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O Sotolongo-Costa

Publications and source records attributed to O Sotolongo-Costa.

6 recordsLinked to original sources
PubMed2003

Bose-Einstein condensation in random directed networks.

We consider the phenomenon of Bose-Einstein condensation in a random growing directed network. The network grows by the addition of vertices and edges. At each time step the network gains a vertex with probability p and an edge with probability 1-p. The new vertex has a fitness (a,b) a,b>0, with probability f(a,b). A vertex with fitness (a,b), with in-degree i and out-degree j, gains a new incoming edge with rate a(i+1) and an outgoing edge with rate b(j+1). The Bose-Einstein condensation occurs as a function of fitness distribution f(a,b).

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PubMed2000

Dynamics of a domain wall in soft-magnetic materials: barkhausen effect and relation with sandpile models

The CZDE model [P. Cizeau, S Zapperi, G. Durin, and H. E. Stanley, Phys. Rev. Lett. 79, 4669 (1997)] for the dynamics of a domain wall in soft-magnetic materials is investigated. The equation of motion for the domain wall is reduced to a dimensionless form where the control parameters are clearly identified. In this way we show that in soft-magnetic materials with low anisotropies the noise can be approximated by a columnar disorder, and perturbation theory gives a good estimate of the avalanche exponents. Moreover, the resulting exponents are found to be identical to those obtained for directed Abelian sandpile models. The analogies and differences with these models and the question of self-organized criticality in the Barkhausen effect are discussed.

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PubMed2000

Universality classes in the random-storage sandpile model

The avalanche statistics in a stochastic sandpile model where toppling takes place with a probability p is investigated. The limiting case p=1 corresponds to the Bak-Tang-Wiesenfeld (BTW) model with a deterministic toppling rule. Based on the moment analysis of the distribution of avalanche sizes we conclude that for 0<p<p(c) the model belongs to the direct percolation universality class while for p(c)<p<1 it belongs to the BTW universality class, where p(c) is identified with the critical probability for directed percolation in the corresponding lattice.

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PubMed1999

Bethe lattice representation for sandpiles.

Avalanches in sandpiles are represented by a process of percolation in a Bethe lattice with a feedback mechanism. The results indicate that the frequency spectrum and probability distribution of avalanches provide a better resemblance to the experimental results than other models using cellular automata simulations. Apparent discrepancies between experiments performed by different authors are reconciled. Critical behavior is expressed here by the critical properties of percolation phenomena.

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