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.
115177586
On higher rank coisotropic A-branes
Abstract This article is devoted to a world sheet analysis of A -type D -branes in N = ( 2 , 2 ) supersymmetric non-linear sigma models. In addition to the familiar Lagrangian submanifolds with flat connection we reproduce the rank one A -branes of Kapustin and Orlov, which are supported on coisotropic submanifolds. The main focus is however on gauge fields of higher rank and on tachyon profiles on brane–antibrane pairs. This will lead to the notion of a complex of coisotropic A -branes. A particular role is played by the noncommutative geometry on the brane world volume. It ensures that brane–antibrane pairs localize again on coisotropic submanifolds.
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.
17709889
Cyclicity of non-associative products on D-branes
The non-commutative geometry of deformation quantization appears in string theory through the effect of a B-field background on the dynamics of D-branes in the topological limit. For arbitrary backgrounds, associativity of the star product is lost, but only cyclicity is necessary for a description of the effective action in terms of a generalized product. In previous work we showed that this property indeed emerges for a non-associative product that we extracted from open string amplitudes in curved background fields. In the present note we extend our investigation through second order in a complete derivative expansion. We establish cyclicity with respect to the Born-Infeld measure and find a logarithmic correction that modifies the Kontsevich formula in an arbitrary background satisfying the generalized Maxwell equation. This equation is the physical equivalent of a divergence-free Θ, which is required for cyclicity already in the associative case.
16254267
Localization and traces in open-closed topological Landau-Ginzburg models
We reconsider the issue of localization in open-closed B-twisted Lan- dau-Ginzburg models with arbitrary Calabi-Yau target. Through careful analsysis of zero-mode reduction, we show that the closed model allows for a one-parameter fam- ily of localization pictures, which generalize the standard residue representation. The parameter λ which indexes these pictures measures the area of worldsheets with S 2 topology, with the residue representation obtained in the limit of small area. In the boundary sector, we find a double family of such pictures, depending on parameters λ andwhich measure the area and boundary length of worldsheets with disk topology. We show that setting � = 0 and varying λ interpolates between the localization picture of the B-model with a noncompact target space and a certain residue representation proposed recently. This gives a complete derivation of the boundary residue formula, starting from the explicit construction of the boundary coupling. We also show that the various localization pictures are related by a semigroup of homotopy equivalences.
117848574
Ablated plasma flow from planar targets
The experimentally observed flow of plasma ablated by a laser from a planar target resembles the nozzle flow of fluid from a circular orifice. This has implications for experimental simulations of spherical laser fusion pellets using planar targets and affects far field ion measurements in planar geometry experiments.
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)