130 research outputs found

### On The Interaction of Gravitational Waves with Magnetic and Electric Fields

The existence of large--scale magnetic fields in the universe has led to the
observation that if gravitational waves propagating in a cosmological
environment encounter even a small magnetic field then electromagnetic
radiation is produced. To study this phenomenon in more detail we take it out
of the cosmological context and at the same time simplify the gravitational
radiation to impulsive waves. Specifically, to illustrate our findings, we
describe the following three physical situations: (1) a cylindrical impulsive
gravitational wave propagating into a universe with a magnetic field, (2) an
axially symmetric impulsive gravitational wave propagating into a universe with
an electric field and (3) a `spherical' impulsive gravitational wave
propagating into a universe with a small magnetic field. In cases (1) and (3)
electromagnetic radiation is produced behind the gravitational wave. In case
(2) no electromagnetic radiation appears after the wave unless a current is
established behind the wave breaking the Maxwell vacuum. In all three cases the
presence of the magnetic or electric fields results in a modification of the
amplitude of the incoming gravitational wave which is explicitly calculated
using the Einstein--Maxwell vacuum field equations.Comment: 15 pages, Latex file, accepted for publication in Physical Review

### Creation of multiple de Sitter universes inside a Schwarzschild black hole

A classical model for the interior structure of a Schwarzshild black hole
which consists in creating multiple de Sitter universes with lightlike
boundaries is proposed.The interaction of the boundaries is studied and a
scenario leading to disconnected de Sitter universes is described.Comment: 4 pages,latex,2 figures;contribution to the Journees Relativistes
199

### Braking--Radiation: An Energy Source for a Relativistic Fireball

If the Schwarzschild black-hole is moving rectilinearly with uniform
3-velocity and suddenly stops, according to a distant observer, then we
demonstrate that this observer will see a spherical light--like shell or
"relativistic fireball" radiate outwards with energy equal to the original
kinetic energy of the black-hole.Comment: 6 pages, LateX2e. Published in Phys. Lett.

### Gravitational Effects on Domain Walls with Curvature Correction

We derive the effective action for a domain wall with small thickness in
curved spacetime and show that, apart from the Nambu term, it includes a
contribution proportional to the induced curvature. We then use this action to
study the dynamics of a spherical thick bubble of false vacuum (de Sitter)
surrounded by an infinite region of true vacuum (Schwarzschild)

### Search For Gravitational Waves Through the Electromagnetic Faraday Rotation

A method is given which renders indirect detection of strong gravitational
waves possible. This is based on the reflection (collision) of a linearly
polarized electromagnetic shock wave from (with) a cross polarized impulsive
and shock gravitational waves in accordance with the general theory of
relativity. This highly non-linear process induces a detectable Faraday
rotation in the polarization vector of the electromagnetic field.Comment: Final version. Minor revision, new figures and references are added.
To appear in Physical Review

### Colliding Plane Impulsive Gravitational Waves

When two non-interacting plane impulsive gravitational waves undergo a
head-on collision, the vacuum interaction region between the waves after the
collision contains backscattered gravitational radiation from both waves. The
two systems of backscattered waves have each got a family of rays (null
geodesics) associated with them. We demonstrate that if it is assumed that a
parameter exists along each of these families of rays such that the modulus of
the complex shear of each is equal then Einstein's vacuum field equations, with
the appropriate boundary conditions, can be integrated systematically to reveal
the well-known solutions in the interaction region. In so doing the mystery
behind the origin of such solutions is removed. With the use of the field
equations it is suggested that the assumption leading to their integration may
be interpreted physically as implying that the energy densities of the two
backscattered radiation fields are equal. With the use of different boundary
conditions this approach can lead to new collision solutions.Comment: 21 pages, LaTeX2

### Reflection of electromagnetic waves from mixtures of plane gravitational and scalar waves

We consider colliding wave packets consisting of hybrid mixtures of
electromagnetic, gravitational and scalar waves. Irrespective of the scalar
field, the electromagnetic wave still reflects from the gravitational wave.
Some reflection processes are given for different choice of packets in which
the Coulomb-like component $\Psi_2$ vanishes. Exact solution for multiple
reflection of an electromagnetic wave from successive impulsive gravitational
waves is obtained in a closed form. It is shown that a succesive sign flip in
the Maxwell spinor arises as a result of encountering with an impulsive train
(i.e. the Dirac's comb curvature) of gravitational waves. Such an observable
effect may be helpful in the detection of gravitational wave bursts.Comment: 20 pages, 3 ps figures, small typos corrected, published versio

### On matching LTB and Vaidya spacetimes through a null hypersurface

In this work the matching of a LTB interior solution representing dust matter
to the Vaidya exterior solution describing null fluid through a null
hypersurface is studied. Different cases in which one is able to smoothly match
these two solutions to Einstein equations along a null hypesurface are
discussed.Comment: 5 pages, to appear in GR

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