Thermal-gravitational instability (TGI) is studied in the protogalactic environment. We extend our previous work, where we found that dense clumps first form out of hot background gas by thermal instability and later a small fraction of them grow to virialized clouds of mass Mc & 6×10 6 M⊙ by gravitational infall and merging. But these clouds have large angular momentum, so they would be diffic...

Here we estimate the magnitude of the signals expected for realistic cosmic neutrino backgrounds in detectors attempting to measure the mechanical forces exerted on macroscopic targets by the elastic scattering of relic neutrinos. We study effects proportional to the weak coupling constant GF and to G 2 F for Dirac and Majorana neutrinos, either relativistic or non-relativistic, both gravitatio...

Using the initial peculiar-velocity field, we analytically study the hierarchical formation of gravitationally bound objects. The field is smoothed over a scale that corresponds to the mass of a given class of objects. Through the Zel’dovich approximation, the smoothed field determines how the objects cluster together to form a new class of more massive objects. The standard cosmological parame...

Despite of still bothering uncertainties and ongoing controversy, the convectively supported neutrino-heating mechanism (1) must be considered as a promising way to explain supernova explosions of massive stars. Neutrinos drive the evolution of the collapsing stellar core and of the forming neutron star and dominate the event energetically by carrying away about 99% of the gravitational binding...

We study the orbits in the MOND theory within a dwarf galaxy of mass Md ∼ 108M⊙ at a distance of ∼ 100kpc from a neighboring galaxy of mass Mg = 5 × 1011M⊙, such as ours. It is assumed that a second mass m << Md is gravitationally bound to Md by a previously calculated potential for the MOND theory. This potential is obtained for a free falling mass Md in a constant external gravitational accel...

The classical phenomenon of the redshift of light in a static gravitational potential, usually called the gravitational redshift, is described in the literature essentially in two ways: On the one hand, the phenomenon is explained through the behavior of clocks which run faster the higher they are located in the potential, whereas the energy and frequency of the propagating photon do not change...

We present a detailed examination of the variational principle for metric general relativity as applied to a " quasilocal " spacetime region M (that is, a region that is both spatially and temporally bounded). Our analysis relies on the Hamiltonian formulation of general relativity, and thereby assumes a foliation of M into spacelike hypersurfaces Σ. We allow for near complete generality in the...

In this paper, we have obtained and presented new relativistic stellar configurations considering an anisotropic fluid distribution with a charge distribution and a gravitational potential Z(x) that depends on an adjustable parameter. The quadratic equation of state based on Feroze and Siddiqui viewpoint is used for the matter distribution. The new solutions can be written in terms of elementar...

The spectra of relic gravitational waves produced as a result of cosmological expansion of the inflationary models are derived in Brans-Dicke (BD)theory of gravity.The time dependence of the very early Hubble parameter and matter energy density are derived from frequency dependent spectrum of relic gravitational waves.Also it is found that Brans-Dicke scalar field contributes to the energy dens...

The Bel-Robinson tensor B αβµν gives a positive definite gravitational energy in the small sphere limit approximation. However, there is an alternative tensor V αβµν which was proposed recently that offers the same positivity as B αβµν does. These two tensors are a basis for expressions which have the desirable non-negative gravitational energy in the small sphere region limit.