Beyond the static: Exploring nonequilibrium string theory via noncrictical M-theory and heterotic E8 tachyon condensation.

by Cynthia Anne Keeler

Initially, studies in string theory concentrated on static spacetime solutions in perturbative regimes. More recent work has expanded the understanding of dynamic spacetime solutions and solutions which do not lie in weakly coupled regimes of the conjectured M-theory. We further examine such solutions through two means: a proposal for noncritical M-theory, and a study of closed string tachyon condensation via a new worldsheet gauge.;We define noncritical M-theory via a double-scaled nonrelativistic Fermi liquid in 2 + 1 dimensions. We find the Type 0A and Type 0B string theories within a class of solutions with good spacetime descriptions. Such solutions have hydrodynamic Fermi surfaces, and also include time-dependent solutions which change dimension or move from Type 0A to Type 0B. Additionally we discover the natural M-theory vacuum, |M〉, and find its exact vacuum energy which suggests a duality to the Debye phonon model.;We analyze this solution |M〉, at finite temperature and at high energy. At large finite temperature, or small Euclidean compactification radius R, the state matches a different M-theory solution at large R. The effective loop coupling scales as 1/R 3. We show that |M〉 at finite temperature 1/R is dual to the topological A-model on the resolved conifold with coupling constant proportional to R.;In the high energy or alpha' ---> infinity limit, we find that the |M〉 state is dual to a massless fermion propagating in AdS 2 x S1 spacetime. This spacetime solves a higher-spin extension of SO(3, 2) conformal Cliern-Simons gravity coupled to a massless Dirac field. The higher-spin extension makes this coupling consistent, and reproduces the symmetry group of the free fermion description of noncritical M-theory.;In our study of closed string tachyon condensation, we first describe a nonsupersymmetric embedding of E8 boundaries in heterotic M-theory which has a nonperturbative instanton instability. We claim this instability becomes the tachyon of the E 8 heterotic string in the perturbative regime. We choose a novel gauge on the worldsheet, in which the worldsheet gravitino eats the goldstino to become propagating at late times. Conformal, but not superconformal, invariance is maintained throughout. Thus we show alternatives to the usual superconformal gauge can provide new insights into nonequilibrium string states.

194 pages, NOOKstudy eTextbook