690 research outputs found
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
Nonlinear absorption of surface acoustic waves by composite fermions
Absorption of surface acoustic waves by a two-dimensional electron gas in a
perpendicular magnetic field is considered. The structure of such system at the
filling factor close to 1/2 can be understood as a gas of {\em composite
fermions}. It is shown that the absorption at can be strongly
nonlinear, while small deviation form 1/2 will restore the linear absorption.
Study of nonlinear absorption allows one to determine the force acting upon the
composite fermions from the acoustic wave at turning points of their
trajectories.Comment: 7 pages, 1 figure, submitted to Europhysics letter
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
Potentials in N=4 superconformal mechanics
Proceeding from nonlinear realizations of (super)conformal symmetries, we
explicitly demonstrate that adding the harmonic oscillator potential to the
action of conformal mechanics does not break these symmetries but modifies the
transformation properties of the (super)fields. We also analyze the possibility
to introduce potentials in N=4 supersymmetric mechanics by coupling it with
auxiliary fermionic superfields. The new coupling we considered does not
introduce new fermionic degrees of freedom - all our additional fermions are
purely auxiliary ones. The new bosonic components have a first order kinetic
term and therefore they serve as spin degrees of freedom. The resulting system
contains, besides the potential term in the bosonic sector, a non-trivial
spin-like interaction in the fermionic sector. The superconformal mechanics we
constructed in this paper is invariant under the full
superconformal group. This invariance is not evident and is achieved within
modified (super)conformal transformations of the superfields.Comment: 12 pages, PACS number: 12.60.J
Mass-Deformed BLG Theory in Light-Cone Superspace
Maximally supersymmetric mass deformation of the Bagger-Lambert-Gustavsson
(BLG) theory corresponds to a {non-central} extension of the d=3 N=8 Poincare
superalgebra (allowed in three dimensions). We obtain its light-cone superspace
formulation which has a novel feature of the dynamical supersymmetry generators
being {cubic} in the kinematical ones. The mass deformation picks a
quaternionic direction, which breaks the SO(8) R-symmetry down to SO(4)xSO(4).
The Hamiltonian of the theory is shown to be a quadratic form of the dynamical
supersymmetry transformations, to all orders in the mass parameter, M, and the
structure constants, f^{a b c d}.Comment: 23 page
The effect of the system polydispersity on voltammograms of nanoparticles electrooxidation
The paper proposes a mathematical model describing electrooxidation of a polydisperse system of metal nanoparticles from the surface of an indifferent macro-electrode. It is shown that the degree of dispersion of a nanoparticle ensemble affects the shape of oxidation voltammograms. When the degree of dispersion rises and the average size of nanoparticles becomes smaller, the range of oxidation potentials increases. The results of the experimental study of electrooxidation of gold nanoparticles with different degrees of dispersion are given. The particles were localized on the surface of graphite screen-printed electrodes. A good agreement between the parameters of the experimental and calculated voltammograms confirms the correctness of the proposed model. © 2012 Springer-Verlag
Molecular Dynamics Study of Charged Dendrimers in Salt-Free Solution: Effect of Counterions
Polyamidoamine (PAMAM) dendrimers, being protonated under physiological
conditions, represent a promising class of nonviral, nano-sized vectors for
drug and gene delivery. We performed extensive molecular dynamics simulations
of a generic model dendrimer in a salt-free solution with dendrimer's terminal
beads positively charged. Solvent molecules as well as counterions were
explicitly included as interacting beads. We find that the size of the charged
dendrimer depends non-monotonically on the strength of electrostatic
interactions demonstrating a maximum when the Bjerrum length equals the
diameter of a bead. Many other structural and dynamic characteristics of
charged dendrimers are also found to follow this pattern. We address such a
behavior to the interplay between repulsive interactions of the charged
terminal beads and their attractive interactions with oppositely charged
counterions. The former favors swelling at small Bjerrum lengths and the latter
promotes counterion condensation. Thus, counterions can have a dramatic effect
on the structure and dynamics of charged dendrimers and, under certain
conditions, cannot be treated implicitly
Non-Gaussian dephasing in flux qubits due to 1/f-noise
Recent experiments by F. Yoshihara et al. [Phys. Rev. Lett. 97, 167001
(2006)] and by K. Kakuyanagi et al. (cond-mat/0609564) provided information on
decoherence of the echo signal in Josephson-junction flux qubits at various
bias conditions. These results were interpreted assuming a Gaussian model for
the decoherence due to 1/f noise. Here we revisit this problem on the basis of
the exactly solvable spin-fluctuator model reproducing detailed properties of
the 1/f noise interacting with a qubit. We consider the time dependence of the
echo signal and conclude that the results based on the Gaussian assumption need
essential reconsideration.Comment: Improved fitting parameters, new figur
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
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