Zero-mass Scalar Field Research Articles

Plane Symmetric String Cosmological Model with Zero Mass Scalar Field in f (R) Gravity

Plane Symmetric String Cosmological Model with Zero Mass Scalar Field in f (R) Gravity

SOME PHYSICAL CHARACTERISTICS OF A FIVE-DIMENSIONAL MASS SCALAR ELECTROMAGNETIC COSMOLOGICAL MODEL

In this paper we are interested to study some important physical aspects of a five dimensional space time which is attained by the interaction of magnetic field and zero mass scalar field in Einstein’s theory of gravitation, where the cosmic parameters X & A are functions of cosmic time t .The concluding remark is focused on the singularity nullity, uniformity, energy condition and about the possession of gravitational field radiation of the space-time.

Five-Dimensional Cosmological Model with One Dimensional Cosmic String Coupled with Zero Mass Scalar Field in Lyra Manifold

A five-dimensional Bianchi type-III string cosmological model is studied with a one-dimensional cosmic string in the presence of zero mass scalar field in the context of the Lyra manifold. Exact solutions of Einstein's field equations are obtained by assuming quadratic equation of state (EoS) of the form p = kρ2 + ρ, where k is a constant and strictly k > 0 . The physical and geometrical aspects of the investigated model are analyzed in detail.

Transit cosmological models coupled with zero-mass scalar field with high redshift in higher derivative theory

The present study deals with a flat FRW cosmological model filled with perfect fluid coupled with the zero-mass scalar field in the higher derivative theory of gravity. We have obtained two types of universe models, the first one is the accelerating universe (power-law cosmology), and the second one is the transit phase model (hyperbolic expansion-law). We have obtained various physical and kinematic parameters and discussed them with observationally constrained values of H0. The transit redshift value is obtained zt=0.414, where the transit model shows signature-flipping and is consistent with recent observations. In our models, the present values of EoS parameter ω0 crosses the cosmological constant value ω0=−1. Also, the present age of the universe is calculated.

English

English

Anisotropic Bianchi Type-I and Type-II Bulk Viscous String Cosmological Models Coupled with Zero Mass Scalar Field

The LRS Bianchi type-I and type-II string cosmological models are studied when the source for the energy momentum tensor is a bulk viscous stiff fluid containing one dimensional strings together with zero-mass scalar field. We have obtained the solutions of the field equations assuming a functional relationship between metric coefficients when the metric is Bianchi type-I and constant deceleration parameter in case of Bianchi type-II metric. The physical and kinematical properties of the models are discussed in each case. The effects of Viscosity on the physical and kinematical properties are also studied.

Kantowski-Sacks Bulk Viscous String Cosmological Models in the Presence of Zero-Mass Scalar Fields

The Kantowski-Sachs cosmological solutions of massive strings have been studied in the presence of zero-mass scalar field coupled with bulk viscosity. It is assumed that the coefficient of bulk viscosity is a power function of energy density of massive strings. Further we have considered the cosmological parameter as a function of cosmic time. We obtained the general solution of the field equations in polynomial and exponential forms respectively. The behaviors of these models are also discussed in the presence as well as in the absence of bulk.

FRW Cosmological Solution in Self Creation Theory

In this paper, we have investigated spatially homogeneous isotropic Friedman-Robertson-Walker cosmological model with bulk viscosity and zero-mass scalar field in the frame work of Barber’s second self-creation theory (Gen. Relativ. Gravit. 14:117, 1982). The cosmological models are obtained with the help of the special law of variation for Hubble’s parameter proposed by Bermann (Nuovo Cimento B 74:182, 1983) and power law relation. Some physical properties of the models are also discussed.

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

Cosmological solutions in the presence of an imperfect fluid and zero-mass scalar field are obtained in higher derivative theory. We investigate both power law and exponential expansion of the universe described by full causal theories proposed by Israel and Stewart. It is observed that energy density, co-efficient of bulk viscosity decrease with time in the presence of massless scalar field and temperature increase with expansion of universe.

Early-Universe and Evolution of the Present Universe: Exact Solution Models

The evolution of the Robertson-Walker type universes consisting of radiating perfect fluid distribution coupled with zero-mass scalar field in which the gravitational parameter G varies with cosmic time t are studied. Unified descriptions of the early evolution of the universe consisting of different phases are investigated. The different properties of the cosmological solutions are discussed and the physical behaviour of the model universes during the radiation-dominated era and also during the big bang scenario are studied. Here we obtain models which are geometrically closed and are thereby ever expanding and evolve from rest from a non-singular hot origin with maximum (finite) energy density and temperature and a small minimum (non-zero) gravitational coupling G.

Rotational perturbations of radiating Universes coupled with zero-mass scalar field

Investigations are made on slowly rotating radiating Universes coupled with a scalar field in the spherically symmetric Einstein formalism, and some new interesting solutions are obtained. Their physical and geometrical properties are studied from various angles. The rotational perturbations of such models are examined in order to substantiate the possibility that the universe is endowed with some rotation. The nature and role of the metric rotation as well as that of the rotation of matter are studied, and the effects of radiation and scalar fields on them are discussed. The models here turn out to be rotating as well as expanding ones, which may be taken as good examples of real astrophysical objects in this universe. The periods of the physical validity and the restrictions on the radii of the models for real astrophysical situations are obtained and discussed. The models obtained here are theoretically satisfactory and therefore there is a possibility that there may be less known objects in this universe which may be represented by our model Universes obtained here and many unknown properties of this universe may be explored and unfolded in the study of these models.

Zero mass scalar field with bulk viscous cosmological solutions in Lyra geometry

In this paper, we have investigated spatially homogeneous isotropic Friedmann cosmological model with bulk viscosity and zero-mass scalar field in Lyra manifold. The cosmological models are obtained with the help of the special law of variation for Hubble’s parameter proposed by Bermann (Nuovo Cimento 74B:182, 1983) and power law relation. Some physical properties of the models are discussed.

GLOBAL MONOPOLES AND SCALAR FIELDS AS THE ELECTROGRAVITY DUAL OF SCHWARZSCHILD SPACE–TIME

We prove that both global monopole and minimally coupled static zero mass scalar field are electrogravity dual of the Schwarzschild solution or flat space and they share the same equation of state, [Formula: see text]. This property was however known for the global monopole space–time while it is for the first time being established for the scalar field. In particular, it turns out that the Xanthopoulos–Zannias scalar field solution is dual to flat space.

Exact self-consistent plane-symmetric solutions of the equations of two interacting fields (spinor field and scalar field)

A spinor field interacting with a zero-mass neutral scalar field is considered for the case of the simplest type of direct interaction, where the interaction Lagrangian has the formLint=1/2 ϕαϕ,αF(S) whereF(S) is an arbitrary function of the spinor field invariantS=ψψ. Exact solutions of the corresponding systems of equations that take into account the natural gravitational field in a plane-symmetric metric are obtained. It is proved that the initial system of equations has regular localized soliton-type solutions only if the energy density of the zero-mass scalar field is negative as it “disengages” from interaction with the spinor field. In two-dimensional space-time the system of field equations we are studying describes the configuration of fields with constant energy densityT00, i.e., no soliton-like solutions exist in this case.

Global monopole in scalar tensor theory

The well known monopole solution of Barriola and Vilenkin (BV) resulting from the breaking of a global SO(3) symmetry is extended in general relativity along with a zero-mass scalar field and also in the Brans-Dicke (BD) theory of gravity. In the case of BD theory, the behaviour of spacetime and other variables such as the BD scalar field and the monopole energy density have been studied numerically. For a monopole along with a zero-mass scalar field, exact solutions are obtained and, depending upon the choice of arbitrary parameters, the solutions either reduce to the BV case or to a pure scalar field solution as special cases. It is interesting to note that unlike the BV case the global monopole in the BD theory does exert a gravitational pull on a test particle moving in its spacetime.

Perfect and viscous fluid cosmological models in presence of scalar fields for anisotropic metric

An exact solution of Einstein equations representing a perfect fluid model in the presence of a zero-mass scalar field is obtained for an anisotropic metric. The effect of dissipative processes on the model is also discussed. Different physically valid forms of the scale factors in the three spatial directions give rise to some distinct models. The physical behaviour of these models is discussed in detail. Some of the perfect fluid models exhibit the ‘cigar’ singularity.

Magneto-viscous fluid cosmological models in presence of zero-mass scalar field

A viscous fluid cosmological model in presence of magnetic field and zero-mass scalar fields is developed. The non-negativity condition of viscous fluid pressure prescribes a certain minimum value oft vis-a-vis of the scale factorQ(t) and at this epoch the model is found to be singularity free.

Viscous fluid cosmological models in the presence of the zero-mass scalar field

The curvature-free (k=0) FRW expanding cosmological model is developed corresponding to interacting viscous fluids and zero-mass scalar fields. In the absence of non-static scalar fields the model exhibits the existence of the initial singularity (Q=0). However, with non-negative coefficient of shear viscosity, in the presence of non-static scalar fields we find thatQ has a minimum value (≠0). If this epoch is treated as the initial one, it may be said that the presence of scalar fields avoids the initial singularity. Other physical behaviour that the model exhibit has been discussed.

Exact Bianchi-type VIII and IX models in the presence of zero-mass scalar fields

Exact Bianchi-type VIII and IX models in the presence of zero-mass scalar fields are presented, when the source of the gravitational field is a perfect fluid withP=ϱ. Some physical and geometrical properties of the models are also discussed.

Rotational perturbations of magneto-viscous fluid universes coupled with zero-mass scalar field

The dynamics of slowly rotating magneto-viscous fluid universe coupled with zero-mass scalar field is investigated, and the rotational perturbations of such models are studied in order to substantiate the possibility that the Universe is endowed with slow rotation, in the course of presentation of several new analytic solutions. Four different cases are taken up in which the nature and role of the metric rotation Ω(r, t) as well as that of the matter rotationω(r,t) are discussed. Except for the case of ‘perfect drag’, the scalar field is found to have a damping effect on the rotational motion. This damping effect is seen to be roughly analogous to the viscosity. The periods of physical validity of some of the models are also found out. Most of the rotating models obtained here come out to be expanding ones as well which may be taken as good examples of real astrophysical situations.