N=2 Super-Yang-Mills Theory from a Chern-Simons Action

We present a Chern-Simons action for N=2 Super-Yang-Mills theory (SYM) in 'full' N=2 superspace (hyperspace) augmented by coordinates of the internal SU(2) group and show that this action can be reduced to the usual SYM action in the Harmonic hyperspace. We also discover that the 'choice' of Harmonic hyperspace is not unique and under suitable conditions, further reduction to the well-known Projective hyperspace is possible.Comment: 1+8+1 pages, 1 figur

Superconformal spaces and implications for superstrings

We clarify some properties of projective superspace by using a manifestly superconformal notation. In particular, we analyze the N=2 scalar multiplet in detail, including its action, and the propagator and its super-Schwinger parameters. The internal symmetry is taken to be noncompact (after Wick rotation), allowing boundary conditions that preserve it off shell. Generalization to N=4 suggests the coset superspace PSU(2,2|4)/OSp(4|4) for the AdS/CFT superstring.Comment: 19 pages, no figures; v2: fixed sign, added note & reference; v3: added note & references, version to appear in Physical Review

Harmonic Twistor Formalism and Transgression on Hyperk\"ahler manifolds

In this paper we continue our study of the fourth order transgression on hyper\"ahler manifolds introduced in the previous paper. We give a local construction for the fourth-order transgression of the Chern character form of an arbitrary vector bundle supplied with a self-dual connection on a four dimensional hyperk\"ahler manifold. The construction is based on the harmonic twistor formalism. Remarkably, the resulted expression for the fourth order transgression is given in terms of the determinant of the $\bar{\partial}$-operator defined on fibers of the twistor fibration.Comment: 10pp., Late

Supersymmetric sigma models and the 't Hooft instantons

Witten's linear sigma model for ADHM instantons possesses a natural $(0,4)$ supersymmetry. We study generalizations of the infrared limit of the model that are invariant under $(4,4)$ supersymmetry. In the case of four space-time dimensions a background with a conformally flat metric and torsion is required. The geometry is specified by a single real scalar function satisfying Laplace's equation. It gives rise to 't Hooft instantons for the gauge group $SU(2)$, instead of the general ADHM instantons for an $SO(n)$ gauge group in the case $(0,4)$.Comment: 11 pages, Latex fil

Covariant Harmonic Supergraphity for N = 2 Super Yang--Mills Theories

We review the background field method for general N = 2 super Yang-Mills theories formulated in the N = 2 harmonic superspace. The covariant harmonic supergraph technique is then applied to rigorously prove the N=2 non-renormalization theorem as well as to compute the holomorphic low-energy action for the N = 2 SU(2) pure super Yang-Mills theory and the leading non-holomorphic low-energy correction for N = 4 SU(2) super Yang-Mills theory.Comment: 17 pages, LAMUPHYS LaTeX, no figures; based on talks given by I. Buchbinder and S. Kuzenko at the International Seminar ``Supersymmetries and Quantum Symmetries'', July 1997, Dubna; to be published in the proceeding

N=4, 3D Supersymmetric Quantum Mechanics in Non-Abelian Monopole Background

Using the harmonic superspace approach, we construct the three-dimensional N=4 supersymmetric quantum mechanics of the supermultiplet (3,4,1) coupled to an external SU(2) gauge field. The off-shell N=4 supersymmetry requires the gauge field to be a static form of the 't Hooft ansatz for the 4D self-dual SU(2) gauge fields, that is a particular solution of Bogomolny equations for BPS monopoles. We present the explicit form of the corresponding superfield and component actions, as well as of the quantum Hamiltonian and N=4 supercharges. The latter can be used to describe a more general N=4 mechanics system, with an arbitrary BPS monopole background and on-shell N=4 supersymmetry. The essential feature of our construction is the use of semi-dynamical spin (4,4,0) multiplet with the Wess-Zumino type action.Comment: 16 pages, reference added, published versio

Manifest supersymmetry and the ADHM construction of instantons

We present the (0,4) superspace version of Witten's sigma model construction for ADHM instantons. We use the harmonic superspace formalism, which exploits the three complex structures common to both (0,4) supersymmetry and self-dual Yang-Mills theory. A novel feature of the superspace formulation is the manifest interplay between the ADHM construction and its twistor counterpart.Comment: minor changes in the text; also an Appendix on off-shell structure of chiral fermion multiplets in (0,4) supersymmetry, and references adde

Relating harmonic and projective descriptions of N=2 nonlinear sigma models

Recent papers have established the relationship between projective superspace and a complexified version of harmonic superspace. We extend this construction to the case of general nonlinear sigma models in both frameworks. Using an analogy with Hamiltonian mechanics, we demonstrate how the Hamiltonian structure of the harmonic action and the symplectic structure of the projective action naturally arise from a single unifying action on a complexified version of harmonic superspace. This links the harmonic and projective descriptions of hyperkahler target spaces. For the two examples of Taub-NUT and Eguchi-Hanson, we show how to derive the projective superspace solutions from the harmonic superspace solutions.Comment: 25 pages; v3: typo fixed in eq (1.36

Worldline Superfield Actions for N=2 Superparticles

We propose doubly supersymmetric actions in terms of n=2(D-2) worldline superfields for N=2 superparticles in D=3,4 and Type IIA D=6 superspaces. These actions are obtained by dimensional reduction of superfield actions for N=1 superparticles in D=4,6 and 10, respectively. We show that in all these models geometrodynamical constraints on target superspace coordinates do not put the theory on the mass shell, so the actions constructed consistently describe the dynamics of the corresponding N=2 superparticles. We also find that in contrast to the IIA D=6 superparticle a chiral IIB D=6 superparticle, which is not obtainable by dimensional reduction from N=1, D=10, is described by superfield constraints which produce dynamical equations. This implies that for the IIB D=6 superparticle the doubly supersymmetric action does not exist in the conventional form.Comment: Latex, 20 pp. Minor corrections, acknowledgements adde

Quantization of entropy in a quasi-two-dimensional electron gas

We demonstrate that the partial entropy of a two-dimensional electron gas (2DEG) exhibits quantized peaks at resonances between the chemical potential and electron levels of size quantization. In the limit of no scattering, the peaks depend only on the subband quantization number and are independent on material parameters, shape of the confining potential, electron effective mass and temperature. The quantization of partial entropy is a signature of a topological phase transition in a 2DEG. In the presence of stationary disorder, the magnitude of peaks decreases. Its deviation from the quantized values is a direct measure of the disorder induced smearing of the electronic density of states.Comment: 4 pages, 2 figure