scholarly journals Scalar-tensor theory with Lagrange multipliers: A way of understanding the cosmological constant problem, and future singularities

2012 ◽  
Vol 85 (2) ◽  
Author(s):  
Diego Sáez-Gómez
Keyword(s):  
Cosmological Constant ◽  
Lagrange Multipliers ◽  
Scalar Tensor Theory ◽  
Cosmological Constant Problem ◽  
Tensor Theory

scholarly journals Study of Antigravity in an F(R) Model and in Brans-Dicke Theory with Cosmological Constant

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
V. K. Oikonomou ◽  
N. Karagiannakis
Keyword(s):  
Cosmological Constant ◽  
Lagrange Multipliers ◽  
Gravitational Constant ◽  
Time Dependent ◽  
Jordan Frame ◽  
Scalar Tensor Theory ◽  
Initial Model ◽  
Tensor Theory ◽  
Multipliers Method ◽  
Dicke Model

We study antigravity, that is, having an effective gravitational constant with a negative sign, in scalar-tensor theories originating from F(R) theory and in a Brans-Dicke model with cosmological constant. For the F(R) theory case, we obtain the antigravity scalar-tensor theory in the Jordan frame by using a variant of the Lagrange multipliers method and we numerically study the time dependent effective gravitational constant. As we will demonstrate by using a specific F(R) model, although there is no antigravity in the initial model, it might occur or not in the scalar-tensor counterpart, mainly depending on the parameter that characterizes antigravity. Similar results hold true in the Brans-Dicke model.

scholarly journals Extremal Cosmological Black Holes in Horndeski Gravity and the Anti-Evaporation Regime

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 210
Author(s):  
Ismael Ayuso ◽  
Diego Sáez-Chillón Gómez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmological Constant ◽  
Linear Order ◽  
Scalar Tensor Theory ◽  
De Sitter ◽  
Tensor Theory ◽  
Effective Cosmological Constant ◽  
Cosmological Black Holes ◽  
Extremal Black Holes

Extremal cosmological black holes are analysed in the framework of the most general second order scalar-tensor theory, the so-called Horndeski gravity. Such extremal black holes are a particular case of Schwarzschild-De Sitter black holes that arises when the black hole horizon and the cosmological one coincide. Such metric is induced by a particular value of the effective cosmological constant and is known as Nariai spacetime. The existence of this type of solutions is studied when considering the Horndeski Lagrangian and its stability is analysed, where the so-called anti-evaporation regime is studied. Contrary to other frameworks, the radius of the horizon remains stable for some cases of the Horndeski Lagrangian when considering perturbations at linear order.

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 GENERALIZED SCALAR–TENSOR THEORY AND THE COSMIC ACCELERATION

2009 ◽  
Vol 18 (03) ◽  
pp. 445-451 ◽  
Author(s):  
NARAYAN BANERJEE ◽  
KOYEL GANGULY
Keyword(s):  
Cosmological Constant ◽  
Functional Form ◽  
Cosmic Acceleration ◽  
Smooth Transition ◽  
Scalar Tensor Theory ◽  
Tensor Theory ◽  
Quintessence Field

In this paper it is shown that a simple functional form of ω(ϕ) in a generalized scalar–tensor theory can drive the present cosmic acceleration without any quintessence field or the cosmological constant Λ. Furthermore, it ensures a smooth transition from a decelerated to an accelerated phase of expansion in the matter-dominated regime.

A brief note on the limit ω →∞ in Weyl geometrical scalar–tensor theory

2021 ◽  
Author(s):  
A. Barros ◽  
C. Romero
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Tensor Theory ◽  
Vacuum Solutions ◽  
Working Out

We obtain vacuum solutions in the presence of a cosmological constant in the context of the Weyl geometrical scalar–tensor theory. We investigate the limit when [Formula: see text] goes to infinity and show by working out the solutions that in this limit there are some cases in which the scalar field tends to a constant (with the implicit consequence of the geometry becoming Riemannian), although the solutions do not reduce to the corresponding Einstein solutions. We have also extended a previous result, known in the literature, by showing that in the case of vacuum with cosmological constant the field equations of the Weyl geometrical scalar–tensor theory are formally identical to Brans–Dicke field equations, even though these theories are not physically equivalent.

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.

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