arXiv subjects
Publications and source records attributed to Hitoshi Nishino.
We present mechanisms for generating conical singularities both in three and four-dimensions in the systems with copies of scalar or chiral multiplets coupled to $N=2$ or $N=1$ supergravity. Our mechanisms are useful for supersymmetry breaking, maintaining the zero cosmological constants in three and four-dimensions. A strong coupling duality connecting these two dimensionalities is also studied.
We present interesting relationship between what are called stationary axisymmetric black hole solutions for the vacuum Einstein equations in the ordinary four-dimensions and exact solutions for self-dual Yang-Mills fields in flat $2+2$ dimensions which are nothing but the consistent backgrounds for $~N=2$~ open superstring. We show that any stationary axisymmetric black hole solution for the former automatically provides an exact solution for the latter. We also give a nice relation between the physical parameters of black holes and an invariant integral analogous to instanton charges for such a self-dual Yang-Mills solution. This result indicates that any general black hole solution in the usual four-dimensions can be the background of $~N=2$~ superstring at the same time. We also give an interesting embedding of stationary axisymmetric solutions into the background of $~N=2$~ closed superstring. Finally we show some indication that the Kerr solution with naked singularity (for $a > m$) is nothing else than the gravitational field generated by a closed string.
We present an alternative $N=(4,0)$ superstring theory, with field content different from that of previously-known $N=(4,0)$ superstring theories. This theory is presented as a non-linear $\s$-model on the coset $SU(n,1) / SU(n) \otimes U(1)$ as the target space-time with torsion, which is coupled to $N=(4,0)$ world-sheet superconformal gravity. Our result indicates that the target space-time for $N=4$ superstring theory does not necessarily have to be a hyper-Kähler or quaternionic Kähler manifold.
We consider the effect of curved two-dimensional space-time on Witten's $N=2$ supersymmetric sigma models interpolating Calabi-Yau hypersurfaces to Landau-Ginzburg models. In order for the former models to have significant connection to superstring theory, only the $N=(1,1)$ or $N=(1,0)$ part of the total $N=(2,2)$ world-sheet supersymmetry is made local. Even though there arises an additional minimizing condition due to a scalar auxiliary field in the supergravity multiplet on curved two-dimensions, the essential feature of the sigma-model relating Calabi-Yau and Landau-Ginzburg models will be maintained. This indicates the validity of these sigma models formulated on curved two-dimensions or curved world-sheets. As a by-product, the coupling of $N=(2,2)$ vector multiplets to other multiplets with $N=(1,1)$ local supersymmetry is developed.
Abstrct: We show that the action of self-dual supersymmetric Yang-Mills theory in four-dimensions, which describes the consistent massless background fields for $~N=2$~ superstring, generates the actions for $~N=1$~ and $~N=2$~ supersymmetric non-Abelian Chern-Simons theories in three-dimensions after appropriate dimensional reductions. Since the latters play important roles for supersymmetric integrable models, this result indicates the fundamental significance of the $~N=2$~ superstring theory controlling (possibly all) supersymmetric integrable models in lower-dimensions.
A mechanism of supersymmetry breaking in two or four-dimensions is given, in which the breaking is related to the Fermat's last theorem. It is shown that supersymmetry is exact at some irrational number points in parameter space, while it is broken at all rational number points except for the origin. Accordingly, supersymmetry is exact {\it almost everywhere}, as well as broken {\it almost everywhere} on the real axis in the parameter space at the same time. This is the first explicit mechanism of supersymmetry breaking with an arbitrarily small change of parameters around any exact supersymmetric model, which is possibly useful for realistically small non-perturbative supersymmetry breakings in superstring model building. As a byproduct, we also give a convenient superpotential for supersymmetry breaking only for irrational number parameters. Our superpotential can be added as a ``hidden'' sector to other useful supersymmetric models.
We show that $N=8$ {\it self-dual} supergravity theory, which is the consistent background for $N=2$ closed superstring theory in $2+2\-$dimensions, can accommodate the recently discovered two-dimensional dilaton gravity black hole solution, {\it via} appropriate dimensional reductions and truncations. Interestingly, the usual dilaton field in this set of solutions emerges from the scalar field in the ${\bf 70}\-$dimensional representation of an intrinsic global $SO(8)$ group. We also give a set of exact solutions, which can be interpreted as the dilaton field on Eguchi-Hanson gravitational instanton background, realized in an $N=1$ self-dual supergravity theory. This suggests that the $N=2$ superstring has a close (even closer) relationship with the two-dimensional black hole solution, which was originally developed in the context of bosonic string and $N=1$ superstring. Our result also provides supporting evidence for the conjecture that the $N=2$ superstring theory is the ``master theory'' of supersymmetric integrable systems in lower-dimensions.
We show that recently formulated four-dimensional self-dual supersymmetric Yang-Mills theory, which is consistent background for open $~N=2$~ superstring, generates two-dimensional $~N=(1,1),~\, N=(1,0) $~ and $~N=(2,0)$~ supersymmetric gauged Wess-Zumino-Novikov-Witten $~\s\-$models on coset manifolds $~G/H$, after appropriate dimensional reductions. This is supporting evidence for the conjecture that the self-dual supersymmetric Yang-Mills theory will generate lower-dimensional supersymmetric integrable models after dimensional reductions.
We give exact solutions for a recently developed ~$N=1$~ locally supersymmetric self-dual gauge theories in $~(2+2)\-$dimensions. We give the exact solutions for an $~SL(2)$~ self-dual Yang-Mills multiplet and what we call ``self-dual tensor multiplet'' on the gravitational instanton background by Eguchi-Hanson. We use a general method to get an $~SL(2)$~ self-dual Yang-Mills solution from any known self-dual gravity solution. Our result is the first example of exact solutions for the coupled system of these $~N=1$~ locally supersymmetric self-dual multiplets in ~$(2+2)\-$dimensions, which is supposed to have strong significance for integrable models in lower-dimensions upon appropriate dimensional reduction or truncation. We also inspect the consistency of our exact solutions as a background for $~N=2$~ superstring coupled to the Wess-Zumino-Witten term in $~\s\-$model formulation.
We study supersymmetry and self-duality in a four-dimensional space-time with the signature (2,2), that we call the Atiyah-Ward space-time. Dirac matrices and spinors, in particular Majorana-Weyl spinors, are investigated in detail. We formulate $ N\ge 1 $ supersymmetric self-dual Yang-Mills theories and self-dual supergravities. An N=1 ``self-dual'' tensor multiplet is constructed and a possible ten-dimensional theory that gives rise to the four-dimensional self-dual supersymmetric theories is found. Instanton solutions are given as the zero modes in the N=2 self-dual Yang-Mills theory. The N=2 superstrings are conjectured to have no possible counter-terms at quantum level to all orders. These self-dual supersymmetric theories are to generate exactly soluble supersymmetric systems in lower dimensions.