2,038 research outputs found
Some constructions of almost para-hyperhermitian structures on manifolds and tangent bundles
In this paper we give some examples of almost para-hyperhermitian structures
on the tangent bundle of an almost product manifold, on the product manifold
, where is a manifold endowed with a mixed 3-structure
and on the circle bundle over a manifold with a mixed 3-structure.Comment: 10 pages; This paper has been presented in the "4th German-Romanian
Seminar on Geometry" Dortmund, Germany, 15-18 July 200
Special Geometry of Euclidean Supersymmetry III: the local r-map, instantons and black holes
We define and study projective special para-Kahler manifolds and show that
they appear as target manifolds when reducing five-dimensional vector
multiplets coupled to supergravity with respect to time. The dimensional
reductions with respect to time and space are carried out in a uniform way
using an epsilon-complex notation. We explain the relation of our formalism to
other formalisms of special geometry used in the literature. In the second part
of the paper we investigate instanton solutions and their dimensional lifting
to black holes. We show that the instanton action, which can be defined after
dualising axions into tensor fields, agrees with the ADM mass of the
corresponding black hole. The relation between actions via Wick rotation, Hodge
dualisation and analytic continuation of axions is discussed.Comment: 72 pages, 2 figure
MĂșsculo ancĂłneo epitroclear. Una infrecuente causa de neuropatĂa cubital del codo
The entrapment neuropathy of the ulnar nerve at the elbow is a frequent pathology with a variety of etiologies. One of them is the presence of an accessory muscle, such as the anconeus epitrochlearis. Although this muscle is frequently found in the general population, it is a rare cause of nerve compression. Despite its similarity to the idiopathic form, there are certain features that may suggest that the compression is due to this accessory muscle. This work reports a representative case in which the anconeus epitrochlearis was discovered during the surgical intervention
Laser assisted decay of quasistationary states
The effects of intense electromagnetic fields on the decay of quasistationary
states are investigated theoretically. We focus on the parameter regime of
strong laser fields and nonlinear effects where an essentially nonperturbative
description is required. Our approach is based on the imaginary time method
previously introduced in the theory of strong-field ionization. Spectra and
total decay rates are presented for a test case and the results are compared
with exact numerical calculations. The potential of this method is confirmed by
good quantitative agreement with the numerical results.Comment: 24 pages, 5 figure
Non-extremal Black Holes, Harmonic Functions, and Attractor Equations
We present a method which allows to deform extremal black hole solutions into
non-extremal solutions, for a large class of supersymmetric and
non-supersymmetric Einstein-Vector-Scalar type theories. The deformation is
shown to be largely independent of the details of the matter sector. While the
line element is dressed with an additional harmonic function, the attractor
equations for the scalars remain unmodified in suitable coordinates, and the
values of the scalar fields on the outer and inner horizon are obtained from
their fixed point values by making specific substitutions for the charges. For
a subclass of models, which includes the five-dimensional STU-model, we find
explicit solutions.Comment: 33 page
Does a relativistic metric generalization of Newtonian gravity exist in 2+1 dimensions?
It is shown that, contrary to previous claims, a scalar tensor theory of
Brans-Dicke type provides a relativistic generalization of Newtonian gravity in
2+1 dimensions. The theory is metric and test particles follow the space-time
geodesics. The static isotropic solution is studied in vacuum and in regions
filled with an incompressible perfect fluid. It is shown that the solutions can
be consistently matched at the matter vacuum interface, and that the Newtonian
behavior is recovered in the weak field regime.Comment: 6 pages, no figures, Revtex4. Some discussions on the physical nature
of the interior solution and on the omega->infinity limit and some references
added. Version to appear in Phys. Rev.
A comparative study to the numerical approximation of random Airy differential equation
The aim of this paper is twofold. First, we deal with the extension to the random framework of the piecewise Fröbenius method to solve Airy differential equations. This extension is based on mean square stochastic calculus. Second, we want to explore the capability to provide not only reliable approximations for both the average and the standard deviation functions associated to the solution stochastic process, but also to save computational time as it happens in dealing with the analogous problem in the deterministic scenario. This includes a comparison of the numerical results with respect to those obtained by other commonly used operational methods such as polynomial chaos and Monte Carlo simulations. To conduct this comparative study, we have chosen the Airy random differential equation because it has highly oscillatory solutions. This feature allows us to emphasize differences between all the considered approaches. © 2011 Elsevier Ltd. All rights reserved.This work has been partially supported by the Spanish M.C.Y.T. and FEDER grants MTM2009-08587, DPI2010-20891-C02-01 as well as the Universitat Politecnica de Valencia grant PAID-06-09 (Ref. 2588).Cortés López, JC.; Jódar Sånchez, LA.; Romero Bauset, JV.; Roselló Ferragud, MD. (2011). A comparative study to the numerical approximation of random Airy differential equation. Computers and Mathematics with Applications. 62(9):3411-3417. https://doi.org/10.1016/j.camwa.2011.08.056S3411341762
Inner Polar Rings and Disks: Observed Properties
A list of galaxies with inner regions revealing polar (or strongly inclined
to the main galactic plane) disks and rings is compiled from the literature
data. The list contains 47 galaxies of all morphological types, from E to Irr.
We consider the statistics of the parameters of polar structures known from
observations. The radii of the majority of them do not exceed 1.5 kpc. The
polar structures are equally common in barred and unbarred galaxies. At the
same time, if a galaxy has a bar (or a triaxial bulge), this leads to the polar
disk stabilization - its axis of rotation usually coincides with the major axis
of the bar. More than two thirds of all considered galaxies reveal one or
another sign of recent interaction or merging. This fact indicates a direct
relation between the external environment and the presence of an inner polar
structure.Comment: 12 pages, 3 figures, accepted to Astrophysical Bulletin. Minor
changes and corrections are still possibl
Conservation of energy and momenta in nonholonomic systems with affine constraints
We characterize the conditions for the conservation of the energy and of the
components of the momentum maps of lifted actions, and of their `gauge-like'
generalizations, in time-independent nonholonomic mechanical systems with
affine constraints. These conditions involve geometrical and mechanical
properties of the system, and are codified in the so-called
reaction-annihilator distribution
Structure of the Collision Zone Between the Nazca Ridge and the Peruvian Convergent Margin: Geodynamic and Seismotectonic Implications
We study the structure and tectonics of the collision zone between the Nazca Ridge (NR) and the Peruvian margin constrained by seismic, gravimetric, bathymetric, and natural seismological data. The NR was formed in an on-ridge setting, and it is characterized by a smooth and broad shallow seafloor (swell) with an estimated buoyancy flux of ~7 Mg/s. The seismic results show that the NR hosts an oceanic lower crust 10â14 km thick with velocities of 7.2â7.5 km/s suggesting intrusion of magmatic material from the hot spot plume to the oceanic plate. Our results show evidence for subduction erosion in the frontal part of the margin likely enhanced by the collision of the NR. The ridge-trench collision zone correlates with the presence of a prominent normal scarp, a narrow continental slope, and (uplifted) shelf. In contrast, adjacent of the collision zone, the slope does not present a topographic scarp and the continental slope and shelf become wider and deeper. Geophysical and geodetic evidence indicate that the collision zone is characterized by low seismic coupling at the plate interface. This is consistent with vigorous subduction erosion enhanced by the subducting NR causing abrasion and increase of fluid pore pressure at the interplate contact. Furthermore, the NR has behaved as a barrier for rupture propagation of megathrust earthquakes (e.g., 1746 Mw 8.6 and 1942 Mw 8.1 events). In contrast, for moderate earthquakes (e.g., 1996 Mw 7.7 and 2011 Mw 6.9 events), the NR has behaved as a seismic asperity nucleating at depths >20 km
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