Poisson-Lie T-duality and complex geometry in N = 2 superconformal WZNW models

Poisson-Lie T-duality in N = 2 superconformal WZNW models on the real Lie groups is considered. It is shown that Poisson-Lie T-duality is governed by the complexifications of the corresponding real groups endowed with Semenov-Tian-Shansky symplectic forms, i.e. Heisenberg doubles. Complex Heisenberg doubles are used to define on the group manifolds of the N = 2 superconformal WZNW models the natural actions of the isotropic complex subgroups forming the doubles. It is proved that with respect to these actions N = 2 superconformal WZNW models admit Poisson-Lie symmetries. The Poisson-Lie T-duality transformation maps each model onto itself but acts non-trivially on the space of classical solutions.     

TeV-scale leptoquarks from GUTs/string/M-theory unification

The question of a possible existence of the “baroleptons” (leptoquarks) at the TeV energy scale is considered. Leptoquark mass and coupling bounds coming from rare meson decays are briefly reviewed.     

Gravity-wave detectors as probes of extra dimensions

If string theory is correct, then our observable Universe may be a 3-dimensional “brane” embedded in a higher-dimensional spacetime. This theoretical scenario should be tested via the state-of-the-art in gravitational experiments—the current and upcoming gravity-wave detectors. Indeed, the existence of extra dimensions leads to oscillations that leave a spectroscopic signature in the gravity-wave signal from black holes. The detectors that have been designed to confirm Einstein's prediction of gravity waves, can in principle also provide tests and constraints on string theory. Fourth Award in the 2005 Essay Competition of the Gravity Research Foundation. - Ed.     

An apparent paradox in the mechanics of strings

We show with a simple example that cases of incompatibility (first displayed by Signorini) between the nonlinear and the linearized version of the same problem occur also in contact problems.

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Sommario Si mostra con un esempio elementare che casi di incompatibilità alla Signorini tra i risultati dello studio non-lineare e di quello linearizzato di uno stesso problema si presentano anche in problemi di contatto.

     

On a Unified Theory of Generalized Branes Coupled to Gauge Fields,Including the Gravitational and Kalb–Ramond Fields

We investigate a theory in which fundamental objects are branes described in terms of higher grade coordinates encoding both the motion of a brane as a whole, and its volume evolution. We thus formulate a dynamics which generalizes the dynamics of the usual branes. Geometrically, coordinates and associated coordinate frame fields {} extend the notion of geometry from spacetime to that of an enlarged space, called Clifford space or C-space. If we start from four-dimensional spacetime, then the dimension of C-space is 16. The fact that C-space has more than four dimensions suggests that it could serve as a realization of Kaluza-Klein idea. The “extra dimensions” are not just the ordinary extra dimensions, they are related to the volume degrees of freedom, therefore they are physical, and need not be compactified. Gauge fields are due to the metric of Clifford space. It turns out that amongst the latter gauge fields there also exist higher grade, antisymmetric fields of the Kalb–Ramond type, and their non-Abelian generalization. All those fields are naturally coupled to the generalized branes, whose dynamics is given by a generalized Howe–Tucker action in curved C-space.     

The Nambu–Goto theory of closed bosonic strings moving in 1 + 3–dimensional Minkowski space: the quantum algebra of observables

A relevant part of the quantum algebra of observables for the closed bosonic strings moving in 1 + 3–dimensional Minkowski space is presented in the form of generating relations involving still one, as yet undetermined, real free parameter.     

Non-static local string in Brans-Dicke theory

A recent investigation showed that a local gauge string with a phenomenological energy momentum tensor, as prescribed by Vilenkin, is inconsistent in Brans-Dicke theory. In this work it has been shown that such a string is indeed consistent if one introduces time dependences in the metric. A set of solutions of full non-linear Einstein’s equations for the interior region of such a string are presented.     

Strings on a plane

Some features for a model of strings moving in 2+1$2+1$ spacetime dimensions are discussed that suggest applications to the quantum Hall effect. These features include edge-state configurations and anyons.