2,642 research outputs found
Einstein-Yang-Mills-Chern-Simons solutions in D=2n+1 dimensions
We investigate finite energy solutions of the
Einstein--Yang-Mills--Chern-Simons system in odd spacetime dimensions, D=2n+1,
with n>1. Our configurations are static and spherically symmetric, approaching
at infinity a Minkowski spacetime background. In contrast with the Abelian
case, the contribution of the Chern-Simons term is nontrivial already in the
static, spherically symmetric limit. Both globally regular, particle-like
solutions and black holes are constructed numerically for several values of D.
These solutions carry a nonzero electric charge and have finite mass. For
globally regular solutions, the value of the electric charge is fixed by the
Chern-Simons coupling constant. The black holes can be thought as non-linear
superpositions of Reissner-Nordstrom and non-Abelian configurations. A
systematic discussion of the solutions is given for D=5, in which case the
Reissner-Nordstrom black hole becomes unstable and develops non-Abelian hair.
We show that some of these non-Abelian configurations are stable under linear,
spherically symmetric perturbations. A detailed discussion of an exact D=5
solution describing extremal black holes and solitons is also provided.Comment: 34 pages, 14 figures; v2: misprints corrected and references adde
Instantonic dyons of Yang-Mills--Chern-Simons models in d=2n+1 dimensions, n>2
We investigate finite energy solutions of Yang-Mills--Chern-Simons systems in
odd spacetime dimensions, d=2n+1, with n>2. This can be carried out
systematically for all n, but the cases n=3,4 corresponding to a 7,8
dimensional spacetime are treated concretely. These are static and spherically
symmetric configurations, defined in a flat Minkowski background. The value of
the electric charge is fixed by the Chern-Simons coupling constant.Comment: 15 pages, 4 figure
Stable black hole solutions with non-Abelian fields
We construct finite mass, asymptotically flat black hole solutions in d=4
Einstein-Yang-Mills theory augmented with higher order curvature terms of the
gauge field. They possess non-Abelian hair in addition to Coulomb electric
charge, and, below some non-zero critical temperature, they are
thermodynamically preferred over the Reissner-Nordstrom solution. Our results
indicate the existence of hairy non-Abelian black holes which are stable under
linear, spherically symmetric perturbations.Comment: 8 pages, 3 figure
Asymptotically flat, stable black hole solutions in Einstein--Yang-Mills--Chern-Simons theory
We construct finite mass, asymptotically flat black hole solutions in d=5
Einstein--Yang-Mills--Chern-Simons theory. Our results indicate the existence
of a second order phase transition between Reissner-Nordstrom solutions and the
non-Abelian black holes which generically are thermodynamically preferred. Some
of the non-Abelian configurations are also stable under linear, spherically
symmetric perturbations. In addition a solution in closed form describing an
extremal black hole with non-Abelian hair is found for a special value of the
Chern-Simons coupling constant.Comment: 9 pages, 3 figure
Nonabelian solutions in N=4, D=5 gauged supergravity
We consider static, nonabelian solutions in N=4, D=5 Romans' gauged
supergravity model. Numerical arguments are presented for the existence of
asymptotically anti-de Sitter configurations in the version of the
theory, with a dilaton potential presenting a stationary point. Considering the
version of the theory with a Liouville dilaton potential, we look for
configurations with unusual topology. A new exact solution is presented, and a
counterterm method is proposed to compute the mass and action.Comment: 15 pages, 4 figure
On a Petrov-type D homogeneous solution
We present a new two-parameter family of solutions of Einstein gravity with
negative cosmological constant in 2+1 dimensions. These solutions are obtained
by squashing the anti-de Sitter geometry along one direction and posses four
Killing vectors. Global properties as well as the four dimensional
generalization are discussed, followed by the investigation of the geodesic
motion. A simple global embedding of these spaces as the intersection of four
quadratic surfaces in a seven dimensional space is obtained. We argue also that
these geometries describe the boundary of a four dimensional nutty-bubble
solution and are relevant in the context of AdS/CFT correspondence.Comment: 20 pages, TeX fil
AdS rotating non-Abelian black holes
We present arguments for the existence of charged, rotating black holes with
equal magnitude angular momenta in Einstein-Yang-Mills theory with
negative cosmological constant. These solutions posses a regular horizon of
spherical topology and approach asymptotically the Anti-de Sitter spacetime
background. The black hole solutions have also an electric charge and a
nonvanishing magnetic flux through the sphere at infinity. Different from the
static case, no regular solution with a nonvanishing angular momenta is found
for a vanishing event horizon radius.Comment: 14 pages, 7 figure
Positive surgical margins in nephron-sparing surgery; the great unknown
There is a currently a general trend towards organ-preserving surgery, and urology is no exception. Specifically, nephron-sparing surgery (NSS) has gained general acceptance for T1a renal cell carcinoma (guidelines recommendations). Moreover T1b, T2 and even T3 stage tumors have been included on the nephron sparing list at some centers. An unresolved issue is that of positive surgical margins (PSM), not only their detection but also the implications for follow up and treatment. This paper highlights data available on risk factors for PSM, their clinical relevance, and possible therapeutic consequences.
From the surgeon’s viewpoint, NSS is a daring and risky surgical procedure. Urological guidelines stress the importance of NSS, and thus the trend is moving in that direction. Unresolved, however, is the problem of PSM. Trifecta, MIC, and pentafecta are applicable concepts which attempt to define the optimal endpoint of NSS, but further elaboration is necessary. Specifically, research needs to focus less on the concept of definitive margins and more on their identification and avoidance. Although some studies suggest that PSMs do not influence overall survival rate, the basic idea of preserving tissue that is not cancerous leads to further medical, social, and psychological considerations
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