4,993 research outputs found
An automata characterisation for multiple context-free languages
We introduce tree stack automata as a new class of automata with storage and
identify a restricted form of tree stack automata that recognises exactly the
multiple context-free languages.Comment: This is an extended version of a paper with the same title accepted
at the 20th International Conference on Developments in Language Theory (DLT
2016
Effects of an embedding bulk fluid on phase separation dynamics in a thin liquid film
Using dissipative particle dynamics simulations, we study the effects of an
embedding bulk fluid on the phase separation dynamics in a thin planar liquid
film. The domain growth exponent is altered from 2D to 3D behavior upon the
addition of a bulk fluid, even though the phase separation occurs in 2D
geometry. Correlated diffusion measurements in the film show that the presence
of bulk fluid changes the nature of the longitudinal coupling diffusion
coefficient from logarithmic to algebraic dependence of 1/s, where s is the
distance between the two particles. This result, along with the scaling
exponents, suggests that the phase separation takes place through the Brownian
coagulation process.Comment: 6 pages, 5 figures. Accepted for publication in Europhys. Let
Magnon-photon coupling in the noncollinear magnetic insulator Cu 2 OSeO 3
Anticrossing behavior between magnons in the noncollinear chiral magnet Cu2OSeO3 and a two-mode X-band microwave resonator was studied in the temperature range 5–100 K. In the field-induced ferrimagnetic phase, we observed a strong-coupling regime between magnons and two microwave cavity modes with a cooperativity reaching 3600. In the conical phase, cavity modes are dispersively coupled to a fundamental helimagnon mode, and we demonstrate that the magnetic phase diagram of Cu2OSeO3 can be reconstructed from the measurements of the cavity resonance frequency. In the helical phase, a hybridized state of a higher-order helimagnon mode and a cavity mode—a helimagnon polariton—was found. Our results reveal a class of magnetic systems where strong coupling of microwave photons to nontrivial spin textures can be observed
Anomalous lateral diffusion in a viscous membrane surrounded by viscoelastic media
We investigate the lateral dynamics in a purely viscous lipid membrane
surrounded by viscoelastic media such as polymeric solutions. We first obtain
the generalized frequency-dependent mobility tensor and focus on the case when
the solvent is sandwiched by hard walls. Due to the viscoelasticity of the
solvent, the mean square displacement of a disk embedded in the membrane
exhibits an anomalous diffusion. An useful relation which connects the mean
square displacement and the solvent modulus is provided. We also calculate the
cross-correlation of the particle displacements which can be applied for
two-particle tracking experiments.Comment: 6 pages, 2 figure
The Complexity of Fixed-Height Patterned Tile Self-Assembly
We characterize the complexity of the PATS problem for patterns of fixed
height and color count in variants of the model where seed glues are either
chosen or fixed and identical (so-called non-uniform and uniform variants). We
prove that both variants are NP-complete for patterns of height 2 or more and
admit O(n)-time algorithms for patterns of height 1. We also prove that if the
height and number of colors in the pattern is fixed, the non-uniform variant
admits a O(n)-time algorithm while the uniform variant remains NP-complete. The
NP-completeness results use a new reduction from a constrained version of a
problem on finite state transducers.Comment: An abstract version appears in the proceedings of CIAA 201
Multiple peak aggregations for the Keller-Segel system
In this paper we derive matched asymptotic expansions for a solution of the
Keller-Segel system in two space dimensions for which the amount of mass
aggregation is , where Previously available asymptotics
had been computed only for the case in which N=1
Fano hypersurfaces and Calabi-Yau supermanifolds
In this paper, we study the geometrical interpretations associated with
Sethi's proposed general correspondence between N = 2 Landau-Ginzburg orbifolds
with integral \hat{c} and N = 2 nonlinear sigma models. We focus on the
supervarieties associated with \hat{c} = 3 Gepner models. In the process, we
test a conjecture regarding the superdimension of the singular locus of these
supervarieties. The supervarieties are defined by a hypersurface \widetilde{W}
= 0 in a weighted superprojective space and have vanishing super-first Chern
class. Here, \widetilde{W} is the modified superpotential obtained by adding as
necessary to the Gepner superpotential a boson mass term and/or fermion
bilinears so that the superdimension of the supervariety is equal to \hat{c}.
When Sethi's proposal calls for adding fermion bilinears, setting the bosonic
part of \widetilde{W} (denoted by \widetilde{W}_{bos}) equal to zero defines a
Fano hypersurface embedded in a weighted projective space. In this case, if the
Newton polytope of \widetilde{W}_{bos} admits a nef partition, then the
Landau-Ginzburg orbifold can be given a geometrical interpretation as a
nonlinear sigma model on a complete intersection Calabi-Yau manifold. The
complete intersection Calabi-Yau manifold should be equivalent to the
Calabi-Yau supermanifold prescribed by Sethi's proposal.Comment: 24 pages, uses JHEP3.cls; v2: minor corrections, references adde
Non-equilibrium thermodynamic study of magnetization dynamics in the presence of spin-transfer torque
The dynamics of magnetization in the presence of spin-transfer torque was
studied. We derived the equation for the motion of magnetization in the
presence of a spin current by using the local equilibrium assumption in
non-equilibrium thermodynamics. We show that, in the resultant equation, the
ratio of the Gilbert damping constant, , and the coefficient, ,
of the current-induced torque, called non-adiabatic torque, depends on the
relaxation time of the fluctuating field . The equality
holds when is very short compared to the time scale of
magnetization dynamics. We apply our theory to current-induced magnetization
reversal in magnetic multilayers and show that the switching time is a
decreasing function of .Comment: 4 pages, 2 figure
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