No Arabic abstract
We construct the lattice gauge theory of the group G_N, the semidirect product of the permutation group S_N with U(1)^N, on an arbitrary Riemann surface. This theory describes the branched coverings of a two-dimensional target surface by strings carrying a U(1) gauge field on the world sheet. These are the non-supersymmetric Matrix Strings that arise in the unitary gauge quantization of a generalized two-dimensional Yang-Mills theory. By classifying the irreducible representations of G_N, we give the most general formulation of the lattice gauge theory of G_N, which includes arbitrary branching points on the world sheet and describes the splitting and joining of strings.
We study simple branched coverings of degree d of the 2- and 3- dimensional sphere branched over oriented links. We demonstrate how to use braid charts to develop embeddings of these into $S^k times D^2$ for $k=2,3 when $d=2,3$. This is an initial part of our study and represents the manuscript submitted to the RIMS workshop at Intelligence of Low Dimensional Topology.
We study the equations of black strings in spacetimes of arbitrary dimensions with a negative cosmological constant and construct numerically non uniform black strings solutions. Our results suggest the existence of a localised black hole in asymptotically locally $AdS$ spacetime. We also present evidences for a dependence of the critical dimension on the horizon radius.The critical dimension represents the dimension where the order of the phase transition between uniform and non uniform black string changes. Finally, we argue that both, the regular asymptotically locally $AdS$ solution and $AdS$ black string solutions with a very small horizon radius, present a negative tension. This turns out to be an unexpected feature of the solutions.
It is proposed that a family of Jackiw-Teitelboim supergravites, recently discussed in connection with matrix models by Stanford and Witten, can be given a complete definition, to all orders in the topological expansion and beyond, in terms of a specific combination of minimal string theories. This construction defines non-perturbative physics for the supergravity that is well-defined and stable. The minimal models come from double-scaled complex matrix models and correspond to the cases $(2Gamma{+}1,2)$ in the Altland-Zirnbauer $(boldsymbol{alpha},boldsymbol{beta})$ classification of random matrix ensembles, where $Gamma$ is a parameter. A central role is played by a non-linear `string equation that naturally incorporates $Gamma$, usually taken to be an integer, counting e.g., D-branes in the minimal models. Here, half-integer $Gamma$ also has an interpretation. In fact, $Gamma{=}{pm}frac12$ yields the cases $(0,2)$ and $(2,2)$ that were shown by Stanford and Witten to have very special properties. These features are manifest in this definition because the relevant solutions of the string equation have special properties for $Gamma{=}{pm}frac12$. Additional special features for other half-integer $Gamma$ suggest new surprises in the supergravity models.
Light-cone gauge NSR string theory in noncritical dimensions should correspond to a string theory with a nonstandard longitudinal part. Supersymmetrizing the bosonic case [arXiv:0909.4675], we formulate a superconformal worldsheet theory for the longitudinal variables X^{pm}, psi^{pm}. We show that with the transverse variables and the ghosts combined, it is possible to construct a nilpotent BRST charge.
The Frenet equation governs the extrinsic geometry of a string in three-dimensional ambient space in terms of the curvature and torsion, which are both scalar functions under string reparameterisations. The description engages a local SO(2) gauge symmetry, which emerges from the invariance of the extrinsic string geometry under local frame rotations around the tangent vector. Here we inquire how to construct the most general SO(2) gauge invariant Hamiltonian of strings, in terms of the curvature and torsion. The construction instructs us to introduce a long-range (self-) interaction between strings, which is mediated by a three dimensional bulk gauge field with a Chern-Simons self-interaction. The results support the proposal that fractional statistics should be prevalent in the case of three dimensional string-like configurations.