Heterotic warped Eguchi-Hanson spectra with five-branes and line bundles

We consider heterotic strings on a warped Eguchi-Hanson space with five-brane and line bundle gauge fluxes. The heterotic string admits an exact CFT description in terms of an asymmetrically gauged SU(2)xSL(2,R) WZW model, in a specific double scaling limit in which the blow-up radius and the string scale are sent to zero simultaneously. This allows us to compute the perturbative 6D spectra for these models in two independent fashions: i) Within the supergravity approximation we employ a representation dependent index; ii) In the double scaling limit we determine all marginal vertex operators of the coset CFT. To achieve agreement between the supergravity and the CFT spectra, we conjecture that the untwisted and the twisted CFT states correspond to the same set of hyper multiplets in supergravity. This is in a similar spirit as a conjectured duality between asymptotically linear dilaton CFTs and little string theory living on NS-five-branes. As the five-brane charge is non-vanishing, heterotic (anti-)five-branes have to be added in order to cancel irreducible gauge anomalies. The local spectra can be combined in such a way that supersymmetry is preserved on the compact resolved T^4/Z_2 orbifold by choosing the local gauge fluxes appropriately.Comment: 1+36 pages LaTe

A Lorentz invariant doubled worldsheet theory

We propose a Lorentz invariant version of Tseytlin's doubled worldsheet theory that makes T-duality covariance of the string manifest. This theory can be derived as a gauge fixed version of Buscher's gauging procedure, in which the left-over gauge field component acts as a Lagrange multiplier. This description can naturally account for fractional linear O(D,D) transformations of the metric and b-field. It is capable of describing non-geometric backgrounds; geometric and non-geometric fluxes are encoded in the doubled anti-symmetric tensor field strength.Comment: 4 pages LaTeX, no figures, discussion of path integral quantization include

Torus partition functions and spectra of gauged linear sigma models

Worldsheet (0,2) gauged linear sigma models are often used to study supersymmetric heterotic string compactifications with non-trivial vector bundles. We make use of supersymmetric localization techniques to determine their one-loop partition functions. In particular we derive conditions which ensure that the full partition function is modular invariant and we propose a method to determine the massless and massive target space matter spectrum.Comment: 4 pages LaTeX; v2: important technical issue resolved, most results essentially unchange

Line bundle embeddings for heterotic theories

In heterotic string theories consistency requires the introduction of a non-trivial vector bundle. This bundle breaks the original ten-dimensional gauge groups $\text{E}_8\times\text{E}_8$ or $\text{SO}(32)$ for the supersymmetric heterotic string theories and $\text{SO}(16) \times \text{SO}(16)$ for the non-supersymmetric tachyon-free theory to smaller subgroups. A vast number of MSSM-like models have been constructed up to now, most of which describe the vector bundle as a sum of line bundles. However, there are several different ways of describing these line bundles and their embedding in the ten-dimensional gauge group. We recall and extend these different descriptions and explain how they can be translated into each other.Comment: 29+1 pages, 7 tables, 1 figure, typos corrected, clarifying remarks and references adde