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The Beagle landing site in Isidis Planitia
The Mars probe Beagle 2 will land in Isidis Planitia. This region satisfies the engineering constraints and has evidence for particularly volatile-rich subsoil. Isidis provides a suitable place for the lander to search for H2O and organic matter
On the thin-shell limit of branes in the presence of Gauss-Bonnet interactions
In this paper we study thick-shell braneworld models in the presence of a
Gauss-Bonnet term. We discuss the peculiarities of the attainment of the
thin-shell limit in this case and compare them with the same situation in
Einstein gravity. We describe the two simplest families of thick-brane models
(parametrized by the shell thickness) one can think of. In the thin-shell
limit, one family is characterized by the constancy of its internal density
profile (a simple structure for the matter sector) and the other by the
constancy of its internal curvature scalar (a simple structure for the
geometric sector). We find that these two families are actually equivalent in
Einstein gravity and that the presence of the Gauss-Bonnet term breaks this
equivalence. In the second case, a shell will always keep some non-trivial
internal structure, either on the matter or on the geometric sectors, even in
the thin-shell limit.Comment: 17 pages, 2 figures, RevTeX 4. Revised version accepted for
publication in Physical Review
Localized gravity and mass hierarchy in D=6 with the Gauss-Bonnet term
We obtain the localized gravity on the intersection of two orthogonal
non-solitonic or solitonic 4-branes in D=6 in the presence of the Gauss-Bonnet
term. The tension of the intersection is allowed to exist unlike the case
without the Gauss-Bonnet term. We show that gravity could be confined to the
solitonic 4-branes for a particular choice of the Gauss-Bonnet coupling. If the
extra dimensions are compactified with the orbifold
symmetry, the mass hierarchy between the Planck scale and the weak scale can be
explained by putting our universe at the TeV intersection of positive tension
located at the orbifold fixed point.Comment: Latex file of 12 page
Higher codimension braneworlds from intersecting branes
We study the matching conditions of intersecting brane worlds in Lovelock
gravity in arbitrary dimension. We show that intersecting various codimension 1
and/or codimension 2 branes one can find solutions that represent
energy-momentum densities localized in the intersection, providing thus the
first examples of infinitesimally thin higher codimension braneworlds that are
free of singularities and where the backreaction of the brane in the background
is fully taken into account.Comment: 20 pages; v2. references and comments added to match the published
versio
Brane cosmology with curvature corrections
We study the cosmology of the Randall-Sundrum brane-world where the
Einstein-Hilbert action is modified by curvature correction terms: a
four-dimensional scalar curvature from induced gravity on the brane, and a
five-dimensional Gauss-Bonnet curvature term. The combined effect of these
curvature corrections to the action removes the infinite-density big bang
singularity, although the curvature can still diverge for some parameter
values. A radiation brane undergoes accelerated expansion near the minimal
scale factor, for a range of parameters. This acceleration is driven by the
geometric effects, without an inflaton field or negative pressures. At late
times, conventional cosmology is recovered.Comment: RevTex4, 8 pages, no figures, minor change
Shear viscosity, instability and the upper bound of the Gauss-Bonnet coupling constant
We compute the dimensionality dependence of for charged black branes
with Gauss-Bonnet correction. We find that both causality and stability
constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in
the infinite dimensionality limit. We further show that higher dimensionality
stabilize the gravitational perturbation. The stabilization of the perturbation
in higher dimensional space-time is a straightforward consequence of the
Gauss-Bonnet coupling constant bound.Comment: 16 pages,3 figures+3 tables,typos corrected, published versio
Warped Phenomenology of Higher-Derivative Gravity
We examine the phenomenological implications at colliders for the existence
of higher-derivative gravity terms as extensions to the Randall-Sundrum model.
Such terms are expected to arise on rather general grounds, e.g., from string
theory. In 5-d, if we demand that the theory be unitary and ghost free, these
new contributions to the bulk action are uniquely of the Gauss-Bonnet form. We
demonstrate that the usual expectations for the production cross section and
detailed properties of graviton Kaluza-Klein resonances and TeV-scale black
holes can be substantially altered by existence of these additional
contributions. It is shown that measurements at future colliders will be highly
sensitive to the presence of such terms.Comment: 29 pages, 8 figure
Generalised Israel Junction Conditions for a Gauss-Bonnet Brane World
In spacetimes of dimension greater than four it is natural to consider higher
order (in R) corrections to the Einstein equations. In this letter generalized
Israel junction conditions for a membrane in such a theory are derived. This is
achieved by generalising the Gibbons-Hawking boundary term. The junction
conditions are applied to simple brane world models, and are compared to the
many contradictory results in the literature.Comment: 4 page
Brane localization of gravity in higher derivative theory
We consider a class of higher order corrections in the form of Euler
densities of arbitrary rank to the standard gravity action in
dimensions. We have previously shown that this class of corrections allows for
domain wall solutions despite the presence of higher powers of the curvature.
In the present paper we explicitly solve the linearized equation of motion for
gravity fluctuations around the domain wall background and show that there
always exist one massless state (graviton) propagating on the wall and a
continuous tower of massive states propagating in the bulk.Comment: 14 pages, Late
Interacting new agegraphic Phantom model of dark energy in non-flat universe
In this paper we consider the new agegraphic model of interacting dark energy
in non-flat universe. We show that the interacting agegraphic dark energy can
be described by a phantom scalar field. Then we show this phantomic description
of the agegraphic dark energy and reconstruct the potential of the phantom
scalar field.Comment: 8 pages, no figur
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