4,814 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.
The Cauchy problem of scalar-tensor theories of gravity
The 3+1 formulation of scalar-tensor theories of gravity (STT) is obtained in
the physical (Jordan) frame departing from the 4+0 covariant field equations.
Contrary to the common belief (folklore), the new system of ADM-like equations
shows that the Cauchy problem of STT is well formulated (in the sense that the
whole system of evolution equations is of first order in the time-derivative).
This is the first step towards a full first order (in time and space)
formulation from which a subsequent hyperbolicity analysis (a well-posedness
determination) can be performed. Several gauge (lapse and shift) conditions are
considered and implemented for STT. In particular, a generalization of the
harmonic gauge for STT allows us to prove the well posedness of the STT using a
second order analysis which is very similar to the one used in general
relativity. Some spacetimes of astrophysical and cosmological interest are
considered as specific applications. Several appendices complement the ideas of
the main part of the paper.Comment: 29 pages Revtex; typos corrected; references added and updated; a
shorter version of this paper was published in Classical and Quantum Gravit
New sources of resistance to bacterial wilt identified in dry bean germplasm collection.
Os objetivos do presente trabalho foram a obtenção de informação preliminar sobre a variabilidade de Curtobacterium pv. flaccumfasciens (Cff) e a identificação de novas fontes de resistência à murcha-de-Curtobacterium no feijoeiro comum. Três isolados de Cff foram inoculados nas cultivares Pérola, Xamego, Rosinha G-2, Diamante Negro e Valente. Como a variação não ambiental foi devida principalmente aos isolados e de cultivares, o isolado Cff CNF 4 foi selecionado para o teste de genótipos de feijoeiro comum para resistência à doença devido à sua maior patogenicidade no conjunto das seis cultivares. Dos 333 acessos testados, 12 apresentaram reação de resistência, enquanto 85 deles apresentaram plantas com reações compatíveis e incompatíveis com o patógeno. As plantas resistentes foram selecionadas e as famílias provenientes delas serão testadas para confirmação de resistência. Os acessos resistentes, e os selecionados que confirmarem sua classe de reação serão incorporadas no programa de melhoramento da Embrapa Arroz e Feijão
Metodologia para avaliação do comportamento fenológico de cultivares de Coffea arabica.
O estudo foi realizado com o objetivo de observar, no momento da colheita, o comportamento fenológico de cultivares de Coffea arabica, para identificar diferenças de uniformidade na maturação e definir ciclos: precoces, médios e tardios em duas safras consecutivas, 2004/2005 e 2005/2006. Os dois anos agrícolas foram bastante distintos climaticamente, fazendo com que as cultivares tivessem comportamentos diferentes, inclusive quanto ao número de floradas significativas, o que proporcionou aumento de desuniformidade na colheita. Com os resultados obtidos, observou que o desenvolvimento fenológico é uma característica altamente influenciada pelo ambiente e, para avaliação de ciclos e uniformidade as cultivares, devem ser avaliadas por mais de duas safras consecutivas
Induced scalarization in boson stars and scalar gravitational radiation
The dynamical evolution of boson stars in scalar-tensor theories of gravity
is considered in the physical (Jordan) frame. We focus on the study of
spontaneous and induced scalarization, for which we take as initial data
configurations on the well-known S-branch of a single boson star in general
relativity. We show that during the scalarization process a strong emission of
scalar radiation occurs. The new stable configurations (S-branch) of a single
boson star within a particular scalar-tensor theory are also presented.Comment: 18 pages, 11 figures. Minor changes to match the published versio
Initial State: Theory Status
I present a brief discussion of the different approaches to the study initial
state effects in heavy ion collisions in view of the recent results from Pb+Pb
and p+p collisions at the LHC.Comment: 8 pages, 6 figures. Contribution to the proceedings of the XXII
International Conference on Ultrarelativistic Nucleus-Nucleus Collisions,
QM2011. Annecy, France, 22-28 May 201
Supergravity with cosmological constant and the AdS group
It is shown that the supersymmetric extension of the Stelle-West formalism
permits the construction of an action for -dimensional N=1 supergravity
with cosmological constant genuinely invariant under the Since the
action is invariant under the supersymmetric extension of the group, the
supersymmetry algebra closes off shell without the need for auxiliary fields.
The limit case , i.e. -dimensional N=1 supergravity invariant
under the Poincar\'{e} supergroup is also discussed.Comment: 10 page
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