Torsion,massive electrodynamics and gravitation induced by scalar fields

The equivalence of Lagrangian containing gravitational, electromagnetic, scalar, and torsion fields is discussed. It is shown that the equation for the variation of the scalar field leads to a torsion wave equation generated by electromagnetic field leads to a torsion wave equation generated by electromagnetic fields. The system is proved to be equivalent to a Proca field coupling torsion non-minimally to a massive photon and having the scalar Higgs field as a strength of this photon-torsion coupling. The generalized Maxwell equations containing the scalar fields are obtained. The torsion potential around the Sun or a more massive collapsing star in the weak field limit is estimated.     

Non-Existence Of <Emphasis Type="Italic">N</Emphasis>-Dimensional Static Plane Symmetric Solutions In Bimetric Relativity Theory

A problem of static plane symmetric metric in the perfect fluid, the mesonic massive scalar field and in their coupling is studied in Rosen’s (1973) bimetric theory of relativity. It was found that the matter field like either perfect fluid or mesonic massive scalar field or their coupling does not survive in bimetric theory of gravitation when the space–time is governed by n-dimensional static plane symmetric metric.     

Singularity-free RW viscous fluid cosmological models in presence of massive scalar fields

Singularity-free Robertson-Walker cosmological models (RWCM) are developed by considering the cosmic matter as composed of an interacting viscous fluid (with zero bulk viscosity) and a massive scalar (meson) field. Solutions are obtained for two different cases, viz., when the Hubble's parameterH is epoch independent and whenH is epoch dependent. A solution corresponding to RWCM with only the massive scalar field as the matter content is also presented. The essential physical behaviour of the models developed are discussed in detail.     

Massive scalar field in the Bianchi Type I space time

A class of exact solutions of Eistein's field equations with attractive massive scalar field in LRS Bianchi type I space time is obtained. It is shown that how the dynamical importance of the scalar field and the shear change in the course of evolution. This revised version was published online in July 2006 with corrections to the Cover Date.     

Torsion and inflation

We show that considering the torsion in early universe, we are led to an inflationary expansion with only a massless scalar field, so avoiding all physical questions that we are facing when working with massive scalar field.     

Incompatibility of five dimensional LRS Bianchi type-V string and mesonic string cosmological models in general relativity

In this paper, we constructed some cosmological models in five dimensional LRS Bianchi type-V space time based on general theory of relativity. Further, it is shown that source density of the meson field does not survive either in massive scalar field or in mass less scalar field. Some physical and geometrical properties of the models are discussed.     

Scalar field instability in multi-dimensional cosmology

The scalar field theory on the background of cosmological models with n(n ≥ 1) spaces of constant curvature is considered. We take the integrable case of Ricci flat internal spaces. The coupling between the scalar and the gravitational fields includes the minimal coupling as well as the conformal case. In the ground state of the scalar field we find the conditions for vacuum instability realized for most of the possible solutions to Einstein's equations if the coupling parameter takes appropriate values. For the excited states of the scalar field we show the induction of massive modes and discuss their properties.     

(Non-)geodesic motion in chameleon Brans Dicke model

Based on Das and Banerjee (Phys. Rev D 78:043512, 2008), we assume there is a non-minimal coupling between scalar field and matter in the Brans-Dicke model. We analyzes the motion of different matter such as, massless scalar field, photon, massless perfect fluid (dust), massive perfect fluid and point particle matter in this study. We show that the motion of massless scalar field and photon can satisfy null geodesic motion only in high frequency limit. Also we find that the motion of the dust and massive perfect fluid is geodesic for L _m =?P and it is non-geodesic for L _m =ρ. Finally, we study the motion of point particle and show that the motion of this kind of matter is like massive perfect fluid.     

Cosmological Massive Scalar Field Interacting with Viscous Fluid

Relativistic cosmological field equations are obtained for a Robertson-Walker space time interacting with viscous fluid and massive scalar field. The cosmological solutions to the field equations are obtained and the nature of the scalar field as well as the viscous fluid are studied. It is found that the solutions obtained are realistic only for a closed Universe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Massive scalar field quasinormal modes of a black hole with quintessence-like matter and a deficit solid angle

Using the third-order WKB approximation, we evaluate the quasinormal frequencies of massive scalar field perturbation around a black hole with quintessence-like matter and a deficit solid angle. The mass u of the scalar field plays an important role in studying the quasinormal frequencies. We find that as the scalar field mass increases when the other parameters are fixed, so do the real parts and the magnitudes of the imaginary parts of the quasinormal frequencies decrease. The imaginary parts are almost linearly related to the real parts.     

Spatially flat R-W cosmological model with massive scalar field

A spatially flat Robertson-Walker R-W cosmological model filled with a massive scalar field has been obtained for Einstein's field equations in the presence of a cosmological constant.     

Anisotropic Bianchi type-I models in string cosmology

The present study deals with a spatially homogeneous and anisotropic Bianchi-I cosmological models representing massive strings. The energy-momentum tensor, as formulated by Letelier (1983), has been used to construct massive string cosmological models for which we assume the expansion scalar in the models is proportional to one of the components of shear tensor. The Einstein’s field equations have been solved by applying a variation law for generalized Hubble’s parameter in Bianchi-I space-time. We have analysed a comparative study of accelerating and decelerating models in the presence of string scenario. The study reveals that massive strings dominate in the decelerating universe whereas strings dominate in the accelerating universe. The strings eventually disappear from the universe for sufficiently large times, which is in agreement with current astronomical observations.     

Plane-symmetric dark energy model with a massive scalar field

Investigation of dark energy models in the presence of scalar fields are attracting several kinds of research because they play a vital role in the discussion of a new scenario of accelerated expansion of the universe. In this paper, we obtain an exact plane-symmetric dark energy cosmological model in the presence of an attractive massive scalar field by solving Einstein field equations using some physically relevant conditions. We have obtained all the cosmological parameters corresponding to the model. We have also presented a physical discussion of our model using a graphical representation of these parameters. The results exhibit an expanding and accelerating dark energy model of the universe, which are consistent with modern cosmological observations.     

Bianchi type–I dark energy cosmological model coupled with a massive scalar field

In the present investigation we are mainly concerned with a massive scalar field in an axially symmetric Bianchi type – I space-time. Einstein field equations are solved to obtain an exact cosmological model. We have used certain physically meaningful conditions for this purpose. Kinematical cosmological parameters are determined, and their dynamical aspects are discussed. It is observed that our model represents accelerated expansion of the Universe. It is observed that our model agrees with the scenario of accelerated expansion of the Universe confirmed by supernova 1a experimental data.     

A study on Bianchi-IX cosmological model

In this paper the inflationary solutions are studied for the Bianchi-IX space-time in presence of a massless scalar field with a flat potential. Also a class of cosmological solutions of massive strings are obtained following the techniques used by Letelier and Stachel. Some solutions are calculated for pure massive strings following the Takabayashi equation of state =(1+w).     

A light scalar field at the origin of galaxy rotation curves

The nature of the dark matter that binds galaxies remains an open question. It is usually assumed to consist in a gas of massive particles with evanescent interactions; however, such particles—which have never been observed directly—should have a clumpy distribution on scales ≤10⁻² kpc, which may be in contradiction with observations. We focus here on an exotic dark matter candidate: a light non-interacting (or only self-interacting) complex scalar field. We investigate the distribution of the field in gravitational interaction with matter, assuming no singularities (like black holes) at the galaxy center. This simplistic model accounts quite well for the rotation curve of low-luminosity spirals. A chi-squared analysis points towards a preferred mass m∼0.4 to 1.6×10⁻²³ eV in absence of self-interaction. A rough calculation shows that allowing for a quartic self-coupling may shift the upper bound to around 1 eV. We conclude that a scalar field is a promising candidate for galactic dark matter. Our comparison should be extended to other rotation curves in order to derive better constraints on the scalar potential. We finally give a hint of the issues that appear when one tries to implement this scenario on cosmological time scales.     

Stochastic coalescence model for terrestrial planetary accretion

A nonequilibrium stochastic coalescence model for terrestrial planetary accretion is developed by using an approximation to the Safronov-Golovin solution for the scalar transport equation with linear kernel. According to this model, formation of comparatively massive objects occurs quite rapidly during the early stages of accretive evolution in a given terrestrial planetesimal population, while during late growth stages, an increasingly substantial fraction of total population mass becomes incorporated into progressively fewer, relatively very large bodies. The model also implies that the (conservative) growth rate of the population's largest member varies directly as its mass, and further suggests that this growth rate may not decline significantly until very nearly final planetary mass is attained.     

Nucleosynthesis in bouncing cosmologies

It is shown that certain anomalies connected with the primordial abundances of light nuclei may be resolved if it is assumed that the Universe oscillates between phases of finite densities. Since general relativity does not produce bouncing models of the Universe, such models are obtained through the introduction of a negative energy scalar field of zero rest mass. It is shown that all the relevant parameters of the dynamics of the model and the nucleosynthesis in it are determined by observations and that a self-consistent picture emerges. The model is capable of admitting more than three neutrino flavours without an embarrassingly high primordial helium content. It is also shown that the calculations could be adapted to described production of light nuclei in compact massive bouncing objects.     

Massive scalar field interacting with viscous fluid distribution in cosmological models

The study of Einstein's field equations describing Robertson-Walker cosmological models with massive scalar field and viscous fluid representing the matter has been made. The problem has been investigated with and without the source density in the wave equation. Corresponding exact solutions of the field equations have been obtained under different physical equations of state: namely, (i) dust distribution, (ii) Zeldovich fluid distribution, (iii) disordered distribution of radiation subject to physically realistic conditions. The physical interpretations of the physically realistic solutions has been investigated. It has been found that physically realistic solutions has been obtained for closed cosmological models only.     

Phase transition in Schwarzschild-de Sitter spacetime

Using a static massive spherically symmetric scalar field coupled to gravity in the Schwarzschild-de Sitter (SdS) background, first we consider some asymptotic solutions near horizon and their local equations of state (E.O.S.) on them. We show that near cosmological and event horizons our scalar field behaves as a dust. At the next step near two pure de Sitter or Schwarzschild horizons we obtain a coupling dependent pressure to energy density ratio. In the case of a minimally coupling this ratio is ?1 which springs to the mind thermodynamical behavior of dark energy. If having a negative pressure behavior near these horizons we concluded that the coupling constant must be ξ<¼. Therefore we derive a new constraint on the value of our coupling ξ. These two different behaviors of unique matter in the distinct regions of spacetime at present era can be interpreted as a phase transition from dark matter to dark energy in the cosmic scales and construct a unified scenario.