529 research outputs found
Non-adiabatic radiative collapse of a relativistic star under different initial conditions
We examine the role of space-time geometry in the non-adiabatic collapse of a
star dissipating energy in the form of radial heat flow, studying its evolution
under different initial conditions. The collapse of a star with interior
comprising of a homogeneous perfect fluid is compared with that of a star
filled with inhomogeneous imperfect fluid with anisotropic pressure. Both the
configurations are spherically symmetric, however, in the latter case, the
physical space of the configurations is assumed to be
inhomogeneous endowed with spheroidal or pseudo-spheroidal geometry. It is
observed that as long as the collapse is shear-free, its evolution depends only
on the mass and size of the star at the onset of collapse.Comment: To appear in Pramana- j. of physic
Global monopole as dual-vacuum solution in Kaluza-Klein spacetime
By application of the duality transformation, which implies interchange of
active and passive electric parts of the Riemann curvature (equivalent to
interchange of Ricci and Einstein tensors) it is shown that the global monopole
solution in the Kaluza-Klein spacetime is dual to the corresponding vacuum
solution. Further we also obtain solution dual to flat space which would in
general describe a massive global monopole in 4-dimensional Euclidean space and
would have massless limit analogus to the 4-dimensional dual-flat solution.Comment: 8 pages, LaTEX versio
Charged relativistic spheres with generalized potentials
A new class of exact solutions of the Einstein-Maxwell system is found in
closed form. This is achieved by choosing a generalised form for one of the
gravitational potentials and a particular form for the electric field
intensity. For specific values of the parameters it is possible to write the
new series solutions in terms of elementary functions. We regain well known
physically reasonable models. A physical analysis indicates that the model may
be used to describe a charged sphere. The influence of the electromagnetic
field on the gravitational interaction is highlighted.Comment: 22 pages, To appear in Math. Meth. Appl. Sc
Exact relativistic model for a superdense star
Assuming that the physical 3-space t = const in a superdense star is spheroidal, a static spherically symmetric model based on an exact solution of Einstein's equations is given which will permit densities of the order of 2 Ă— 1014 gm cm-3, radii of the order of a few kilometers and masses up to about four times the solar mass
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