Supersymmetric Reflection Matrices

We briefly review the general structure of integrable particle theories in 1+1 dimensions having N=1 supersymmetry. Examples are specific perturbed superconformal field theories (of Yang-Lee type) and the N=1 supersymmetric sine-Gordon theory. We comment on the modifications that are required when the N=1 supersymmetry algebra contains non-trivial topological charges.Comment: 7 pages, Revtex, 2 figures, talk given at the International Seminar on Supersymmetry and Quantum Field Theory, dedicated to the memory of D.V.Volkov, Kharkov (Ukraine), January 5-7, 199

Atomic scale lattice distortions and domain wall profiles

We present an atomic scale theory of lattice distortions using strain related variables and their constraint equations. Our approach connects constrained {\it atomic length} scale variations to {\it continuum} elasticity and describes elasticity at several length scales. We apply the approach to a two-dimensional square lattice with a monatomic basis, and find the elastic deformations and hierarchical atomic relaxations in the vicinity of a domain wall between two different homogeneous strain states. We clarify the microscopic origin of gradient terms, some of which are included phenomenologically in Ginzburg-Landau theory, by showing that they are anisotropic.Comment: 6 figure

QUIT-for-TAT and the Endogenous Structure of Cooperation in Voluntary Dilemmas

The ability to select and reject partners creates a powerful means of supporting cooperation when a common set of actors faces repeated possibilities for playing the prisoner’s dilemmas with each other, a common situation that we refer to as a voluntary dilemma. The cooperative quit-for-tat (QFT) strategy that maintains all relationships with mutually cooperative partners but quits any relationship after a defection can maintain cooperation in voluntary dilemmas by joining together and excluding nasty and exploitative strategies. We develop the implications of the QFT model for the dynamics and structure of mutual cooperation, and test these implications in an experimental voluntary dilemma. The results confirm that the simple QFT model accounts for observed dynamics and structure of cooperative relationships, and that high-scoring subjects follow strategies that resemble QFT. We discuss the relative importance of niceness, forgiveness, and optimistic search in accounting for the success of QFT strategies, and note that the observed clustering of cooperators in this experimental setting is an artifact rather than a necessary support for cooperation

Spin-Coupled Local Distortions in Multiferroic Hexagonal HoMnO3

Local structural measurements have been performed on hexagonal HoMnO3 in order to ascertain the specific changes in bond distances which accompany magnetic ordering transitions. The transition from paramagnetic to the antiferromagetic (noncollinear) phase near ~70 K is dominated by changes in the a-b plane Mn-Mn bond distances. The spin rotation transition near ~40 K involves both Mn-Mn and nearest neighbor Ho-Mn interactions while the low temperature transition below 10 K involves all interactions, Mn-Mn, Ho-Mn (nearest and next nearest) and Ho-Ho correlations. These changes in bond distances reveal strong spin-lattice coupling. The similarity in magnitude of the change in J(Mn-Mn) and J(Ho-Mn) enhances the system frustration. The structural changes are interpreted in terms of a model of competing spin order and local structural distortions. Density functional calculations are used to estimate the energies associated with ionic displacements. The calculations also reveal asymmetric polarization of the charge density of Ho, O3 and O4 sites along the z-axis in the ferroelectric phase. This polarization facilitates coupling between Ho atoms on neighboring planes normal to the z-axis.Comment: 8 figure

ZZ-Branes of N=2 Super-Liouville Theory

We study conformal boundary conditions and corresponding one-point functions of the N=2 super-Liouville theory using both conformal and modular bootstrap methods. We have found both continuous (`FZZT-branes') and discrete (`ZZ-branes') boundary conditions. In particular, we identify two different types of the discrete ZZ-brane solutions, which are associated with degenerate fields of the N=2 super-Liouville theory.Comment: 26 page

Meta-Stable Brane Configurations with Seven NS5-Branes

We present the intersecting brane configurations consisting of NS-branes, D4-branes(and anti D4-branes) and O6-plane, of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua in four dimensional N=1 supersymmetric SU(N_c) x SU(N_c') x SU(N_c'') gauge theory with a symmetric tensor field, a conjugate symmetric tensor field and bifundamental fields. We also describe the intersecting brane configurations of type IIA string theory corresponding to the nonsupersymmetric meta-stable vacua in the above gauge theory with an antisymmetric tensor field, a conjugate symmetric tensor field, eight fundamental flavors and bifundamentals. These brane configurations consist of NS-branes, D4-branes(and anti D4-branes), D6-branes and O6-planes.Comment: 34pp, 9 figures; Improved the draft and added some footnotes; Figure 1, footnote 7 and captions of Figures 7,8,9 added or improved and to appear in CQ