Related papers: String Network and U-Duality
We study static, spherically symmetric, and purely magnetic solutions of SU(2) $\times$ SU(2) gauge supergravity in four dimensions. A systematic analysis of the supersymmetry conditions reveals solutions which preserve 1/8 of the…
The notion of a space-time uncertainty principle in string theory is clarified and further developed. The motivation and the derivation of the principle are first reviewed in a reasonably self-contained way. It is then shown that the…
We investigate interactions between branes of various dimensions, both charged and uncharged, in three non-supersymmetric string models. These include the $USp(32)$ and $U(32)$ orientifold projections of the type IIB and type $0$B strings,…
We use string duality to describe instanton induced spontaneous supersymmetry breaking in string compactifications with additional background fields. Dynamical supersymmetry breaking by space-time instantons in the heterotic string theory…
We propose a unified approach to a general class of codimension-2 defects in field theories with non-trivial duality symmetries and discuss various constructions of such "duality defects" in diverse dimensions. In particular, in d=4 we…
In these lectures we review how some of the recent developments in string theory are closely related to generic properties of supersymmetry. Lectures given at the Nato Advanced Study Institute on "Strings, Branes and Dualities", Cargese,…
After reviewing briefly the classical examples of duality in four dimensional field theory we present a generalisation to arbitrary dimensions and to p-form fields. Then we explain how U-duality may become part of a larger non abelian…
By studying 2d string compactifications with half-maximal supersymmetry in a variety of duality frames, we find a natural physical setting for understanding Umbral moonshine. Near points in moduli space with enhanced gauge symmetry, we find…
We study BPS-saturated classical solutions for the world-sheet theory of a D-string in the presence of a point charge. These solutions are interpreted as describing planar 3-string junctions, which arise because the original D-string is…
We investigate the correspondence between existence/stability of BPS states in type II string theory compactified on a Calabi-Yau manifold and BPS solutions of four dimensional N=2 supergravity. Some paradoxes emerge, and we propose a…
We study junctions of supersymmetric domain walls in N=1 supergravity theories in four dimensions, coupled to a chiral superfield with quartic superpotential having $Z_3$ symmetry. After deriving a BPS equation of the domain wall junction,…
With our current level of understanding, the problem of making string theory predictions is not one of "solving" the theory, but rather of trying to determine whether there are any generic expectations. Within this context, we discuss what…
When reduced from $10$ to $10-d$ dimensions tree-level string theory exhibits an $O(d,d)$ symmetry. This symmetry, which is closely related to T-duality, appears only after certain field redefinitions. We find a simple form for a subset of…
U duality transformations must act on a basis of states that form complete multiplets of the U group, at any coupling, even though the states may not be mass degenerate, as for a broken symmetry. Similarly, if superstring theory is related…
The symmetry classification method is applied to the string-like scalar fields in two-dimensional space-time. When the configurational space is three-dimensional and reducible we present the complete list of the systems admiting higher…
We consider the problem of extremizing the tension for BPS strings in D=6 supergravities with different number of supersymmetries. General formulae for fixed scalars and a discussion of degenerate directions is given. Quantized moduli,…
In type II string theories, we examine intersecting brane constructions containing brane-antibrane pairs suspended between 5-branes, and more general non-BPS constructions. The tree-level spectra are obtained in each case. We identify…
We show how one can get solitonic strings in a six-dimensional (2,0) supersymmetric theory by incorporating a nonlinear interaction term. We derive a zero force condition between parallel strings, and compute a metric on a moduli space…
The N = 3 string models are special solutions of the type II perturbative string theories. We present explicit expressions for the helicity supertraces,which count the number of the perturbative BPS multiplets. Assuming the non-perturbative…
We consider heterotic string theories in nine and eight dimensions. We identify the disconnected part of the spacetime gauge group by studying the outer automorphism of the charge lattices. The absence of the global symmetry indicates the…