345 research outputs found
Lo sguardo sottile di Viktor Popkov
No full textIl testo traccia il rapporto tra Viktor Popkov e Renato Guttus
Popkov, Viktor Efimovič
No full textLa voce enciclopedica è dedicata all’artista Viktor Efimovič Popkov. La scheda rientra nel progetto avente lo scopo di presentare al pubblico italiano le tendenze e le personalità principali della scena artistica contemporanea russa
Hierarchy of boundary driven phase transitions in multi-species particle systems
No full textLAVORO IN CORSO DI STAMP
Dissipative cooling towards phantom Bethe states in boundary driven XXZ spin chain
No full textA dissipative method that allows to access family of phantom Bethe-states
(PBS) of boundary driven XXZ spin chains, is introduced. The method consists in
coupling the ends of the open spin chain to suitable dissipative magnetic baths
to force the edge spins to satisfy specific boundary conditions necessary for
the PBS existence. Cumulative monotonous depopulation of the non-chiral
components of the density matrix with growing dissipation amplitude is
analogous to the depopulation of high-energy states in response to thermal
cooling. Compared to generic states, PBS have strong chirality, nontrivial
topology and carry high spin currents.Comment: 5 pages, 4 figure
Optimal transport and von Neumann entropy in a Heisenberg XXZ chain out of equilibrium
No full textIn this paper we investigate the spin currents and the von Neumann entropy (vNE) of a Heisenberg XXZ
chain in contact with twisted XY-boundary magnetic reservoirs by means of the Lindblad master equation. Exact
solutions for the stationary reduced density matrix are explicitly constructed for chains of small sizes by using a
quantum symmetry operation of the system. These solutions are then used to investigate the optimal transport in
the chain in terms of the vNE. As a result we show that the maximal spin current always occurs in the proximity
of minima of the vNE and for particular choices of parameters (coupling with reservoirs and anisotropy) it can
exactly coincide with them. As the coupling is increased, current reversals may occur and in the limit of strong
coupling we show that minima of the vNE tend to zero, meaning that the maximal transport is achieved in this
case with states that are very close to pure states
Reduced-density-matrix spectrum and block entropy of permutationally invariant many-body systems
No full textSpectral properties of the reduced density matrix (RDM) of permutational invariant quantum many-body systems are investigated. The RDM block diagonalization which accounts for all symmetries of the Hamiltonian is achieved. The analytical expression of the RDM spectrum is provided for arbitrary parameters and rigorously proved in the thermodynamical limit. The existence of several sum rules and recurrence relations among RDM eigenvalues is also demonstrated and the distribution function of RDM eigenvalues (including degeneracies) characterized. In particular, we prove that the distribution function approaches a two-dimensional Gaussian in the limit of large subsystem sizes n >> 1. As a physical application we discuss the von Neumann entropy (VNE) of a block of size n for a system of hard-core bosons on a complete graph, as a function of n and of the temperature T. The occurrence of a crossover of VNE from purely logarithmic behavior at T=0 to a purely linear behavior in n for T >= T-c, is demonstrated
Anticoarsening and complex dynamics of step bunches on vicinal surfaces during sublimation
No full textHydrodynamic limit of multichain driven diffusive models
No full textA class of models, generalizing asymmetric exclusion process for many parallel interacting channels, is
proposed. We couple the models with boundary reservoirs, study boundary-driven phase transitions, and show
that usually taken hydrodynamic description fails. The adequate hydrodynamic limit is then derived. We
support our findings with Monte Carlo simulations of the original stochastic system
Behavior of magnetic currents in anisotropic Heisenberg spin chains out of equilibrium
No full textThe behavior of the magnetic currents in one-dimensional Heisenberg XXZ spin chains kept out of equilibrium by boundary driving fields is investigated. In particular, the dependence of the spin currents on the anisotropy parameter Delta and on the boundary fields is studied both analytically and numerically in the framework of the Lindblad master equation formalism. We show that the spin current can be maximized with appropriate choices of the boundary fields, and for odd system sizes, N, we demonstrate the existence of additional symmetries that cause the current to be an odd function of Delta. From direct numerical integrations of the quantum master equation, we find that for an arbitrary N the current J(z)(N) vanishes for Delta = 0, while for Delta negative it alternates its sign with the system size. In the gapless critical region |Delta| 1 we find that J(z) (N) similar to exp(-alpha N). A simple mean-field approach, which predicts rather well the values of J(z) (N) for the gapped region and the values of the absolute current maxima in the critical region, is developed. The existence of two different stationary solutions for the mean-field density matrix in the whole parameter range is also demonstrated
Asymmetric simple exclusion process with periodic boundary driving
No full textWe consider the asymmetric simple exclusion process (ASEP) on a semi-infinite chain which is coupled at the end to a reservoir with a particle density that changes periodically in time. It is shown that the density profile assumes a time-periodic sawtoothlike shape. This shape does not depend on initial conditions and is found analytically in the hydrodynamic limit. In a finite system, the stationary state is shown to be governed by effective boundary densities and the extremal flux principle. Effective boundary densities are determined numerically via Monte Carlo simulations and compared with those given by mean-field approach and numerical integration of the hydrodynamic limit equation which is the Burgers equation. Our results extend straightforwardly beyond the ASEP to a wide class of driven diffusive systems with one conserved particle species
- …
