99 research outputs found
Black holes with gravitational hair in higher dimensions
A new class of vacuum black holes for the most general gravity theory leading to second order field equations in the metric in even dimensions is presented. These space-times are locally AdS in the asymptotic region, and are characterized by a continuous parameter that does not enter in the conserve charges, nor it can be reabsorbed by a coordinate transformation: it is therefore a purely gravitational hair. The black holes are constructed as a warped product of a two-dimensional space-time, which resembles the r-t plane of the BTZ black hole, times a warp factor multiplying the metric of a D-2-dimensional Euclidean base manifold, which is restricted by a scalar equation. It is shown that all the Noether charges vanish. Furthermore, this is consistent with the Euclidean action approach: even though the black hole has a finite temperature, both the entropy and the mass vanish. Interesting examples of base manifolds are given in eight dimensions which are products of Thurston geometries, giving then a nontrivial topology to the black hole horizon. The possibility of introducing a torsional hair for these solutions is also discussed
Exact Black Holes and Universality in the Backreaction of non-linear Sigma Models with a potential in (A)dS4
The aim of this paper is to construct accelerated, stationary and
axisymmetric exact solutions of the Einstein theory with self interacting
scalar fields in (A)dS4. To warm up, the backreaction of the (non)-minimally
coupled scalar field is solved, the scalar field equations are integrated and
all the potentials compatible with the metric ansatz and Einstein gravity are
found. With these results at hand the non-linear sigma model is tackled. The
scalar field Lagrangian is generic; neither the coupling to the curvature,
neither the metric in the scalar manifold nor the potential, are fixed ab
initio. The unique assumption in the analysis is the metric ansatz: it has the
form of the most general Petrov type D vacuum solution of general relativity;
it is a a cohomogeneity two Weyl rescaling of the Carter metric and therefore
it has the typical Plebanski-Demianski form with two arbitrary functions of one
variable and one arbitrary functions of two variables. It is shown, by an
straightforward manipulation of the field equations, that the metric is
completely integrable without necessity of specifiying anything in the scalar
Lagrangian. This results in that the backreaction of the scalar fields, within
this class of metrics, is universal. The metric functions generically show an
explicit dependence on a dynamical exponent that allows to smoothly connect
this new family of solutions with the actual Plebanski-Demianski spacetime. The
remaining field equations imply that the scalar fields follow geodesics in the
scalar manifold with an affine parameter given by a non-linear function of the
spacetime coordinates and define the on-shell form of the potential plus a
functional equation that it has to satisfy. Finally, a general family of (A)dS4
static hairy black holes is explicitly constructed and its properties are
outlined.Comment: Several typos correcte
Kerr-Schild spacetimes with (A)dS background
General properties of Kerr-Schild spacetimes with (A)dS background in
arbitrary dimension are studied. It is shown that the geodetic Kerr-Schild
vector k is a multiple WAND of the spacetime. Einstein Kerr-Schild spacetimes
with non-expanding k are shown to be of Weyl type N, while the expanding
spacetimes are of type II or D. It is shown that this class of spacetimes obeys
the optical constraint. This allows us to solve Sachs equation, determine
r-dependence of boost weight zero components of the Weyl tensor and discuss
curvature singularities.Comment: 17 pages, minor change
Hairy planar black holes in higher dimensions
We construct exact hairy planar black holes in D-dimensional AdS gravity.
These solutions are regular except at the singularity and have stress-energy
that satisfies the null energy condition. We present a detailed analysis of
their thermodynamical properties and show that the first law is satisfied. We
also discuss these solutions in the context of AdS/CFT duality and construct
the associated c-function.Comment: 18 pages, no figures; v2: title changed, typos fixe
Einstein-Katz action, variational principle, Noether charges and the thermodynamics of AdS-black holes
Neoadjuvant Treatment for Nonmetastatic Pancreatic Cancer
Pancreatic adenocarcinoma is one of the most lethal malignancies among solid tumors. Unfortunately, several patients are diagnosed at metastatic stage or with unresectable disease due to vascular compromise involving the pancreas without any chance of curative treatment. There are also two other groups of patients: resectable patients at upfront diagnosis and “borderline resectable” pancreatic cancer patients. This last group represents those patients where surgery is not always possible without a preoperative treatment allowing surgeons to perform an R0 resection. Achieving an R0 resection is the only curative option for pancreatic cancer patients; nevertheless, many R0-resected patients will relapse within 2 years from surgery. Despite adjuvant treatment, reported median overall survival is only 28 months for patients with resectable pancreatic adenocarcinoma; thus, neoadjuvant treatment has been explored in order to improve survival. We aim to describe the controversial reported data and to show the recommendations that are suggested for these patients; however, we need to remark that there is no strong data that support neoadjuvant treatment. Currently, clinical trials are ongoing, and probably soon this approach will become a standard of care among borderline resectable patients and probably in selected resectable patients too
On hidden broken nonlinear superconformal symmetry of conformal mechanics and nature of double nonlinear superconformal symmetry
We show that for positive integer values of the parameter in the
conformal mechanics model the system possesses a hidden nonlinear
superconformal symmetry, in which reflection plays a role of the grading
operator. In addition to the even -generators, the
superalgebra includes odd integrals, which form the pair of
spin- representations of the bosonic subalgebra and anticommute for
order polynomials of the even generators. This hidden symmetry, however,
is broken at the level of the states in such a way that the action of the odd
generators violates the boundary condition at the origin. In the earlier
observed double nonlinear superconformal symmetry, arising in the
superconformal mechanics for certain values of the boson-fermion coupling
constant, the higher order symmetry is of the same, broken nature.Comment: 8 pages; typos correcte
Charged C-metric with conformally coupled scalar field
We present a generalisation of the charged C-metric conformally coupled with
a scalar field in the presence of a cosmological constant. The solution is
asymptotically flat or a constant curvature spacetime. The spacetime metric has
the geometry of a usual charged C-metric with cosmological constant, where the
mass and charge are equal. When the cosmological constant is absent it is found
that the scalar field only blows up at the angular pole of the event horizon.
The presence of the cosmological constant can generically render the scalar
field regular where the metric is regular, pushing the singularity beyond the
event horizon. For certain cases of enhanced acceleration with a negative
cosmological constant, the conical singularity disappears all together and the
scalar field is everywhere regular. The black hole is then rather a black
string with its event horizon extending all the way to asymptotic infinity and
providing itself the necessary acceleration.Comment: regular article, no figures, typos corrected, to appear in Classical
and Quantum Gravit
A new cubic theory of gravity in five dimensions: Black hole, Birkhoff's theorem and C-function
We present a new cubic theory of gravity in five dimensions which has second
order traced field equations, analogous to BHT new massive gravity in three
dimensions. Moreover, for static spherically symmetric spacetimes all the field
equations are of second order, and the theory admits a new asymptotically
locally flat black hole. Furthermore, we prove the uniqueness of this solution,
study its thermodynamical properties, and show the existence of a C-function
for the theory following the arguments of Anber and Kastor (arXiv:0802.1290
[hep-th]) in pure Lovelock theories. Finally, we include the
Einstein-Gauss-Bonnet and cosmological terms and we find new asymptotically AdS
black holes at the point where the three maximally symmetric solutions of the
theory coincide. These black holes may also possess a Cauchy horizon.Comment: 21 pages, no figures, V2: two appendices and some references added,
V3: New section on the generalization to arbitrary higher order. Analogy with
BHT new massive gravity Lagrangian made more precise, V4: Typos corrected. To
appear in CQ
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