Random walk and diffusion of hard spherical particles in quenched systems: Reaching the continuum limit on a lattice

2000 ◽  
Vol 113 (20) ◽  
pp. 9109-9112 ◽  
Author(s):  
Jean-François Mercier ◽  
Gary W. Slater
1992 ◽  
Vol 182 (4) ◽  
pp. 593-598 ◽  
Author(s):  
Jaume Masoliver ◽  
Josep M. Porrà ◽  
George H. Weiss

2006 ◽  
Vol 21 (07) ◽  
pp. 1493-1502 ◽  
Author(s):  
NIKOS KALOGEROPOULOS

We argue that the geodesic rule, for global defects, is a consequence of the randomness of the values of the Goldstone field ϕ in each causally connected volume. As these volumes collide and coalescence, ϕ evolves by performing a random walk on the vacuum manifold [Formula: see text]. We derive a Fokker–Planck equation that describes the continuum limit of this process. Its fundamental solution is the heat kernel on [Formula: see text], whose leading asymptotic behavior establishes the geodesic rule.


2005 ◽  
Vol 5 (3) ◽  
pp. 223-241
Author(s):  
A. Carpio ◽  
G. Duro

AbstractUnstable growth phenomena in spatially discrete wave equations are studied. We characterize sets of initial states leading to instability and collapse and obtain analytical predictions for the blow-up time. The theoretical predictions are con- trasted with the numerical solutions computed by a variety of schemes. The behavior of the systems in the continuum limit and the impact of discreteness and friction are discussed.


Author(s):  
Timothy R. Field ◽  
Robert J. A. Tough

The illumination of single population behaviour subject to the processes of birth, death and immigration has provided a basis for the discussion of the non-Gaussian statistical and temporal correlation properties of scattered radiation. As a first step towards the modelling of its spatial correlations, we consider the populations supported by an infinite chain of discrete sites, each subject to birth, death and immigration and coupled by migration between adjacent sites. To provide some motivation, and illustrate the techniques we will use, the migration process for a single particle on an infinite chain of sites is introduced and its diffusion dynamics derived. A certain continuum limit is identified and its properties studied via asymptotic analysis. This forms the basis of the multi-particle model of a coupled population subject to single site birth, death and immigration processes, in addition to inter-site migration. A discrete rate equation is formulated and its generating function dynamics derived. This facilitates derivation of the equations of motion for the first- and second-order cumulants, thus generalizing the earlier results of Bailey through the incorporation of immigration at each site. We present a novel matrix formalism operating in the time domain that enables solution of these equations yielding the mean occupancy and inter-site variances in the closed form. The results for the first two moments at a single time are used to derive expressions for the asymptotic time-delayed correlation functions, which relates to Glauber’s analysis of an Ising model. The paper concludes with an analysis of the continuum limit of the birth–death–immigration–migration process in terms of a path integral formalism. The continuum rate equation and evolution equation for the generating function are developed, from which the evolution equation of the mean occupancy is derived, in this limit. Its solution is provided in closed form.


1997 ◽  
Vol 12 (31) ◽  
pp. 2331-2340 ◽  
Author(s):  
L. Chekhov ◽  
K. Zarembo

We calculate an effective action and measure induced by the integration over the auxiliary field in the matrix model recently proposed to describe IIB superstrings. It is shown that the measure of integration over the auxiliary matrix is uniquely determined by locality and reparametrization invariance of the resulting effective action. The large-N limit of the induced measure for string coordinates is discussed in detail. It is found to be ultralocal and, thus, is possibly irrelevant in the continuum limit. The model of the GKM type is considered in relation to the effective action problem.


Author(s):  
C.G. BENEVENTANO ◽  
E.M. SANTANGELO

We study a family of local boundary conditions for the Dirac problem corresponding to the continuum limit of graphene, both for nanoribbons and nanodots. We show that, among the members of such family, MIT bag boundary conditions are the ones which are in closest agreement with available experiments. For nanotubes of arbitrary chirality satisfying these last boundary conditions, we evaluate the Casimir energy via zeta function regularization, in such a way that the limit of nanoribbons is clearly determined.


2018 ◽  
Vol 117 (9-12) ◽  
pp. 1351-1359 ◽  
Author(s):  
Frank E. Marshall ◽  
Nicole Moon ◽  
Thomas D. Persinger ◽  
David J. Gillcrist ◽  
Nelson E. Shreve ◽  
...  

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