19,769 research outputs found
Non-Anticommutative Deformations of N=(1,1) Supersymmetric Theories
We discuss chirality-preserving nilpotent deformations of four-dimensional
N=(1,1) Euclidean harmonic superspace and their implications in N=(1,1)
supersymmetric gauge and hypermultiplet theories, basically following
[hep-th/0308012] and [hep-th/0405049]. For the SO(4) x SU(2) invariant
deformation, we present non-anticommutative Euclidean analogs of the N=2 gauge
multiplet and hypermultiplet off-shell actions. As a new result, we consider a
specific non-anticommutative hypermultiplet model with N=(1,0) supersymmetry.
It involves free scalar fields and interacting right-handed spinor fields.Comment: Latex file, 15 pages, Submitted to Proceedings of the Seminar
``Classical and Quantum Integrable Systems'' (Dubna, Russia, January 26-29,
2004), v.2 with minor correction
Self-Dual N=2 Born-Infeld Theory Through Auxiliary Superfields
There is an evidence that the N=2 Born-Infeld theory with spontaneously
broken N=4 supersymmetry exhibits self-duality. We perform a further check of
this hypothesis by constructing a new representation for the N=2 Born-Infeld
action through the auxiliary chiral superfield U. In such a formulation,
self-duality is equivalent to U(1) invariance of the U interaction. We
explicitly calculate the auxiliary interaction up to the 10th order and show
its U(1) duality invariance, thus proving that the original action is self-dual
to the same order. We also suggest a new method of recursive computation of the
N=2 Born-Infeld action in the standard formulation, based solely on the
nonlinear realization of the N=4 central charge on the N=2 superfield strengths
W, \bar W.Comment: 1 + 31 pages, substantial revision: an important Note and Appendix C
added; section 2 corrected and expanded; some typos, eq. (5.13) and Appendix
B correcte
A model of gravitation with global U(1)-symmetry
It is shown that an embedding of the general relativity space into a flat
space gives a model of gravitation with the global symmetry and the
discrete one. The last one may be transformed into the symmetry
of the unified model, and the demand of independence of and
transformations leads to the estimate where
is an analog of the Weinberg angle of the standard model.Comment: 7 page
Relativistic cross sections of mass stripping and tidal disruption of a star by a super-massive rotating black hole
[abbreviated] We consider the problem of tidal disruption of a star by a
super-massive Kerr black hole. Using a numerically fast Lagrangian model of the
tidally disrupted star we survey the parameter space of the problem and find
the regions in the parameter space where the total disruption of the star or a
partial mass loss take place as a result of fly-by around the black hole. Our
treatment is based on General Relativity, and we consider the range of the
black hole masses where the tidal disruption competes with the relativistic
effect of direct capture of the star by the black hole. We find that our
results can be represented on the plane of specific orbital angular momenta of
the star . We calculate the contours of a given mass
loss of the star on this plane, referred to as the tidal cross sections, for a
given black hole mass , rotational parameter and inclination of the
trajectory of the star with respect to the black hole equatorial plane. It is
shown that the tidal cross sections can be approximated as circles symmetric
above the axis , and shifted with respect to the origin of the
coordinates in direction of negative . The radii and shifts of
these circles are obtained numerically for the black hole masses in the range
and different values of . It is
shown that when the tidal disruption takes place for and when the tidal disruption is possible for .Comment: 11 pages, 16 figures, A&A in press, the text is clarified, the title
and the abstract shown in text are change
Soliton-Magnon Scattering in Two-Dimensional Isotropic Ferromagnets
It is studied the scattering of magnons by the 2d topological
Belavin-Polyakov soliton in isotropic ferromagnet. Analytical solutions of the
scattering problem are constructed: (i) exactly for any magnon wave vectors for
the partial wave with the azimuthal number m=1 (translational mode), and (ii)
in the long- and short-wave limits for the rest modes. The magnon mode
frequencies are found for the finite size magnets. An effective equation of the
soliton motion is constructed. The magnon density of states, connected with the
soliton-magnon interaction, is found in a long-wave approximation.Comment: 4 pages, REVTe
Chirality tunneling in mesoscopic antiferromagnetic domain walls
We consider a domain wall in the mesoscopic quasi-one-dimensional sample
(wire or stripe) of weakly anisotropic two-sublattice antiferromagnet, and
estimate the probability of tunneling between two domain wall states with
different chirality. Topological effects forbid tunneling for the systems with
half-integer spin S of magnetic atoms which consist of odd number of chains N.
External magnetic field yields an additional contribution to the Berry phase,
resulting in the appearance of two different tunnel splittings in any
experimental setup involving a mixture of odd and even N, and in oscillating
field dependence of the tunneling rate with the period proportional to 1/N.Comment: 4 pages + 2 figures, references correcte
Constrained superpotentials in harmonic gauge theories with 8 supercharges
We consider D-dimensional supersymmetric gauge theories with 8 supercharges
(D<6,) in the framework of harmonic superspaces. The effective
Abelian low-energy action for D=5 contains the free and Chern-Simons terms.
Effective superfield actions for D<4 can be written in terms of
the superpotentials satisfying the superfield constraints and (6-D)-dimensional
Laplace equations. The role of alternative harmonic structures is discussed.Comment: LATEX file, 9 pages, version published in Teor. Mat. Fi
Impurity center in a semiconductor quantum ring in the presence of a radial electric field
The problem of an impurity electron in a quantum ring (QR) in the presence of
a radially directed strong external electric field is investigated in detail.
Both an analytical and a numerical approach to the problem are developed. The
analytical investigation focuses on the regime of a strong wire-electric field
compared to the electric field due to the impurity. An adiabatic and
quasiclassical approximation is employed. The explicit dependencies of the
binding energy of the impurity electron on the electric field strength,
parameters of the QR and position of the impurity within the QR are obtained.
Numerical calculations of the binding energy based on a finite-difference
method in two and three dimensions are performed for arbitrary strengths of the
electric field. It is shown that the binding energy of the impurity electron
exhibits a maximum as a function of the radial position of the impurity that
can be shifted arbitrarily by applying a corresponding wire-electric field. The
maximal binding energy monotonically increases with increasing electric field
strength. The inversion effect of the electric field is found to occur. An
increase of the longitudinal displacement of the impurity typically leads to a
decrease of the binding energy. Results for both low- and high-quantum rings
are derived and discussed. Suggestions for an experimentally accessible set-up
associated with the GaAs/GaAlAs QR are provided.Comment: 16 pages, 8 figure
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