arXiv subjects

Gabriele Gotti

Publications and source records attributed to Gabriele Gotti.

3 recordsLinked to original sources

arXiv2023

Relaxation dynamics and finite-size effects in a simple model of condensation

We consider a simple, purely stochastic model characterized by two conserved quantities (mass density $a$ and energy density $h$) which is known to display a condensation transition when $h > 2a^2$: in the localized phase a single site hosts a finite fraction of the whole energy. Its equilibrium properties in the thermodynamic limit are known and in a recent paper (Gabriele Gotti, Stefano Iubini, Paolo Politi, Phys. Rev. E 103, 052133 (2021)) we studied the transition for finite systems. Here we analyze finite-size effects on the energy distribution and on the relaxation dynamics, showing that extremely large systems should be studied in order to observe the asymptotic distribution and even larger systems should be simulated in order to observe the expected relaxation dynamics.

cond-mat.stat-mech↗

arXiv2022

Condensation induced by coupled transport processes

Several lattice models display a condensation transition in real space when the density of a suitable order parameter exceeds a critical value. We consider one of such models with two conservation laws, in a one-dimensional open setup where the system is attached to two external reservoirs. Both reservoirs impose subcritical boundary conditions at the chain ends. When such boundary conditions are equal, the system is in equilibrium below the condensation threshold and no condensate can appear. Instead, when the system is kept out of equilibrium, localization may arise in an internal portion of the lattice. We discuss the origin of this phenomenon, the relevance of the number of conservation laws, and the effect of the pinning of the condensate on the dynamics of the out-of-equilibrium state.

cond-mat.stat-mech↗

arXiv2021

Finite-size localization scenarios in condensation transitions

We consider the phenomenon of condensation of a globally conserved quantity $H=\sum_{i=1}^N ε_i$ distributed on $N$ sites, occurring when the density $h= H/N$ exceeds a critical density $h_c$. We numerically study the dependence of the participation ratio $Y_2=\langle ε_i^2\rangle/(Nh^2)$ on the size $N$ of the system and on the control parameter $δ= (h-h_c)$, for various models: (i)~a model with two conservation laws, derived from the Discrete NonLinear Schrödinger equation; (ii)~the continuous version of the Zero Range Process class, for different forms of the function $f(ε)$ defining the factorized steady state. Our results show that various localization scenarios may appear for finite $N$ and close to the transition point. These scenarios are characterized by the presence or the absence of a minimum of $Y_2$ when plotted against $N$ and by an exponent $γ\geq 2$ defined through the relation $N^* \simeq δ^{-γ}$, where $N^*$ separates the delocalized region ($N\ll N^*$, $Y_2$ vanishes with increasing $N$) from the localized region ($N\gg N^*$, $Y_2$ is approximately constant). We finally compare our results with the structure of the condensate obtained through the single-site marginal distribution.

cond-mat.stat-mech↗