74 research outputs found
Hadronic mass and q^2 moments of charmless semileptonic B decay distributions
We report OPE predictions for hadronic mass and q^2 moments in inclusive
semileptonic B decays without charm, taking into account experimental cuts on
the charged lepton energy and on the hadronic invariant mass, and address the
related theoretical uncertainty.Comment: 16 pages, 1 figure; v3: we have corrected a mistake in the code that
produced the numerical results; tables replaced, small changes in the tex
Gauge-invariant fluctuations of scalar branes
A generalization of the Bardeen formalism to the case of warped geometries is
presented. The system determining the gauge-invariant fluctuations of the
metric induced by the scalar fluctuations of the brane is reduced to a set of
Schr\"odinger-like equations for the Bardeen potentials and for the canonical
normal modes of the scalar-tensor action. Scalar, vector and tensor modes of
the geometry are classified according to four-dimensional Lorentz
transformations. While the tensor modes of the geometry live on the brane
determining the corrections to Newton law, the scalar and and vector
fluctuations exhibit non normalizable zero modes and are, consequently, not
localized on the brane. The spectrum of the massive modes of the fluctuations
is analyzed using supersymmetric quantum mechanics.Comment: 29 pages in Latex styl
The Randall-Sundrum Scenario with an Extra Warped Dimension
We investigate a scenario with two four-branes embedded in six dimensions.
When the metric is periodic and compact in one of the dimensions parallel to
the branes, the value of the effective cosmological constant for the remaining
five dimensions can assume a variety of values, determined by the dependence of
the metric on the sixth dimension. The picture that emerges resembles the
Randall-Sundrum model but with an extra warped dimension that allows the usual
brane-bulk fine tuning to be satisfied without finely tuning any of the
parameters in the underlying six dimensional theory. Although the action
contains terms with four derivatives of the metric, we show that when the
branes have a finite, natural thickness, such terms have only a small effect on
the Randall-Sundrum structure. The presence of these four derivative terms also
allows a configuration that resembles that produced by a domain wall but which
results from gravity alone.Comment: 12 pages, 3 figures, requires harvmac and picte
Thick de Sitter 3-Branes, Dynamic Black Holes and Localization of Gravity
The embedding of a thick de Sitter 3-brane into a five-dimensional bulk is
studied, assuming a scalar field with potential is present in the bulk. A class
of solutions is found in closed form that can represent a thick de Sitter
3-brane interpolating either between two dynamical black holes with a topology or between two Rindler-like spacetimes with a topology. The gravitational field is localized in a small region near
the center of the 3-brane. The analysis of graviton fluctuations shows that a
zero mode exists and separates itself from a set of continuous modes by a mass
gap. The existence of such a mass gap is shown to be universal. The scalar
perturbations are also studied and shown to be stable.Comment: the study of scalar perturbations and some relevant references have
been added. The most used definition for mass in de Sitter space has been
adopte
Expanding Cosmologies in Brane Geometries
Five dimensional gravity coupled, both in the bulk and on a brane, to a
scalar Liouville field yields a geometry confined to a strip around the brane
and with time dependent scale factors for the four geometry. In various limits
known models can be recovered as well as a temporally expanding four geometry
with a warp factor falling exponentially away from the brane. The effective
theory on the brane has a time dependent Planck mass and ``cosmological
constant''. Although the scale factor expands, the expansion is not an
acceleration.Comment: 7 pages, LaTex/RevTex
Scalar normal modes of higher dimensional gravitating kinks
The scalar normal modes of higher dimensional gravitating kink solutions are
derived. By perturbing to second order the gravity and matter parts of the
action in the background of a five-dimensional kink, the effective Lagrangian
of the scalar fluctuations is derived and diagonalized in terms of a single
degree of freedom which invariant under infinitesimal diffeomorphisms. The
spectrum of the normal modes is discussed and applied to the analysis of short
distance corrections to Newton law.Comment: 20 pages in Latex styl
Self-gravitating domain walls and the thin-wall limit
We analyse the distributional thin wall limit of self gravitating scalar
field configurations representing thick domain wall geometries. We show that
thick wall solutions can be generated by appropiate scaling of the thin wall
ones, and obtain an exact solution for a domain wall that interpolates between
AdS_4 asymptotic vacua and has a well-defined thin wall limit.Solutions
representing scalar field configurations obtained via the same scaling but that
do not have a thin wall limit are also presented.Comment: 10 pages, revte
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
Analytic continuations of de Sitter thick domain wall solutions
We perform some analytic continuations of the de Sitter thick domain wall
solutions obtained in our previous paper hep-th/0201130 in the system of
gravity and a scalar field with an axion-like potential. The obtained new
solutions represent anti-de Sitter thick domain walls and cosmology. The
anti-de Sitter domain wall solutions are periodic, and correspondingly the
cosmological solutions represent cyclic universes. We parameterize the
axion-like scalar field potential and determine the parameter regions of each
type of solutions.Comment: Additons in section 5, 8 pages, 7 figures, RevTe
Critical phenomena of thick branes in warped spacetimes
We have investigated the effects of a generic bulk first-order phase
transition on thick Minkowski branes in warped geometries. As occurs in
Euclidean space, when the system is brought near the phase transition an
interface separating two ordered phases splits into two interfaces with a
disordered phase in between. A remarkable and distinctive feature is that the
critical temperature of the phase transition is lowered due to pure geometrical
effects. We have studied a variety of critical exponents and the evolution of
the transverse-traceless sector of the metric fluctuations.Comment: revtex4, 4 pages, 4 figures, some comments added, typos corrected,
published in PR
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