27,623 research outputs found
Conductivity and entanglement entropy of high dimensional holographic superconductors
We investigate the dependence of the conductivity and the entanglement
entropy on the space-time dimensionality in two holographic
superconductors: one dual to a quantum critical point with spontaneous symmetry
breaking, and the other modeled by a charged scalar that condenses at a
sufficiently low temperature in the presence of a Maxwell field. In both cases
the gravity background is asymptotically Anti de Sitter (AdS). In the large
limit we obtain explicit analytical results for the conductivity at zero
temperature and the entanglement entropy by a expansion. We show that the
entanglement entropy is always smaller in the broken phase. As dimensionality
increases, the entanglement entropy decreases, the coherence peak in the
conductivity becomes narrower and the ratio between the energy gap and the
critical temperature decreases. These results suggest that the condensate
interactions become weaker in high spatial dimensions.Comment: 38 pages, 7 figure
Energy-Entropy-Momentum integration of discrete thermo-visco-elastic dynamics.
A novel time integration scheme is presented for the numerical solution of the dynamics of discrete systems consisting of point masses and thermo-visco-elastic springs. Even considering fully coupled constitutive laws for the elements, the obtained solutions strictly preserve the two laws of thermo dynamics and the symmetries of the continuum evolution equations. Moreover, the unconditional control over the energy and the entropy growth have the effect of stabilizing the numerical solution, allowing the use of larger time steps than those suitable for comparable implicit algorithms. Proofs for these claims are provided in the article as well as numerical examples that illustrate the performance of the method
A Mobile App to Manage Children Dental Anxiety: Context and Approach
Anxiety and fear related to dentistry interventions have been identified as problems affecting children. This reduces their
quality of life and may have a negative impact on aspects such as sleep, self –esteem, mood, social relationships, and
other psychological issues.The ARCADE project aims to design and develop a technological solution to manage children
dental anxiety. This solution consists on a mobile system co-designed with children. An ecological momentary
intervention is proposed using this solution before, during and after dentistry treatments. This paper presents a
methodological approach to develop the project
Publishing performance in economics: Spanish rankings (1990-1999)
This paper contributes to the growing literature that analyses the Spanish publishing performance in Economics throughout the 1990s. Several bibliometric indicators are used in order to provide Spanish rankings (of both institutions and individual authors) based on Econlit journals. Further, lists of the ten most influential authors and articles over that period, in terms of citations, are reported.Publicad
Exploring jet-launching conditions for SFXTs
In the magneto-centrifugal mechanism for jet formation, accreting neutron
stars are assumed to produce relativistic jets only if their surface magnetic
field is weak enough ( G). However, the most common manifestation
of neutron stars are pulsars, whose magnetic field distribution peaks at G. If the neutron star magnetic field has at least this strength
at birth, it must decay considerably before jets can be launched in binary
systems. We study the magnetic field evolution of a neutron star that accretes
matter from the wind of a high-mass stellar companion so that we can constrain
the accretion rate and the impurities in the crust, which are necessary
conditions for jet formation. We solved the induction equation for the
diffusion and convection of the neutron star magnetic field confined to the
crust, assuming spherical accretion in a simpliflied one-dimensional treatment.
We incorporated state-of-the-art microphysics, including consistent thermal
evolution profiles, and assumed two different neutron star cooling scenarios
based on the superfluidity conditions at the core. We find that in this
scenario, magnetic field decay at long timescales is governed mainly by the
accretion rate, while the impurity content and thermal evolution of the neutron
star play a secondary role. For accretion rates
M yr, surface magnetic fields can decay up to four orders of
magnitude in 10 yr, which is the timescale imposed by the evolution
of the high-mass stellar companion in these systems. Based on these results, we
discuss the possibility of transient jet-launching in strong wind-accreting
high-mass binary systems like supergiant fast X-ray transients.Comment: 8 pages, 8 figures. Accepted for publication in A&
An educational tool to assist the design process of switched reluctance machines
The design of electric machines is a hot topic in the syllabuses of several undergraduate and
graduate courses. With the development of hybrid and electrical vehicles, this subject is gaining
more popularity, especially in electrical engineering courses. This paper presents a computeraided
educational tool to guide engineering students in the design process of a switched
reluctance machine (SRM). A step-by-step design procedure is detailed and a user guide
interface (GUI) programmed in the Matlab® environment developed for this purpose is shown.
This GUI has been proved a useful tool to help the students to validate the results obtained in
their lecture assignments, while aiding to achieve a better understanding of the design process of
electric machines. A validation of the educational tool is done by means of finite element
method (FEM) simulations.Postprint (author's final draft
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