Linear Sigma Models of H and KK Monopoles

We propose a gauged linear sigma model of k H-monopoles. We also consider the T-dual of this model describing KK-monopoles and clarify the meaning of "winding coordinate" studied recently in hep-th/0507204.Comment: 13 pages, lanlmac; V3:added argument on the nature of disk instanto

Anti-gravitating BPS monopoles and dyons

We show that the exact static, i.e. `anti-gravitating', magnetic multi monopole solutions of the Einstein/Maxwell/dilaton-YM/Higgs equations found by Kastor, London, Traschen, and the authors, for arbitrary non-zero dilaton coupling constant $a$, are equivalent to the string theory BPS magnetic monopole solutions of Harvey and Liu when $a=\sqrt{3}$. For this value of $a$, the monopole solutions also solve the equations of five-dimensional supergravity/YM theory. We also discuss some features of the dyon solutions obtained by boosting in the fifth dimension and some features of the moduli space of anti-gravitating multi-monopoles.Comment: 15 pp. Phyzz

Puffed Noncommutative Nonabelian Vortices

We present new solutions of noncommutative gauge theories in which coincident unstable vortices expand into unstable circular shells. As the theories are noncommutative, the naive definition of the locations of the vortices and shells is gauge-dependent, and so we define and calculate the profiles of these solutions using the gauge-invariant noncommutative Wilson lines introduced by Gross and Nekrasov. We find that charge 2 vortex solutions are characterized by two positions and a single nonnegative real number, which we demonstrate is the radius of the shell. We find that the radius is identically zero in all 2-dimensional solutions. If one considers solutions that depend on an additional commutative direction, then there are time-dependent solutions in which the radius oscillates, resembling a braneworld description of a cyclic universe. There are also smooth BIon-like space-dependent solutions in which the shell expands to infinity, describing a vortex ending on a domain wall.Comment: 21 pages, 3 eps figures. v2: published version, analytic solution adde

Toda systems in closed string tachyon condensation

We consider $tt^*$ equations appearing in the study of localized tachyon condensations. They are described by various Toda system when we consider the condensation by the lowest tachyon corresponding to the monomial $xy$. The tachyon potential is calculated as a solution to these equations. The Toda system appearing in the deformation of \C^2/\Z_n by $xy$ is identical to that of $D_n$ singularity deformed by $x$. For \C^3/\Z_n with $xyz$ deformation, we find only generic non-simple form, similar to the case appearing in \C/\Z_5\to \C/\Z_3 and we discuss the difficulties in these cases.Comment: 20 pages, no figur

Classical and Thermodynamic Stability of Black Branes

It is argued that many non-extremal black branes exhibit a classical Gregory-Laflamme instability if, and only if, they are locally thermodynamically unstable. For some black branes, the Gregory-Laflamme instability must therefore disappear near extremality. For the black $p$-branes of the type II supergravity theories, the Gregory-Laflamme instability disappears near extremality for $p=1,2,4$ but persists all the way down to extremality for $p=5,6$ (the black D3-brane is not covered by the analysis of this paper). This implies that the instability also vanishes for the near-extremal black M2 and M5-brane solutions.Comment: 21 pages, LaTeX. v2: Various points clarified, typos corrected and reference adde

The M Theory Five-Brane and the Heterotic String

Brane actions with chiral bosons present special challenges. Recent progress in the description of the two main examples -- the M theory five-brane and the heterotic string -- is described. Also, double dimensional reduction of the M theory five-brane on K3 is shown to give the heterotic string.Comment: 13 pages, latex, no figures; ICTP Conference Proceeding

Complex structure moduli stability in toroidal compactifications

In this paper we present a classification of possible dynamics of closed string moduli within specific toroidal compactifications of Type II string theories due to the NS-NS tadpole terms in the reduced action. They appear as potential terms for the moduli when supersymmetry is broken due to the presence of D-branes. We particularise to specific constructions with two, four and six-dimensional tori, and study the stabilisation of the complex structure moduli at the disk level. We find that, depending on the cycle on the compact space where the brane is wrapped, there are three possible cases: i) there is a solution inside the complex structure moduli space, and the configuration is stable at the critical point, ii) the moduli fields are driven towards the boundary of the moduli space, iii) there is no stable solution at the minimum of the potential and the system decays into a set of branes.Comment: 24 pages, JHEP3.cls, 19 figures. A few references adde

FERMION ZERO MODES AND BLACK-HOLE HYPERMULTIPLETS WITH RIGID SUPERSYMMETRY

The gravitini zero modes riding on top of the extreme Reissner-Nordstrom black-hole solution of N=2 supergravity are shown to be normalizable. The gravitini and dilatini zero modes of axion-dilaton extreme black-hole solutions of N=4 supergravity are also given and found to have finite norms. These norms are duality invariant. The finiteness and positivity of the norms in both cases are found to be correlated with the Witten-Israel-Nester construction; however, we have replaced the Witten condition by the pure-spin-3/2 constraint on the gravitini. We compare our calculation of the norms with the calculations which provide the moduli space metric for extreme black holes. The action of the N=2 hypermultiplet with an off-shell central charge describes the solitons of N=2 supergravity. This action, in the Majumdar-Papapetrou multi-black-hole background, is shown to be N=2 rigidly supersymmetric.Comment: 18 pages, LaTe

Born-Infeld particles and Dirichlet p-branes

Born-Infeld theory admits finite energy point particle solutions with $\delta$-function sources, BIons. I discuss their role in the theory of Dirichlet $p$-branes as the ends of strings intersecting the brane when the effects of gravity are ignored. There are also topologically non-trivial electrically neutral catenoidal solutions looking like two $p$-branes joined by a throat. The general solution is a non-singular deformation of the catenoid if the charge is not too large and a singular deformation of the BIon solution for charges above that limit. The intermediate solution is BPS and Coulomb-like. Performing a duality rotation we obtain monopole solutions, the BPS limit being a solution of the abelian Bogolmol'nyi equations. The situation closely resembles that of sub and super extreme black-brane solutions of the supergravity theories. I also show that certain special Lagrangian submanifolds of ${\Bbb C}^p$, $p=3,4,5$, may be regarded as supersymmetric configurations consisting of $p$-branes at angles joined by throats which are the sources of global monopoles. Vortex solutions are also exhibited.Comment: 40 pages Latex file, no figure

Solitonic Strings and BPS Saturated Dyonic Black Holes

We consider a six-dimensional solitonic string solution described by a conformal chiral null model with non-trivial $N=4$ superconformal transverse part. It can be interpreted as a five-dimensional dyonic solitonic string wound around a compact fifth dimension. The conformal model is regular with the short-distance (`throat') region equivalent to a WZW theory. At distances larger than the compactification scale the solitonic string reduces to a dyonic static spherically-symmetric black hole of toroidally compactified heterotic string. The new four-dimensional solution is parameterised by five charges, saturates the Bogomol'nyi bound and has nontrivial dilaton-axion field and moduli fields of two-torus. When acted by combined T- and S-duality transformations it serves as a generating solution for all the static spherically-symmetric BPS-saturated configurations of the low-energy heterotic string theory compactified on six-torus. Solutions with regular horizons have the global space-time structure of extreme Reissner-Nordstrom black holes with the non-zero thermodynamic entropy which depends only on conserved (quantised) charge vectors. The independence of the thermodynamic entropy on moduli and axion-dilaton couplings strongly suggests that it should have a microscopic interpretation as counting degeneracy of underlying string configurations. This interpretation is supported by arguments based on the corresponding six-dimensional conformal field theory. The expression for the level of the WZW theory describing the throat region implies a renormalisation of the string tension by a product of magnetic charges, thus relating the entropy and the number of oscillations of the solitonic string in compact directions.Comment: 27 Pages, uses RevTeX (solution for the axion field corrected, erratum to appear in Phys. Rev. D