1,720,983 research outputs found
Asymptotics of Brownian integrals and pressure. Bose – Einstein statistics
No full textThis paper studies the asymptotics of the Brownian integrals with paths restricted to a bounded domain of Rν , when the domain is dilated to infinity. The framework is that of the Bose- Einstein statistics with paths observed within random time intervals which are integer multiplies of some fixed β > 0. The three first terms of the asymptotics are found explicitly via the functional integrals. In the case of a gas of interacting Brownian loops an expression for the volume term of the asymptotics of the log-partition function is found and the correction term is proved by order to be the boundary area of the domain
A Two-Dimensional Random Walk in Random Environment Exhibiting Strongly Sub- diffusive Behavior: Computer Simulations
No full text
An Integral Equation Method for the Solution of the Burgers Equation
No full textWe consider the Burgers equation in the plane without external forces. It is known that for suitable initial data the corresponding complex solution has singularities at finite time [6]. The numerical solution of this equation can be seen as a first step in the study of the well-known problem of understanding the solutions of Navier-Stokes equations. The numerical solution of the Burgers equation is computed by using a proper integral equation. We describe the results obtained with this numerical method, and some possible extensions of the proposed method to deal with more practical problems
The analysis of the standardized precipitation index in the mediterranean area: large-scale patterns
No full textThe analysis of the standardized precipitation index in the mediterranean area: regional patterns
No full textTesting and Implementing Some New Algorithms Using the FFTW Library on Massively Parallel Supercomputers
No full textThe aim of this paper is to provide a strategy for overcoming the limits of codes employing the FFTW library by implementing a more powerful parallel domain decomposition algorithm and by refining the auto-tuning mechanism that is already implemented in this library. In the first part of this paper we identify some of the major performance bottlenecks present in the current FFTW implementation, in particular the auto-tuning mechanism provided in FFTW. To do this we have tested for the first time on a Blue Gene/Q system a 2D Parallel Domain Decomposition algorithm provided by the 2DECOMP&FFT library. We found that on massively parallel supercomputers such as Blue Gene/Q clusters the performance of this new algorithm is significantly higher. To demonstrate the benefits of the algorithm in a real application we included the library in a CFD code, BlowupNS, where we found a marked improvement in parallel scalability
Computer simulations for some one-dimensional models of random walks in fluctuating random environment
No full textSummary: "We report some results of computer simulations for two models of random walks in random environment (rwre) on the one-dimensional lattice Z for fixed space-time configuration of the environment (`quenched rwre'): a `Markov model' with Markov dependence in time, and a `quasi-stationary' model with long range space-time correlations. We compare the corresponding results for a model with an i.i.d. (in space-time) environment. In the range of times available to us the quenched distributions of the random walk displacement are far from Gaussian, but as the behavior is similar for all three models one cannot exclude asymptotic Gaussianity, which is proved for the model with i.i.d. environment. We also report results on the random drift and on some time correlations which show a clear power decay.'
Convergence to a Stationary State and Diffusion for a Charged Particle in a Standing Medium
No full textWe study a one-dimensional semi-infinite system of identical particles driven by a constant force acting on the first particle. Particles interact through elastic collisions. At the initial time particles are at rest and the interparticle distances are i.i.d. random variables with minimal distance d>0. We show that if d is lage enough the dynamics has a strong cluster property and the system as seen from the first particle converges for large times to a limiting distribution
Diffusion and Einstein Relation for a Massive Particle in a One-Dimensional Free Gas: Numerical Evidence
No full textA computer simulation is used to investigate the motion of a marked particle of
mass M in a free gas of particles with mass m = 1, for large times. Previous
results seem to indicate a non-Wiener behavior for the rescaled trajectory when
M ~ m. The results reported here, with better statistics, are compatible with the
Wiener hypothesis. The Einstein relation between mobility and diffusion coefficient
is also investigated. The results indicate that it holds both for M = m and
for M ≠m
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