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C F Moukarzel

Publications and source records attributed to C F Moukarzel.

3 recordsLinked to original sources

Shortest paths on systems with power-law distributed long-range connections.

We discuss shortest-path lengths l(r) on periodic rings of size L supplemented with an average of pL randomly located long-range links whose lengths are distributed according to P(l) approximately l(-mu). Using rescaling arguments and numerical simulation on systems of up to 10(7) sites, we show that a characteristic length xi exists such that l(r) approximately r for r >xi. For small p we find that the shortest-path length satisfies the scaling relation l(r,mu,p)/xi=f(mu,r/xi). Three regions with different asymptotic behaviors are found, respectively: (a) mu>2 where theta(s)=1, (b) 1<mu<2 where 0<theta(s)(mu)<1/2, and (c) mu<1 where l(r) behaves logarithmically, i.e., theta(s)=0. The characteristic length xi is of the form xi approximately p(-nu) with nu=1/(2-mu) in region (b), but depends on L as well in region (c). A directed model of shortest paths is solved and compared with numerical results.

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Directed rigidity and bootstrap percolation in 1+1 dimensions.

We study directed rigidity percolation (equivalent to directed bootstrap percolation) on three different lattices: square, triangular, and augmented triangular. The first two of these display a first-order transition at p=1, while the augmented triangular lattice shows a continuous transition at a nontrivial p(c). On the augmented triangular lattice we find, by extensive numerical simulation, that the the directed rigidity percolation transition belongs to the same universality class as the directed percolation. The same conclusion is reached by studying its surface critical behavior, i.e., the spreading of rigidity from finite clusters close to a nonrigid wall. Near the discontinuous transition at p=1 on the triangular lattice, we are able to calculate the finite-size behavior of the density of rigid sites analytically. Our results are confirmed by numerical simulation.

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Spreading and shortest paths in systems with sparse long-range connections.

Spreading according to simple rules (e.g., of fire or diseases) and shortest-path distances are studied on d-dimensional systems with a small density p per site of long-range connections ("small-world" lattices). The volume V(t) covered by the spreading quantity on an infinite system is exactly calculated in all dimensions as a function of time t. From this, the average shortest-path distance l(r) can be calculated as a function of Euclidean distance r. It is found that l(r) approximately r for r r(c). The characteristic length r(c), which governs the behavior of shortest-path lengths, diverges logarithmically with L for all p>0.

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