arXiv subjects

Juan M. Lopez

Publications and source records attributed to Juan M. Lopez.

22 records · Page 2Linked to original sources

arXiv1998

Nonequilibrium roughening transition in a simple model of fungal growth in 1+1 dimensions

We introduce a simple model of yeast-like growth of fungi colonies, which exhibits a continuous roughening transition far from equilibrium from a smooth ($α= 0$) to rough phase ($α= 1/2$) in 1+1 dimensions. At the transition some scaling exponents are calculated by mapping the problem onto a directed percolation process. The model reproduces the roughening transition observed in some experiments of fungal growth

cond-mat.stat-mech↗

arXiv1998

Anomalous Scaling of Fracture Surfaces

We argue that fracture surfaces may exhibit anomalous dynamic scaling properties akin to what occurs in some models of kinetic roughening. We determine the complete scaling behavior of the local fluctuations of a brittle fracture in a granite block from experimental data. We obtain a global roughness exponent $χ= 1.2$ which differs from the local one, $χ_{loc} = 0.79$. Implications on fracture physics are discussed.

cond-mat.stat-mech↗

arXiv1997

Interface dynamics at the depinning transition

We study the local scaling properties of driven interfaces in disordered media modeled by the Edwards-Wilkinson equation with quenched noise. We find that, due to the super-rough character of the interface close to the depinning transition, the local width exhibits an anomalous temporal scaling. It does not saturate at a characteristic time $t_s(l) \sim l^z$ as expected, but suffers an anomalous temporal crossover to a different time regime $t^{β_*}$, where $β_* \simeq 0.21 $. This is associated with the existence of a local roughness exponent $α_{loc} \simeq 1$ that differs from the global one $α\simeq 1.2$. The relevance of the typical size of pinned sites regions near the critical point is investigated and the definition of the critical depinning is dicussed.

cond-mat↗

arXiv1997

Super-roughening versus intrinsic anomalous scaling of surfaces

In this paper we study kinetically rough surfaces which display anomalous scaling in their local properties such as roughness, or height-height correlation function. By studying the power spectrum of the surface and its relation to the height-height correlation, we distinguish two independent causes for anomalous scaling. One is super-roughening (global roughness exponent larger than or equal to one), even if the spectrum behaves non anomalously. Another cause is what we term an intrinsically anomalous spectrum, in whose scaling an independent exponent exists, which induces different scaling properties for small and large length scales (that is, the surface is not self-affine). In this case, the surface does not need to be super-rough in order to display anomalous scaling. In both cases, we show how to extract the independent exponents and scaling relations from the correlation functions, and we illustrate our analysis with two exactly solvable examples. One is the simplest linear equation for molecular beam epitaxy , well known to display anomalous scaling due to super-roughening. The second example is a random diffusion equation, which features anomalous scaling independent of the value of the global roughness exponent below or above one.

cond-mat.stat-mech↗