304 research outputs found

### On cosmological-type solutions in multi-dimensional model with Gauss-Bonnet term

A (n + 1)-dimensional Einstein-Gauss-Bonnet (EGB) model is considered. For
diagonal cosmological-type metrics, the equations of motion are reduced to a
set of Lagrange equations. The effective Lagrangian contains two
"minisuperspace" metrics on R^n. The first one is the well-known 2-metric of
pseudo-Euclidean signature and the second one is the Finslerian 4-metric that
is proportional to n-dimensional Berwald-Moor 4-metric. When a
"synchronous-like" time gauge is considered the equations of motion are reduced
to an autonomous system of first-order differential equations. For the case of
the "pure" Gauss-Bonnet model, two exact solutions with power-law and
exponential dependence of scale factors (with respect to "synchronous-like"
variable) are obtained. (In the cosmological case the power-law solution was
considered earlier in papers of N. Deruelle, A. Toporensky, P. Tretyakov and S.
Pavluchenko.) A generalization of the effective Lagrangian to the Lowelock case
is conjectured. This hypothesis implies existence of exact solutions with
power-law and exponential dependence of scale factors for the "pure" Lowelock
model of m-th order.Comment: 24 pages, Latex, typos are eliminate

### On avoiding cosmological oscillating behavior for S-brane solutions with diagonal metrics

In certain string inspired higher dimensional cosmological models it has been
conjectured that there is generic, chaotic oscillating behavior near the
initial singularity -- the Kasner parameters which characterize the asymptotic
form of the metric "jump" between different, locally constant values and
exhibit a never-ending oscillation as one approaches the singularity. In this
paper we investigate a class of cosmological solutions with form fields and
diagonal metrics which have a "maximal" number of composite electric S-branes.
We look at two explicit examples in D=4 and D=5 dimensions that do not have
chaotic oscillating behavior near the singularity. When the composite branes
are replaced by non-composite branes chaotic oscillatingComment: Corrected typos, published in Phys. Rev. D72, 103511 (2005

### Black-brane solution for C_2 algebra

Black p-brane solutions for a wide class of intersection rules and Ricci-flat
``internal'' spaces are considered. They are defined up to moduli functions H_s
obeying non-linear differential equations with certain boundary conditions
imposed. A new solution with intersections corresponding to the Lie algebra C_2
is obtained. The functions H_1 and H_2 for this solution are polynomials of
degree 3 and 4.Comment: 12 pages, Latex, submitted to J. Math. Phy

### On analogues of black brane solutions in the model with multicomponent anisotropic fluid

A family of spherically symmetric solutions with horizon in the model with
m-component anisotropic fluid is presented. The metrics are defined on a
manifold that contains a product of n-1 Ricci-flat "internal" spaces. The
equation of state for any s-th component is defined by a vector U^s belonging
to R^{n + 1}. The solutions are governed by moduli functions H_s obeying
non-linear differential equations with certain boundary conditions imposed. A
simulation of black brane solutions in the model with antisymmetric forms is
considered. An example of solution imitating M_2-M_5 configuration (in D =11
supergravity) corresponding to Lie algebra A_2 is presented.Comment: 8 pages, Latex, references and several equations and examples are
added, typos are eliminate

### Hyperbolic Kac-Moody Algebra from Intersecting p-branes

A subclass of recently discovered class of solutions in multidimensional
gravity with intersecting p-branes related to Lie algebras and governed by a
set of harmonic functions is considered. This subclass in case of three
Euclidean p-branes (one electric and two magnetic) contains a cosmological-type
solution (in 11-dimensional model with two 4-forms) related to hyperbolic
Kac-Moody algebra ${\cal F}_3$ (of rank 3). This solution describes the
non-Kasner power-law inflation.Comment: 15 pages, Latex. A talk presented at the Second Winter School on
Branes, Fields and Math. Phys. (Seoul, Korea). Corrected version. Journ.
ref.: J. Math. Phys., 40, (1999) 4072-4083; Corrigenda to appea

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