32,539 research outputs found
B\"acklund transformations in 2D dilaton gravity
We give a B\"acklund transformation connecting a generic 2D dilaton gravity
theory to a generally covariant free field theory. This transformation provides
an explicit canonical transformation relating both theories.Comment: LaTeX file, 7 page
The Dirac particle on central backgrounds and the anti-de Sitter oscillator
It is shown that, for spherically symmetric static backgrounds, a simple
reduced Dirac equation can be obtained by using the Cartesian tetrad gauge in
Cartesian holonomic coordinates. This equation is manifestly covariant under
rotations so that the spherical coordinates can be separated in terms of
angular spinors like in special relativity, obtaining a pair of radial
equations and a specific form of the radial scalar product. As an example, we
analytically solve the anti-de Sitter oscillator giving the formula of the
energy levels and the form of the corresponding eigenspinors.Comment: 16 pages, Late
VVV Survey Microlensing Events in the Galactic Center Region
IndexaciĂłn: Scopus.We search for microlensing events in the highly reddened areas surrounding the Galactic center using the near-IR observations with the VISTA Variables in the VĂa LĂĄctea Survey (VVV). We report the discovery of 182 new microlensing events, based on observations acquired between 2010 and 2015. We present the color-magnitude diagrams of the microlensing sources for the VVV tiles b332, b333, and b334, which were independently analyzed, and show good qualitative agreement among themselves. We detect an excess of microlensing events in the central tile b333 in comparison with the other two tiles, suggesting that the microlensing optical depth keeps rising all the way to the Galactic center. We derive the Einstein radius crossing time for all of the observed events. The observed event timescales range from t E = 5 to 200 days. The resulting timescale distribution shows a mean timescale of days for the complete sample (N = 182 events), and days if restricted only for the red clump (RC) giant sources (N = 96 RC events). There are 20 long timescale events ( days) that suggest the presence of massive lenses (black holes) or disk-disk event. This work demonstrates that the VVV Survey is a powerful tool to detect intermediate/long timescale microlensing events in highly reddened areas, and it enables a number of future applications, from analyzing individual events to computing the statistics for the inner Galactic mass and kinematic distributions, in aid of future ground- and space-based experiments.http://iopscience.iop.org/article/10.3847/2041-8213/aa9b29/met
Spurious finite-size instabilities in nuclear energy density functionals: spin channel
It has been recently shown, that some Skyrme functionals can lead to
non-converging results in the calculation of some properties of atomic nuclei.
A previous study has pointed out a possible link between these convergence
problems and the appearance of finite-size instabilities in symmetric nuclear
matter (SNM) around saturation density.
We show that the finite-size instabilities not only affect the ground state
properties of atomic nuclei, but they can also influence the calculations of
vibrational excited states in finite nuclei. We perform systematic fully-self
consistent Random Phase Approximation (RPA) calculations in spherical
doubly-magic nuclei. We employ several Skyrme functionals and vary the
isoscalar and isovector coupling constants of the time-odd term
. We determine critical values of these
coupling constants beyond which the RPA calculations do not converge because
RPA the stability matrix becomes non-positive.By comparing the RPA calculations
of atomic nuclei with those performed for SNM we establish a correspondence
between the critical densities in the infinite system and the critical coupling
constants for which the RPA calculations do not converge. We find a
quantitative stability criterion to detect finite-size instabilities related to
the spin term of a functional. This
criterion could be easily implemented into the standard fitting protocols to
fix the coupling constants of the Skyrme functional
Extended Skyrme Equation of State in asymmetric nuclear matter
We present a new equation of state for infinite systems (symmetric,
asymmetric and neutron matter) based on an extended Skyrme functional
constrained by microscopic Brueckner-Bethe-Goldstone results. The resulting
equation of state reproduces with very good accuracy the main features of
microscopic calculations and it is compatible with recent measurements of two
times Solar-mass neutron stars. We provide all necessary analytical expressions
to facilitate a quick numerical implementation of quantities of astrophysical
interest
Electrically charged finite energy solutions of an and an Higgs-Chern-Simons--Yang-Mills-Higgs systems in dimensions
We study spherically symmetric finite energy solutions of two
Higgs-Chern-Simons--Yang-Mills-Higgs (HCS-YMH) models in dimensions, one
with gauge group and the other with . The Chern-Simons (CS)
densities are defined in terms of both the Yang-Mills (YM) and Higgs fields and
the choice of the two gauge groups is made so they do not vanish. The solutions
of the model carry only electric charge and zero magnetic charge, while
the solutions of the model are dyons carrying both electric and
magnetic charges like the Julia-Zee (JZ) dyon. Unlike the latter however, the
electric charge in both models receives an important contribution from the CS
dynamics. We pay special attention to the relation between the energies and
charges of these solutions. In contrast with the electrically charged JZ dyon
of the Yang-Mills-Higgs (YMH) system, whose mass is larger than that of the
electrically neutral (magnetic monopole) solutions, the masses of the
electrically charged solutions of our HCS-YMH models can be smaller than their
electrically neutral counterparts in some parts of the parameter space. To
establish this is the main task of this work, which is performed by
constructing the HCS-YMH solutions numerically. In the case of the
HCS-YMH, we have considered the question of angular momentum, and it turns out
that it vanishes.Comment: 20 pages, 10 figure
- âŠ