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

σ\sigma-models on the quantum group manifolds SLq(2,R)SL_{q}(2,R), SLq(2,R)/Uh(1)SL_{q}(2,R)/U_{h}(1), Cq(2∣0)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 AdS3AdS_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