Gravitational repulsion in the Einstein-zero-mass scalar theory

1984 ◽  
Vol 62 (7) ◽  
pp. 629-631 ◽  
Author(s):  
K. D. Krori ◽  
J. C. Sarmah ◽  
D. Goswami
Keyword(s):  
Scalar Field ◽  
Recent Work ◽  
Scalar Theory ◽  
Zero Mass ◽  
Gravitational Repulsion ◽  
Particle Velocities

In this paper we extend a recent work by McGruder by investigating gravitational repulsion in the Einstein-zero-mass scalar theory. We notice that in the presence of a scalar field, gravitational repulsion is possible for particle velocities lower than those required in the pure Einstein (Schwarzschild) field. The zero-mass scalar field has acquired particular importance recently because of a suggestion by Weinberg and Wilczek that there should exist a pseudoscalar boson, the so-called axion, of negligible mass. The work of Peccei and Quinn has lent further support to the idea of axions.

Rotational perturbations of Friedmann universes in Einstein zero mass scalar theory

1983 ◽  
Vol 61 (5) ◽  
pp. 744-747 ◽  
Author(s):  
K. D. Krori ◽  
J. C. Sarmah ◽  
D. Goswami
Keyword(s):  
Scalar Field ◽  
Recent Work ◽  
Scalar Boson ◽  
Scalar Theory ◽  
Evolution Of The Universe ◽  
Damping Effect ◽  
Zero Mass ◽  
Pseudo Scalar ◽  
The Universe

In an extension of a recent work by Bayin and Cooperstock, we investigate in this paper rotational perturbations of Friedmann universes in Einstein zero mass scalar theory. We find that except in the case of "perfect dragging", the zero mass scalar field has a damping effect on the rotation of matter. One of the three cases studied here shows that the scalar field may exist only during a certain interval in the course of the evolution of the universe. The zero mass scalar field has acquired particular importance recently because of a suggestion by Weinberg and Wilczek that there should exist a pseudo-scalar boson, the so-called axion, of negligible mass. The work of Peccei and Quinn has lent further support to the idea of axions.

scholarly journals Weak cosmic censorship with self-interacting scalar and bound on charge to mass ratio

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Yan Song ◽  
Tong-Tong Hu ◽  
Yong-Qiang Wang
Keyword(s):  
Scalar Field ◽  
Scalar Fields ◽  
Cosmic Censorship ◽  
Mass Ratio ◽  
Quartic Coupling ◽  
Scalar Theory ◽  
Free Scalar ◽  
The One ◽  
Nonzero Scalar ◽  
Large Charge

Abstract We study the model of four-dimensional Einstein-Maxwell-Λ theory minimally coupled to a massive charged self-interacting scalar field, parameterized by the quartic and hexic couplings, labelled by λ and β, respectively. In the absence of scalar field, there is a class of counterexamples to cosmic censorship. Moreover, we investigate the full nonlinear solution with nonzero scalar field included, and argue that these counterexamples can be removed by assuming charged self-interacting scalar field with sufficiently large charge not lower than a certain bound. In particular, this bound on charge required to preserve cosmic censorship is no longer precisely the weak gravity bound for the free scalar theory. For the quartic coupling, for λ < 0 the bound is below the one for the free scalar fields, whereas for λ > 0 it is above. Meanwhile, for the hexic coupling the bound is always above the one for the free scalar fields, irrespective of the sign of β.

scholarly journals RECONSTRUCTING A STRING-INSPIRED NONMINIMALLY COUPLED QUINTOM MODEL

2009 ◽  
Vol 18 (08) ◽  
pp. 1291-1301 ◽  
Author(s):  
M. R. SETARE ◽  
J. SADEGHI ◽  
A. R. AMANI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
String Theory ◽  
Scalar Curvature ◽  
Recent Work ◽  
Nonminimal Coupling ◽  
Tachyon Field ◽  
Dynamical Dark Energy

Motivated by the recent work of Zhang and Chen,1we generalize their work to the nonminimally coupled case. We consider a quintom model of dark energy with a single scalar field T given by a Lagrangian inspired by a tachyonic Lagrangian in string theory. We consider nonminimal coupling of the tachyon field to the scalar curvature, and then we reconstruct this model in the light of three forms of parametrization for dynamical dark energy.

Causal viscous universe coupled with zero-mass scalar field in higher derivative theory

2011 ◽  
Vol 334 (1) ◽  
pp. 187-191 ◽  
Author(s):  
N. Ibotombi Singh ◽  
S. Surendra Singh ◽  
S. Romaleima Devi
Keyword(s):  
Scalar Field ◽  
Zero Mass ◽  
Higher Derivative

scholarly journals A smooth constant-roll to a slow-roll modular inflation transition

2018 ◽  
Vol 27 (02) ◽  
pp. 1850009 ◽  
Author(s):  
V. K. Oikonomou
Keyword(s):  
Field Theory ◽  
Scalar Field ◽  
Dynamical Evolution ◽  
Smooth Transition ◽  
The Novel ◽  
Scalar Theory ◽  
Stability Properties ◽  
Slow Roll ◽  
Stable Attractor ◽  
The Stability

In this work, we investigate how a smooth transition from a constant-roll to a slow-roll inflationary era may be realized in the context of a canonical scalar field theory. We study in some detail the dynamical evolution of the cosmological system, and we investigate whether a stable attractor exists, both numerically and analytically. We also investigate the slow-roll era and as we demonstrate, the partially compatibility of the resulting scalar theory may be achieved with the potential of the latter belonging to a class of modular inflationary potentials. The novel features of the constant-roll to slow-roll transition which we achieved are firstly that it is not compelling for the slow-roll era to last for [Formula: see text]–60 [Formula: see text]-foldings, but it may last for a smaller number of [Formula: see text]-foldings, since some [Formula: see text]-foldings may occur during the constant-roll era. Secondly, when the slow-roll era occurs after the constant-roll era, the graceful exit from inflation may occur, a feature absent in the constant-roll scenario, due to the stability properties of the final attractor in the constant-roll case.

Braneworld mimetic f(R) gravity

2019 ◽  
Vol 16 (03) ◽  
pp. 1950042 ◽  
Author(s):  
Kourosh Nozari ◽  
Naser Sadeghnezhad
Keyword(s):  
Scalar Field ◽  
Recent Work ◽  
Friedmann Equation ◽  
Equation Of Motion ◽  
Einstein’S Field Equations ◽  
Field Equations ◽  
Einstein's Field Equations ◽  
Bulk Scalar Field ◽  
Codazzi Equations ◽  
Mimetic Gravity

Following our recent work on braneworld mimetic gravity, in this paper, we study an extension of braneworld mimetic gravity to the case that the gravitational sector on the brane is modified in the spirit of [Formula: see text] theories. We assume the physical 5D bulk metric in the Randall–Sundrum II braneworld scenario consists of a 5D scalar field (which mimics the dark sectors on the brane) and an auxiliary 5D metric. We find the 5D Einstein’s field equations and the 5D equation of motion of the bulk scalar field in this setup. By using the Gauss–Codazzi equations, we obtain the induced Einstein’s field equations on the brane. Finally, by adopting the FRW background, we find the Friedmann equation on the brane in this [Formula: see text] mimetic braneworld setup.

scholarly journals Thin-shell wormholes in (2 + 1)-dimensional Einstein-scalar theory

2017 ◽  
Vol 32 (10) ◽  
pp. 1750064 ◽  
Author(s):  
S. Habib Mazharimousavi ◽  
Z. Amirabi ◽  
M. Halilsoy
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Thin Shell ◽  
Infinite Class ◽  
Btz Black Hole ◽  
Scalar Theory ◽  
Potential Barriers ◽  
Field Extensions ◽  
Linear Perturbations ◽  
Thin Shell Wormholes

We present an infinite class of one-parameter scalar field extensions to the Bañados, Teitelboim and Zanelli (BTZ) black hole in 2 + 1 dimensions. By virtue of the scalar charge, the thin-shell wormhole supported by a linear fluid at the throat becomes stable against linear perturbations. More interestingly, we provide an example of thin-shell wormhole which is strictly stable in the sense that it is confined in between two classically intransmissible potential barriers.

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