Supergravity Solutions for Harmonic, Static and Flux S-Branes

We seek S-brane solutions in D=11 supergravity which can be characterized by a harmonic function H on the flat transverse space. It turns out that the Einstein's equations force H to be a linear function of the transverse coordinates. The codimension one H=0 hyperplane can be spacelike, timelike or null and the spacelike case reduces to the previously obtained SM2 or SM5 brane solutions. We then consider static S-brane configurations having smeared timelike directions where the transverse Lorentzian symmetry group is broken down to its maximal orthogonal subgroup. Assuming that the metric functions depend on a radial spatial coordinate, we construct explicit solutions in D=11 supergravity which are non-supersymmetric and asymptotically flat. Finally, we obtain spacelike fluxbrane backgrounds which have timelike electric or magnetic fluxlines extending from past to future infinity.Comment: 22 pages, v2: references adde

S-brane Actions

We derive effective actions for Spacelike branes (S-branes) and find a solution describing the formation of fundamental strings in the rolling tachyon background. The S-brane action is a Dirac-Born-Infeld action for Euclidean worldvolumes defined in the context of time-dependent tachyon condensation of non-BPS branes. It includes gauge fields and in particular a scalar field associated with translation along the time direction. We show that the BIon spike solutions constructed in this system correspond to the production of a confined electric flux tube (a fundamental string) at late time of the rolling tachyon.Comment: 10 pages, 1 figure. References added, typos correcte

Anti-de-Sitter Island-Universes from 5D Standing Waves

We construct simple standing wave solutions in a 5D space-time with a ghost scalar field. The nodes of these standing waves are 'islands' of 4D Minkowski space-time. For the 5D model with increasing (decreasing) warp factor there are a finite (infinite) number of nodes and thus Minkowski island-universes having different parameters, such as gravitational and cosmological constants. This feature is similar to the assumptions of the landscape models, which postulate a large number of universes with different parameters. This standing wave solution also provides a new localization mechanism - matter fields can reside only on Minkowski 'islands', where the background space-time does not oscillate.Comment: 14 page pre-print format. Discussion about connection to Weyl gravity added and "E&M" localization method added. To be published MPL

Regular S-Brane Backgrounds

We construct time-dependent S-brane solutions to the supergravity field equations in various dimensions which (unlike most such geometries) do not contain curvature singularities. The configurations we consider are less symmetric than are earlier solutions, with our simplest solution being obtained by a simple analytical continuation of the Kerr geometry. We discuss in detail the global structure and properties of this background. We then generalize it to higher dimensions and to include more complicated field configurations - like non vanishing scalars and antisymmetric tensor gauge potentials - by the usual artifice of applying duality symmetries.Comment: 22 pages, 3 figures. Typos in eq.(2.6) correcte

Massless particles on supergroups and AdS3 x S3 supergravity

Firstly, we study the state space of a massless particle on a supergroup with a reparameterization invariant action. After gauge fixing the reparameterization invariance, we compute the physical state space through the BRST cohomology and show that the quadratic Casimir Hamiltonian becomes diagonalizable in cohomology. We illustrate the general mechanism in detail in the example of a supergroup target GL(1|1). The space of physical states remains an indecomposable infinite dimensional representation of the space-time supersymmetry algebra. Secondly, we show how the full string BRST cohomology in the particle limit of string theory on AdS3 x S3 renders the quadratic Casimir diagonalizable, and reduces the Hilbert space to finite dimensional representations of the space-time supersymmetry algebra (after analytic continuation). Our analysis provides an efficient way to calculate the Kaluza-Klein spectrum for supergravity on AdS3 x S3. It may also be a step towards the identification of an interesting and simpler subsector of logarithmic supergroup conformal field theories, relevant to string theory.Comment: 16 pages, 10 figure

Particle Production on Half S-brane

In this paper we will study quantum field theory of fluctuation modes around the rolling tachyon solution on non-BPS D-brane effective action. The goal of this paper is to study particle production during the decay of non-BPS D-brane and explore possible relation with minisuperspace calculation. We find that the number of particles produced on half S-brane exponentially grows for large time which suggests that linearised approximation breaks down and also that backreaction of fluctuation field on classical solution should be taken into account.Comment: 24 pages,v1.references adde

Emergence of gaussianity in the thermodynamic limit of interacting fermions

Systems of interacting fermions can give rise to ground states whose correlations become effectively free-fermion-like in the thermodynamic limit, as shown by Baxter for a class of integrable models that include the one-dimensional XYZ spin-½ chain. Here, we quantitatively analyze this behavior by establishing the relation between system size and correlation length required for the fermionic gaussianity to emerge. Importantly, we demonstrate that this behavior can be observed through the applicability of Wick's theorem, and thus, it is experimentally accessible. To establish the relevance of our results to possible experimental realizations of XYZ-related models, we demonstrate that the emergent gaussianity is insensitive to weak variations in the range of interactions, coupling inhomogeneities, and local random potentials

Dynamics of intersecting brane systems -- Classification and their applications --

We present dynamical intersecting brane solutions in higher-dimensional gravitational theory coupled to dilaton and several forms. Assuming the forms of metric, form fields, and dilaton field, we give a complete classification of dynamical intersecting brane solutions with/without M-waves and Kaluza-Klein monopoles in eleven-dimensional supergravity. We apply these solutions to cosmology and black holes. It is shown that these give FRW cosmological solutions and in some cases Lorentz invariance is broken in our world. If we regard the bulk space as our universe, we may interpret them as black holes in the expanding universe. We also discuss lower-dimensional effective theories and point out naive effective theories may give us some solutions which are inconsistent with the higher-dimensional Einstein equations.Comment: 44 pages; v2: minor corrections, references adde

Localized Intersections of Non-Extremal p-branes and S-branes

A class of solutions to Supergravity in 10 or 11 dimensions is presented which extends the non-standard or semi-local intersections of Dp-branes to the case of non-extremal p-branes. The type of non-extremal solutions involved in the intersection is free and we provide two examples involving black-branes and/or D-\bar{D} systems. After a rotation among the time coordinate and a relatively transverse radial direction the solutions admit the interpretation of an intersection among D-branes and S-branes. We speculate on the relevance of these configurations both to study time dependent phenomena in the AdS/CFT correspondence as well as to construct cosmological brane-world scenarios within String Theory admitting accelerating expansion of the Universe.Comment: 31 pages, latex file; v2: typos corrected and references adde