405 research outputs found
Lorentz violating electrodynamics
After summarizing the most interesting results in the calculation of
synchrotron radiation in the Myers-Pospelov effective model for Lorentz
invariance violating (LIV) electrodynamics, we present a general unified way of
describing the radiation regime of LIV electrodynamics which include the
following three different models : Gambini-Pullin, Ellis et al. and
Myers-Pospelov. Such unification reduces to the standard approach of radiation
in a dispersive and absortive (in general) medium with a given index of
refraction. The formulation is presented up to second order in the LIV
parameter and it is explicitly applied to the synchrotron radiation case.Comment: 11 pages, extended version of the talk given by L.F. Urrutia in the
VI Mexican School: Approaches to Quantum Gravity, Playa del Carmen, Mexico,
Nov. 2004. Minor chages in the text and added reference
A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
We present a mode identification based on new high-resolution time-series
spectra of the non-radially pulsating Delta Scuti star FG~Vir (HD 106384, V =
6.57, A5V). From 2002 February to June a global Delta Scuti Network (DSN)
campaign, utilizing high-resolution spectroscopy and simultaneous photometry
has been conducted for FG~Vir in order to provide a theoretical pulsation
model. In this campaign we have acquired 969 Echelle spectra covering 147 hours
at six observatories. The mode identification was carried out by analyzing line
profile variations by means of the Fourier parameter fit method, where the
observational Fourier parameters across the line are fitted with theoretical
values. This method is especially well suited for determining the azimuthal
order m of non-radial pulsation modes and thus complementary with the method of
Daszynska-Daszkiewicz (2002) which does best at identifying the degree l. 15
frequencies between 9.2 and 33.5 c/d were detected spectroscopically. We
determined the azimuthal order m of 12 modes and constrained their harmonic
degree l. Only modes of low degree (l <= 4) were detected, most of them having
axisymmetric character mainly due to the relatively low projected rotational
velocity of FG Vir. The detected non-axisymmetric modes have azimuthal orders
between -2 and 1. We derived an inclination of 19 degrees, which implies an
equatorial rotational rate of 66 km/s.Comment: 14 pages, 26 figure
Revisión del complejo de géneros de chinches de encaje del Nuevo Mundo <i>Tigava</i> (Hemiptera: Heteroptera: Tingidae), con la descripción de dos nuevos géneros y dos nuevas especies y una clave para géneros
The lace bug (Tingidae) genera belonging to the New World Tigava complex are reviewed. The two new genera and new species Mexicotingis brailovskyi, from MĂ©xico, and Paraceratotingis convergens, from Venezuela, are described. Diagnoses, descriptions, and digital color photographs of the new taxa, diagnoses and digital photographs of the heads and pronota of all genera, an updated checklist and distributions of the included species, and a key to genera are provided to help distinguish these closely related Tingidae.Se revisan los gĂ©neros de chinches de encaje (Tingidae) del Nuevo Mundo pertenecientes al complejo Tigava. Se describen dos nuevos gĂ©neros y especies Mexicotingis brailovskyi de MĂ©xico, y Paraceratotingis convergens, de Venezuela. Se brindan diagnosis, descripciones, y fotos en color de los nuevos taxa, diagnosis y fotografĂas de la cabeza y el pronoto de todos los gĂ©neros, una lista actualizada de las distribuciones de todas sus especies, y una clave para gĂ©neros para distinguir estos Tingidae estrechamente emparentados.Facultad de Ciencias Naturales y Muse
Stochastic approach to inflation II: classicality, coarse-graining and noises
In this work we generalize a previously developed semiclassical approach to
inflation, devoted to the analysis of the effective dynamics of coarse-grained
fields, which are essential to the stochastic approach to inflation. We
consider general non-trivial momentum distributions when defining these fields.
The use of smooth cutoffs in momentum space avoids highly singular quantum
noise correlations and allows us to consider the whole quantum noise sector
when analyzing the conditions for the validity of an effective classical
dynamical description of the coarse-grained field. We show that the weighting
of modes has physical consequences, and thus cannot be considered as a mere
mathematical artifact. In particular we discuss the exponential inflationary
scenario and show that colored noises appear with cutoff dependent amplitudes.Comment: 18 pages, revtex, no figure
Duality for symmetric second rank tensors. II. The linearized gravitational field
The construction of dual theories for linearized gravity in four dimensions
is considered. Our approach is based on the parent Lagrangian method previously
developed for the massive spin-two case, but now considered for the zero mass
case. This leads to a dual theory described in terms of a rank two symmetric
tensor, analogous to the usual gravitational field, and an auxiliary
antisymmetric field. This theory has an enlarged gauge symmetry, but with an
adequate partial gauge fixing it can be reduced to a gauge symmetry similar to
the standard one of linearized gravitation. We present examples illustrating
the general procedure and the physical interpretation of the dual fields. The
zero mass case of the massive theory dual to the massive spin-two theory is
also examined, but we show that it only contains a spin-zero excitation.Comment: 20 pages, no figure
Dual theories for mixed symmetry fields. Spin-two case: (1,1) versus (2,1) Young symmetry type fields
We show that the parent Lagrangian method gives a natural generalization of
the dual theories concept for non p-form fields. Using this generalization we
construct here a three-parameter family of Lagrangians that are dual to the
Fierz-Pauli description of a free massive spin-two system. The dual field is a
three-index tensor T, which dinamically belongs to the (2,1) representation of
the Lorentz group. As expected, the massless limit of our Lagrangian, which is
parameter independent, has two propagating degrees of freedom per space point.Comment: 10 pages, no figure
Pulsar motions from neutrino oscillations induced by a violation of the equivalence principle
We analize a possible explanation of the pulsar motions in terms of resonant
neutrino transitions induced by a violation of the equivalence principle (VEP).
Our approach, based on a parametrized post-Newtonian (PPN) expansion, shows
that VEP effects give rise to highly directional contributions to the neutrino
oscillation length. These terms induce anisotropies in the linear and angular
momentum of the emitted neutrinos, which can account for both the observed
translational and rotational pulsar motions. The violation needed to produce
the actual motions is completely compatible with the existing bounds.Comment: 6 pages, no figure
- âŠ