1,742 research outputs found
Skyrmion and Skyrme-Black holes in de Sitter spacetime
Numerical arguments are presented for the existence of regular and black hole
solutions of the Einstein-Skyrme equations with a positive cosmological
constant. These classical configurations approach asymptotically the de Sitter
spacetime. The main properties of the solutions and the differences with
respect to the asymptotically flat ones are discussed. It particular our
results suggest that, for a positive cosmological constant, the mass evaluated
as timelike infinity in infinite. Special emphasis is set to De Sitter black
holes Skyrmions which display two horizons.Comment: 11 pages, 4 figure
Rotating Boson Stars and Q-Balls
We consider axially symmetric, rotating boson stars. Their flat space limits
represent spinning Q-balls. We discuss their properties and determine their
domain of existence. Q-balls and boson stars are stationary solutions and exist
only in a limited frequency range. The coupling to gravity gives rise to a
spiral-like frequency dependence of the boson stars. We address the flat space
limit and the limit of strong gravitational coupling. For comparison we also
determine the properties of spherically symmetric Q-balls and boson stars.Comment: 22 pages, 18 figure
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
Einstein-Yang-Mills solutions in higher dimensional de Sitter spacetime
We consider particle-like and black holes solutions of the
Einstein-Yang-Mills system with positive cosmological constant in d>4 spacetime
dimensions. These configurations are spherically symmetric and present a
cosmological horizon for a finite value of the radial coordinate, approaching
asymptotically the de Sitter background. In the usual Yang--Mills case we find
that the mass of these solutions, evaluated outside the cosmological horizon at
future/past infinity generically diverges for d>4. Solutions with finite mass
are found by adding to the action higher order gauge field terms belonging to
the Yang--Mills hierarchy. A discussion of the main properties of these
solutions and their differences from those to the usual Yang-Mills model, both
in four and higher dimensions is presented.Comment: 17 pages, 8 figure
Modeling planar degenerate wetting and anchoring in nematic liquid crystals
We propose a simple surface potential favoring the planar degenerate
anchoring of nematic liquid crystals, i.e., the tendency of the molecules to
align parallel to one another along any direction parallel to the surface. We
show that, at lowest order in the tensorial Landau-de Gennes order-parameter,
fourth-order terms must be included. We analyze the anchoring and wetting
properties of this surface potential. In the nematic phase, we find the desired
degenerate planar anchoring, with positive scalar order-parameter and some
surface biaxiality. In the isotropic phase, we find, in agreement with
experiments, that the wetting layer may exhibit a uniaxial ordering with
negative scalar order-parameter. For large enough anchoring strength, this
negative ordering transits towards the planar degenerate state
Fourier-Space Crystallography as Group Cohomology
We reformulate Fourier-space crystallography in the language of cohomology of
groups. Once the problem is understood as a classification of linear functions
on the lattice, restricted by a particular group relation, and identified by
gauge transformation, the cohomological description becomes natural. We review
Fourier-space crystallography and group cohomology, quote the fact that
cohomology is dual to homology, and exhibit several results, previously
established for special cases or by intricate calculation, that fall
immediately out of the formalism. In particular, we prove that {\it two phase
functions are gauge equivalent if and only if they agree on all their
gauge-invariant integral linear combinations} and show how to find all these
linear combinations systematically.Comment: plain tex, 14 pages (replaced 5/8/01 to include archive preprint
number for reference 22
MLA Research Agenda. Systematic Review Project. Team Updates Presentation. MLA Annual Meeting Supplement. May 17, 2015
Most of the 15 systematic review teams provided one-page summaries of their progress to date in compiling systematic reviews on one of 15 top-ranked important research projects. This builds upon an earlier Delphi study that was reported here: Eldredge JD, Ascher MT, Holmes HN, Harris MR. The new Medical Library Association research agenda: final results from a three-phase Delphi study. J Med Libr Assoc. 2012 Jul;100(3):214-8. doi: 10.3163/1536-5050.100.3.012. PubMed PMID: 22879811; PubMed Central PMCID: PMC3411260
- …