Noncommutative Solitons: Moduli Spaces, Quantization, Finite Theta Effects and Stability

We find the N-soliton solution at infinite theta, as well as the metric on the moduli space corresponding to spatial displacements of the solitons. We use a perturbative expansion to incorporate the leading 1/theta corrections, and find an effective short range attraction between solitons. We study the stability of various solutions. We discuss the finite theta corrections to scattering, and find metastable orbits. Upon quantization of the two-soliton moduli space, for any finite theta, we find an s-wave bound state.Comment: Second revision: Discussions of translation zero-modes in section 4 and scales in section 5 improved; web addresses of movies changed. First revision: Section 6 is rewritten (thanks to M. Headrick for pointing out a mistake in the original version); some references and acknowledgements added. 21 pages, JHEP style, Hypertex, 1 figure, 3 MPEG's at: http://www.physto.se/~unge/traj1.mpg http://www.physto.se/~unge/traj2.mpg http://www.physto.se/~unge/traj3.mp

Linearizing Generalized Kahler Geometry

The geometry of the target space of an N=(2,2) supersymmetry sigma-model carries a generalized Kahler structure. There always exists a real function, the generalized Kahler potential K, that encodes all the relevant local differential geometry data: the metric, the B-field, etc. Generically this data is given by nonlinear functions of the second derivatives of K. We show that, at least locally, the nonlinearity on any generalized Kahler manifold can be explained as arising from a quotient of a space without this nonlinearity.Comment: 31 pages, some geometrical aspects clarified, typos correcte

New supersymmetric sigma-model duality

We study dualities in off-shell 4D N = 2 supersymmetric sigma-models, using the projective superspace approach. These include (i) duality between the real O(2n) and polar multiplets; and (ii) polar-polar duality. We demonstrate that the dual of any superconformal sigma-model is superconformal. Since N = 2 superconformal sigma-models (for which target spaces are hyperkahler cones) formulated in terms of polar multiplets are naturally associated with Kahler cones (which are target spaces for N = 1 superconformal sigma-models), polar-polar duality generates a transformation between different Kahler cones. In the non-superconformal case, we study implications of polar-polar duality for the sigma-model formulation in terms of N = 1 chiral superfields. In particular, we find the relation between the original hyperkahler potential and its dual. As an application of polar-polar duality, we study self-dual models.Comment: 41 pages; V2: a reference added; V3: published versio

The effect of chemistry and thermal fluctuations on charge injection barriers at aluminum/polyolefin interfaces

Charge injection at metal/polymer interfaces is a critical process in many technological devices, including high voltage capacitors and cables in which polyolefin materials, such as polyethylene (PE) and polypropylene (PP), are often used as insulation materials. We use simulations based on density-functional theory to study charge injection at aluminum/PE and aluminum/PP interfaces. Specifically, we investigate the influence of incorporating a variety of polar chemical impurities at the PE and PP chain ends on electron and hole injection barriers. Crucially, we account for the effect of thermal disorder by considering ensembles of thousands of interface structures obtained from ab initio molecular dynamics trajectories at 373 K. We show that the mean injection barrier can change by up to 1.1 eV for Al/PE and 0.6 eV for Al/PP, as compared to the pristine case, depending on which chemical impurity is introduced. We also show that the spread of injection barriers from thermal fluctuations also depends strongly on the chemistry of the impurity. The observed trends can be understood with a simple model based on thermal fluctuations of the dipole moment density associated with the chemical impurity at the interface. We further verify this model by considering larger interface models with lower impurity densities. Our results demonstrate that small chemical modifications, which may arise from oxidation, for example, have a significant influence on charge injection barriers in metal/polyolefin interfaces

Effective K\"ahler Potentials

We compute the $1$-loop effective K\"ahler potential in the most general renormalizable $N=1$ $d=4$ supersymmetric quantum field theory.Comment: 11 pages, Late

Euclidean Supersymmetry, Twisting and Topological Sigma Models

We discuss two dimensional N-extended supersymmetry in Euclidean signature and its R-symmetry. For N=2, the R-symmetry is SO(2)\times SO(1,1), so that only an A-twist is possible. To formulate a B-twist, or to construct Euclidean N=2 models with H-flux so that the target geometry is generalised Kahler, it is necessary to work with a complexification of the sigma models. These issues are related to the obstructions to the existence of non-trivial twisted chiral superfields in Euclidean superspace.Comment: 8 page