843 research outputs found
BPS and non-BPS states in a supersymmetric Landau-Ginzburg theory
We analyze the spectrum of the N=(2,2) supersymmetric Landau-Ginzburg theory
in two dimensions with superpotential W=X^{n+2}-lambda X^2. We find the full
BPS spectrum of this theory by exploiting the direct connection between the UV
and IR limits of the theory. The computation utilizes results from the
Picard-Lefschetz theory of singularities and its extension to boundary
singularities. The additional fact that this theory is integrable requires that
the BPS states do not close under scattering. This observation fixes the masses
of non-BPS states as well.Comment: 27 pages, 12 figure
On the Classification of Quasihomogeneous Functions
We give a criterion for the existence of a non-degenerate quasihomogeneous
polynomial in a configuration, i.e. in the space of polynomials with a fixed
set of weights, and clarify the relation of this criterion to the necessary
condition derived from the formula for the Poincar\'e polynomial. We further
prove finiteness of the number of configurations for a given value of the
singularity index. For the value 3 of this index, which is of particular
interest in string theory, a constructive version of this proof implies an
algorithm for the calculation of all non-degenerate configurations.Comment: 12 page
Longitudinal Losses Due to Breathing Mode Excitation in Radiofrequency Linear Accelerators
Transverse breathing mode oscillations in a particle beam can couple energy
into longitudinal oscillations in a bunch of finite length and cause
significant losses. We develop a model that illustrates this effect and explore
the dependence on mismatch size, space-charge tune depression, longitudinal
focusing strength, bunch length, and RF bucket length
Two-dimensional topological gravity and equivariant cohomology
In this paper, we examine the analogy between topological string theory and
equivariant cohomology. We also show that the equivariant cohomology of a
topological conformal field theory carries a certain algebraic structure, which
we call a gravity algebra. (Error on page 9 corrected: BRS current contains
total derivatives.)Comment: 18 page
Universality in Voltage-driven Nonequilibrium Phase Transitions
We consider the non-equilibrium ferromagnetic transition of a mesoscopic
sample of a resistive Stoner ferromagnet coupled to two paramagnetic leads. The
transition is controlled by either the lead temperature T or the transport
voltage V applied between the leads. We calculate the T and V dependence of the
magnetization. For systems with a flat density of states we find within
mean-field theory that even at finite bias the magnetization does not depend on
the position along the sample axis, although the charge density and other
quantities do vary. This may be relevant for possible spintronics applications.
In addition, we establish a generalized control parameter in terms of T and V
which allows for a universal description of the temperature- and voltage-driven
transition.Comment: 12 pages, 4 figures. J. Low Temp. Phys., published version.
Discussion of the relation to quantum phase transitions, cond-mat/0607256,
has been adde
Resonances and O-curves in Hamiltonian systems
We investigate the problem of the existence of trajectories asymptotic to
elliptic equilibria of Hamiltonian systems in the presence of resonances.Comment: 12 page
Versal deformations of a Dirac type differential operator
If we are given a smooth differential operator in the variable its normal form, as is well known, is the simplest form
obtainable by means of the \mbox{Diff}(S^1)-group action on the space of all
such operators. A versal deformation of this operator is a normal form for some
parametric infinitesimal family including the operator. Our study is devoted to
analysis of versal deformations of a Dirac type differential operator using the
theory of induced \mbox{Diff}(S^1)-actions endowed with centrally extended
Lie-Poisson brackets. After constructing a general expression for tranversal
deformations of a Dirac type differential operator, we interpret it via the
Lie-algebraic theory of induced \mbox{Diff}(S^1)-actions on a special Poisson
manifold and determine its generic moment mapping. Using a Marsden-Weinstein
reduction with respect to certain Casimir generated distributions, we describe
a wide class of versally deformed Dirac type differential operators depending
on complex parameters
On the averaging principle for one-frequency systems. An application to satellite motions
This paper is related to our previous works [1][2] on the error estimate of
the averaging technique, for systems with one fast angular variable. In the
cited references, a general method (of mixed analytical and numerical type) has
been introduced to obtain precise, fully quantitative estimates on the
averaging error. Here, this procedure is applied to the motion of a satellite
in a polar orbit around an oblate planet, retaining only the J_2 term in the
multipole expansion of the gravitational potential. To exemplify the method,
the averaging errors are estimated for the data corresponding to two Earth
satellites; for a very large number of orbits, computation of our estimators is
much less expensive than the direct numerical solution of the equations of
motion.Comment: LaTeX, 35 pages, 12 figures. The final version published in Nonlinear
Dynamic
- …