11,119 research outputs found
Plant diversity to support humans in a CELSS ground based demonstrator
A controlled ecological life support system (CELSS) for human habitation in preparation for future long duration space flights is considered. The success of such a system depends upon the feasibility of revitalization of food resources and the human nutritional needs which are to be met by these food resources. Edible higher plants are prime candidates for the photoautotrophic components of this system if nutritionally adequate diets can be derived from these plant sources to support humans. Human nutritional requirements information based on current knowledge are developed for inhabitants envisioned in the CELSS ground based demonstrator. Groups of plant products that can provide the nutrients are identified
Existence of global strong solutions in critical spaces for barotropic viscous fluids
This paper is dedicated to the study of viscous compressible barotropic
fluids in dimension . We address the question of the global existence
of strong solutions for initial data close from a constant state having
critical Besov regularity. In a first time, this article show the recent
results of \cite{CD} and \cite{CMZ} with a new proof. Our result relies on a
new a priori estimate for the velocity, where we introduce a new structure to
\textit{kill} the coupling between the density and the velocity as in
\cite{H2}. We study so a new variable that we call effective velocity. In a
second time we improve the results of \cite{CD} and \cite{CMZ} by adding some
regularity on the initial data in particular is in . In this
case we obtain global strong solutions for a class of large initial data on the
density and the velocity which in particular improve the results of D. Hoff in
\cite{5H4}. We conclude by generalizing these results for general viscosity
coefficients
The (restricted) Inomata-McKinley spinor representation and the underlying topology
The so called Inomata-McKinley spinors are a particular solution of the
non-linear Heisenberg equation. In fact, free linear massive (or mass-less)
Dirac fields are well known to be represented as a combination of
Inomata-McKinley spinors. More recently, a subclass of Inomata-McKinley spinors
were used to describe neutrino physics. In this paper we show that Dirac
spinors undergoing this restricted Inomata-McKinley decomposition are
necessarily of the first type, according to the Lounesto classification.
Moreover, we also show that this type one subclass spinors has not an exotic
counterpart. Finally, implications of these results are discussed, regarding
the understanding of the spacetime background topology.Comment: 7 pages, to appear in EP
Braneworld Remarks in Riemann-Cartan Manifolds
We analyze the projected effective Einstein equation in a 4-dimensional
arbitrary manifold embedded in a 5-dimensional Riemann-Cartan manifold. The
Israel-Darmois matching conditions are investigated, in the context where the
torsion discontinuity is orthogonal to the brane. Unexpectedly, the presence of
torsion terms in the connection does not modify such conditions whatsoever,
despite of the modification in the extrinsic curvature and in the connection.
Then, by imposing the Z_2-symmetry, the Einstein equation obtained via
Gauss-Codazzi formalism is extended, in order to now encompass the torsion
terms. We also show that the factors involving contorsion change drastically
the effective Einstein equation on the brane, as well as the effective
cosmological constant.Comment: 7 pages. A corrected misprint in def.(18), and the respective terms
in Eqs.(20-23). All physical consequences remain unchange
Gravitational constraints of dS branes in AdS Einstein-Brans-Dicke bulk
We derive the full projected Einstein-Brans-Dicke gravitational equations
associated with a n-dimensional brane embedded in a (n+1)-dimensional bulk. By
making use of general conditions, as the positivity of the Brans-Dicke
parameter and the effective Newton gravitational constant as well, we are able
to constrain the brane cosmological constant in terms of the brane tension, the
Brans-Dicke scalar field, and the trace of the stress tensor on the brane, in
order to achieve a brane. Applying these constraints to a specific
five-dimensional model, a lower bound for the scalar field on the brane is
elicited without solving the full equations. It is shown under which conditions
the brane effective cosmological constant can be ignored in the brane projected
gravitational field equations, suggesting a different fine tuning between the
brane tension and the bulk cosmological.Comment: 9 pages, revTe
Schwarzschild generalized black hole horizon and the embedding space
By performing a Taylor expansion along the extra dimension of a metric
describing a black hole on a brane, we explore the influence of the embedding
space on the black hole horizon. In particular, it is shown that the existence
of a Kottler correction of the black hole on the brane, in a viable braneworld
scenario, might represent the radius of the black string collapsing to zero,
for some point(s) on the black string axis of symmetry along the extra
dimension. Further scrutiny on such black hole corrections by braneworld
effects is elicited, the well-known results in the literature are recovered as
limiting cases, and we assert and show that when the radius of the black string
transversal section is zero, as one moves away from the brane into the bulk, is
indeed a singularity.Comment: 7 pages, to appear in European Phys. J.
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