476 research outputs found
Asymptotic Behavior of the Gowdy Spacetimes
We present new evidence in support of the Penrose's strong cosmic censorship
conjecture in the class of Gowdy spacetimes with spatial topology.
Solving Einstein's equations perturbatively to all orders we show that
asymptotically close to the boundary of the maximal Cauchy development the
dominant term in the expansion gives rise to curvature singularity for almost
all initial data. The dominant term, which we call the ``geodesic loop
solution'', is a solution of the Einstein's equations with all space
derivatives dropped. We also describe the extent to which our perturbative
results can be rigorously justified.Comment: 30 page
Blow-Up of Test Fields Near Cauchy Horizons
The behaviour of test fields near a compact Cauchy horizon is investigated.
It is shown that solutions of nonlinear wave equations on Taub spacetime with
generic initial data cannot be continued smoothly to both extensions of the
spacetime through the Cauchy horizon. This is proved using an energy method.
Similar results are obtained for the spacetimes of Moncrief containing a
compact Cauchy horizon and for more general matter models.Comment: 10 pages, Plain TeX, MPA-AR-92-
Global constants in (2+1)--dimensional gravity
The extended conformal algebra (so)(2,3) of global, quantum, constants of
motion in 2+1 dimensional gravity with topology R x T^2 and negative
cosmological constant is reviewed. It is shown that the 10 global constants
form a complete set by expressing them in terms of two commuting spinors and
the Dirac gamma matrices. The spinor components are the globally constant
holonomy parameters, and their respective spinor norms are their quantum
commutators.Comment: 14 pages, to appear in Classical and Quantum Gravity, Spacetime
Safari: Essays in Honor of Vincent Moncrief on the Classical Physics of
Strong Gravitational Field
Dipole Perturbations of the Reissner-Nordstrom Solution: The Polar Case
The formalism developed by Chandrasekhar for the linear polar perturbations
of the Reissner-Nordstrom solution is generalized to include the case of dipole
(l=1) perturbations. Then, the perturbed metric coefficients and components of
the Maxwell tensor are computed.Comment: 16 pages, LaTeX, no figures. Submitted for publication in Physical
Review
The Mixmaster Spacetime, Geroch's Transformation and Constants of Motion
We show that for -symmetric spacetimes on a constant of
motion associated with the well known Geroch transformation, a functional
, quadratic in gravitational momenta, is strictly positive
in an open subset of the set of all -symmetric initial data, and
therefore not weakly zero. The Mixmaster initial data appear to be on the
boundary of that set. We calculate the constant of motion perturbatively for
the Mixmaster spacetime and find it to be proportional to the minisuperspace
Hamiltonian to the first order in the Misner anisotropy variables, i.e. weakly
zero. Assuming that is exactly zero for the Mixmaster spacetime, we show
that Geroch's transformation, when applied to the Mixmaster spacetime, gives a
new \mbox{-symmetric} solution of the vacuum Einstein equations, globally
defined on \mbox{},which is non-homogeneous and
presumably exhibits Mixmaster-like complicated dynamical behavior.Comment: 25 pages, preprint YCTP-20-93, Revte
Gravitational waves in general relativity: XIV. Bondi expansions and the ``polyhomogeneity'' of \Scri
The structure of polyhomogeneous space-times (i.e., space-times with metrics
which admit an expansion in terms of ) constructed by a
Bondi--Sachs type method is analysed. The occurrence of some log terms in an
asymptotic expansion of the metric is related to the non--vanishing of the Weyl
tensor at Scri. Various quantities of interest, including the Bondi mass loss
formula, the peeling--off of the Riemann tensor and the Newman--Penrose
constants of motion are re-examined in this context.Comment: LaTeX, 28pp, CMA-MR14-9
Static Black Hole Solutions without Rotational Symmetry
We construct static black hole solutions that have no rotational symmetry.
These arise in theories, including the standard electroweak model, that include
charged vector mesons with mass . In such theories, a magnetically
charged Reissner-Nordstrom black hole with horizon radius less than a critical
value of the order of is classically unstable against the development
of a nonzero vector meson field just outside the horizon, indicating the
existence of static black hole solutions with vector meson hair. For the case
of unit magnetic charge, spherically symmetric solutions of this type have
previously been studied. For other values of the magnetic charge, general
arguments show that any new solution with hair cannot be spherically symmetric.
In this paper we develop and apply a perturbative scheme (which may have
applicability in other contexts) for constructing such solutions in the case
where the Reissner-Nordstrom solution is just barely unstable. For a few low
values of the magnetic charge the black holes retain a rotational symmetry
about a single axis, but this axial symmetry disappears for higher charges.
While the vector meson fields vanish exponentially fast at distances greater
than , the magnetic field and the metric have higher multipole
components that decrease only as powers of the distance from the black hole.Comment: 42 pages, phyzzx. 4 figures (PostScript, 1.7 MB when uncompressed)
available by email from the Authors on reques
On Further Generalization of the Rigidity Theorem for Spacetimes with a Stationary Event Horizon or a Compact Cauchy Horizon
A rigidity theorem that applies to smooth electrovac spacetimes which
represent either (A) an asymptotically flat stationary black hole or (B) a
cosmological spacetime with a compact Cauchy horizon ruled by closed null
geodesics was given in a recent work \cite{frw}. Here we enlarge the framework
of the corresponding investigations by allowing the presence of other type of
matter fields. In the first part the matter fields are involved merely
implicitly via the assumption that the dominant energy condition is satisfied.
In the second part Einstein-Klein-Gordon (EKG), Einstein-[non-Abelian] Higgs
(E[nA]H), Einstein-[Maxwell]-Yang-Mills-dilaton (E[M]YMd) and
Einstein-Yang-Mills-Higgs (EYMH) systems are studied. The black hole event
horizon or, respectively, the compact Cauchy horizon of the considered
spacetimes is assumed to be a smooth non-degenerate null hypersurface. It is
proven that there exists a Killing vector field in a one-sided neighborhood of
the horizon in EKG, E[nA]H, E[M]YMd and EYMH spacetimes. This Killing vector
field is normal to the horizon, moreover, the associated matter fields are also
shown to be invariant with respect to it. The presented results provide
generalizations of the rigidity theorems of Hawking (for case A) and of
Moncrief and Isenberg (for case B) and, in turn, they strengthen the validity
of both the black hole rigidity scenario and the strong cosmic censor
conjecture of classical general relativity.Comment: 25 pages, LaTex, a shortened version, including a new proof for lemma
5.1, the additional case of Einstein-Yang-Mills-Higgs systems is also
covered, to appear in Class. Quant. Gra
The Quantum Modular Group in (2+1)-Dimensional Gravity
The role of the modular group in the holonomy representation of
(2+1)-dimensional quantum gravity is studied. This representation can be viewed
as a "Heisenberg picture", and for simple topologies, the transformation to the
ADM "Schr{\"o}dinger picture" may be found. For spacetimes with the spatial
topology of a torus, this transformation and an explicit operator
representation of the mapping class group are constructed. It is shown that the
quantum modular group splits the holonomy representation Hilbert space into
physically equivalent orthogonal ``fundamental regions'' that are interchanged
by modular transformations.Comment: 23 pages, LaTeX, no figures; minor changes and clarifications in
response to referee (basic argument and conclusions unaffected
Strong Cosmic Censorship and Causality Violation
We investigate the instability of the Cauchy horizon caused by causality
violation in the compact vacuum universe with the topology , which Moncrief and Isenberg considered. We show that if
the occurrence of curvature singularities are restricted to the boundary of
causality violating region, the whole segments of the boundary become curvature
singularities. This implies that the strong cosmic censorship holds in the
spatially compact vacuum space-time in the case of the causality violation.
This also suggests that causality violation cannot occur for a compact
universe.Comment: corrected version, 8 pages, one eps figure is include
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