14,882 research outputs found
Dissipative processes in superfluid quark matter
We present some results about dissipative processes in fermionic superfluids
that are relevant for compact stars. At sufficiently low temperatures the
transport properties of a superfluid are dominated by phonons. We report the
values of the bulk viscosity, shear viscosity and thermal conductivity of
phonons in quark matter at extremely high density and low temperature. Then, we
present a new dissipative mechanism that can operate in compact stars and that
is named "rocket term". The effect of this dissipative mechanism on superfluid
r-mode oscillations is sketched.Comment: 6 pages, 1 figure. Prepared for QCD@work 2010 - International
Workshop on QCD - Theory and Experiment, 20-23 June 2010, Martina Franca -
Valle d'Itria - Ital
Lattice two-body problem with arbitrary finite range interactions
We study the exact solution of the two-body problem on a tight-binding
one-dimensional lattice, with pairwise interaction potentials which have an
arbitrary but finite range. We show how to obtain the full spectrum, the bound
and scattering states and the "low-energy" solutions by very efficient and
easy-to-implement numerical means. All bound states are proven to be
characterized by roots of a polynomial whose degree depends linearly on the
range of the potential, and we discuss the connections between the number of
bound states and the scattering lengths. "Low-energy" resonances can be located
with great precission with the methods we introduce. Further generalizations to
include more exotic interactions are also discussed.Comment: 6 pages, 3 figure
HeteroGenius: A Framework for Hybrid Analysis of Heterogeneous Software Specifications
Nowadays, software artifacts are ubiquitous in our lives being an essential
part of home appliances, cars, cell phones, and even in more critical
activities like aeronautics and health sciences. In this context software
failures may produce enormous losses, either economical or, in the worst case,
in human lives. Software analysis is an area in software engineering concerned
with the application of diverse techniques in order to prove the absence of
errors in software pieces. In many cases different analysis techniques are
applied by following specific methodological combinations that ensure better
results. These interactions between tools are usually carried out at the user
level and it is not supported by the tools. In this work we present
HeteroGenius, a framework conceived to develop tools that allow users to
perform hybrid analysis of heterogeneous software specifications.
HeteroGenius was designed prioritising the possibility of adding new
specification languages and analysis tools and enabling a synergic relation of
the techniques under a graphical interface satisfying several well-known
usability enhancement criteria. As a case-study we implemented the
functionality of Dynamite on top of HeteroGenius.Comment: In Proceedings LAFM 2013, arXiv:1401.056
RVB signatures in the spin dynamics of the square-lattice Heisenberg antiferromagnet
We investigate the spin dynamics of the square-lattice spin-1/2 Heisenberg
antiferromagnet by means of an improved mean field Schwinger boson calculation.
By identifying both, the long range N\'eel and the RVB-like components of the
ground state, we propose an educated guess for the mean field triplet
excitation consisting on a linear combination of local and bond spin flips to
compute the dynamical structure factor. Our main result is that when this
triplet excitation is optimized in such a way that the corresponding sum rule
is fulfilled, we recover the low and high energy spectral weight features of
the experimental spectrum. In particular, the anomalous spectral weight
depletion at found in recent inelastic neutron scattering experiments
can be attributed to the interference of the triplet bond excitations of the
RVB component of the ground state. We conclude that the Schwinger boson theory
seems to be a good candidate to adequately interpret the dynamic properties of
the square-lattice Heisenberg antiferromagnet.Comment: 6 pages with 3 figure
Children's emotion understanding: A meta-analysis of training studies.
BACKGROUND: In the course of development, children show increased insight and understanding of emotions-both of their own emotions and those of others. However, little is known about the efficacy of training programs aimed at improving children's understanding of emotion. OBJECTIVES: To conduct an effect size analysis of trainings aimed at three aspects of emotion understanding: external aspects (i.e., the recognition of emotional expressions, understanding external causes of emotion, understanding the influence of reminders on present emotions); mental aspects (i.e., understanding desire-based emotions, understanding belief-based emotions, understanding hidden emotions); and reflective aspects (i.e., understanding the regulation of an emotion, understanding mixed emotions, understanding moral emotions). DATA SOURCES: A literature search was conducted using PubMed, PsycInfo, the Cochrane Library, and manual searches. REVIEW METHODS: The search identified 19 studies or experiments including a total of 749 children with an average age of 86 months (S.D.=30.71) from seven different countries. RESULTS: Emotion understanding training procedures are effective for improving external (Hedge's g = 0.62), mental (Hedge's g = 0.31), and reflective (Hedge's g = 0.64) aspects of emotion understanding. These effect sizes were robust and generally unrelated to the number and lengths of training sessions, length of the training period, year of publication, and sample type. However, training setting and social setting moderated the effect of emotion understanding training on the understanding of external aspects of emotion. For the length of training session and social setting, we observed significant moderator effects of training on reflective aspects of emotion. CONCLUSION: Emotion understanding training may be a promising tool for both preventive intervention and the psychotherapeutic process. However, more well-controlled studies are needed.R34 MH086668 - NIMH NIH HHS; R01 AT007257 - NCCIH NIH HHS; R21 MH101567 - NIMH NIH HHS; R34 MH099311 - NIMH NIH HHS; R21 MH102646 - NIMH NIH HHS; K23 MH100259 - NIMH NIH HHS; R01 MH099021 - NIMH NIH HH
Bulk viscosity in a cold CFL superfluid
We compute one of the bulk viscosity coefficients of cold CFL quark matter in
the temperature regime where the contribution of mesons, quarks and gluons to
transport phenomena is Boltzmann suppressed. In that regime dissipation occurs
due to collisions of superfluid phonons, the Goldstone modes associated to the
spontaneous breaking of baryon symmetry. We first review the hydrodynamics of
relativistic superfluids, and remind that there are at least three bulk
viscosity coefficients in these systems. We then compute the bulk viscosity
coefficient associated to the normal fluid component of the superfluid. In our
analysis we use Son's effective field theory for the superfluid phonon, amended
to include scale breaking effects proportional to the square of the strange
quark mass m_s. We compute the bulk viscosity at leading order in the scale
breaking parameter, and find that it is dominated by collinear splitting and
joining processes. The resulting transport coefficient is zeta=0.011 m_s^4/T,
growing at low temperature T until the phonon fluid description stops making
sense. Our results are relevant to study the rotational properties of a compact
star formed by CFL quark matter.Comment: 19 pages, 2 figures; one reference added, version to be published in
JCA
Gapless color-flavor locked phase in quark and hybrid stars
We study the effects of the gapless color-flavor locked (gCFL) phase on the
equation of state of strongly interacting matter in the range of baryonic
chemical potential involved in a compact star. We analyze the possibility of a
phase transition from hadronic matter to gCFL quark matter and we discuss, for
different values of the strange quark mass and diquark coupling strength, the
existence of a gCFL phase in quark or hybrid stars. The mass-radius relation
and the structure of compact stars containing the gCFL phase are shown and the
physical relevance of this superconducting phase inside a stellar object is
also discussed.Comment: 7 pages, 11 figure
- …