465 research outputs found
Topological stripelike coreless textures with inner incommensurability in two-dimensional Heisenberg antiferromagnet
For two-dimensional Heisenberg antiferromagnet we present an analysis of
topological coreless excitations having a stripe form. These textures are
characterized by singularities at boundaries. A detailed classification of the
stripe textures results in a certain analogy with the coreless excitations in
phase: Mermin-Ho and Anderson-Toulouse coreless vortices. The
excitations of the last type may have a low bulk energy. The stripe textures
may be observed as an occurrence of short-range incommensurate order in the
antiferromagnetic environment
Bose-Einstein condensation of semi-hard bosons in S=1 dimerized organic compound F2PNNNO
An analysis of the energy spectrum and the magnetization curve of
two-dimensional organic antiferromagnet F2PNNNO with a spin-one dimerized
structure shows that a behavior of the compound in an external magnetic field
can be explained within a lattice boson model with an extended Pauli's
exclusion principle, i.e. no more than two bosons per a dimer. The unusual
magnetization curve observed experimentally in the compound reflects a sequence
of phase transitions intrinsic for a lattice boson system with strong on-site
and inter-site repulsions due to a tuning of magnon density by the applied
magnetic field
Duality and fluctuation relations for statistics of currents on cyclic graphs
We consider stochastic motion of a particle on a cyclic graph with
arbitrarily periodic time dependent kinetic rates. We demonstrate duality
relations for statistics of currents in this model and in its continuous
version of a diffusion in one dimension. Our duality relations are valid beyond
detailed balance constraints and lead to exact expressions that relate
statistics of currents induced by dual driving protocols. We also show that
previously known no-pumping theorems and some of the fluctuation relations,
when they are applied to cyclic graphs or to one dimensional diffusion, are
special consequences of our duality.Comment: 2 figure, 6 pages (In twocolumn). Accepted by JSTA
Particle current in symmetric exclusion process with time-dependent hopping rates
In a recent study, (Jain et al 2007 Phys. Rev. Lett. 99 190601), a symmetric
exclusion process with time-dependent hopping rates was introduced. Using
simulations and a perturbation theory, it was shown that if the hopping rates
at two neighboring sites of a closed ring vary periodically in time and have a
relative phase difference, there is a net DC current which decreases inversely
with the system size. In this work, we simplify and generalize our earlier
treatment. We study a model where hopping rates at all sites vary periodically
in time, and show that for certain choices of relative phases, a DC current of
order unity can be obtained. Our results are obtained using a perturbation
theory in the amplitude of the time-dependent part of the hopping rate. We also
present results obtained in a sudden approximation that assumes large
modulation frequency.Comment: 17 pages, 2 figure
Edge Magnetoplasmons in Quantum Hall Line Junction Systems
A quantum Hall line junction system consists of a one-dimensional Luttinger
liquid (LL) and two chiral channels that allow density waves incident upon and
reflected by the LL to be measured separately. We demonstrate that interactions
in a quantum Hall line junction system can be probed by studying edge
magnetoplasmon absorption spectra and their polarization dependences. Strong
interactions in the junction lead to collective modes that are isolated in
either Luttinger liquid or contact subsystems.Comment: 4 pages, 3 figures, submitted to Phys. Rev. B Rapid Communicatio
Theory of standing spin waves in finite-size chiral spin soliton lattice
We present a theory of standing spin wave (SSW) in a monoaxial chiral
helimagnet. Motivated by experimental findings on the magnetic field-dependence
of the resonance frequency in thin films of CrNbS[Goncalves
et al., Phys. Rev. B95, 104415 (2017)], we examine the SSW over a chiral
soliton lattice (CSL) excited by an ac magnetic field applied parallel and
perpendicular to the chiral axis. For this purpose, we generalize Kittel-Pincus
theories of the SSW in ferromagnetic thin films to the case of non-collinear
helimagnet with the surface end spins which are softly pinned by an anisotropy
field. Consequently, we found there appear two types of modes. One is a Pincus
mode which is composed of a long-period Bloch wave and a short-period ripple
originated from the periodic structure of the CSL. Another is a short-period
Kittel ripple excited by space-periodic perturbation which exists only in the
case where the ac field is applied perpendicular the chiral axis. We
demonstrate that the existence of the Pincus mode and the Kittel ripple is
consistent with experimentally found double resonance profile.Comment: 17 pages, 14 figure
Comparison of Two Methods for Assaying Reducing Sugars in the Determination of Carbohydrase Activities
The Nelson-Somogyi (NS) and 3,5-dinitrosalicylic acid (DNS) assays for
reducing sugars are widely used in measurements of carbohydrase activities against different
polysaccharides. Using twelve commercial enzyme preparations, the comparison of the NS and DNS
assays in determination of cellulase, β-glucanase, xylanase, and β-mannanase activities was carried out. When cellulase activities against CMC were measured,
the DNS assay gave activity values, which were typically 40–50% higher than those obtained with the NS assay.
In the analysis of the xylanase, β-mannanase, and β-glucanase activities, the overestimations by the DNS assay were much more pronounced (the observed differences in the activities were 3- to 13-fold). Reasons for preferential use of
the NS assay for measuring activities of carbohydrases other than cellulases are discussed
Geometric phase for non-Hermitian Hamiltonian evolution as anholonomy of a parallel transport along a curve
We develop a new interpretation of the geometric phase in evolution with a
non-Hermitian real value Hamiltonian by relating it to the angle developed
during the parallel transport along a closed curve by a unit vector triad in
the 3D-Minkovsky space. We also show that this geometric phase is responsible
for the anholonomy effects in stochastic processes considered in [N. A.
Sinitsyn and I. Nemenman, EPL {\bf 77}, 58001 (2007)], and use it to derive the
stochastic system response to periodic parameter variations.Comment: 10 pages 2 figure
Generation of spin motive force in a soliton lattice
The generation of a spin motive force in a chiral helimagnet due to the action of two crossed magnetic fields is considered. The cases of pulsed and periodic magnetic fields directed along the helical axis under a perpendicular dc field are analyzed. It is shown that, in the case of a pulsed field, the spin motive force is related to dissipation, whereas in a periodic field, there is a reactive component that is not related to damping processes. © 2013 Pleiades Publishing, Ltd
Stochastic pump effect and geometric phases in dissipative and stochastic systems
The success of Berry phases in quantum mechanics stimulated the study of
similar phenomena in other areas of physics, including the theory of living
cell locomotion and motion of patterns in nonlinear media. More recently,
geometric phases have been applied to systems operating in a strongly
stochastic environment, such as molecular motors. We discuss such geometric
effects in purely classical dissipative stochastic systems and their role in
the theory of the stochastic pump effect (SPE).Comment: Review. 35 pages. J. Phys. A: Math, Theor. (in press
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