Comment on the GRT-LRS Bianchi type V solutions

The points raised by Lorenz-Petzold (1985) on our paper (1983) are discussed. It is shown that the conclusions drawn by him are not substantiated.     

Size of ambiplasma domains in the Universe

Assuming that the initial state of the Universe can be simulated by a thin large-scale homogeneous ambiplasma described by fluid type equations for charged particles (both matter and antimatter particles), stability calculations have been carried out of the various normal modes which might be supported by such a system. The present simplified analysis does not lead to the formation of matter-antimatter symmetric domains smaller than the size of the proto-metagalaxy (Alfvén, 1981) from the initial state of the Universe.     

Slowly Rotating Cosmological Universe Filled with Viscous Fluid

A study of the slowly rotating cosmological universe filled with viscous fluid has been made by assuming the matter angular velocity Ω is proportional to the metric angular velocity Ω and the Universe is expanding under the Hubble's law. The physical properties of the solutions obtained are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sun as a star: Rotation rates from the Ca K-index

Daily measurements for 18 months made at Tucson of the Ca K-index in integrated sunlight have been used to derive solar rotation rates. Power spectral analysis shows that one can obtain a well defined value of solar rotation rate in a period of six months, provided the data are fairly continuous. One might suppose it is possible to study the variation of solar (or stellar) rotation rate with time, a variation arising from a combination of differential rotation and shifts in the active latitude. A comparison between our observed rates and the prevailing dominant activity zones does not support this supposition, at least for the interval studied. Rather, our rates seem to depend on the circumstances of sampling and active region birth and decay.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Early Cosmological Models with Bulk Viscosity in Brans-Dicke Theory

The effect of time dependent bulk viscosity on the evolution of Friedmann models with zero curvature in Brans-Dicke theory is studied. The solutions of the field equations with ‘gamma-law’ equation of state p = (γ-1) ρ, where γ varies continuously as the Universe expands, are obtained by using the power-law relation φ = bR ⁿ , which lead to models with constant deceleration parameter. We obtain solutions for the inflationary period and radiation dominated era of the universe. The physical properties of cosmological solutions are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Strong-plane shock waves in optically-thin atmospheres in magnetogasdynamics

In this paper, similarity solutions for the propagation of strong-plane shock waves in optically-thin grey atmospheres are obtained in the presence of a magnetic field. Density and magnetic field are constant in the undisturbed gaseous medium in front of the shock. Planck's diffusion approximation has been taken into account in this problem and a comparative study has been made between the results of ordinary gasdynamics and magnetogasdynamics.     

A self-similar flow of self-gravitating gas behind a shock wave with increasing energy,I

Self-similar flows of self-gravitating gas behind a spherical shock wave which are driven out by a propelling contact surface, propagating in a nonuniform atmosphere at rest, are investigated. The total energy content of the flow between a shock front and contact surface is taken to be time-dependent. In brief, the self-similar homothermal flows of self-gravitating gas behind a shock wave and Roche's model case are also studied in the present paper.     

Some inhomogeneous cosmological models of plane symmetry with electromagnetic field

Some inhomogeneous cosmological models of plane symmetry in presence of electromagnetic field have been obtained. Various physical and geometrical properties of the models with some special cases are also discussed.     

Plane-symmetric universes in general relativity

Plane-symmetric solutions of Einstein's field equations in vacuum, in the presence of electromagnetic fields and with cosmological constant are explored in null coordinates. The gravitational field of an infinite plane (uncharged and charged both) is thus obtained in a simple and systematic way. The method adopted for these solutions has possibilities of generalization.