339 research outputs found
Gravity from Local Lorentz Violation
In general relativity, gravitational waves propagate at the speed of light,
and so gravitons are massless. The masslessness can be traced to symmetry under
diffeomorphisms. However, another elegant possibility exists: masslessness can
instead arise from spontaneous violation of local Lorentz invariance. We
construct the corresponding theory of gravity. It reproduces the
Einstein-Hilbert action of general relativity at low energies and temperatures.
Detectable signals occur for sensitive experiments, and potentially profound
implications emerge for our theoretical understanding of gravity.Comment: 6 pages, accepted in General Relativity and Gravitatio
Bosonic string - Kaluza Klein theory exact solutions using 5D-6D dualities
We present the explicit formulae which allow to transform the general
solution of the 6D Kaluza--Klein theory on a 3--torus into the special solution
of the 6D bosonic string theory on a 3--torus as well as into the general
solution of the 5D bosonic string theory on a 2--torus. We construct a new
family of the extremal solutions of the 3D chiral equation for the
SL(4,R)/SO(4) coset matrix and interpret it in terms of the component fields of
these three duality related theories.Comment: 13 pages in LaTe
Purely electromagnetic spacetimes
Electrovacuum solutions devoid of usual mass sources are classified in the
case of one, two and three commuting Killing vectors. Three branches of
solutions exist. Electromagnetically induced mass terms appear in some of them.Comment: 8 page
Generating anisotropic fluids from vacuum Ernst equations
Starting with any stationary axisymmetric vacuum metric, we build anisotropic
fluids. With the help of the Ernst method, the basic equations are derived
together with the expression for the energy-momentum tensor and with the
equation of state compatible with the field equations. The method is presented
by using different coordinate systems: the cylindrical coordinates
and the oblate spheroidal ones. A class of interior solutions matching with
stationary axisymmetric asymptotically flat vacuum solutions is found in oblate
spheroidal coordinates. The solutions presented satisfy the three energy
conditions.Comment: Version published on IJMPD, title changed by the revie
BPS Force Balances via Spin-Spin Interactions
We study two systems of BPS solitons in which spin-spin interactions are
important in establishing the force balances which allow static, multi-soliton
solutions to exist. Solitons in the Israel-Wilson-Perjes (IWP) spacetimes each
carry arbitrary, classical angular momenta. Solitons in the Aichelburg-Embacher
"superpartner" spacetimes carry quantum mechanical spin, which originates in
the zero-modes of the gravitino field of N=2 supergravity in an extreme
Reissner-Nordstrom background. In each case we find a cancellation between
gravitational spin-spin and magnetic dipole-dipole forces, in addition to the
usual one between Newtonian gravitational attraction and Coulombic
electrostatic repulsion. In both cases, we analyze the forces between two
solitons by treating one of the solitons as a probe or test particle, with the
appropriate properties, moving in the background of the other. In the IWP case,
the equation of motion for a spinning test particle, originally due to
Papapetrou, includes a coupling between the background curvature and the spin
of the test particle. In the superpartner case, the relevant equation of motion
follows from a kappa-symmetric superparticle action.Comment: 11 page
Sp(4,R)/GL(2,R) Matrix Structure of Geodesic Solutions for Einstein--Maxwell--Dilaton--Axion Theory
The constructed matrix operator defines the family of
isotropic geodesic containing vacuum point lines in the target space of the
stationary D=4 Einstein--Maxwell--dilaton--axion theory. This operator is used
to derive a class of solutions which describes a point center system with
nontrivial values of mass, parameter NUT, as well as electric, magnetic,
dilaton and axion charges. It is shown that this class contains both particular
solutions Majumdar--Papapetrou--like black holes and massless asymptotically
nonflat naked singularities.Comment: 20 pages, RevTex, no figures, Submitted to Phys.Rev.
Stationary perturbations and infinitesimal rotations of static Einstein-Yang-Mills configurations with bosonic matter
Using the Kaluza-Klein structure of stationary spacetimes, a framework for
analyzing stationary perturbations of static Einstein-Yang-Mills configurations
with bosonic matter fields is presented. It is shown that the perturbations
giving rise to non-vanishing ADM angular momentum are governed by a
self-adjoint system of equations for a set of gauge invariant scalar
amplitudes. The method is illustrated for SU(2) gauge fields, coupled to a
Higgs doublet or a Higgs triplet. It is argued that slowly rotating black holes
arise generically in self-gravitating non-Abelian gauge theories with bosonic
matter, whereas, in general, soliton solutions do not have rotating
counterparts.Comment: 8 pages, revtex, no figure
Equilibrium configurations of two charged masses in General Relativity
An asymptotically flat static solution of Einstein-Maxwell equations which
describes the field of two non-extreme Reissner - Nordstr\"om sources in
equilibrium is presented. It is expressed in terms of physical parameters of
the sources (their masses, charges and separating distance). Very simple
analytical forms were found for the solution as well as for the equilibrium
condition which guarantees the absence of any struts on the symmetry axis. This
condition shows that the equilibrium is not possible for two black holes or for
two naked singularities. However, in the case when one of the sources is a
black hole and another one is a naked singularity, the equilibrium is possible
at some distance separating the sources. It is interesting that for
appropriately chosen parameters even a Schwarzschild black hole together with a
naked singularity can be "suspended" freely in the superposition of their
fields.Comment: 4 pages; accepted for publication in Phys. Rev.
Physical properties of Tolman-Bayin solutions: some cases of static charged fluid spheres in general relativity
In this article, Einstein-Maxwell space-time has been considered in
connection to some of the astrophysical solutions as previously obtained by
Tolman (1939) and Bayin (1978). The effect of inclusion of charge into these
solutions has been investigated thoroughly and also the nature of fluid
pressure and mass density throughout the sphere have been discussed.
Mass-radius and mass-charge relations have been derived for various cases of
the charged matter distribution. Two cases are obtained where perfect fluid
with positive pressures give rise to electromagnetic mass models such that
gravitational mass is of purely electromagnetic origin.Comment: 15 pages, 12 figure
Classical gravitational spin-spin interaction
I obtain an exact, axially symmetric, stationary solution of Einstein's
equations for two massless spinning particles. The term representing the
spin-spin interaction agrees with recently published approximate work. The
spin-spin force appears to be proportional to the inverse fourth power of the
coordinate distance between the particles.Comment: six pages, no figures, journal ref:accepted for Classical and Quantum
Gravit
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