arXiv subjects

G. Giugliarelli

Publications and source records attributed to G. Giugliarelli.

4 recordsLinked to original sources

arXiv1999

Polymer Adsorption on Fractal Walls

Polymer adsorption on fractally rough walls of varying dimensionality is studied by renormalization group methods on hierarchical lattices. Exact results are obtained for deterministic walls. The adsorption transition is found continuous for low dimension $d_w$ of the adsorbing wall and the corresponding crossover exponent $ϕ$ monotonically increases with $d_w$, eventually overcoming previously conjectured bounds. For $d_w$ exceeding a threshold value $d_w^*$, $ϕ$ becomes 1 and the transition turns first--order. $d_w^*>d_{saw}$, the fractal dimension of the polymer in the bulk. An accurate numerical approach to the same problem with random walls gives evidence of the same scenario.

cond-mat.stat-mech↗

arXiv1996

Reentrant Wetting Transition of a Rough Wall

A $2D$ model describing depinning of an interface from a rough, self-affine substrate, is studied by transfer matrix methods. The phase diagram is determined for several values of the roughness exponent, $ζ_S$, of the attractive wall. For all $ζ_S>0$ the following scenario is observed. In first place, in contrast to the case of a flat wall ($ζ_S=0$), for wall attraction energies between zero and a $ζ_S$-dependent positive value, the substrate is always wet. Furthermore, in a small range of attraction energies, a dewetting transition first occurs as T increases, followed by a wetting one. This unusual reentrance phenomenon seems to be a peculiar feature of self-affine roughness, and does not occur, e. g., for periodically corrugated substrates.

cond-mat.stat-mech↗

arXiv1995

Discontinuous Interface Depinning from a Rough Wall

Depinning of an interface from a random self--affine substrate with roughness exponent $ζ_S$ is studied in systems with short--range interactions. In 2$D$ transfer matrix results show that for $ζ_S<1/2$ depinning falls in the universality class of the flat case. When $ζ_S$ exceeds the roughness ($ζ_0=1/2$) of the interface in the bulk, geometrical disorder becomes relevant and, moreover, depinning becomes \underline{discontinuous}. The same unexpected scenario, and a precise location of the associated tricritical point, are obtained for a simplified hierarchical model. It is inferred that, in 3$D$, with $ζ_0=0$, depinning turns first--order already for $ζ_S>0$. Thus critical wetting may be impossible to observe on rough substrates.

cond-mat↗

arXiv1994

Solid--on--Solid Model for Adsorption on Self--Affine Substrate: A Transfer Matrix Approach

We study a $d=2$ discrete solid--on--solid model of complete wetting of a rough substrate with random self--affine boundary, having roughness exponent $ζ_s$. A suitable transfer matrix approach allows to discuss adsorption isotherms, as well as geometrical and thermal fluctuations of the interface. For $ζ_s\leq 1/2$ the same wetting exponent $ψ=1/3$ as for flat substrate is obtained for the dependence of the coverage, $θ$, on the chemical potential, $h$ ($θ\sim h^{-ψ}$ for $h\to 0$). The expected existence of a zero temperature fixed point, leading to $ψ=ζ_s /(2-ζ_s)$ for $ζ_s>1/2$, is verified numerically in spite of an unexpected, very slow convergence to asymptotics.

cond-mat↗