Notes on discrete torsion in orientifolds (2009)
In this short note we discuss discrete torsion in orientifolds. In particular, we apply the physical understanding of discrete torsion worked out several years ago, as group actions on B fields, to...
Elliptic genera of Landau-Ginzburg models over nontrivial spaces (2009)
In this paper, we discuss elliptic genera of (2,2) and (0,2) supersymmetric Landau-Ginzburg models over nontrivial spaces, i.e., nonlinear sigma models on nontrivial noncompact manifolds with...
Naval Sea Systems Command Military Sealift Command (2008)
Mr. Thomas, H. Peirce, Mr. Edwin, B. Schimler, Dr. Donald Liu, Mr. Robert, ...
This document has been approved for public release and salq its distribution is unlimited SHIP STRUCTURE COMMITTEE SHIP STRUCTUR=OMMITTEE The SHIP STRUCTURE COMMITTEE is constituted to prosecute a...
Non-birational twisted derived equivalences in abelian GLSMs (2007)
Caldararu, A., Distler, J., Hellerman, S., Pantev, T., Sharpe, E.
In this paper we discuss some examples of abelian gauged linear sigma models realizing twisted derived equivalences between non-birational spaces, and realizing geometries in novel fashions. Examples...
GLSM's for partial flag manifolds (2007)
In this paper we outline some aspects of nonabelian gauged linear sigma models. First, we review how partial flag manifolds (generalizing Grassmannians) are described physically by nonabelian gauged...
Heterotic compactifications with principal bundles for general groups and general levels (2007)
We examine to what extent heterotic string worldsheets can describe arbitrary E8xE8 gauge fields. The traditional construction of heterotic strings builds each E8 via a Spin(16)/Z2 subgroup,...
Derived categories and stacks in physics (2006)
In this note we review how both derived categories and stacks enter physics. The physical realization of each has many formal similarities. For example, in both cases, equivalences are realized via...
Cluster decomposition, T-duality, and gerby CFT's (2006)
Hellerman, S., Henriques, A., Pantev, T., Sharpe, E., Ando, M.
In this paper we study CFT's associated to gerbes. These theories suffer from a lack of cluster decomposition, but this problem can be resolved: the CFT's are the same as CFT's for disconnected...
Notes on certain other (0,2) correlation functions (2006)
In this paper we shall describe some correlation function computations in perturbative heterotic strings that generalize B model computations. On the (2,2) locus, correlation functions in the B model...
Notes on correlation functions in (0,2) theories (2005)
In this note we shall review recent work on generalizing rational curve counting to perturbative heterotic theories.
GLSM's for gerbes (and other toric stacks) (2005)
In this paper we will discuss gauged linear sigma model descriptions of toric stacks. Toric stacks have a simple description in terms of (symplectic, GIT) ${\bf C}^{\times}$ quotients of homogeneous...
String compactifications on Calabi-Yau stacks (2005)
In this paper we study string compactifications on Deligne-Mumford stacks. The basic idea is that all such stacks have presentations to which one can associate gauged sigma models, where the group...
Notes on gauging noneffective group actions (2005)
In this paper we study sigma models in which a noneffective group action has been gauged. Such gauged sigma models turn out to be different from gauged sigma models in which an effectively-acting...
Evaluation of the new social work degree qualification in England : wider perspectives (2005)
Manthorpe, J., Moriarty, J., Hussein, S., Huxley, P., Evans, S., Orme, J., ...
The evaluation of the new social work degree qualification in England : wider perspectives (2005)
Manthorpe, J., Moriarty, J., Hussein, S., Huxley, P., Evans, S., Orme, J., ...
Notes on Certain (0,2) Correlation Functions (2004)
In this paper we shall describe some correlation function computations in perturbative heterotic strings that, for example, in certain circumstances can lend themselves to a heterotic generalization...
Mathematical Aspects of D-branes (2004)
In these notes we review recent work on describing D-branes with nonzero Higgs vevs in terms of sheaves, which gives a physical on-shell D-brane interpretation to more sheaves than previously...
Spectra of D-branes with Higgs vevs (2003)
Donagi, R., Katz, S., Sharpe, E.
In this paper we continue previous work on counting open string states between D-branes by considering open strings between D-branes with nonzero Higgs vevs, and in particular, nilpotent Higgs vevs,...
Lectures on D-branes and Sheaves (2003)
These notes are a writeup of lectures given at the twelfth Oporto meeting on ``Geometry, Topology, and Physics,'' and at the Adelaide workshop ``Strings and Mathematics 2003,'' primarily geared...
The Taming of Closed Time-like Curves (2003)
Biswas, R, Keski-Vakkuri, E, Leigh, R G, Nowling, S, Sharpe, E
We formulate QFT on a $R^{1,d}/Z_2$ orbifold, in a manner which is invariant under the $Z_2$ time and space reversal. This is a background with closed time-like curves. It is also relevant for the...
Discrete Torsion and Shift Orbifolds (2003)
In this paper we make two observations related to discrete torsion. First, we observe that an old obscure degree of freedom (momentum/translation shifts) in (symmetric) string orbifolds is related to...
D-branes, B fields, and Ext groups (2003)
Caldararu, A., Katz, S., Sharpe, E.
In this paper we extend previous work on calculating massless boundary Ramond sector spectra of open strings to include cases with nonzero flat B fields. In such cases, D-branes are no longer...
D-branes, orbifolds, and Ext groups (2002)
Katz, S., Pantev, T., Sharpe, E.
In this note we extend previous work on massless Ramond spectra of open strings connecting D-branes wrapped on complex manifolds, to consider D-branes wrapped on smooth complex orbifolds. Using...
Kahler Cone Substructure (1998)
To define a consistent perturbative geometric heterotic compactification the bundle is required to satisfy a subtle constraint known as ``stability,'' which depends upon the Kahler form. This...
Notes on Bundles on K3s (1998)
In this technical note we describe a new (to the physics literature) construction of bundles on Calabi-Yaus. We primarily study this construction in the special case of K3 surfaces, for which...
In this article we review some recent developments in heterotic compactifications. In particular we review an ``inherently toric'' description of certain sheaves, called equivariant sheaves, that has...
Conjectures on (0,2) Mirror Symmetry (1998)
In this paper we conjecture a reformulation of the monomial-divisor mirror map for (2,2) mirror symmetry, valid at a boundary of the moduli space, that is easily extended to also include tangent...
Sheaves on Toric Varieties for Physics (1997)
In this paper we give an inherently toric description of a special class of sheaves (known as equivariant sheaves) over toric varieties, due in part to A. A. Klyachko. We apply this technology to...
Notes on Heterotic Compactifications (1997)
In this technical note we describe a pair of results on heterotic compactifications. First, we give an example demonstrating that the usual statement of the anomaly-freedom constraint for...
Extremal Transitions in Heterotic String Theory (1997)
In this paper we study extremal transitions between heterotic string compactifications, i.e., transitions between pairs (M,V) where M is a Calabi-Yau manifold and V a gauge bundle. Bundle transitions...
Boundary Superpotentials (1996)
In this paper we work out explicit lagrangians describing superpotential coupling to the boundary of a 5D orientifold, as relevant to a number of quasi-realistic models of nature. We also make a...