2,901 research outputs found

### Infinite hierarchies of exact solutions of the Einstein and Einstein-Maxwell equations for interacting waves and inhomogeneous cosmologies

For space-times with two spacelike isometries, we present infinite
hierarchies of exact solutions of the Einstein and Einstein--Maxwell equations
as represented by their Ernst potentials. This hierarchy contains three
arbitrary rational functions of an auxiliary complex parameter. They are
constructed using the so called `monodromy transform' approach and our new
method for the solution of the linear singular integral equation form of the
reduced Einstein equations. The solutions presented, which describe
inhomogeneous cosmological models or gravitational and electromagnetic waves
and their interactions, include a number of important known solutions as
particular cases.Comment: 7 pages, minor correction and reduction to conform with published
versio

### Nonstatic AdS_2 Branes and the Isometry Group of AdS_3 Spacetime

For the D-branes on the SL(2,R) WZW model we present a particular choice of
outer automorphism for the gluing condition of currents that leads to a special
AdS_2 brane configuration. This configuration is shown to be a static solution
in the cylindrical coordinates, and a nonstatic solution in the Poincar\'e
coordinates to the nonlinear equation of motion for the Dirac-Born-Infeld
action of a D-string. The generalization of it gives a family of nonstatic
AdS_2 brane solutions. They are deomonstrated to transform to each other under
the isometry group of AdS_3 spacetime.Comment: 11 pages, LaTeX2e, no figure

### Fuzzy Algebrae of the General Kaehler Coset Space G/H\otimesU(1)^k

We study the fuzzy structure of the general Kaehler coset space
G/S\otimes{U(1)}^k deformed by the Fedosov formalism. It is shown that the
Killing potentials satisfy the fuzzy algebrae working in the Darboux
coordinates.Comment: 8 pages, LaTex, no figur

### Gravitational Dielectric Effect and Myers Effect

In this paper we study the gravitational dielectric phenomena of a D2-brane
in the background of Kaluza-Klein monopoles and D6-branes. In both cases the
spherical D2-brane with nonzero radius becomes classical solution of the
D2-brane action. We also investigate the gravitational Myers effect in the
background of D6-branes. This phenomenon occurs since the tension of the
D2-brane balances with the repulsive force between D0-branes and D6-branes.Comment: 17 pages, 4 figures, The argument on the stability of the spehrical
D2-D0 bound state is modified and clarified in the appendix, The effect of
background R-R field are included, reference added, version appeared in PR

### $\sigma$-models on the quantum group manifolds $SL_{q}(2,R)$, $SL_{q}(2,R)/U_{h}(1)$, $C_{q}(2|0)$ and infinitesimal trasformations

The differential and variational calculus on the $SL_{q}(2,R)$ group is
constructed. The spontaneous breaking symmetry in the WZNW model with
$SL_{q}(2,R)$ quantum group symmetry and in the $\sigma$-models with
${SL_{q}(2,R)/U_{h}(1)}$ ,$C_{q}(2|0)$ quantum group symmetry is considered.
The Lagrangian formalism over the quantum group manifolds is discussed. The
classical solution of $C_{q}(2|0)$ {$\sigma$}-model is obtained.Comment: LaTex, 7 page

### Accuracy of one-dimensional collision integral in the rigid spheres approximation

The accuracy of calculation of spectral line shapes in one-dimensional
approximation is studied analytically in several limiting cases for arbitrary
collision kernel and numerically in the rigid spheres model. It is shown that
the deviation of the line profile is maximal in the center of the line in case
of large perturber mass and intermediate values of collision frequency. For
moderate masses of buffer molecules the error of one-dimensional approximation
is found not to exceed 5%.Comment: LaTeX, 24 pages, 8 figure

### New $AdS_3$ Branes and Boundary States

We examine D-branes on $AdS_3$, and find a three-brane wrapping the entire
$AdS_3$, in addition to 1-branes and instantonic 2-branes previously discussed
in the literature. The three-brane is found using a construction of Maldacena,
Moore, and Seiberg. We show that all these branes satisfy Cardy's condition and
extract the open string spectrum on them.Comment: 18 pages, late

### Notes on noncommutative supersymmetric gauge theory on the fuzzy supersphere

In these notes we review Klimcik's construction of noncommutative gauge
theory on the fuzzy supersphere. This theory has an exact SUSY gauge symmetry
with a finite number of degrees of freedom and thus in principle it is amenable
to the methods of matrix models and Monte Carlo numerical simulations. We also
write down in this article a novel fuzzy supersymmetric scalar action on the
fuzzy supersphere

### The gauge algebra of double field theory and Courant brackets

We investigate the symmetry algebra of the recently proposed field theory on
a doubled torus that describes closed string modes on a torus with both
momentum and winding. The gauge parameters are constrained fields on the
doubled space and transform as vectors under T-duality. The gauge algebra
defines a T-duality covariant bracket. For the case in which the parameters and
fields are T-dual to ones that have momentum but no winding, we find the gauge
transformations to all orders and show that the gauge algebra reduces to one
obtained by Siegel. We show that the bracket for such restricted parameters is
the Courant bracket. We explain how these algebras are realised as symmetries
despite the failure of the Jacobi identity.Comment: 25 pages, LaTe

### Expanded Strings in the Background of NS5-branes via a M2-brane, a D2-brane and D0-branes

Classical configurations of a M2-brane, a D2-brane and D0-branes are
investigated in the background of an infinite array of M5-branes or NS5-branes.
On the M2-brane, we discuss three kinds of configurations, such as a sphere, a
cylinder and a torus-like one. These are stabilized by virtue of the background
fluxes of M5-branes. The torus-like M2-brane configuration has winding and
momentum numbers of 11th direction, and in terms of the type IIA superstring
theory, this corresponds to a torus-like D2-brane with electric and magnetic
fluxes on it. We also reproduce the same configuration from a non-abelian
Born-Infeld action for D0-branes. It will be a construction of closed strings
from D0-branes. An electric flux quantization condition on the D2-brane is also
discussed in terms of D0-branes.Comment: 33 pages, 6 figures, references and footnote added, confusing
expressions and introduction are improved, version to appear in JHE

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