413 research outputs found
Antiperiodic solitons of the Goldstone model on S^1
Our purpose is to present all static solutions of the Goldstone model on a
circle in 1+1 dimensions with an antiperiodicity condition imposed on the
scalar fields. Jacobi elliptic and standard trigonometric functions are used to
express the solutions found and stability analysis of the latter is what
follows. Classically stable quasi-topological solitons are identified.Comment: 12 pages, 3 figures, 3 references added, some corrections made.
Accepted for publication in Nonlinearit
Non-Extreme and Ultra-Extreme Domain Walls and Their Global Space-Times
Non-extreme walls (bubbles with two insides) and ultra-extreme walls (bubbles
of false vacuum decay) are discussed. Their respective energy densities are
higher and lower than that of the corresponding extreme (supersymmetric),
planar domain wall. These singularity free space-times exhibit non-trivial
causal structure analogous to certain non-extreme black holes. We focus on
anti-de~Sitter--Minkowski walls and comment on Minkowski--Minkowski walls with
trivial extreme limit, as well as walls adjacent to de~Sitter space-times with
no extreme limit.Comment: Revised version, 4 pages of REVTEX, UPR-546-T/Rev. Two figures not
included. This version contains further elaboration of the space-time causal
structur
Invariant Regularization of Anomaly-Free Chiral Theories
We present a generalization of the Frolov-Slavnov invariant regularization
scheme for chiral fermion theories in curved spacetimes. local gauge symmetries
of the theory, including local Lorentz invariance. The perturbative scheme
works for arbitrary representations which satisfy the chiral gauge anomaly and
the mixed Lorentz-gauge anomaly cancellation conditions. Anomalous theories on
the other hand manifest themselves by having divergent fermion loops which
remain unregularized by the scheme. Since the invariant scheme is promoted to
also include local Lorentz invariance, spectator fields which do not couple to
gravity cannot be, and are not, introduced. Furthermore, the scheme is truly
chiral (Weyl) in that all fields, including the regulators, are left-handed;
and only the left-handed spin connection is needed. The scheme is, therefore,
well suited for the study of the interaction of matter with all four known
forces in a completely chiral fashion. In contrast with the vectorlike
formulation, the degeneracy between the Adler-Bell-Jackiw current and the
fermion number current in the bare action is preserved by the chiral
regularization scheme.Comment: 28pgs, LaTeX. Typos corrected. Further remarks on singlet current
Protecting the conformal symmetry via bulk renormalization on Anti deSitter space
The problem of perturbative breakdown of conformal symmetry can be avoided,
if a conformally covariant quantum field phi on d-dimensional Minkowski
spacetime is viewed as the boundary limit of a quantum field Phi on
d+1-dimensional anti-deSitter spacetime (AdS). We study the boundary limit in
renormalized perturbation theory with polynomial interactions in AdS, and point
out the differences as compared to renormalization directly on the boundary. In
particular, provided the limit exists, there is no conformal anomaly. We
compute explicitly the "fish diagram" on AdS_4 by differential renormalization,
and calculate the anomalous dimension of the composite boundary field phi^2
with bulk interaction Phi^4.Comment: 40 page
Scalar field quantization on the 2+1 dimensional black hole background
The quantization of a massless conformally coupled scalar field on the 2+1
dimensional Anti de Sitter black hole background is presented. The Green's
function is calculated, using the fact that the black hole is Anti de Sitter
space with points identified, and taking into account the fact that the black
hole spacetime is not globally hyperbolic. It is shown that the Green's
function calculated in this way is the Hartle-Hawking Green's function. The
Green's function is used to compute , which is
regular on the black hole horizon, and diverges at the singularity. A particle
detector response function outside the horizon is also calculated and shown to
be a fermi type distribution. The back-reaction from is calculated exactly and is shown to give rise to a curvature
singularity at and to shift the horizon outwards. For a horizon
develops, shielding the singularity. Some speculations about the endpoint of
evaporation are discussed.Comment: CTP 2243, 24 pages, RevTex. (The backreaction section is extended,
and some confusing notation has been changed
Thick domain wall universes
We investigate the spacetime of a thick gravitating domain wall for a general
potential . Using general analytical arguments we show that all
nontrivial solutions fall into two categories: those interpretable as an
isolated domain wall with a cosmological event horizon, and those which are
pure false vacuum de Sitter solutions. Although this latter solution is always
unstable to the field rolling coherently to its true vacuum, we show that there
is an additional instability to wall formation if the scalar field does not
couple too strongly to gravity. Using the and sine-Gordon
models as illustrative examples, we investigate the phase space of the
gravitating domain wall in detail numerically, following the solutions from
weak to strong gravity. We find excellent agreement with the analytic work.
Then, we analyse the domain wall in the presence of a cosmological constant
finding again the two kinds of solutions, wall and de Sitter, even in the
presence of a negative cosmological constant.Comment: 20 pages revtex, epsfig, references added, some conclusions altere
Local and global gravitational aspects of domain wall space-times
Local and global gravitational effects induced by eternal vacuum domain walls
are studied. We concentrate on thin walls between non-equal and non-positive
cosmological constants on each side of the wall. These vacuum domain walls fall
in three classes depending on the value of their energy density : (1)\
extreme walls with are planar, static walls
corresponding to supersymmetric configurations, (2)\ non-extreme walls with
correspond to
expanding bubbles with observers on either side of the wall being {\em
inside\/} the bubble, and (3)\ ultra-extreme walls with represent the bubbles of false
vacuum decay. On the sides with less negative cosmological constant, the
extreme, non-extreme, and ultra-extreme walls exhibit no, repulsive, and
attractive effective ``gravitational forces,'' respectively. These
``gravitational forces'' are global effects not caused by local curvature.
Since the non-extreme wall encloses observers on both sides, the supersymmetric
system has the lowest gravitational mass accessable to outside observers. It is
conjectured that similar positive mass protection occurs in all physical
systems and that no finite negative mass object can exist inside the universe.
We also discuss the global space-time structure of these singularity free
space-times and point out intriguing analogies with the causal structure of
black holes.Comment: UPR-565-T, 26 REVTEX pages, 10 figures available upon reques
On classical super-radiance in Kerr-Newman-anti-de Sitter black holes
We study in detail the modes of a classical scalar field on a
Kerr-Newman-anti-de Sitter (KN-AdS) black hole. We construct sets of basis
modes appropriate to the two possible boundary conditions (``reflective'' and
``transparent'') at time-like infinity, and consider whether super-radiance is
possible. If we employ ``reflective'' boundary conditions, all modes are
non-super-radiant. On the other hand, for ``transparent'' boundary conditions,
the presence of super-radiance depends on our definition of positive frequency.
For those KN-AdS black holes having a globally time-like Killing vector, the
natural choice of positive frequency leads to no super-radiance. For other
KN-AdS black holes, there is a choice of positive frequency which gives no
super-radiance, but for other choices there will, in general, be
super-radiance.Comment: 23 pages, 3 figures, v2: minor changes, references adde
Quantum Properties of Topological Black Holes
We examine quantum properties of topological black holes which are
asymptotically anti--de Sitter. First, massless scalar fields and Weyl spinors
which propagate in the background of an anti--de Sitter black hole are
considered in an exactly soluble two--dimensional toy model. The Boulware--,
Unruh--, and Hartle--Hawking vacua are defined. The latter results to coincide
with the Unruh vacuum due to the boundary conditions necessary in
asymptotically adS spacetimes. We show that the Hartle--Hawking vacuum
represents a thermal equilibrium state with the temperature found in the
Euclidean formulation. The renormalized stress tensor for this quantum state is
well--defined everywhere, for any genus and for all solutions which do not have
an inner Cauchy horizon, whereas in this last case it diverges on the inner
horizon. The four--dimensional case is finally considered, the equilibrium
states are discussed and a luminosity formula for the black hole of any genus
is obtained. Since spacelike infinity in anti--de Sitter space acts like a
mirror, it is pointed out how this would imply information loss in
gravitational collapse. The black hole's mass spectrum according to
Bekenstein's view is discussed and compared to that provided by string theory.Comment: 31 pages, one additional figure, enlarged discussion of the higher
genus case, comment on the mass and new references adde
Radiation from accelerated black holes in an anti-de Sitter universe
We study gravitational and electromagnetic radiation generated by uniformly
accelerated charged black holes in anti-de Sitter spacetime. This is described
by the C-metric exact solution of the Einstein-Maxwell equations with a
negative cosmological constant Lambda. We explicitly find and interpret the
pattern of radiation that characterizes the dependence of the fields on a null
direction from which the (timelike) conformal infinity is approached. This
directional pattern exhibits specific properties which are more complicated if
compared with recent analogous results obtained for asymptotic behavior of
fields near a de Sitter-like infinity. In particular, for large acceleration
the anti-de Sitter-like infinity is divided by Killing horizons into several
distinct domains with a different structure of principal null directions, in
which the patterns of radiation differ.Comment: 19 pages, 11 colour figures, submitted to Phys. Rev. D [Low quality
figures are included in this version because of arXive size restrictions. The
version with the standard quality figures is available at
http://utf.mff.cuni.cz/~podolsky/jppubl.htm.
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