2,398 research outputs found
Dilaton Stabilization in (A)dS Spacetime with Compactified Dimensions
We investigate dilaton stabilization in a higher-dimensional theory. The
background geometry is based on an eleven-dimensional Kaluza-Klein/supergravity
model, which is assumed to be a product of four-dimensional de Sitter (dS_4)
spacetime and a seven sphere. The dilaton potential has a local minimum
resulting from contributions of the cosmological constant, the curvature of the
internal spacetime and quantum effects of the background scalar, vector,
spinor, and tensor fields. The dilaton settles down to the local minimum, and
the scale of the extra dimensions eventually become time independent. Our
four-dimensional universe evolves from dS_4 into AdS_4 after stabilization of
the extra dimension.Comment: 43 pages, 12 figures, PTPTeX. Accepted for publication in Progress of
Theoretical Physic
Cosmology in p-brane systems
We present time-dependent solutions in the higher-dimensional gravity which
are related to supergravity in the particular cases. Here, we consider p-branes
with a cosmological constant and the intersections of two and more branes. The
dynamical description of p-branes can be naturally obtained as the extension of
static solutions. In the presence of a cosmological constant, we find
accelerating solutions if the dilaton is not dynamical. In the case of
intersecting branes, the field equations normally indicate that time-dependent
solutions in supergravity can be found if only one harmonic function in the
metric depends on time. However, if the special relation between dilaton
couplings to antisymmetric tensor field strengths is satisfied, one can find a
new class of solutions where all harmonic functions depend on time. We then
apply our new solutions to study cosmology, with and without performing
compactifications.Comment: 45 pages, typos corrected, references are improve
Self-Tuning Dark Energy in Brane World Cosmology
Recently, the self-tuning mechanism of cancellation of vacuum energy has been
proposed in which our universe is a flat 3-brane in a 5-dimensional spacetime.
In this letter, the self-tuning mechanism of dark energy is proposed by
considering the cosmological matter in the brane world. In our model, the bulk
scalar field takes the role of the dark energy and its value is slowly varying
in time. The claim is that even if the enormous amount of vacuum energy exists
on the brane we can adjust the present value of the dark energy to be
consistent with the current observations. In this self-tuning mechanism, the
existence of the constant of integration associated with the bulk scalar is
crucial.Comment: 11pages, LaTe
Probe brane dynamics on cosmological brane backgrounds
We consider the dynamics of a single probe brane on various cosmological
brane backgrounds. The on-shell condition of the static probe brane leads to
the supersymmetric intersection rules for static BPS configurations, though the
cosmological backgrounds do not preserve any supersymmetries. This is a
remarkable feature associated with the cosmological backgrounds because in the
static background the on-shell condition of the static brane gives no
constraint on the brane configuration. Furthermore, it follows that under this
condition there is no velocity-independent force for the probe brane even on
the cosmological backgrounds.Comment: 14 pages, LaTeX, typos corrected, Journal versio
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