International Journal of Modern Physics D

On the basis of the beaming model, we have derived a relation between the observed polarization (P^ob) and the observed magnitude (m^ob), log P^ob = -0.4(k-1)m^ob+C, which indicates that the observed polarization is anti-correlated with the observed magnitude. Making use of the optical data of polarization and magnitude observed simultaneously for 47 blazars, we found that there is a significant anti-correlation between the observed polarization and the observed magnitude in the V-band, the linear regression equation of which is , with the correlation coefficient of γ = -0.4537 and the chance probability of p = 1.360×10^-3. Obviously, the statistical results are consistent with the theoretical results derived by the beaming model. Our results of both theory and statistical analysis of the data observed simultaneously are consistent with the observations of 3C345, Mrk421.

In addition, using these data, we have also analyzed the relation between the maximum optical polarization ( in the V-band) and the maximum infrared polarization ( in the H-band). For 20 objects with both the maximum optical and infrared polarization, a linear regression analysis gives a strong correlation of , with a correlation coefficient of γ = 0.9071 and a chance probability of p < 1.0 ×10^-4. The results suggest that both the infrared and optical emissions of blazars originate from the synchrotron radiation.

Experimental discovery of the gravitomagnetic fields generated by translational and/or rotational currents of matter is one of primary goals of modern gravitational physics. The rotational (intrinsic) gravitomagnetic field of the Earth is currently measured by the Gravity Probe B. The present paper makes use of a parametrized post-Newtonian (PN) expansion of the Einstein equations to demonstrate how the extrinsic gravitomagnetic field generated by the translational current of matter can be measured by observing the relativistic time delay caused by a moving gravitational lens. We prove that measuring the extrinsic gravitomagnetic field is equivalent to testing the relativistic effect of the aberration of gravity caused by the Lorentz transformation of the gravitational field. We show that the recent Jovian deflection experiment is a null-type experiment testing the Lorentz invariance of the gravitational field (aberration of gravity), thus, confirming existence of the extrinsic gravitomagnetic field associated with the orbital motion of Jupiter with accuracy 20%. We comment on physically inadequate interpretations of the Jovian deflection experiment given by a number of researchers who are not experts in modern VLBI techniques and the subtleties of JPL ephemeris. We propose to measure the aberration of gravity effect more accurately by observing the gravitational deflection of light by the Sun and processing VLBI observations in the geocentric frame with respect to which the Sun is moving with velocity ~30 km/s.

We treat the adiabatic matter creation process in various three-brane models by applying the thermodynamics of open systems. The matter creation rate is found to affect the evolution of the scale factor and energy density of the universe. We find a modification at the early stages of cosmic dynamics. In GB and RS brane worlds, by choosing appropriate parameters we obtain the standard scenario, while the warped DGP model has different solutions. During later stages, since matter creation is negligible, the evolution reduces to FRW expansion, in the RS and GB models.

The Plebański–Demiański metric, and those that can be obtained from it by taking coordinate transformations in certain limits, include the complete family of space–times of type D with an aligned electromagnetic field and a possibly non-zero cosmological constant. Starting with a new form of the line element which is better suited both for physical interpretation and for identifying different subfamilies, we review this entire family of solutions. Our metric for the expanding case explicitly includes two parameters which represent the acceleration of the sources and the twist of the repeated principal null congruences, the twist being directly related to both the angular velocity of the sources and their NUT-like properties. The non-expanding type D solutions are also identified. All special cases are derived in a simple and transparent way.

In a previous paper, we determined the statistical distributions for various classes of QSO absorption systems in the framework of the CDM model of the universe with a mass distribution of dark matter halos as given by the Press Schechter mechanism. These were shown to be consistent with the observed distributions for reasonable choices of model parameters. In this paper, we generate Voigt profiles of C IV lines associated with Damped Lyman Alpha systems in the framework of this model, taking into account rotation of disks and random motion of clouds embedded in galactic halos. We compare these with the profiles for a sample of 32 Damped Lyman Alpha systems collected from the literature by performing several statistical tests. These tests compare the width and the degree of asymmetry in the line profiles produced by the rotation of randomly inclined disks and the random velocity of clouds in the galactic halos, with the corresponding quantities in the observed profiles. We find that the kinematic properties predicted by the model are in good agreement with observations provided the disk thickness is about ten thousand times smaller than its radius, which indicates that the material in the disks is concentrated in dense clouds with roughly unit covering factor.

We analyze the flat behavior of the rotational curves in some galaxies in the framework of a dilatonic, current-carrying string. We determine the expression of the tangential velocity of test objects following a stable circular equatorial orbit in this space–time.

We give an exact solution of the 5D Einstein equations which in 4D can be interpreted as a spherically symmetric dissipative distribution of matter, with heat flux, whose effective density and pressure are nonstatic, nonuniform, and satisfy the equation of state of radiation. The matter satisfies the usual energy and thermodynamic conditions. The energy density and temperature are related by the Stefan–Boltzmann law. The solution admits a homothetic Killing vector in 5D, which induces the existence of self-similar symmetry in 4D, where the line element as well as the dimensionless matter quantities are invariant under a simple "scaling" group.

We calculate the maximum mass of the class of compact stars described by the Vaidya–Tikekar²⁷ model. The model permits a simple method of systematically fixing bounds on the maximum possible mass of cold compact stars with a given value of radius or central density or surface density. The relevant equations of state are also determined. Although simple, the model is capable of describing the general features of the recently observed very compact stars. For the calculation, no prior knowledge of the equation of state (EOS) is required. This is in contrast to earlier calculations for maximum mass which were done by choosing first the relevant EOSs and using those to solve the TOV equation with appropriate boundary conditions. The bounds obtained by us are comparable and, in some cases, more restrictive than the earlier results.

A special law of variation for Hubble's parameter in anisotropic space–time models that yields a constant value of the deceleration parameter is presented. Also, a spatially homogeneous and anisotropic but locally rotationally symmetric (LRS) Bianchi type-II cosmological model is studied with a perfect fluid and constant deceleration parameter. Assuming the equation of state p = γρ, where 0≤γ≤1, and using a special law of variation for the Hubble parameter, we are able to construct many new solutions to Einstein's field equations of LRS Bianchi type-II for four different physical models (dust, radiation, Zel'dovich and vacuum). We discuss the solutions with power-law and exponential expansion and examine a particular class of models. A detailed study of kinematic, geometrical and observational properties is carried out.

In the framework of black hole spectroscopy, we extend the results obtained for a charged black hole in an asymptotically flat space–time to the scenario with non-vanishing negative cosmological constant. In particular, exploiting Hamiltonian techniques, we construct the area spectrum for an AdS Reissner–Nordstrøm black hole.