1,068 research outputs found
Azimuthal electric field in a static rotationally symmetric (2+1)-dimensional spacetime
The fundamental metrics, which describe any static three-dimensional
Einstein-Maxwell spacetime (depending only on a unique spacelike coordinate),
are found. In this case there are only three independent components of the
electromagnetic field: two for the vector electric field and one for the scalar
magnetic field. It is shown that we can not have any superposition of these
components of the electric and magnetic fields in this kind of static
gravitational field. One of the electrostatic Einstein-Maxwell solutions is
related to the magnetostatic solution by a duality mapping, while the second
electrostatic gravitational field must be solved separately. Solutions induced
by the more general (2+1)-Maxwell tensor on the static cylindrically symmetric
spacetimes are studied and it is shown that all of them are also connected by
duality mappings.Comment: 5 pages, Final versio
Accelerated FRW Solutions in Chern-Simons Gravity
We consider a five-dimensional Einstein-Chern-Simons action which is composed
of a gravitational sector and a sector of matter, where the gravitational
sector is given by a Chern-Simons gravity action instead of the
Einstein-Hilbert action and where the matter sector is given by the so called
perfect fluid. It is shown that (i) the Einstein-Chern-Simons (EChS) field
equations subject to suitable conditions can be written in a similar way to the
Einstein-Maxwell field equations; (ii) these equations have solutions that
describe accelerated expansion for the three possible cosmological models of
the universe, namely, spherical expansion, flat expansion and hyperbolic
expansion when , a parameter of theory, is greater than zero. This
result allow us to conjeture that this solutions are compatible with the era of
Dark Energy and that the energy-momentum tensor for the field , a
bosonic gauge field from the Chern-Simons gravity action, corresponds to a form
of positive cosmological constant.
It is also shown that the EChS field equations have solutions compatible with
the era of matter: (i) In the case of an open universe, the solutions
correspond to an accelerated expansion () with a minimum scale
factor at initial time that, when the time goes to infinity, the scale factor
behaves as a hyperbolic sine function. (ii) In the case of a flat universe, the
solutions describing an accelerated expansion whose scale factor behaves as a
exponencial function when time grows. \item In the case of a closed universe it
is found only one solution for a universe in expansion, which behaves as a
hyperbolic cosine function when time grows.Comment: 58 pages, 24 figure
Born-Infeld black holes in the presence of a cosmological constant
We construct asymptotically anti-deSitter (and deSitter) black hole solutions
of Einstein-Born-Infeld theory in arbitrary dimension. We critically analyse
their geometries and discuss their thermodynamic properties.Comment: 10 Pages, 6 Figures, LaTeX, to appear in Phys. Letts.
Phantom cosmologies and fermions
Form invariance transformations can be used for constructing phantom
cosmologies starting with conventional cosmological models. In this work we
reconsider the scalar field case and extend the discussion to fermionic fields,
where the "phantomization" process exhibits a new class of possible accelerated
regimes. As an application we analyze the cosmological constant group for a
fermionic seed fluid.Comment: 5 pages, version which was accepted for publication in CQ
No Black Hole Theorem in Three-Dimensional Gravity
A common property of known black hole solutions in (2+1)-dimensional gravity
is that they require a negative cosmological constant. In this letter, it is
shown that a (2+1)-dimensional gravity theory which satisfies the dominant
energy condition forbids the existence of a black hole to explain the above
situation.Comment: 3 pages, no figures, to be published in Physical Review Letter
Advanced Video-Based Processing for Low-Cost Damage Assessment of Buildings under Seismic Loading in Shaking Table Tests
This paper explores the potential of a low-cost, advanced video-based technique for the
assessment of structural damage to buildings caused by seismic loading. A low-cost, high-speed video
camera was utilized for the motion magnification processing of footage of a two-story reinforcedconcrete
frame building subjected to shaking table tests. The damage after seismic loading was
estimated by analyzing the dynamic behavior (i.e., modal parameters) and the structural deformations
of the building in magnified videos. The results using the motion magnification procedure were
compared for validation of the method of the damage assessment obtained through analyses of
conventional accelerometric sensors and high-precision optical markers tracked using a passive
3D motion capture system. In addition, 3D laser scanning to obtain an accurate survey of the
building geometry before and after the seismic tests was carried out. In particular, accelerometric
recordings were also processed and analyzed using several stationary and nonstationary signal
processing techniques with the aim of analyzing the linear behavior of the undamaged structure and
the nonlinear structural behavior during damaging shaking table tests. The proposed procedure
based on the analysis of magnified videos provided an accurate estimate of the main modal frequency
and the damage location through the analysis of the modal shapes, which were confirmed using
advanced analyses of the accelerometric data. Consequently, the main novelty of the study was
the highlighting of a simple procedure with high potential for the extraction and analysis of modal
parameters, with a special focus on the analysis of the modal shape’s curvature, which provides
accurate information on the location of the damage in a structure, while using a noncontact and
low-cost method
General analysis of self-dual solutions for the Einstein-Maxwell-Chern-Simons theory in (1+2) dimensions
The solutions of the Einstein-Maxwell-Chern-Simons theory are studied in
(1+2) dimensions with the self-duality condition imposed on the Maxwell field.
We give a closed form of the general solution which is determined by a single
function having the physical meaning of the quasilocal angular momentum of the
solution. This function completely determines the geometry of spacetime, also
providing the direct computation of the conserved total mass and angular
momentum of the configurations.Comment: 3 pages, REVTEX file, no figure
Long-Term Clinical Consequences of Intense, Uninterrupted Endurance Training in Olympic Athletes
n/
Liver fluke (Fasciola hepatica) naturally infecting introduced European brown hare (Lepus europaeus) in northern Patagonia: phenotype, prevalence and potential risk
ARTÍCULO PUBLICADO EN REVISTA EXTERNA. Fascioliasis has recently been included in the WHO list of Neglected Zoonotic Diseases. Besides being a major veterinary health problem, fascioliasis has large underdeveloping effects on the human communities affected. Though scarcely considered in fascioliasis epidemiology, it is well recognized that both native and introduced wildlife species may play a significant role as reservoirs of the disease. The objectives are to study the morphological characteristics of Fasciola hepatica adults and eggs in a population of Lepus europaeus, to assess liver fluke prevalence, and to analyze the potential reservoir role of the European brown hare in northern Patagonia, Argentina, where fascioliasis is endemic. Measures of F. hepatica found in L. europaeus from northern Patagonia demonstrate that the liver fluke is able to fully develop in wild hares and to shed normal eggs through their faeces. Egg shedding to the environment is close to the lower limit obtained for pigs, a domestic animal whose epidemiological importance in endemic areas has already been highlighted. The former, combined with the high prevalence found (14.28%) suggest an even more important role in the transmission cycle than previously considered. The results obtained do not only remark the extraordinary plasticity and adaptability of this trematode species to different host species, but also highlight the role
of the European brown hare, and other NIS, as reservoirs capable for parasite spillback to domestic and native cycle, representing a potentially important, but hitherto neglected, cause of disease emergence. Sitio de la revista: https://pubmed.ncbi.nlm.nih.gov/26204194
Topological Born-Infeld-dilaton black holes
We construct a new analytic solution of Einstein-Born-Infeld-dilaton theory
in the presence of Liouville-type potentials for the dilaton field. These
solutions describe dilaton black holes with nontrivial topology and nonlinear
electrodynamics. Black hole horizons and cosmological horizons in these
spacetimes, can be a two-dimensional positive, zero or negative constant
curvature surface. The asymptotic behavior of these solutions are neither flat
nor (A)dS. We calculate the conserved and thermodynamic quantities of these
solutions and verify that these quantities satisfy the first law of black hole
thermodynamics.Comment: 15 pages, 7 figures, references added, to appear in Phys. Lett.
- …