Muneto Nitta

Supersymmetric nonlinear sigma models as gauge theories

Supersymmetric nonlinear sigma models are obtained from linear sigma models by imposing supersymmetric constraints. If we introduce auxiliary chiral and vector superfields, these constraints can be expressed by D-terms and F-terms depending on the target manifolds. Auxiliary vector superfields appear as gauge fields without kinetic terms. If there are no D-term constraints, the target manifolds are always non-compact manifolds. When all the degrees of freedom in these non-compact directions are eliminated by gauge symmetries, the target manifold becomes compact. All supersymmetric nonlinear sigma models, whose target manifolds are the hermitian symmetric spaces, are successfully formulated as gauge theories.

Bogomol’nyi-Prasad-Sommerfield walls and junctions in supersymmetric nonlinear sigma models

BPS walls and junctions are studied in N = 1 SUSY nonlinear sigma models in four spacetime dimensions. New BPS junction solutions connecting N discrete vacua are found for nonlinear sigma models with several chiral scalar superfields. A nonlinear sigma model with a single chiral scalar superfield is also found which has a moduli space of the topology of S and admits BPS walls and junctions connecting arbitrary points in moduli space. SUSY condition in nonlinear sigma models are classified either as stationary points of superpotential or singularities of the Kähler metric in field space. The total number of SUSY vacua is invariant under holomorphic field redefinitions if we count “runaway vacua” also.

Ricci flat Kahler manifolds from supersymmetric gauge theories

Abstract Using techniques of supersymmetric gauge theories, we present the Ricci-flat metrics on non-compact Kahler manifolds whose conical singularity is repaired by the Hermitian symmetric space. These manifolds can be identified as the complex line bundles over the Hermitian symmetric spaces. Each of the metrics contains a resolution parameter which controls the size of these base manifolds, and the conical singularity appears when the parameter vanishes.

MODULI SPACE OF GLOBAL SYMMETRY IN N=1 SUPERSYMMETRIC THEORIES AND THE QUASI-NAMBU–GOLDSTONE BOSONS

We derive the moduli space of the global symmetry in N=1 supersymmetric theories. We show that, at the generic points, it coincides with the space of quasi-Nambu–Goldstone (QNG) bosons, which appear besides the ordinary Nambu–Goldstone (NG) bosons when the global symmetry G breaks down spontaneously to its subgroup H with preservation of N=1 supersymmetry. At the singular points, most of the NG bosons change to QNG bosons and the unbroken global symmetry is enhanced. The G orbits parametrized by the NG bosons are the fiber at the moduli space and the singular points correspond to the point where the H orbit (in the G orbit) shrinks. We also show that the low energy effective Lagrangian is the arbitrary function of the moduli parameters.

Supersymmetric Extension of the Non-Abelian Scalar-Tensor Duality

The field theory dual to the Freedman-Townsend model of a non-Abelian anti-symmetric tensor field is a nonlinear sigma model on the group manifold G. This can be extended to the duality between the Freedman-Townsend model coupled to Yang-Mills fields and a nonlinear sigma model on a coset space G/H. We present the supersymmetric extension of this duality and find that the target space of this nonlinear sigma model is a complex coset space, G C /H C .

Supersymmetric nonlinear sigma models on Ricci-flat Kähler manifolds with O(N) symmetry

Abstract We propose a class of N =2 supersymmetric nonlinear sigma models on the Ricci-flat Kahler manifolds with O( N ) symmetry.

Quantum Equivalence of Auxiliary Field Methods in Supersymmetric Theories

Quantumcorrections to Legendre transform ations are shown to cancel to all orders in supersymmetric theories in path integral formalism. Using this result, Lagrangians for auxiliary fields are generalized to non-quadratic forms. In supersymmetric effective nonlinear Lagrangians, the arbitrariness due to the existence of quasi Nambu-Goldstone bosons is shown to disappear when local auxiliary gauge fields are introduced.

A Note on Conifolds

Abstract We present the Ricci-flat metric and its Kahler potential on the conifold with the O ( N ) isometry, whose conical singularity is repaired by the complex quadric surface Q N −2 = SO ( N )/ SO ( N −2)× U (1).

Neutral bions in the CPN-1 model for resurgence

Classical configurations in the CP^{N-1} model on R^1 x S^1 is studied with twisted boundary conditions. Starting from fractional instantons with the Z_N twisted boundary conditions, we review briefly the relevance of our study to resurgence phenomenon in field theory. We consider primarily configurations composed of multiple fractional instantons, called neutral bions, which are identified as perturbative infrared renormalons. We construct an explicit ansatz corresponding to topologically trivial configurations containing one fractional instanton (nu=1/N) and one fractional anti-instanton (nu=-1/N), which is guaranteed to become a solution of field equations asymptotically for large separations. The attractive interactions between the instanton constituents from small to large separations are found to be consistent with the standard separated-instanton calculus. Our results suggest that the ansatz enables us to study bions and the related physics for a wide range of separations. This talk is mainly based on our recent work published in JHEP 1406, 164 (2014) [arXiv:1404.7225 [hep-th]].

Neutral bions in the

Classical configurations in the CP^{N-1} model on R^1 x S^1 is studied with twisted boundary conditions. Starting from fractional instantons with the Z_N twisted boundary conditions, we review briefly the relevance of our study to resurgence phenomenon in field theory. We consider primarily configurations composed of multiple fractional instantons, called neutral bions, which are identified as perturbative infrared renormalons. We construct an explicit ansatz corresponding to topologically trivial configurations containing one fractional instanton (nu=1/N) and one fractional anti-instanton (nu=-1/N), which is guaranteed to become a solution of field equations asymptotically for large separations. The attractive interactions between the instanton constituents from small to large separations are found to be consistent with the standard separated-instanton calculus. Our results suggest that the ansatz enables us to study bions and the related physics for a wide range of separations. This talk is mainly based on our recent work published in JHEP 1406, 164 (2014) [arXiv:1404.7225 [hep-th]].