4,381 research outputs found
Van Der Waals Black Holes in dimensions
We generalize the recent solution proposed by Rajagopal et al. to arbitrary
number of dimensions and horizon topologies. We comment on the regime of
validity of these solution. Among our main results, we argue that the Van Der
Waals (VDW) black hole (BH) metric is to be interpreted as a near horizon
metric. This is supported by inspecting the energy conditions. We analyze the
limiting cases of a perfect fluid, interacting points and non interacting balls
gas equation of state and map them to known black holes. Finally, we provide a
case study by comparing the Reissner-Nordstr\"om and VDW BH close to the
horizon and show that they are qualitatively similar for some range of the
horizon radius.Comment: 14 p., 4 figure
Supergravity on an Atiyah-Hitchin Base
We construct solutions to five dimensional minimal supergravity using an
Atiyah-Hitchin base space. In examining the structure of solutions we show that
they generically contain a singularity either on the Atiyah-Hitchin bolt or at
larger radius where there is a singular solitonic boundary. However for most
points in parameter space the solution exhibits a velocity of light surface
(analogous to what appears in a Goedel space-time) that shields the
singularity. For these solutions, all closed time-like curves are causally
disconnected from the rest of the space-time in that they exist within the
velocity of light surface, which null geodesics are unable to cross. The
singularities in these solutions are thus found to be hidden behind the
velocity of light surface and so are not naked despite the lack of an event
horizon. Outside of this surface the space-time is geodesically complete,
asymptotically flat and can be arranged so as not to contain closed time-like
curves at infinity. The rest of parameter space simply yields solutions with
naked singularities.Comment: 29 pages, 5 figures, citations added, analytic solution added,
figures changed, main results unaltere
On black strings & branes in Lovelock gravity
It is well known that black strings and branes may be constructed in pure
Einstein gravity simply by adding flat directions to a vacuum black hole
solution. A similar construction holds in the presence of a cosmological
constant. While these constructions fail in general Lovelock theories, we show
that they carry over straightforwardly within a class of Lovelock gravity
theories that have (locally) unique constant curvature vacua.Comment: 12 pages, Latex, references addde
A Journal for the Astronomical Computing Community?
One of the Birds of a Feather (BoF) discussion sessions at ADASS XX
considered whether a new journal is needed to serve the astronomical computing
community. In this paper we discuss the nature and requirements of that
community, outline the analysis that led us to propose this as a topic for a
BoF, and review the discussion from the BoF session itself. We also present the
results from a survey designed to assess the suitability of astronomical
computing papers of different kinds for publication in a range of existing
astronomical and scientific computing journals. The discussion in the BoF
session was somewhat inconclusive, and it seems likely that this topic will be
debated again at a future ADASS or in a similar forum.Comment: 4 pages, no figures; to appear in proceedings of ADASS X
Black Hole Chemistry
The mass of a black hole has traditionally been identified with its energy.
We describe a new perspective on black hole thermodynamics, one that identifies
the mass of a black hole with chemical enthalpy, and the cosmological constant
as thermodynamic pressure. This leads to an understanding of black holes from
the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids,
reentrant phase transitions, and triple points. Both charged and rotating black
holes exhibit novel chemical-type phase behaviour, hitherto unseen.Comment: 12 pages, Essay written for the Gravity Research Foundation 2014
Awards for Essays on Gravitatio
Another Mass Gap in the BTZ Geometry?
We attempt the construction of perturbative rotating hairy black holes and
boson stars, invariant under a single helical Killing field, in 2+1-dimensions
to complete the perturbative analysis in arbitrary odd dimension recently put
forth in \cite{Stotyn:2011ns}. Unlike the higher dimensional cases, we find
evidence for the non-existence of hairy black holes in 2+1-dimensions in the
perturbative regime, which is interpreted as another mass gap, within which the
black holes cannot have hair. The boson star solutions face a similar
impediment in the background of a conical singularity with a sufficiently high
angular deficit, most notably in the zero-mass BTZ background where boson stars
cannot exist at all. We construct such boson stars in the AdS_3 background as
well as in the background of conical singularities of periodicities
\pi,2\pi/3,\pi/2.Comment: 13 pages, 2 appendices, Invited Contribution to an IOP special volume
of Journal of Physics A in honor of Stuart Dowker's 75th birthday, v2:
discussion in section 4 expande
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