8069802
Star products from open strings in curved backgrounds
We define a non-commutative product for arbitrary gauge and B-field backgrounds in terms of correlation functions of open strings. While off-shell correlations are, of course, not conformally invariant, it turns out that, at least to first derivative order, our product has the trace property and is associative up to surface terms if the background fields are put on-shell. No on-shell conditions for the inserted functions are needed, but it is essential to include the full contribution of the Born-Infeld measure. We work with a derivative expansion and avoid any topological limit, which would effectively constrain H.
118748347
Quantum A-infinity Structures for Open-Closed Topological Strings
We study factorizations of topological string amplitudes on higher genus Riemann surfaces with multiple boundary components and find quantum A-infinity relations, which are the higher genus analog of the (classical) A-infinity relations on the disk. For topological strings with $\hat c=3$ the quantum A-infinity relations are trivially satisfied on a single D-brane, whereas in a multiple D-brane configuration they may be used to compute open higher genus amplitudes recursively from disk amplitudes. This can be helpful in open Gromov--Witten theory in order to determine open string higher genus instanton corrections. Finally, we find that the quantum A-infinity structure cannot quite be recast into a quantum master equation on the open string moduli space.
117052654
Phases Of N=2 Theories In 1+1 Dimensions With Boundary
We study B-type D-branes in linear sigma models with Abelian gauge groups. The most important finding is the grade restriction rule. It classifies representations of the gauge group on the Chan-Paton factor, which can be used to define a family of D-branes over a region of the Kahler moduli space that connects special points of different character. As an application, we find a precise, transparent relation between D-branes in various geometric phases as well as free orbifold and Landau-Ginzburg points. The result reproduces and unifies many of the earlier mathematical results on equivalences of D-brane categories, including the McKay correspondence and Orlov's construction.
15499337
Orientifolds and D-branes in $N=2$ gauged linear sigma models
We study parity symmetries and boundary conditions in the framework of gauged linear sigma models. This allows us to investigate the Kaehler moduli dependence of the physics of D-branes as well as orientifolds in a Calabi-Yau compactification. We first determine the parity action on D-branes and define the set of orientifold-invariant D-branes in the linear sigma model. Using probe branes on top of orientifold planes, we derive a general formula for the type (SO vs Sp) of orientifold planes. As applications, we show how compactifications with and without vector structure arise naturally at different real slices of the Kaehler moduli space of a Calabi-Yau compactification. We observe that orientifold planes located at certain components of the fixed point locus can change type when navigating through the stringy regime.
85352748
Orientifolds of N = 2 gauged linear sigma models
We study B-type parities in the framework of the linear sigma model. Geometrically, B-type parities correspond to parity reversal combined with a holomorphic involution. The linear sigma model provides a framework to investigate such orientifolds away from the geometric regime.
137638473
Preheat Studies on Laser Ablatively-Accelerated Foils.
Abstract : The achievement of laser fusion requires the inward acceleration of pellet shells to very high velocity without excessive preheat of the pellet fuel. In a study of ablatively accelerated thin planar Al foils, we have determined the complete time history of the rear surface temperatures, and evaluated the energy transport mechanisms that contribute to the heating. Extrapolation to larger, reactor-sized pellets indicates that preheat is minimal at low laser irradiances. (Author)