226 research outputs found
Geometric invariance of mass-like asymptotic invariants
We study coordinate-invariance of some asymptotic invariants such as the ADM
mass or the Chru\'sciel-Herzlich momentum, given by an integral over a
"boundary at infinity". When changing the coordinates at infinity, some terms
in the change of integrand do not decay fast enough to have a vanishing
integral at infinity; but they may be gathered in a divergence, thus having
vanishing integral over any closed hypersurface. This fact could only be
checked after direct calculation (and was called a "curious cancellation"). We
give a conceptual explanation thereof.Comment: 13 page
On Israel-Wilson-Perjes black holes
We show, under certain conditions, that regular Israel-Wilson-Perj\'es black
holes necessarily belong to the Majumdar-Papapetrou family
On non-existence of static vacuum black holes with degenerate components of the event horizon
We present a simple proof of the non-existence of degenerate components of
the event horizon in static, vacuum, regular, four-dimensional black hole
spacetimes. We discuss the generalisation to higher dimensions and the
inclusion of a cosmological constant.Comment: latex2e, 9 pages in A
On higher dimensional black holes with abelian isometry group
We consider (n+1)--dimensional, stationary, asymptotically flat, or
Kaluza-Klein asymptotically flat black holes, with an abelian --dimensional
subgroup of the isometry group satisfying an orthogonal integrability
condition. Under suitable regularity conditions we prove that the area of the
group orbits is positive on the domain of outer communications, vanishing only
on its boundary and on the "symmetry axis". We further show that the orbits of
the connected component of the isometry group are timelike throughout the
domain of outer communications. Those results provide a starting point for the
classification of such black holes. Finally, we show non-existence of zeros of
static Killing vectors on degenerate Killing horizons, as needed for the
generalisation of the static no-hair theorem to higher dimensions
The isometry groups of asymptotically flat, asymptotically empty space-times with timelike ADM four-momentum
We give a complete classification of all connected isometry groups, together
with their actions in the asymptotic region, in asymptotically flat,
asymptotically vacuum space--times with timelike ADM four--momentum.Comment: Latex with amssymb, 16 page
Radiative spacetimes approaching the Vaidya metric
We analyze a class of exact type II solutions of the Robinson-Trautman family
which contain pure radiation and (possibly) a cosmological constant. It is
shown that these spacetimes exist for any sufficiently smooth initial data, and
that they approach the spherically symmetric Vaidya-(anti-)de Sitter metric. We
also investigate extensions of the metric, and we demonstrate that their order
of smoothness is in general only finite. Some applications of the results are
outlined.Comment: 12 pages, 3 figure
A uniqueness theorem for degenerate Kerr-Newman black holes
We show that the domains of dependence of stationary, -regular,
analytic, electrovacuum space-times with a connected, non-empty, rotating,
degenerate event horizon arise from Kerr-Newman space-times
Towards uniqueness of degenerate axially symmetric Killing horizon
We examine the linearized equations around extremal Kerr horizon and give
some arguments towards stability of the horizon with respect to generic
(non-symmetric) linear perturbation of near horizon geometry.Comment: 17 page
Topological censorship for Kaluza-Klein space-times
The standard topological censorship theorems require asymptotic hypotheses
which are too restrictive for several situations of interest. In this paper we
prove a version of topological censorship under significantly weaker
conditions, compatible e.g. with solutions with Kaluza-Klein asymptotic
behavior. In particular we prove simple connectedness of the quotient of the
domain of outer communications by the group of symmetries for models which are
asymptotically flat, or asymptotically anti-de Sitter, in a Kaluza-Klein sense.
This allows one, e.g., to define the twist potentials needed for the reduction
of the field equations in uniqueness theorems. Finally, the methods used to
prove the above are used to show that weakly trapped compact surfaces cannot be
seen from Scri.Comment: minor correction
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