16 research outputs found
Thick brane in 7D and 8D spacetimes
We consider a thick brane model supported by two interacting scalar fields in
7D and 8D general relativity. Using the special type of a potential energy, we
obtain numerically the regular asymptotically flat vacuum solutions. A
possibility of obtaining the similar solutions for an arbitrary number of the
extra spatial dimensions is estimated.Comment: 3 Ref's are adde
de Sitter branes with a bulk scalar
We propose new braneworld models arising from a scalar field in the bulk. In
these examples, the induced on--brane line element is de Sitter (or anti de
Sitter) and the bulk (five dimensional) Einstein equations can be exactly
solved to obtain warped spacetimes. The solutions thus derived are single and
two-brane models -- one with {\em thin} branes while the other one of the {\em
thick} variety. The field profiles and the potentials are obtained and analysed
for each case. We note that for the {\em thick} brane scenario the field
profile resembles a kink, whereas for one or more {\em thin} branes, it is
finite and bounded in the domain of the extra dimension. We have also addressed
the localisation of gravity and other matter fields on the brane for these
braneworld models.Comment: 18 pages, 5 figures. Substantial changes and new results. To appear
in GR
q-Form fields on p-branes
In this paper, we give one general method for localizing any form (q-form)
field on p-branes with one extra dimension, and apply it to some typical
p-brane models. It is found that, for the thin and thick Minkowski branes with
an infinite extra dimension, the zero mode of the q-form fields with q<(p-1)/2
can be localized on the branes. For the thick Minkowski p-branes with one
finite extra dimension, the localizable q-form fields are those with q<p/2, and
there are also some massive bound Kaluza-Klein modes for these q-form fields on
the branes. For the same q-form field, the number of the bound Kaluza-Klein
modes (but except the scalar field (q=0)) increases with the dimension of the
p-branes. Moreover, on the same p-brane, the q-form fields with higher q have
less number of massive bound KK modes. While for a family of pure geometrical
thick p-branes with a compact extra dimension, the q-form fields with q<p/2
always have a localized zero mode. For a special pure geometrical thick
p-brane, there also exist some massive bound KK modes of the q-form fields with
q<p/2, whose number increases with the dimension of the p-brane.Comment: 14 pages, 2 figures, published versio
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
Localization of gravity on a de Sitter thick braneworld without scalar fields
In this work we present a simple thick braneworld model that is generated by
an intriguing interplay between a 5D cosmological constant with a de Sitter
metric induced in the 3-brane without the inclusion of scalar fields. We show
that 4D gravity is localized on this brane, provide analytic expressions for
the massive Kaluza-Klein (KK) fluctuation modes and also show that the spectrum
of metric excitations displays a mass gap. We finally present the corrections
to Newton's law due to these massive modes. This model has no naked
singularities along the fifth dimension despite the existence of a mass gap in
the graviton spectrum as it happens in thick branes with 4D Poincare symmetry,
providing a simple model with very good features: the curvature is completely
smooth along the fifth dimension, it localizes 4D gravity and the spectrum of
gravity fluctuations presents a mass gap, a fact that rules out the existence
of phenomenologically dangerous ultralight KK excitations in the model. We
finally present our solution as a limit of scalar thick branes.Comment: 11 pages in latex, no figures, title and abstract changed, a new
section and some references adde