1,485 research outputs found
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
Harmonicity in N=4 supersymmetry and its quantum anomaly
The holomorphicity property of N=1 superpotentials or of N=2 F-terms
involving vector multiplets is generalized to the case of N=4 1/2-BPS effective
operators defined in harmonic superspace. The resulting harmonicity equations
are shown to control the moduli dependence of the couplings of higher
dimensional operators involving powers of the N=4 Weyl superfield, computed by
N=4 topological amplitudes. These equations can also be derived on the string
side, exhibiting an anomaly from world-sheet boundary contributions that leads
to recursion relations for the non-analytic part of the couplings.Comment: 36 page
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
Supersymmetric sigma models and the 't Hooft instantons
Witten's linear sigma model for ADHM instantons possesses a natural
supersymmetry. We study generalizations of the infrared limit of the model that
are invariant under 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 ,
instead of the general ADHM instantons for an gauge group in the case
.Comment: 11 pages, Latex fil
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
Harmonic space and quaternionic manifolds
We find a principle of harmonic analyticity underlying the quaternionic
(quaternion-K\"ahler) geometry and solve the differential constraints which
define this geometry. To this end the original -dimensional quaternionic
manifold is extended to a bi-harmonic space. The latter includes additional
harmonic coordinates associated with both the tangent local group and
an extra rigid group rotating the complex structures. Then the
constraints can be rewritten as integrability conditions for the existence of
an analytic subspace in the bi-harmonic space and solved in terms of two
unconstrained potentials on the analytic subspace. Geometrically, the
potentials have the meaning of vielbeins associated with the harmonic
coordinates. We also establish a one-to-one correspondence between the
quaternionic spaces and off-shell supersymmetric sigma-models coupled to
supergravity. The general sigma-model Lagrangian when written in
the harmonic superspace is composed of the quaternionic potentials. Coordinates
of the analytic subspace are identified with superfields describing
matter hypermultiplets and a compensating hypermultiplet of supergravity.
As an illustration we present the potentials for the symmetric quaternionic
spaces.Comment: 44 pages, LATEX, JHU-TIPAC-920023, ENSLAPP-L-405-92, MPI-Ph/92-8
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
Gauging N=4 Supersymmetric Mechanics
We argue that off-shell dualities between d=1 supermultiplets with different
sets of physical bosonic components and the same number of fermionic ones are
related to gauging some symmetries in the actions of the supermultiplets with
maximal sets of physical bosons. Our gauging procedure uses off-shell
superfields and so is manifestly supersymmetric. We focus on N=4 supersymmetric
mechanics and show that various actions of the multiplet (3,4,1) amount to some
gauge choices in the gauged superfield actions of the linear or nonlinear
(4,4,0) multiplets. In particular, the conformally invariant (3,4,1)
superpotential is generated by the Fayet-Iliopoulos term of the gauge
superfield. We find a new nonlinear variant of the multiplet (4,4,0), such that
its simplest superfield action produces the most general 4-dim hyper-K\"ahler
metric with one triholomorphic isometry as the bosonic target metric. We also
elaborate on some other instructive examples of N=4 superfield gaugings,
including a non-abelian gauging which relates the free linear (4,4,0) multiplet
to a self-interacting (1,4,3) multiplet.Comment: 32 pages, minor amendments in Sect. 2, version to appear in Nucl.
Phys.
Current induced light emission and light induced current in molecular tunneling junctions
The interaction of metal-molecule-metal junctions with light is considered
within a simple generic model. We show, for the first time, that light induced
current in unbiased junctions can take place when the bridging molecule is
characterized by a strong charge-transfer transition. The same model shows
current induced light emission under potential bias that exceeds the molecular
excitation energy. Results based on realistic estimates of molecular-lead
coupling and molecule-radiation field interaction suggest that both effects
should be observable.Comment: 5 pages, 3 figures, RevTeX
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