1,605 research outputs found
Spatio-temporal detection of Kelvin waves in quantum turbulence simulations
We present evidence of Kelvin excitations in space-time resolved spectra of
numerical simulations of quantum turbulence. Kelvin waves are transverse and
circularly polarized waves that propagate along quantized vortices, for which
the restitutive force is the tension of the vortex line, and which play an
important role in theories of superfluid turbulence. We use the
Gross-Pitaevskii equation to model quantum flows, letting an initial array of
well-organized vortices develop into a turbulent bundle of intertwined vortex
filaments. By achieving high spatial and temporal resolution we are able to
calculate space-time resolved mass density and kinetic energy spectra. Evidence
of Kelvin and sound waves is clear in both spectra. Identification of the waves
allows us to extract the spatial spectrum of Kelvin waves, clarifying their
role in the transfer of energ
The photino sector and a confining potential in a supersymetric Lorentz-symmetry-violating model
We study the spectrum of the minimal supersymmetric extension of the
Carroll-Field-Jackiw model for Electrodynamics with a topological
Chern-Simons-like Lorentz-symmetry violating term. We identify a number of
independent background fermion condensates, work out the gaugino dispersion
relation and propose a photonic effective action to consider aspects of
confinement induced by the SUSY background fermion condensates, which also
appear to signal Lorentz-symmetry violation in the photino sector of the
action. Our calculations of the static potential are carried out within the
framework of the gauge-invariant but path-dependent variables formalism which
are alternative to the Wilson loop approach. Our results show that the
interaction energy contains a linear term leading to the confinement of static
probe charges.Comment: 11 pages, photino dispersion relation is extended to included the
case the photino acquires mass through spontaneous SUSY breakin
Interaction of colloids with a nematic-isotropic interface
The Landau-de Gennes free energy is used to calculate the interaction between
long cylindrical colloids and the nematic-isotropic (NI) interface. This
interaction has two contributions: one is specific of liquid crystals and
results from the deformation of the director field close to the particles or to
the interface, while the other is generic and results from wetting and surface
tension effects.
Deep in the nematic phase the director field of long cylindrical colloids,
with strong homeotropic anchoring, exhibits two half-integer defect lines. As
the colloid moves towards the interface, the director configuration changes
through a series of discontinuous transitions, where one or two of the defects
are annihilated. In addition, the NI interface bends towards the colloid in
order to minimize the elastic free energy in the nematic. In the isotropic
phase, the colloid is surrounded by a thin nematic layer that reduces the
surface free energy under favorable wetting conditions.
The interaction has a well-defined minimum near the interface. In this region
the director and interfacial structures are complex and cannot be described
analytically. Using the numerical results for the Landau-de Gennes free energy
in the harmonic region, we obtained simple scaling laws for the (linear) force
on the colloid
The BTZ black hole as a Lorentz-flat geometry
It is shown that 2+1 dimensional anti-de Sitter spacetimes are Lorentz-flat.
This means, in particular, that any simply-connected patch of the BTZ black
hole solution can be endowed with a Lorentz connection that is locally pure
gauge. The result can be naturally extended to a wider class of black hole
geometries and point particles in three-dimensional spacetime.Comment: 2 page
Biología y ecología del calamar Dosidicus gigas (Cephalopoda) en aguas chilenas: una revisión
Indexación: Web of Science; Scielo.ABSTRACT. The jumbo squid Dosidicus gigas is the most abundant cephalopod species in the southeastern Pacific Ocean, which supports the biggest cephalopod fishery in the world. Due to its growing economic importance, the population growth and distributional expansion of this squid is being increasingly studied. Nevertheless, some basic features of the biology of D. gigas are still unknown or have been poorly investigated. In this review we summarize the known information regarding the biology and ecology of this species in the southeastern Pacific Ocean; we focus on the Chilean region in order to propose hypotheses and research lines for a better understanding the life history of this organism. Available data on the size structure, reproduction and genetics of D. gigas allows us to propose hypotheses related to the squid's life history traits. Based on the current literature and publications of colleagues, we propose two hypotheses regarding the effect of spatial variation on the life history of D. gigas. Hypothesis 1: Squids mature at large sizes and spawn in oceanic waters with warm temperatures where paralarvae and juveniles develop. Immature squids migrate near shore to feed, grow and mature, and then return to the offshore sites to spawn. Hypothesis 2: Alternatively, juvenile D. gigas in the oceanic zone do not migrate to coastal waters and mature at small sizes compared to individuals living near the coast that mature at larger size and migrate to oceanic waters to spawn. We provide background information about the feeding behavior and parasitism of this species, suggesting that D. gigas is an important trophic link in the southeastern Pacific marine ecosystem. However, more studies on the feeding habits, reproduction and parasite load are needed not only to test hypotheses proposed in this study, but also to advance the overall knowledge of this species.RESUMEN. Dosidicus gigas, es el calamar más abundante en el Pacífico suroriental, manteniendo la mayor pesquería mundial de cefalópodos. Su creciente importancia económica, ha motivado el aumento de estudios asociados al crecimiento de sus poblaciones y su expansión geográfica. Sin embargo, algunas características biológicas básicas de esta especie son desconocidas o escasamente estudiadas. En esta revisión, se resume la información sobre la biología y ecología de esta especie para el Pacífico suroriental y se proponen hipótesis y líneas de investigación para el mejor entendimiento de su historia de vida. Los datos sobre estructura de tamaños, reproducción y aspectos genéticos de la especie, permiten avanzar en las hipótesis relacionadas con la historia de vida de estos rasgos. Hipótesis 1: Los calamares maduran a gran tamaño y desovan en aguas oceánicas con temperaturas cálidas, donde paralarvas y juveniles se desarrollan. Los calamares inmaduros migran hacia la costa para alimentarse, crecer y madurar, y luego vuelven a los sitios en alta mar para desovar. Hipótesis 2: Alternativamente, los juveniles de D. gigas en la zona oceánica no migran a las aguas costeras y maduran pequeños en comparación a los individuos que viven cerca de la costa que maduran a un tamaño más grande y migran a las aguas oceánicas para desovar. Se proponen dos hipótesis acerca de la variación espacial de la historia de vida. Además, se proporciona el marco relativo a la alimentación y parasitismo del calamar, que coloca a D. gigas como un importante nexo trófico en los ecosistemas marinos del Pacífico suroriental. No obstante, se necesitan más estudios relacionados con alimentación, reproducción y carga parasitaria del calamar para poner a prueba las hipótesis propuestas en este trabajo.http://ref.scielo.org/hpft7
Sistema de controle de horas extras.
Editores técnicos: Joseani Mesquita Antunes, Ana Lídia Variani Bonato, Márcia Barrocas Moreira Pimentel
Aspects of CPT-even Lorentz-symmetry violating physics in a supersymmetric scenario
Background fermion condensates in a landscape dominated by global SUSY are
reassessed in connection with a scenario where Lorentz symmetry is violated in
the bosonic sector (actually, the photon sector) by a -even -term. An
effective photonic action is discussed that originates from the supersymmetric
background fermion condensates. Also, the photino mass emerges in terms of a
particular condensate contrary to what happens in the -violation.
Finally, the interparticle potential induced by the effective photonic action
is investigated and a confining profile is identified.Comment: 14 pages. arXiv admin note: text overlap with arXiv:1102.3777 by
other author
Envisioning and evolving: Future evolution of the concept and the practice of service design
ervice Design is evolving from an emerging field, breaking new ground in the design and service research areas, to a more mature stage, developing a set of fundamental concepts, methods and principles that can provide the foundation for its further significance and impact in both research and practice. This paper reflects on the roots and recent evolution of service design in terms of fundamental concepts, methods and outcomes, taking into account the papers in the Envisioning and Evolving track. It considers how the growing interrelation with close fields of service research is introducing useful “contaminations” and reports how the Service perspective is revealing its potential to bring life to technical and entrenched systems. It goes on to argue that design should aim to bring services to life to prove its real, distinguishing value and contribution
Evolving Lorentzian wormholes supported by phantom matter with constant state parameters
In this paper we study the possibility of sustaining an evolving wormhole via
exotic matter made out of phantom energy. We show that this exotic source can
support the existence of evolving wormhole spacetimes. Explicitly, a family of
evolving Lorentzian wormholes conformally related to another family of
zero-tidal force static wormhole geometries is found in Einstein gravity.
Contrary to the standard wormhole approach, where first a convenient geometry
is fixed and then the matter distribution is derived, we follow the
conventional approach for finding solutions in theoretical cosmology. We derive
an analytical evolving wormhole geometry by supposing that the radial tension
(which is negative to the radial pressure) and the pressure measured in the
tangential directions have barotropic equations of state with constant state
parameters. At spatial infinity this evolving wormhole, supported by this
anisotropic matter, is asymptotically flat, and its slices constant are
spaces of constant curvature. During its evolution the shape of the wormhole
expands with constant velocity, i.e without acceleration or deceleration, since
the scale factor has strictly a linear evolution.Comment: 9 pages, 2 figures, Accepted for publication in Phys. Rev.
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