18 research outputs found
Conical singularities regularized in warped six-dimensional flux compactification and their induced brane cosmology
We discuss the regularization of codimension-2 singularities in warped
six-dimensional Einstein-Maxwell axisymmetric models by replacing them by
codimension-1 branes of a ring form, situated around the axis of symmetry.
Further we consider the case of one capped regularized conical brane of
codimension one and study the cosmological evolution which is induced on it as
it moves in between the known {\it static} bulk and cap solutions. We present
the resulting brane Friedmann equation which gives a dominant five-dimensional
energy density term at high energies and a term linear to the energy
density at low energies with, however, negative coefficient in the small
four-brane radius limit (i.e. with negative effective Newton's constant)Comment: 14 page
Geometrical Tachyon Dynamics in the Background of a Bulk Tachyon Field
We study the dynamics of a D3-brane moving in the background of a bulk
tachyon field of a D3-brane solution of Type-0 string theory. We show that the
dynamics on the probe D3-brane can be described by a geometrical tachyon field
rolling down its potential which is modified by a function of the bulk tachyon
and inflation occurs at weak string coupling, where the bulk tachyon condenses,
near the top of the geometrical tachyon potential. We also find a late
accelerating phase when the bulk tachyon asymptotes to zero which in the
geometrical tachyon picture corresponds to the minimum of the geometrical
potential.Comment: 27 pages, 2 figures, accepted for publication in JHE
String-Like BTZ on Codimension-2 Braneworlds in the Thin Brane Limit
We consider five-dimensional gravity with a Gauss-Bonnet term in the bulk and
an induced gravity term on a 2-brane of codimension-2. We show that this system
admits BTZ black holes on the 2-brane which are extended into the bulk with
regular horizons.Comment: Title changed, reference added, shortened to match the published
version in Physical Review Letter
Regularization of conical singularities in warped six-dimensional compactifications
We study the regularization of the codimension-2 singularities in
six-dimensional Einstein-Maxwell axisymmetric models with warping. These
singularities are replaced by codimension-1 branes of a ring form, situated
around the axis of symmetry. We assume that there is a brane scalar field with
Goldstone dynamics, which is known to generate a brane energy momentum tensor
of a particular structure necessary for the above regularization to be
successful. We study these compactifications in both a non-supersymmetric and a
supersymmetric setting. We see that in the non-supersymmetric case, there is a
restriction to the admissible warpings and furthermore to the quantum numbers
of the bulk gauge field and the brane scalar field. On the contrary, in the
supersymmetric case, the warping can be arbitrary.Comment: 22 pages, 1 figure, comments adde
Black Holes on Thin 3-branes of Codimension-2 and their Extension into the Bulk
We discuss black hole solutions in six-dimensional gravity with a
Gauss-Bonnet term in the bulk and an induced gravity term on a thin 3-brane of
codimension-2. We show that these black holes can be localized on the brane,
and they can further be extended into the bulk by a warp function. These
solutions have regular horizons and no other curvature singularities appear
apart from the string-like ones. The projection of the Gauss-Bonnet term on the
brane imposes a constraint relation which requires the presence of matter in
the extra dimensions.Comment: 23 pages, no figures, minor corrections, version to appear in Nuclear
Physics
Perturbations of Gauss-Bonnet Black Strings in Codimension-2 Braneworlds
We derive the Lichnerowicz equation in the presence of the Gauss-Bonnet term.
Using the modified Lichnerowicz equation we study the metric perturbations of
Gauss-Bonnet black strings in Codimension-2 Braneworlds.Comment: 26 pages, no figures, clarifying comments and one reference added, to
be published in JHE
Curvaton Dynamics in Brane-worlds
We study the curvaton dynamics in brane-world cosmologies. Assuming that the
inflaton field survives without decay after the end of inflation, we apply the
curvaton reheating mechanism to Randall-Sundrum and to its curvature
corrections: Gauss-Bonnet, induced gravity and combined Gauss-Bonnet and
induced gravity cosmological models. In the case of chaotic inflation and
requiring suppression of possible short-wavelength generated gravitational
waves, we constraint the parameters of a successful curvaton brane-world
cosmological model. If density perturbations are also generated by the curvaton
field then, the fundamental five-dimensional mass could be much lower than the
Planck massComment: 47 pages, 1 figure, references added, to be published in JCA