1,169 research outputs found
Growth Histories in Bimetric Massive Gravity
We perform cosmological perturbation theory in Hassan-Rosen bimetric gravity
for general homogeneous and isotropic backgrounds. In the de Sitter
approximation, we obtain decoupled sets of massless and massive scalar
gravitational fluctuations. Matter perturbations then evolve like in Einstein
gravity. We perturb the future de Sitter regime by the ratio of matter to dark
energy, producing quasi-de Sitter space. In this more general setting the
massive and massless fluctuations mix. We argue that in the quasi-de Sitter
regime, the growth of structure in bimetric gravity differs from that of
Einstein gravity.Comment: 28 pages + appendix, 11 figure
Submanifolds in five-dimensional pseudo-Euclidean spaces and four-dimensional FRW universes
Equations for submanifolds, which correspond to embeddings of the
four-dimensional FRW universes in five-dimensional pseudo-Euclidean spaces, are
presented in convenient form in general case. Several specific examples are
considered.Comment: 7 pages, LaTeX, the mathematical part of this paper is based on the
withdrawn preprint arXiv:1012.0320 [gr-qc
Phase diagram of dense neutral three-flavor quark matter
We study the phase diagram of dense, locally neutral three-flavor quark
matter as a function of the strange quark mass, the quark chemical potential,
and the temperature, employing a general nine-parameter ansatz for the gap
matrix. At zero temperature and small values of the strange quark mass, the
ground state of matter corresponds to the color-flavor-locked (CFL) phase. At
some critical value of the strange quark mass, this is replaced by the recently
proposed gapless CFL (gCFL) phase. We also find several other phases, for
instance, a metallic CFL (mCFL) phase, a so-called uSC phase where all colors
of up quarks are paired, as well as the standard two-flavor
color-superconducting (2SC) phase and the gapless 2SC (g2SC) phase.Comment: 14 pages, 11 figures, references added; the version accepted for
publication in Nucl. Phys.
Can Theta/N Dependence for Gluodynamics be Compatible with 2 pi Periodicity in Theta ?
In a number of field theoretical models the vacuum angle \theta enters
physics in the combination \theta/N, where N stands generically for the number
of colors or flavors, in an apparent contradiction with the expected 2 \pi
periodicity in \theta. We argue that a resolution of this puzzle is related to
the existence of a number of different \theta dependent sectors in a finite
volume formulation, which can not be seen in the naive thermodynamic limit V ->
\infty. It is shown that, when the limit V -> \infty is properly defined,
physics is always 2 \pi periodic in \theta for any integer, and even rational,
values of N, with vacuum doubling at certain values of \theta. We demonstrate
this phenomenon in both the multi-flavor Schwinger model with the bosonization
technique, and four-dimensional gluodynamics with the effective Lagrangian
method. The proposed mechanism works for an arbitrary gauge group.Comment: minor changes in the discussion, a few references are adde
Thermal rates for baryon and anti-baryon production
We use a form of the fluctuation-dissipation theorem to derive formulas
giving the rate of production of spin-1/2 baryons in terms of the fluctuations
of either meson or quark fields. The most general formulas do not assume
thermal or chemical equilibrium. When evaluated in a thermal ensemble we find
equilibration times on the order of 10 fm/c near the critical temperature in
QCD.Comment: 22 pages, 4 tables and 2 figures, REVTe
Updated resonance photo-decay amplitudes to 2 GeV
We present the results of an energy-dependent and set of single-energy
partial-wave analyses of single-pion photoproduction data. These analyses
extend from threshold to 2 GeV in the laboratory photon energy, and update our
previous analyses to 1.8 GeV. Photo-decay amplitudes are extracted for the
baryon resonances within this energy range. We consider two photoproduction sum
rules and the contributions of two additional resonance candidates found in our
most recent analysis of elastic scattering data. Comparisons are made
with previous analyses.Comment: Revtex, 26 pages, 3 figures. Postscript figures available from
ftp://clsaid.phys.vt.edu/pub/pr or indirectly from
http://clsaid.phys.vt.edu/~CAPS
Uso de semivariograma escalonado na variabilidade espacial da textura do solo em uma área de terra preta arqueológica sob floresta em Manicoré - AM
Os solos predominantes na região Amazônica pertencem à classe dos Latossolos e Argissolos, caracterizado por seu alto grau de intemperismo e baixa fertilidade natural, em contraste, ocorrem à s Terras Pretas Arqueológicas com elevada fertilidade natural e alto teor de matéria orgânica, coloração escura, presença de artefatos cerâmicos indÃgenas incorporados a matriz do horizonte superficiais do solo. O objetivo deste trabalho foi investigar o uso de semivariograma escalonado na variabilidade espacial da textura do solo em uma área de terra preta arqueológica sob floresta em Manicoré, AM. A área em estudo encontra-se na região do municÃpio de Manicoré – AM, no km 210 a 30 km da comunidade do Santo Antônio do Matupi, as margens da BR 230, rodovia transamazônica. As áreas são de Terra Pretas Arqueológicas (TPA) sob Floresta nativa, onde foi estabelecido o mapeamento de uma malha de 6 x 6 m, nas profundidades de amostragem 0,0 - 0,05, 0,05 - 0,10 e 0,10 - 0,20 m, totalizando 88 pontos georreferenciados totalizando 264 pontos amostrais nas 3 profundidades. Em seguida realizou-se analise textural para determinar areia, silte e argila. Os resultados foram tratados estaticamente por meio de analise descritivas e geoestatistica. Todas as variáveis analisadas apresentaram estrutura de dependência espacial, e ajustaram-se ao modelo exponencial. Nos semivariograma individuais o GDE foi classificado como fraco e moderado e os semivariograma escalonados o GDE foi classificado como moderado e forte. Os semivariograma escalonado apresentaram alcance maiores que o espaçamento da malha variando entre 17,59 a 30 m
Compact stars made of fermionic dark matter
Compact stars consisting of fermions with arbitrary masses and interaction
strengths are studied by solving the structure equation of general relativity,
the Tolman-Oppenheimer-Volkoff equations. Scaling solutions are derived for a
free and an interacting Fermi gas and tested by numerical calculations. We
demonstrate that there is a unique mass-radius relation for compact stars made
of free fermions which is independent of the fermion mass. For sufficiently
strong interactions, the maximum stable mass of compact stars and its radius
are controlled by the parameter of the interaction, both increasing linearly
with the interaction strength. The mass-radius relation for compact stars made
of strongly interacting fermions shows that the radius remains approximately
constant for a wide range of compact star masses.Comment: 19 pages, 8 figures, refs. added, version to appear in Physical
Review
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.
Non-Linear Axion Dynamics and Formation of Cosmological Pseudo-Solitons
The -dimensional evolution of an inhomogeneous axion field
configuration around the QCD epoch is studied numerically, including important
non-linear effects due to the attractive self-interaction. It is found that
axion perturbations on scales corresponding to causally disconnected regions at
can lead to very dense pseudo-soliton configurations we
call axitons. These configurations evolve to axion miniclusters with present
density \rho_a \ga 10^{-8}\,{\rm g \, cm^{-3}}. This is high enough for the
collisional process to lead to Bose--Einstein relaxation in
the gravitationally bound clumps of axions, forming Bose stars.Comment: 27 pages plus 13 figures (upon request: [email protected]),
LaTeX, FNAL--PUB--93/335--
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