arXiv subjects

Leticia Cugliandolo

Publications and source records attributed to Leticia Cugliandolo.

8 recordsLinked to original sources

arXiv2026

Active Quantum Particles from Engineered Dissipation

We introduce and characterize different models for an active quantum particle where activity arises from engineered dissipation-- specifically, from a suitably coupled nonequilibrium environment. These include a model of a particle moving on a lattice with coherent and dissipative hopping, as well as quantum generalizations of well-studied models of active behavior, such as the active Ornstein-Uhlenbeck process, run-and-tumble dynamics, and the active Brownian particle. Despite the different microscopic mechanisms at play, we show that all these models display key features of active motion. Notably, we observe a crossover from diffusive to active-diffusive behavior at long times, leading to an effective Péclet number, as well as a strong sensitivity to boundary conditions which, in our open quantum system context, arises from the Liouville skin effect. We discuss the role of quantum fluctuations and experimental realizations with superconducting circuits or cold gases, closing with perspectives for many-body effects in quantum active matter.

quant-ph↗

arXiv2020

A constrained TAP approach for disordered spin models: application to the mixed spherical case

We revisit the metastability properties of the mixed p-spin spherical disordered models. Firstly, using known methods, we show that there is temperature chaos in a broad range of temperatures. Secondly, we modify the definition of the Thouless-Anderson-Palmer free energy density by including constraints that enforce a chosen overlap between the searched metastable states and another reference state, that could be a characteristic one of a different temperature. We argue that this refined analysis provides clues to understand the weird behaviour of the low temperature relaxation dynamics of these models, and suggests ways to improve the treatment of the initial conditions to overcome the difficulties encountered so far.

cond-mat.dis-nn↗

arXiv2009

Fluctuations and effective temperatures in coarsening

We study dynamic fluctuations in non-disordered finite dimensional ferromagnetic systems quenched to the critical point and the low-temperature phase. We investigate the fluctuations of two two-time quantities, called $χ$ and $C$, the averages of which %$<χ>$, $ $ yield the self linear response and correlation function. We introduce a restricted average of the $χ$'s, summing over all configurations with a given value of $C$. We find that the restricted average $<χ>_C$ obeys a scaling form, and that the slope of the scaling function approaches the universal value $X_\infty $ of the limiting effective temperature in the long-time limit and for $C\to 0$. Our results tend to confirm the expectation that time-reparametrization invariance is not realized in coarsening systems at criticality. Finally, we discuss possible experimental tests of our proposal.

cond-mat.stat-mech↗

arXiv2008

Driven quantum coarsening

We study the driven dynamics of quantum coarsening. We analyze models of M-component rotors coupled to two electronic reservoirs at different chemical potentials that generate a current threading through the system. In the large M limit we derive the dynamical phase diagram as a function of temperature, strength of quantum fluctuations, voltage and coupling to the leads. We show that the slow relaxation in the ordering phase is universal. On large time and length scales the dynamics are analogous to stochastic classical ones, even for the quantum system driven out of equilibrium at zero temperature. We argue that our results apply to generic driven quantum coarsening.

cond-mat.dis-nn↗

arXiv2005

Out-of-equilibrium dynamics of the vortex glass

We study the relaxational dynamics of flux lines in high-temperature superconductors with random pinning using Langevin dynamics. At high temperatures the dynamics is stationary and the fluctuation dissipation theorem (FDT) holds. At low temperatures the system does not equilibrate with its thermal bath: a simple multiplicative aging is found, the FDT is violated and we found that an effective temperature characterizes the slow modes of the system. The generic features of the evolution -- scaling laws -- are dictated by the ones of the single elastic line in a random environment.

cond-mat.supr-con↗

arXiv2004

Memory effects in classical and quantum mean-field disordered models

We apply the Kovacs experimental protocol to classical and quantum p-spin models. We show that these models have memory effects as those observed experimentally in super-cooled polymer melts. We discuss our results in connection to other classical models that capture memory effects. We propose that a similar protocol applied to quantum glassy systems might be useful to understand their dynamics.

cond-mat.dis-nn↗

arXiv2002

Effective temperature in driven vortex lattices with random pinning

We study numerically correlation and response functions in non-equilibrium driven vortex lattices with random pinning. From a generalized fluctuation-dissipation relation we calculate an effective transverse temperature in the fluid moving phase. We find that the effective temperature decreases with increasing driving force and becomes equal to the equilibrium melting temperature when the dynamic transverse freezing occurs. We also discuss how the effective temperature can be measured experimentally from a generalized Kubo formula.

cond-mat.supr-con↗

arXiv1995

Mode-Coupling Approximations, Glass Theory and Disordered Systems

We discuss the general link between mode-coupling like equations (which serve as the basis of some recent theories of supercooled liquids) and the dynamical equations governing mean-field spin-glass models, or the dynamics of a particle in a random potential. The physical consequences of this interrelation are underlined. It suggests to extend the mode-coupling approximation to temperatures well below the freezing temperature, in which aging effects become important. In this regime we suggest some new experiments in order to test a non-trivial prediction of the Mode-Coupling picture, which is a generalized relation between the short ($β$) and long ($α$) time regimes.

cond-mat↗