arXiv subjects

M. J. Alava

Publications and source records attributed to M. J. Alava.

42 records · Page 3Linked to original sources

arXiv2000

Energy landscapes in random systems, driven interfaces and wetting

We discuss the zero-temperature susceptibility of elastic manifolds with quenched randomness. It diverges with system size due to low-lying local minima. The distribution of energy gaps is deduced to be constant in the limit of vanishing gaps by comparing numerics with a probabilistic argument. The typical manifold response arises from a level-crossing phenomenon and implies that wetting in random systems begins with a discrete transition. The associated ``jump field'' scales as $ \sim L^{-5/3}$ and $L^{-2.2}$ for (1+1) and (2+1) dimensional manifolds with random bond disorder.

cond-mat.dis-nn↗

arXiv2000

Self-organized criticality and interface depinning transitions

We discuss the relation between self-organized criticality and depinning transitions by mapping sandpile models to equations that describe driven interfaces in random media. This equivalence yields a continuum description and gives insight about various ways of reaching the depinning critical point: slow drive (self-organized criticality), fixed density simulations, tuning the interface velocity (extremal drive criticality), or tuning the driving force. We obtain a scaling relation for the correlation length exponent for sandpiles.

cond-mat.stat-mech↗

arXiv1998

Disorder, Order, and Domain Wall Roughening in the 2d Random Field Ising Model

Ground states and domain walls are investigated with exact combinatorial optimization in two-dimensional random field Ising magnets. The ground states break into domains above a length scale that depends exponentially on the random field strength squared. For weak disorder, this paramagnetic structure has remnant long-range order of the percolation type. The domain walls are super-rough in ordered systems with a roughness exponent $ζ$ close to 6/5. The interfaces exhibit rare fluctuations and multiscaling reminiscent of some models of kinetic roughening and hydrodynamic turbulence.

cond-mat.dis-nn↗

arXiv1998

Quasi-static cracks and minimal energy surfaces

We compare the roughness of minimal energy(ME) surfaces and scalar ``quasi-static'' fracture surfaces(SQF). Two dimensional ME and SQF surfaces have the same roughness scaling, w sim L^zeta (L is system size) with zeta = 2/3. The 3-d ME and SQF results at strong disorder are consistent with the random-bond Ising exponent zeta (d >= 3) approx 0.21(5-d) (d is bulk dimension). However 3-d SQF surfaces are rougher than ME ones due to a larger prefactor. ME surfaces undergo a ``weakly rough'' to ``algebraically rough'' transition in 3-d, suggesting a similar behavior in fracture.

cond-mat↗

arXiv1995

Growth and Structure of Random Fibre Clusters and Cluster Networks

We study the properties of 2D fibre clusters and networks formed by deposition processes. We first examine the growth and scaling properties of single clusters. We then consider a network of such clusters, whose spatial distribution obeys some effective pair distribution function. In particular, we derive an expression for the two-point density autocorrelation function of the network, which includes the internal structure of a cluster and the effective cluster-cluster pair distribution function. This formula can be applied to obtain information about nontrivial correlations in fibre networks.

cond-mat↗

arXiv1994

Planar random networks with flexible fibers

The transition in random fiber networks from two-dimensional to three-dimensional planar structure driven by increasing coverage (total fiber length per unit area) is studied with a deposition model. At low coverage the network geometry depends on the scale-free product of fiber length and coverage while at high coverage it depends on a scale-free combination of flexibility, width and thickness of the fibers. With increasing coverage the roughness of the free surface decouples from the substrate, faster when fibers are stiffer. In the high coverage region roughness decreases exponentially with increasing fiber flexibility.

cond-mat↗