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The Impact Of Cold Dark Matter Variants On The Halos Of The First Stars And Galaxies: Angular Momentum And Vortex Creation In BEC Dark Matter
If cold dark matter elementary particles form a Bose-Einstein condensate, their superfluidity may distinguish them from other forms of cold dark matter, including the creation of quantum vortices. We have shown that such vortices are favored in strongly-coupled condensates. Vortex creation causes central densities to drop, thus affecting the dynamics of the gaseous baryonic component and subsequently star formation.Astronom
Rapidly Rotating Bose-Einstein Condensates in Homogeneous Traps
We extend the results of a previous paper on the Gross-Pitaevskii description
of rotating Bose-Einstein condensates in two-dimensional traps to confining
potentials of the form V(r) = r^s, . Writing the coupling constant
as we study the limit . We derive rigorously the
leading asymptotics of the ground state energy and the density profile when the
rotation velocity \Omega tends to infinity as a power of . The case
of asymptotically homogeneous potentials is also discussed.Comment: LaTex2e, 16 page
Rapidly Rotating Bose-Einstein Condensates in Strongly Anharmonic Traps
We study a rotating Bose-Einstein Condensate in a strongly anharmonic trap
(flat trap with a finite radius) in the framework of 2D Gross-Pitaevskii
theory. We write the coupling constant for the interactions between the gas
atoms as and we are interested in the limit (TF
limit) with the angular velocity depending on . We derive
rigorously the leading asymptotics of the ground state energy and the density
profile when tends to infinity as a power of . If
a ``hole'' (i.e., a region where the
density becomes exponentially small as ) develops for
above a certain critical value. If
the hole essentially exhausts the container and a ``giant vortex'' develops
with the density concentrated in a thin layer at the boundary. While we do not
analyse the detailed vortex structure we prove that rotational symmetry is
broken in the ground state for .Comment: LaTex2e, 28 pages, revised version to be published in Journal of
Mathematical Physic
Analytical galactic models with mild stellar cusps
In the past two decades, it has been established by high-resolution
observations of early-type galaxies that their nuclear surface brightness and
corresponding stellar mass densities are characterized by cusps. In this paper,
we present a new spherical analytical model family describing mild cuspy
centres. We study isotropic and anisotropic models of Osipkov-Merritt type. It
is shown that the associated distribution functions and intrinsic velocity
dispersions can be represented analytically in a unified way in terms of
hypergeometric series, allowing thus a straightforward comparison of these
important global quantities for galaxies having underlying mass densities which
may differ significantly in their degree of central cuspiness or radial
falloff.Comment: 9 pages, 2 figures; accepted for publication in MNRAS; different
format than previous versio
Flat Central Density Profile and Constant DM Surface Density in Galaxies from Scalar Field Dark Matter
The scalar field dark matter (SFDM) model proposes that galaxies form by
condensation of a scalar field (SF) very early in the universe forming
Bose-Einstein Condensates (BEC) drops, i.e., in this model haloes of galaxies
are gigantic drops of SF. Here big structures form like in the LCDM model, by
hierarchy, thus all the predictions of the LCDM model at big scales are
reproduced by SFDM. This model predicts that all galaxies must be very similar
and exist for bigger redshifts than in the LCDM model. In this work we show
that BEC dark matter haloes fit high-resolution rotation curves of a sample of
thirteen low surface brightness galaxies. We compare our fits to those obtained
using a Navarro-Frenk-White and Pseudo-Isothermal (PI) profiles and found a
better agreement with the SFDM and PI profiles. The mean value of the
logarithmic inner density slopes is -0.27 +/- 0.18. As a second result we find
a natural way to define the core radius with the advantage of being
model-independent. Using this new definition in the BEC density profile we find
that the recent observation of the constant dark matter central surface density
can be reproduced. We conclude that in light of the difficulties that the
standard model is currently facing the SFDM model can be a worthy alternative
to keep exploring further.Comment: Submitted to MNRAS, 9 pages, 32 Figures, 2 Tables.The paper with
better resolution figures can be downloaded at
"http://estudiantes.fis.cinvestav.mx/vrobles/SFDMfile.pd
Assumptions behind grammatical approaches to code-switching: when the blueprint is a red herring
Many of the so-called ‘grammars’ of code-switching are based on various underlying assumptions, e.g. that informal speech can be adequately or appropriately described in terms of ‘‘grammar’’; that deep, rather than surface, structures are involved in code-switching; that one ‘language’ is the ‘base’ or ‘matrix’; and that constraints derived from existing data are universal and predictive. We question these assumptions on several grounds. First, ‘grammar’ is arguably distinct from the processes driving speech production. Second, the role of grammar is mediated by the variable, poly-idiolectal repertoires of bilingual speakers. Third, in many instances of CS the notion of a ‘base’ system is either irrelevant, or fails to explain the facts. Fourth, sociolinguistic factors frequently override ‘grammatical’ factors, as evidence from the same language pairs in different settings has shown. No principles proposed to date account for all the facts, and it seems unlikely that ‘grammar’, as conventionally conceived, can provide definitive answers. We conclude that rather than seeking universal, predictive grammatical rules, research on CS should focus on the variability of bilingual grammars
Dynamical Boson Stars
The idea of stable, localized bundles of energy has strong appeal as a model
for particles. In the 1950s John Wheeler envisioned such bundles as smooth
configurations of electromagnetic energy that he called {\em geons}, but none
were found. Instead, particle-like solutions were found in the late 1960s with
the addition of a scalar field, and these were given the name {\em boson
stars}. Since then, boson stars find use in a wide variety of models as sources
of dark matter, as black hole mimickers, in simple models of binary systems,
and as a tool in finding black holes in higher dimensions with only a single
killing vector. We discuss important varieties of boson stars, their dynamic
properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in
Relativity; major revision in 201