3,763 research outputs found
Black String Solutions with arbitrary Tension
We consider 1+4 dimensional black string solutions which are invariant under
translation along the fifth direction. The solutions are characterized by the
two parameters, mass and tension, of the source. The Gregory-Laflamme solution
is shown to be characterized by the tension whose magnitude is one half of the
mass per unit length of the source. The general black string solution with
arbitrary tension is presented and its properties are discussed.Comment: 10 page
Pulsar Magnetosphere : A General Relativistic Treatment
A fully general relativistic description of the pulsar magnetosphere is
provided. To be more concrete, a study of the pulsar magnetosphere is performed
in the context of general relativistic magnetohydrodynamics (MHD) employing the
so-called Grad-Shafranov approach. Not surprisingly, the resulting
Grad-Shafranov equations and all the other related general relativistic MHD
equations turn out to take essentially the same structures as those for the
(rotating) black hole magnetosphere. Other different natures between the two
cases including the structure of singular surfaces of MHD flows in each
magnetosphere are essentially encoded in the different spacetime (metric)
contents. In this way, the pulsar and the black hole magnetospheres can be
described in an unified fashion. Particularly, the direction of poloidal
currents circulating in the neutron star magnetosphere turns out to be the same
as that of currents circulating in the black hole magnetosphere which, in turn,
leads to the pulsar and the black hole spin-downs via the ``magnetic braking''.Comment: 42 pages, 3 figures, Mon. Not. R. Astron. Soc.(MNRAS), in pres
Dynamics of false vacuum bubbles with nonminimal coupling
We study the dynamics of false vacuum bubbles. A nonminimally coupled scalar
field gives rise to the effect of negative tension. The mass of a false vacuum
bubble from outside observer's point of view can be positive, zero, or
negative. The interior false vacuum has de Sitter geometry, while the exterior
true vacuum background can have geometry depending on the vacuum energy. We
show that there exist expanding false vacuum bubbles without the initial
singularity in the past.Comment: 17 pages, 13 figure
Bremsstrahlung Radiation At a Vacuum Bubble Wall
When charged particles collide with a vacuum bubble, they can radiate strong
electromagnetic waves due to rapid deceleration. Owing to the energy loss of
the particles by this bremsstrahlung radiation, there is a non-negligible
damping pressure acting on the bubble wall even when thermal equilibrium is
maintained. In the non-relativistic region, this pressure is proportional to
the velocity of the wall and could have influenced the bubble dynamics in the
early universe.Comment: 6 pages, 2 figures, revtex, to appear in JKP
Spacetime structure of 5D hypercylindrical vacuum solutions with tension
We investigate geometrical properties of 5D cylindrical vacuum solutions with
a transverse spherical symmetry. The metric is uniform along the fifth
direction and characterized by tension and mass densities. The solutions are
classified by the tension-to-mass ratio. One particular example is the
well-known Schwarzschild black string which has a curvature singularity
enclosed by a horizon. We focus mainly on geometry of other solutions which
possess a naked singularity. The light signal emitted by an object approaching
the singularity reaches a distant observer with finite time, but is infinitely
red-shifted.Comment: revtex4, 5 pages, 2 figures. To appear in the proceedings of the 10th
Asia Pacific Physics Conference (APPC10), Pohang, Korea, 21-24 Aug. 2007.
Submitted to J. Korean Phys. Soc. Penrose diagram has been adde
Cosmic Microwave Background Radiation anisotropy with primordial magnetic fields
Galactic magnetic fields are observed of order , but their
origin is not definitely known yet. In this paper we consider the primordial
magnetic fields generated in the early universe and analyse their effects on
the density perturbations and the CMBR anisotropy. We assume that the random
magnetic fields have the power law spectrum and satisfy the force-free field
condition.
The peak heights of the CMBR anisotropy are shown to be shifted upward
depending on the magnetic field strengths relative to the no-magnetic field
case.Comment: 22 pages, 5 figure
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