International Journal of Modern Physics D

In this paper, using Einstein, Landau and Lifshitz's energy–momentum complexes both in general relativity and teleparallel gravity, we calculate the total energy distribution (due to matter and fields, including gravitation) associated with locally rotationally symmetric (LRS) Bianchi type II cosmological models. We show that energy densities in these different gravitation theories are the same, so they agree with each other. We obtain the result that the total energy is zero. This result agrees with previous works of Cooperstock and Israelit, Rosen, Johri et al., Banerjee and Sen, Vargas, Aydogdu and Saltı. Moreover, our result supports the viewpoints of Albrow and Tryon.

In this letter, we work out the secular precession of the spin of a gyroscope in geodesic motion around a central mass in the framework of the Dvali–Gabadadze–Porrati multidimensional gravity model. Such an effect, which depends on the mass of the central body and on the orbit radius of the gyroscope, contrary to the precessions of the orbital elements of the orbit of a test body, is far too small to be detected.

In this note, we show that the latest determinations of the residual perihelion advances of the inner planets of the Solar System, obtained by accounting for almost all known Newtonian and post-Newtonian orbital effects, yield only very broad constraints on the cosmological constant Λ. Indeed, from, e.g., arcseconds per century for Mercury, one gets -2 × 10^-34km^-2 < Λ < 4 × 10^-35km^-2. The currently accepted value for Λ, obtained from many independent cosmological and large-scale measurements, amounts to almost 10^-46km^-2.

In this article, we study higher-dimensional cosmological models with quark–gluon plasma in the context of general relativity. For this purpose, we consider quark–gluon plasma as a perfect fluid in the higher-dimensional universes. After solving Einstein's field equations, we have analyzed this matter for the different types of universes in the higher- and four-dimensional universes. Also, we have discussed the features of obtained solutions.

The coincidence excess between the gravitational wave detectors EXPLORER and NAUTILUS observed in the ten-day period 7–17 September 1998 is the largest ever observed. The event occurred mainly at the sidereal hour 4, when the detectors axes were perpendicular to the Galactic disk. This excess occurred during a period of intense activity of the black hole candidate XTE J1550-564, and within days of the giant flare from the magnetar SGR1900+14.

The Einstein–Maxwell-dilaton field equations are considered for four-dimensional Bianchi type-V and VI₀ models. The general solutions are obtained and their properties are discussed.

We derive source-free Maxwell-like equations in flat space–time for any helicity j by comparing the transformation properties of the 2(2j+1) states that carry the manifestly covariant representations of the inhomogeneous Lorentz group with the transformation properties of the two helicity j states that carry the irreducible representations of this group. The set of constraints so derived involves a pair of curl equations and a pair of divergence equations. These reduce to the free-field Maxwell equations for j = 1 and the analogous equations coupling the gravito-electric and the gravito-magnetic fields for j = 2.

By using cluster analysis, we select a galaxy pair sample in the Sloan Great Wall and study its various properties. We find that in the Sloan Great Wall pair sample, most galaxies are brighter and smaller, and that there is a tendency for pair galaxies to have similar luminosity and size.

In this work, we study the gravitational influence of the material extending from Uranus orbit to the Kuiper belt and beyond on objects moving within these regions. We conclude that a density distribution given by generates a constant acceleration towards the Sun on those objects, which, with the proper amount of mass, accounts for the blue shift detected on the Pioneers space crafts. We also discuss the effect of this gravitational pull on Neptune, and comment on the possible origin of such a matter distribution.

The (2+1)-dimensional geodesic circularly symmetric solutions of Einstein-massless-scalar field equations with negative cosmological constant are found and their local and global properties are studied. It is found that one of them represents gravitational collapse where black holes are always formed.

Our purpose is to recast the KK model in terms of ADM variables. We examine and solve the problem of the consistency of this approach, with particular care about the role of the cylindricity hypothesis. We show in detail how the KK reduction commutes with the ADM slicing procedure and how this leads to a well-defined and unique ADM reformulation. This allows us to consider the Hamiltonian formulation of the model and moreover it can be viewed as the first step for the Ashtekar reformulation of the KK scheme. Moreover, we show how the time component of the gage vector arises naturally from the geometrical constraints of the dynamics; this is a positive check for the autoconsistency of the KK theory and for an Hamiltonian description of the dynamics which will take into account the compactification scenario; this result enforces the physical meaning of the KK model.

We derive a general covariant symplectic structure which leads to holonomic and anholonomic formulations of Hamilton equations of motion related to the hydrodynamic picture of mechanics. Such a structure can be achieved starting from generic bilinear Hamiltonians, constructed by covariant vector, bivector or tensor fields. This feature is gage-free and it realizes a deep link toward canonical quantization for interactions like electromagnetism, gravity and Dirac fields.

This paper deals with a study of the cylindrically symmetric accretion of dark energy with equation of state p = wρ onto wiggly straight cosmic strings, interpreting that the accreted energy only contributes the extent of the wiggliness, but consistently leaves invariant the unperturbed line density μ₀. We have obtained that when w > -1, the perturbed linear energy density in the string core gradually increases tending to a finite maximum value as time increases, for all considered dark energy models. Where the dominant energy condition is violated, all such models predict a steady decreasing of the perturbed linear energy density μ of the cosmic strings as phantom energy is being accreted. The final state of the string after such an accretion process is a wiggleless defect. It is argued however, that if accreation of phantom energy would proceed by successive quantum steps, then the defect would continue losing perturbed linear energy density beyond μ₀, until a minimum nonzero value which can be smaller than that corresponding to the unperturbed string.

The analysis of the observational data for the secular perihelion precession of Mercury, Earth, and Mars, based on the EPM2004 ephemerides, results in new upper limits on density of dark matter in the solar system.