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.

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.

scholarly journals Mimetic-metric-torsion with induced axial mode and phantom barrier crossing

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Sourav Sur ◽  
Ashim Dutta ◽  
Hiyang Ramo Chothe
Keyword(s):  
Scalar Field ◽  
Conformal Symmetry ◽  
Red Shift ◽  
Dark Sector ◽  
Axial Mode ◽  
Evolution Of The Universe ◽  
Parity Symmetry ◽  
Phantom Barrier ◽  
Pseudo Scalar ◽  
The Universe

AbstractWe extend the basic formalism of mimetic-metric-torsion gravity theory, in a way that the mimetic scalar field can manifest itself geometrically as the source of not just the trace mode of torsion, but its axial (or, pseudo-trace) mode as well. Specifically, we consider the mimetic field to be (i) coupled explicitly to the well-known Holst extension of the Riemann–Cartan action, and (ii) identified with the square of the associated Barbero–Immirzi field, presumably a pseudo-scalar. The conformal symmetry originally prevaling in the theory would still hold, as the associated Cartan transformations do not affect the torsion pseudo-trace, and hence the Holst term. Demanding the theory to preserve the spatial parity symmetry as well, we show a geometric unification of the cosmological dark sector, and the feasibility of a super-accelerating regime in the course of evolution of the universe. From the observational perspective, assuming the cosmological evolution profile to be very close to that for $$\varLambda $$ Λ CDM, we further illustrate a smooth crossing of the so-called phantom barrier at a low red-shift, albeit with a restricted parametric domain. Subsequently, we determine the extent of the super-acceleration by examining the evolution of the relevant torsion parameters.

scholarly journals The investigation of detectability of the relic gravitational waves based on the WMAP-9 and Planck

2017 ◽  
Vol 26 (02) ◽  
pp. 1750003 ◽  
Author(s):  
Basem Ghayour
Keyword(s):  
Scalar Field ◽  
Gravitational Waves ◽  
Crucial Role ◽  
Planck Data ◽  
Evolution Of The Universe ◽  
Cosmological Observations ◽  
Relic Gravitational Waves ◽  
The Waves ◽  
The Universe ◽  
General Range

The generated relic gravitational waves underwent several stages of evolution of the universe such as inflation and reheating. These stages were affected on the shape of spectrum of the waves. As well known, at the end of inflation, the scalar field [Formula: see text] oscillates quickly around some point where potential [Formula: see text] has a minimum. The end of inflation stage played a crucial role on the further evolution stages of the universe because particles were created and collisions of the created particles were responsible for reheating the universe. There is a general range for the frequency of the spectrum [Formula: see text])[Formula: see text]Hz. It is shown that the reheating temperature can affect on the frequency of the spectrum as well. There is constraint on the temperature from cosmological observations based on WMAP-9 and Planck. Therefore, it is interesting to estimate allowed value of frequencies of the spectrum based on general range of reheating temperature like few MeV [Formula: see text] GeV, WMAP-9 and Planck data then compare the spectrum with sensitivity of future detectors such as LISA, BBO and ultimate-DECIGIO. The obtained results of this comparison give us some more chance for detection of the relic gravitational waves.

scholarly journals Dynamics of two-scalar-field cosmological models beyond the exponential potential

2017 ◽  
Vol 26 (14) ◽  
pp. 1750164 ◽  
Author(s):  
Yu Li
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Cosmological Models ◽  
The Other ◽  
Late Time ◽  
Exponential Potential ◽  
Multiple Attractors ◽  
Evolution Of The Universe ◽  
The Universe

In this paper, we discuss the dynamics of two- scalar-field cosmological models. Unlike in the situation of exponential potential, we find that there are late-time attractors in which one scalar field dominates the energy density of universe and the other one decay. We also discuss the possibility of multiple attractors model which is useful to realize the evolution of the universe from a scaling era to recent acceleration era. We also give the conditions of the existence of multiple attractors.

Generalized tachyonic dark energy

2022 ◽  
Author(s):  
Elham Nouri ◽  
Hossein Motavalli ◽  
Amin Rezaei Akbarieh
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Matter Field ◽  
Cosmic Acceleration ◽  
Coefficient Function ◽  
Tachyon Field ◽  
Evolution Of The Universe ◽  
Coupling Parameters ◽  
Tachyonic Dark Energy ◽  
The Universe

In this paper, a generalized tachyonic dark energy scenario is presented in the framework of a homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker (FLRW) flat universe, in which a noncanonical scalar field is coupled to gravity nonminimally. By utilizing the Noether symmetry method, we found the explicit form of both potential density and coupling function, as a function of the scalar field. It is found that the tachyon field acts as the source of inflation and accelerates the evolution of the universe in the early times considerably. While, in the late times, gravitational sources are a pressureless matter field together with the tachyon field, which is the nature of dark energy and plays an essential role in the deceleration-acceleration phase transition of the universe. Further, the role of the coefficient function of tachyon potential, alongside the potential, is considered in the evolution of the universe. It is shown that this model involves a cosmological degeneracy in the sense that different coupling parameters and tachyonic potentials may be equivalent to the same cosmological standards such as the cosmic acceleration, age, equation of state and mean Hubble of the FLRW universe. The physical characteristics of the main cosmological observables are studied in detail, which suggests that the generalized tachyon field is a remarkable dark energy candidate.

Frame dragging in Einstein and Einstein zero mass scalar cosmologies

1983 ◽  
Vol 61 (8) ◽  
pp. 1198-1204
Author(s):  
K. D. Krori ◽  
J. C. Sarmah ◽  
D. Goswami
Keyword(s):  
Angular Velocity ◽  
Cosmological Model ◽  
Inertial Frame ◽  
Frame Dragging ◽  
Evolution Of The Universe ◽  
Zero Mass ◽  
Isotropic Cosmological Model ◽  
Scalar Theories ◽  
Rotating Shell ◽  
The Universe

We investigate in this paper the perturbations caused by a spherical rotating shell in a closed homogeneous and isotropic cosmological model in Einstein and Einstein zero mass scalar theories. It is found from our solutions that in both theories the inertial frame at the origin is dragged with the angular velocity of the rotating shell during only a certain interval in the evolution of the universe when the shell covers the whole universe.

Ultralight massive photons in Stueckelberg QED cosmology with self- and curvature non-minimal couplings

2020 ◽  
Vol 98 (2) ◽  
pp. 130-133
Author(s):  
Rami Ahmad El-Nabulsi
Keyword(s):  
Vector Field ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Hubble Parameter ◽  
Accelerated Expansion ◽  
Evolution Of The Universe ◽  
Kinetic Coupling ◽  
Massive Particles ◽  
The Universe ◽  
Massive Photons

In this communication, we study non-minimal massive Stueckelberg QED for the evolution of the universe in the presence of non-minimal kinetic coupling to itself and to the curvature and where massive photons in the theory are of the order of the Hubble parameter or ultralight mass. By adopting the idea that the gauge vector field depends on the Hubble parameter, we observe that the universe is undergoing accelerated expansion with time and is dominated by quintessence, a decaying scalar field, and ultra-light massive photons. The existence of massive photons or massive particles of light is therefore able to explain the current acceleration of the quintessential universe in the absence of a cosmological constant.

scholarly journals Gauss–Bonnet term corrections in scalar field cosmology

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Igor Fomin
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Einstein Gravity ◽  
Minimal Coupling ◽  
Evolution Of The Universe ◽  
Scalar Field Cosmology ◽  
The Universe ◽  
Bonnet Term ◽  
Inflationary Models

AbstractThe influence of non-minimal coupling of a scalar field and the Gauss–Bonnet term on the inflationary stage of evolution of the universe is investigated in this paper. The main cosmological effects of such a coupling were considered. The deviations between Einstein–Gauss–Bonnet inflation and standard one based on Einstein gravity were determined. The corrections of a weak GB coupling preserving the type of the scalar field potential to standard inflationary models is considered as well.

scholarly journals Strengthening the de Sitter swampland conjecture in warm inflation

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Robert Brandenberger ◽  
Vahid Kamali ◽  
Rudnei O. Ramos
Keyword(s):  
Scalar Field ◽  
Lower Bound ◽  
Entropy Production ◽  
Field Theories ◽  
De Sitter ◽  
Superstring Theory ◽  
Inflaton Field ◽  
Warm Inflation ◽  
Evolution Of The Universe ◽  
The Universe

Abstract The de Sitter constraint on the space of effective scalar field theories consistent with superstring theory provides a lower bound on the slope of the potential of a scalar field which dominates the evolution of the Universe, e.g., a hypothetical inflaton field. Whereas models of single scalar field inflation with a canonically normalized field do not obey this constraint, it has been claimed recently in the literature that models of warm inflation can be made compatible with it in the case of large dissipation. The de Sitter constraint is known to be derived from entropy considerations. Since warm inflation necessary involves entropy production, it becomes necessary to determine how this entropy production will affect the constraints imposed by the swampland conditions. Here, we generalize these entropy considerations to the case of warm inflation and show that the condition on the slope of the potential remains essentially unchanged and is, hence, robust even in the warm inflation dynamics. We are then able to conclude that models of warm inflation indeed can be made consistent with the swampland criteria.

Sign in / Sign up

Export Citation Format

Share Document