1,316 research outputs found
Higher dimensional gravity invariant under the Poincare group
It is shown that the Stelle-West Grignani-Nardelli-formalism allows, both
when odd dimensions and when even dimensions are considered, constructing
actions for higher dimensional gravity invariant under local Lorentz rotations
and under local Poincar\`{e} translations. It is also proved that such actions
have the same coefficients as those obtained by Troncoso and Zanelli in ref.
Class. Quantum Grav. 17 (2000) 4451.Comment: 7 pages, Latex, accepted in Phys. Rev.
Grau de dependencia entre a leitura fibrografica a SL 2,5% e o comprimento comercial do algodao.
bitstream/item/33354/1/GRAU-DE-DEPENDENCIA.pd
Analysing Charges in even dimensions
Lanczos-Lovelock theories of gravity, in its first order version, are studied
on asymptotically locally anti de Sitter spaces. It is shown that
thermodynamics satisfies the standard behavior and an expression for entropy is
found for this formalism. Finally a short analysis of the algebra of conserved
charges is displayed
Repetibilidade e número de avaliações necessárias à seleção de clones de cajueiro anão precoce
O objetivo deste trabalho foi estimar o coeficiente de repetibilidade e determinar o numero adequado de avaliacoes necessarias a selecao de clones de cajueiro anao precoce para caracteres de producao e porte da planta. A metodologia aplicada para estimacao constou da utilizacao dos componentes principais obtidos da matriz de covariancias e variancias fenotipicas. Avaliou-se em trinta clones a altura da planta (AP), odiametro da copa (DC) e a producao de castanha (PROD), durante cinco anos. Constatou-se, ainda, que sao suficientes duas avaliacoes pa AP e DC e tres para PROD na selecao de clones.bitstream/CNPAT-2010/4779/1/Bp-023.pd
Clones de aceroleira: BRS 235 ou apodi, BRS 236 ou cereja, BRS 237 ou roxinha e BRS 238 ou frutacor.
bitstream/CNPAT/7853/1/ct_87.pd
Black holes with topologically nontrivial AdS asymptotics
Asymptotically locally AdS black hole geometries of dimension d > 2 are
studied for nontrivial topologies of the transverse section. These geometries
are static solutions of a set of theories labeled by an integer 0 < k <
[(d-1)/2] which possess a unique globally AdS vacuum. The transverse sections
of these solutions are d-2 surfaces of constant curvature, allowing for
different topological configurations. The thermodynamic analysis of these
solutions reveals that the presence of a negative cosmological constant is
essential to ensure the existence of stable equilibrium states. In addition, it
is shown that these theories are holographically related to [(d-1)/2] different
conformal field theories at the boundary.Comment: 13 Pages, 3 figures, two columns, Revtex, last version for PR
Gauss-Bonnet Black Holes in AdS Spaces
We study thermodynamic properties and phase structures of topological black
holes in Einstein theory with a Gauss-Bonnet term and a negative cosmological
constant. The event horizon of these topological black holes can be a
hypersurface with positive, zero or negative constant curvature. When the
horizon is a zero curvature hypersurface, the thermodynamic properties of black
holes are completely the same as those of black holes without the Gauss-Bonnet
term, although the two black hole solutions are quite different. When the
horizon is a negative constant curvature hypersurface, the thermodynamic
properties of the Gauss-Bonnet black holes are qualitatively similar to those
of black holes without the Gauss-Bonnet term. When the event horizon is a
hypersurface with positive constant curvature, we find that the thermodynamic
properties and phase structures of black holes drastically depend on the
spacetime dimension and the coefficient of the Gauss-Bonnet term: when
, the properties of black hole are also qualitatively similar to the
case without the Gauss-Bonnet term, but when , a new phase of locally
stable small black hole occurs under a critical value of the Gauss-Bonnet
coefficient, and beyond the critical value, the black holes are always
thermodynamically stable. However, the locally stable small black hole is not
globally preferred, instead a thermal anti-de Sitter space is globally
preferred. We find that there is a minimal horizon radius, below which the
Hawking-Page phase transition will not occur since for these black holes the
thermal anti de Sitter space is always globally preferred.Comment: Revtex, 17 pages with 9 eps figures, v2: section II removed and
references added, the version to appear in PR
Thermodynamic and gravitational instability on hyperbolic spaces
We study the properties of anti--de Sitter black holes with a Gauss-Bonnet
term for various horizon topologies (k=0, \pm 1) and for various dimensions,
with emphasis on the less well understood k=-1 solution. We find that the zero
temperature (and zero energy density) extremal states are the local minima of
the energy for AdS black holes with hyperbolic event horizons. The hyperbolic
AdS black hole may be stable thermodynamically if the background is defined by
an extremal solution and the extremal entropy is non-negative. We also
investigate the gravitational stability of AdS spacetimes of dimensions D>4
against linear perturbations and find that the extremal states are still the
local minima of the energy. For a spherically symmetric AdS black hole
solution, the gravitational potential is positive and bounded, with or without
the Gauss-Bonnet type corrections, while, when k=-1, a small Gauss-Bonnet
coupling, namely, \alpha << {l}^2 (where l is the curvature radius of AdS
space), is found useful to keep the potential bounded from below, as required
for stability of the extremal background.Comment: Shortened to match published (PRD) version, 18 pages, several eps
figure
Cosmic acceleration from asymmetric branes
We consider a single 3-brane sitting in between two different five
dimensional spacetimes. On each side of the brane, the bulk is a solution to
Gauss-Bonnet gravity, although the bare cosmological constant, funda mental
Planck scale, and Gauss-Bonnet coupling can differ. This asymmetry leads to
weighted junction conditions across the brane and interesting brane cosmology.
We focus on two special cases: a generalized Randall-Sundrum model without any
Gauss-Bonnet terms, and a stringy model, without any bare cosmological
constants, and positive Gauss-Bonnet coupling. Even though we assume there is
no vacuum energy on the brane, we find late time de Sitter cosmologies can
occur. Remarkably, in certain parameter regions, this acceleration is preceded
by a period of matter/radiation domination, with , all the
way back to nucleosynthesis.Comment: Version appearing in CQ
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