Random Walks
Mostrando 13-24 de 39 artigos, teses e dissertações.
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13. Statistical physics of random searches
We apply the theory of random walks to quantitatively describe the general problem of how to search efficiently for randomly located objects that can only be detected in the limited vicinity of a searcher who typically has a finite degree of "free will" to move and search at will. We illustrate Lévy flight search processes by comparison to Brownian random w
Brazilian Journal of Physics. Publicado em: 2001-03
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14. Stretched exponential relaxation and independent relaxation modes
We discuss the origin of stretched exponential relaxation in disordered Ising spin systems by writing the master equation on the phase space, and the evolution of local and global spin autocorrelation functions, in terms of independent relaxation modes, which are eigenvectors of the time evolution operator. In this sense it is shown that when the relaxation
Brazilian Journal of Physics. Publicado em: 2000-12
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15. Nonequilibrium kinetic Ising models: phase transitions and universality classes in one dimension
Nonequilibrium kinetic Ising models evolving under the competing effect of spin flips at zero temperature and Kawasaki-type spin-exchange kinetics at infinite temperature T are investigated here in one dimension from the point of view of phase transition and critical behaviour. Branching annihilating random walks with an even number of offspring (on the part
Brazilian Journal of Physics. Publicado em: 2000-03
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16. Discrete-time random walks on diagrams (graphs) with cycles.
After a review of the diagram method for continuous-time random walks on graphs with cycles, the method is extended to discrete-time random walks. The basic theorems carry over formally from continuous time to discrete time. Three problems in tennis probabilities are used to illustrate random walks on discrete-time diagrams with cycles.
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17. A modified gambler's ruin model of polyethylene chains in the amorphous region.
Polyethylene chains in the amorphous region between two crystalline lamellae M unit apart are modeled as random walks with one-step memory on a cubic lattice between two absorbing boundaries. These walks avoid the two preceding steps, though they are not true self-avoiding walks. Systems of difference equations are introduced to calculate the statistics of t
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18. Scaling behavior of random knots
Using numerical simulations we investigate how overall dimensions of random knots scale with their length. We demonstrate that when closed non-self-avoiding random trajectories are divided into groups consisting of individual knot types, then each such group shows the scaling exponent of ≈0.588 that is typical for self-avoiding walks. However, when all gen
The National Academy of Sciences.
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19. Further properties of random walks on diagrams (graphs) with and without cycles.
Three problems are considered. The first is the relation between ensemble-averaged state probabilities in a random walk with absorption and time-averaged state probabilities in the corresponding closed diagram. The second problem is concerned with random walks on diagrams with cycles in which the cycle completion rates and probabilities may depend on the "re
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20. Self-avoiding random walks at finite concentrations: The bulk phase limit
In infinitely dilute solutions, macromolecules exhibit non-Gaussian distributions for their end-to-end separations. This occurs under such circumstances because intramolecular interactions are more important than intermolecular forces. On the other hand, when a macromolecular solution becomes so concentrated that it approaches its bulk phase, then the end-to
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21. Diffusion at finite speed and random walks
Diffusion, which occurs with infinite speed, results from a random walk with steps of finite speed. We resolve this paradox and derive a modified diffusion equation with finite speed.
National Academy of Sciences.
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22. Discrete mechanics and special relativistic random walks
Random walks with step lengths equal to the shortest possible physically meaningful distances are considered from the point of view of special relativity involving two observers moving uniformly with respect to each other. A requirement of statistical equivalence of the probability distributions seen by those observers leads to the Lorentz transformations, p
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23. Self-avoiding random walks on lattice strips
A self-avoiding walk on an infinitely long lattice strip of finite width will asymptotically exhibit an end-to-end separation proportional to the number of steps. A proof of this proposition is presented together with comments concerning an earlier attempt to deal with the matter. In addition, some unproved, yet “obvious,” conjectures concerning self-avo
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24. Random walks and generalized master equations with internal degrees of freedom
We present an extension of the continuous-time random walk formalism to include internal states and to establish the connection to generalized master equations with internal states. The theory allows us to calculate physical observables from which we can extract the characteristic parameters of the internal states of the system under study.