1,654 research outputs found
Cosmic magnetic fields and dark energy in extended electromagnetism
We discuss an extended version of electromagnetism in which the usual gauge
fixing term is promoted into a physical contribution that introduces a new
scalar state in the theory. This new state can be generated from vacuum quantum
fluctuations during an inflationary era and, on super-Hubble scales, gives rise
to an effective cosmological constant. The value of such a cosmological
constant coincides with the one inferred from observations as long as inflation
took place at the electroweak scale. On the other hand, the new state also
generates an effective electric charge density on sub-Hubble scales that
produces both vorticity and magnetic fields with coherent lengths as large as
the present Hubble horizon.Comment: 4 pages, 2 figures. Contribution to the proceedings of Spanish
Relativity Meeting 2010, Granada, Spain, 6-10 September 201
Metastability of non-reversible mean-field Potts model with three spins
We examine a non-reversible, mean-field Potts model with three spins on a set
with points. Without an external field, there are three
critical temperatures and five different metastable regimes. The analysis can
be extended by a perturbative argument to the case of small external fields. We
illustrate the case of large external fields with some phenomena which are not
present in the absence of external field.Comment: 34 pages, 12 figure
Effects of biasing on the galaxy power spectrum at large scales
n this paper we study the effect of biasing on the power spectrum at large
scales. We show that even though non-linear biasing does introduce a white
noise contribution on large scales, the behavior of the
matter power spectrum on large scales may still be visible and above the white
noise for about one decade. We show, that the Kaiser biasing scheme which leads
to linear bias of the correlation function on {\em large} scales, also
generates a linear bias of the {\rm power spectrum} on rather small scales.
This is a consequence of the divergence on small scales of the pure
Harrison-Zeldovich spectrum. However, biasing becomes k-dependent when we damp
the underlying power spectrum on small scales. We also discuss the effect of
biasing on the baryon acoustic oscillations.Comment: 9 pages, 4 figures. One figure and comments clarifying the linear
biasing on small scales and references added. V3 version accepted in PR
On the chemical ladder of esters. Detection and formation of ethyl formate in the W51 e2 hot molecular core
The detection of organic molecules with increasing complexity and potential
biological relevance is opening the possibility to understand the formation of
the building blocks of life in the interstellar medium. One of the families of
molecules with astrobiological interest are the esters, whose simplest member,
methyl formate, is rather abundant in star-forming regions. The next step in
the chemical complexity of esters is ethyl formate, CHOCHO. Only two
detections of this species have been reported so far, which strongly limits our
understanding of how complex molecules are formed in the interstellar medium.
We have searched for ethyl formate towards the W51 e2 hot molecular core, one
of the most chemically rich sources in the Galaxy and one of the most promising
regions to study prebiotic chemistry, especially after the recent discovery of
the PO bond, key in the formation of DNA. We have analyzed a spectral line
survey towards the W51 e2 hot molecular core, which covers 44 GHz in the 1, 2
and 3 mm bands, carried out with the IRAM 30m telescope. We report the
detection of the trans and gauche conformers of ethyl formate. A Local
Thermodynamic Equilibrium analysis indicates that the excitation temperature is
7810 K and that the two conformers have similar source-averaged column
densities of (2.00.3)10 cm and an abundance of
10. We compare the observed molecular abundances of ethyl formate
with different competing chemical models based on grain surface and gas-phase
chemistry. We propose that grain-surface chemistry may have a dominant role in
the formation of ethyl formate (and other complex organic molecules) in hot
molecular cores, rather than reactions in the gas phase.Comment: Accepted in A&A; 11 pages, 6 figures, 7 Table
Analysis of the quark sector in the 2HDM-III with a four-zero Yukawa texture using the most recent data on the CKM matrix
In this letter we analyse, in the context of the general 2-Higgs Doublet
Model, the structure of the Yukawa matrices, , by assuming a four-zero texture ansatz for their definition. In this
framework, we obtain compact expressions for , which are reduced to the Cheng and Sher ansatz with the difference that
they are obtained naturally as a direct consequence of the invariants of the
fermion mass matrices. Furthermore, in order to avoid large flavour violating
effects coming from charged Higgs exchange, we consider the main flavour
constraints on the off-diagonal terms of Yukawa texture {{}} (). We perform a -fit
based on current experimental data on the quark masses and the
Cabibbo-Kobayashi-Maskawa mixing matrix . Hence, we obtain
the allowed ranges for the parameters at
1 for several values of . The results are in complete
agreement with the bounds obtained taking into account constraints on Flavour
Changing Neutral Currents reported in the literature.Comment: 12 pages, 1 figure. Version accepted in Phys. Lett.
MsWH: A multi-sensory hardware platform for capturing and analyzing physiological emotional signals
This paper presents a new physiological signal acquisition multi-sensory platform for emotion detection: Multi-sensor Wearable Headband (MsWH). The system is capable of recording and analyzing five different physiological signals: skin temperature, blood oxygen saturation, heart rate (and its variation), movement/position of the user (more specifically of his/her head) and electrodermal activity/bioimpedance. The measurement system is complemented by a porthole camera positioned in such a way that the viewing area remains constant. Thus, the user''s face will remain centered regardless of its position and movement, increasing the accuracy of facial expression recognition algorithms. This work specifies the technical characteristics of the developed device, paying special attention to both the hardware used (sensors, conditioning, microprocessors, connections) and the software, which is optimized for accurate and massive data acquisition. Although the information can be partially processed inside the device itself, the system is capable of sending information via Wi-Fi, with a very high data transfer rate, in case external processing is required. The most important features of the developed platform have been compared with those of a proven wearable device, namely the Empatica E4 wristband, in those measurements in which this is possible
Lesiones esqueléticas asociadas al síndrome de Papillon-Lefèvre
Se presentan dos casos de Síndrome de Papillon-Lefèvre que se asocian
a osteolisis espontánea de los metatarsianos y las falanges de los dedos de
los pies. Esta asociación no había sido descrita con anterioridad.Two case s of Papillon-Lefèvre syndrome associated with spontaneous
osteolysis of the phalanges and metatarsals of the toe s are
presented. This association has not been previously reported
de Sitter relativity: a natural scenario for an evolving Lambda
The dispersion relation of de Sitter special relativity is obtained in a
simple and compact form, which is formally similar to the dispersion relation
of ordinary special relativity. It is manifestly invariant under change of
scale of mass, energy and momentum, and can thus be applied at any energy
scale. When applied to the universe as a whole, the de Sitter special
relativity is found to provide a natural scenario for the existence of an
evolving cosmological term, and agrees in particular with the present-day
observed value. It is furthermore consistent with a conformal cyclic view of
the universe, in which the transition between two consecutive eras occurs
through a conformal invariant spacetime.Comment: V1: 11 pages. V2: Presentation changes, new discussion added, 13
page
Dynamical large deviations for a boundary driven stochastic lattice gas model with many conserved quantities
We prove the dynamical large deviations for a particle system in which
particles may have different velocities. We assume that we have two infinite
reservoirs of particles at the boundary: this is the so-called boundary driven
process. The dynamics we considered consists of a weakly asymmetric simple
exclusion process with collision among particles having different velocities
Who Is Eating the Outflow?: High-Angular Resolution Study of an Intermediate-Mass Protostar in L1206
Up to now only a few intermediate-mass molecular outflows have been studied
with enough high-angular resolution. The aim of this work is to study in detail
the intermediate-mass YSO IRAS 22272+6358A, which is embedded in L1206, and its
molecular outflow, in order to investigate the interaction of the outflow with
the dense protostellar material, and to compare their properties with those of
lower mas counterparts. We carried out OVRO observations of the 2.7 mm
continuum emission, CO(1-0), C18O(1-0), and HC3N(12-11) in order to map with
high-angular resolution the core of L1206, and to derive the properties of the
dust emission, the molecular outflow and the dense protostellar envelope. The
2.7 mm continuum emission has been resolved into four sources, labeled OVRO~1,
2, 3, and 4. The intermediate-mass Class~0/I object OVRO 2, with a mass traced
by the dust emission of 14.2 Msun, is the source associated with IRAS
22272+6358A. The CO(1-0) observations have revealed a very collimated outflow
driven by OVRO 2, at a PA ~140 degr, that has a very weak southeastern red lobe
and a much stronger northwestern blue lobe. Photodissociation toward the red
lobe produced by the ionization front coming from the bright-rimmed diffuse HII
region could be responsible of the morphology of the outflow. The spatial
correlation between the outflow and the elongated dense protostellar material
traced by HC3N(12-11) suggests an interaction between the molecular outflow and
the protostellar envelope. Shocks produced by the molecular outflow, and
possibly by the shock front preceding the ionization front could account for
the southern enhancement of HC3N. The properties of the intermediate-mass
protostar OVRO 2 and the molecular outflow are consistent with those of lower
mass counterparts.Comment: 14 pages, 12 figures, 5 tables. Accepted for publication by A&
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