumes and to higher values of the scalar field. These displacements are state dependent, and in particular, they depend on the peak of the Gaussian profile, which measures the momentum of the scalar field. Moreover, for those semiclassical states, the bounce remains symmetric, as in the vanishing cosmological constant case. However, we show that the behavior of the volume is more intricate for generic states, leading in general to a non-symmetric bounce.

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