814 research outputs found
Fluctuations for the Ginzburg-Landau Interface Model on a Bounded Domain
We study the massless field on , where is a bounded domain with smooth boundary, with Hamiltonian
\CH(h) = \sum_{x \sim y} \CV(h(x) - h(y)). The interaction \CV is assumed
to be symmetric and uniformly convex. This is a general model for a
-dimensional effective interface where represents the height. We
take our boundary conditions to be a continuous perturbation of a macroscopic
tilt: for , , and
continuous. We prove that the fluctuations of linear
functionals of about the tilt converge in the limit to a Gaussian free
field on , the standard Gaussian with respect to the weighted Dirichlet
inner product for some explicit . In a subsequent article,
we will employ the tools developed here to resolve a conjecture of Sheffield
that the zero contour lines of are asymptotically described by , a
conformally invariant random curve.Comment: 58 page
-particle condensate states in O
The existence of a rotational band with the +C()
cluster structure, in which three particles in C() are
locally condensed, is demonstrated near the four- threshold of O
in agreement with experiment. This is achieved by studying structure and
scattering for the +C() system in a unified way. A
drastic reduction (quenching) of the moment of the inertia of the state
at 15.1 MeV just above the four- threshold in O suggests that it
could be a candidate for the superfluid state in -particle
condensation.Comment: 5 pages, 3 figure
Determination of Pinning Parameters in Flux Creep-Flow Model for E-J characteristics of High Temperature Superconductors by using Differential Evolution
The pinning parameters such as strength of pinning force, temperature dependence of pinning force and so on using in flux creep-flow model to explain electric field vs current density (E-J) characteristics were determined by Differential Evolution (DE). DE is one of the methods in Evolutionary Computation (EC) to find an optimization of a problem. First, a model data of E-J characteristics in which the pinning parameters were given was prepared, and it was confirmed that DE can find the given pinning parameters from the model data. Then, DE and mesh method were used to determine the pinning parameters in experimental E-J characteristics of GdBa2CuO7-δ high temperature superconductor. In mesh method, the all combinations of pinning parameters with constant interval for each parameter are calculated, and best set of pinning parameters is selected. It was found that DE shows better performance than mesh method in terms of calculation time and accuracy for determining pinning parameters
Nuclear Alpha-Particle Condensates
The -particle condensate in nuclei is a novel state described by a
product state of 's, all with their c.o.m. in the lowest 0S orbit. We
demonstrate that a typical -particle condensate is the Hoyle state
( MeV, state in C), which plays a crucial role for
the synthesis of C in the universe. The influence of antisymmentrization
in the Hoyle state on the bosonic character of the particle is
discussed in detail. It is shown to be weak. The bosonic aspects in the Hoyle
state, therefore, are predominant. It is conjectured that -particle
condensate states also exist in heavier nuclei, like O,
Ne, etc. For instance the state of O at MeV
is identified from a theoretical analysis as being a strong candidate of a
condensate. The calculated small width (34 keV) of ,
consistent with data, lends credit to the existence of heavier Hoyle-analogue
states. In non-self-conjugated nuclei such as B and C, we discuss
candidates for the product states of clusters, composed of 's,
triton's, and neutrons etc. The relationship of -particle condensation
in finite nuclei to quartetting in symmetric nuclear matter is investigated
with the help of an in-medium modified four-nucleon equation. A nonlinear order
parameter equation for quartet condensation is derived and solved for
particle condensation in infinite nuclear matter. The strong qualitative
difference with the pairing case is pointed out.Comment: 71 pages, 41 figures, review article, to be published in "Cluster in
Nuclei (Lecture Notes in Physics) - Vol.2 -", ed. by C. Beck,
(Springer-Verlag, Berlin, 2011
Soft and hard wall in a stochastic reaction diffusion equation
We consider a stochastically perturbed reaction diffusion equation in a
bounded interval, with boundary conditions imposing the two stable phases at
the endpoints. We investigate the asymptotic behavior of the front separating
the two stable phases, as the intensity of the noise vanishes and the size of
the interval diverges. In particular, we prove that, in a suitable scaling
limit, the front evolves according to a one-dimensional diffusion process with
a non-linear drift accounting for a "soft" repulsion from the boundary. We
finally show how a "hard" repulsion can be obtained by an extra diffusive
scaling.Comment: 33 page
Open Problems in Particle Condensation
particle condensation is a novel state in nuclear systems. We
briefly review the present status on the study of particle
condensation and address the open problems in this research field:
particle condensation in heavier systems other than the Hoyle state, linear
chain and particle rings, Hoyle-analogue states with extra neutrons,
particle condensation related to astrophysics, etc.Comment: 12 pages. To be published in J. of Phys. G special issue on Open
Problems in Nuclear Structure (OPeNST
A note on a local ergodic theorem for an infinite tower of coverings
This is a note on a local ergodic theorem for a symmetric exclusion process
defined on an infinite tower of coverings, which is associated with a finitely
generated residually finite amenable group.Comment: Final version to appear in Springer Proceedings in Mathematics and
Statistic
Tightness for a stochastic Allen--Cahn equation
We study an Allen-Cahn equation perturbed by a multiplicative stochastic
noise which is white in time and correlated in space. Formally this equation
approximates a stochastically forced mean curvature flow. We derive uniform
energy bounds and prove tightness of of solutions in the sharp interface limit,
and show convergence to phase-indicator functions.Comment: 27 pages, final Version to appear in "Stochastic Partial Differential
Equations: Analysis and Computations". In Version 4, Proposition 6.3 is new.
It replaces and simplifies the old propositions 6.4-6.
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