80 results on '"Dragi Karevski"'
Search Results
2. Some speculations about local thermalization of nonequilibrium extended quantum systems
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Michele Coppola and Dragi Karevski
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Physics and Astronomy (miscellaneous) ,Statistical Mechanics (cond-mat.stat-mech) ,FOS: Physical sciences ,Condensed Matter Physics ,Condensed Matter - Statistical Mechanics - Abstract
We discuss the possibility of defining an emergent local temperature in extended quantum many-body systems evolving out of equilibrium. For the most simple case of free-fermionic systems, we give an explicit formula for the effective temperature in the case of, not necessarily unitary, Gaussian preserving dynamics. In this framework, we consider the hopping fermions on a one-dimensional lattice submitted to randomly distributed projective measurements of the local occupation numbers. We show from the average over many quantum trajectories that the effective temperature relaxes exponentially towards infinity., 13 pages, 1 figure
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- 2023
3. Scaling of fronts and entanglement spreading during a domain wall melting
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Stefano Scopa and Dragi Karevski
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Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,General Physics and Astronomy ,FOS: Physical sciences ,General Materials Science ,Physical and Theoretical Chemistry ,Quantum Physics (quant-ph) ,Condensed Matter - Statistical Mechanics - Abstract
We revisit the out-of-equilibrium physics arising during the unitary evolution of a one-dimensional XXZ spin chain initially prepared in a domain wall state $\vert\psi_0\rangle=\vert\dots \uparrow\uparrow\downarrow\downarrow\dots\rangle$. In absence of interactions, we review the exact lattice calculation of several conserved quantities, including e.g. the magnetization and the spin current profiles. At large distances $x$ and times $t$, we show how these quantities allow for a ballistic scaling behavior in terms of the scaling variable $\zeta= x/t$, with exactly computable scaling functions. In such a limit of large space-time scales, we show that the asymptotic behavior of the system is suitably captured by the local occupation function of spinless fermionic modes, whose semi-classical evolution in phase space is given by a Euler hydrodynamic equation. Similarly, analytical results for the asymptotic fronts dynamics are obtained for the interacting chain via Generalized Hydrodynamics. In the last part of the work, we include large-scale quantum fluctuations on top of the semi-classical hydrodynamic background in the form of a conformal field theory that lives along the evolving Fermi contour. With this procedure, dubbed quantum generalized hydrodynamics, it is possible to obtain exact asymptotic results for the entanglement spreading during the melting dynamics., Comment: 40 pages, 9 figures; To appear in Eur. Phys. J. Spec. Top
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- 2023
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4. Wigner dynamics for quantum gases under inhomogeneous gain and loss processes with dephasing
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Michele Coppola, Gabriel T. Landi, Dragi Karevski, and HEP, INSPIRE
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Statistical Mechanics (cond-mat.stat-mech) ,Quantum Gases (cond-mat.quant-gas) ,FOS: Physical sciences ,Condensed Matter - Quantum Gases ,Condensed Matter - Statistical Mechanics ,[PHYS.COND] Physics [physics]/Condensed Matter [cond-mat] - Abstract
We present a Wigner function-based approach for the particle density evolution in fermionic and bosonic open quantum many-body systems, including the effects of dephasing. In particular, we focus on chains of non-interacting particles coupled to Lindblad baths. The dissipative processes, described by linear and quadratic jump operators, are modulated by inhomogeneous couplings. Following a semi-classical approach, we find the differential equation governing the Wigner function evolution, which can be solved in closed form in some particular cases. We check the accuracy of the Wigner approach in different scenarios (i.e. Gaussian jump rates), describing the density evolution and the transport phenomena in terms of classical quasi-particles., 12 pages, 8 figures
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- 2023
5. Gradient corrections to the local-density approximation in the one-dimensional Bose gas
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François Riggio, Yannis Brun, Dragi Karevski, Alexandre Faribault, and Jérôme Dubail
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Condensed Matter::Quantum Gases ,Quantum Gases (cond-mat.quant-gas) ,FOS: Physical sciences ,Condensed Matter - Quantum Gases - Abstract
The local density approximation (LDA) is the central technical tool in the modeling of quantum gases in trapping potentials. It consists in treating the gas as an assembly of independent mesoscopic fluid cells at equilibrium with a local chemical potential, and it is justified when the correlation length is larger than the size of the cells. The LDA is often regarded as a crude approximation, particularly in the ground state of the one-dimensional (1D) Bose gas, { where the correlation length is "therefore said to be" infinite (in the sense that correlation functions decay as a power law).} Here we take another look at the LDA. The local density $\rho(x)$ is viewed as a functional of the trapping potential $V(x)$, to which one applies a gradient expansion. The zeroth order in that expansion is the LDA. The first-order correction in the gradient expansion vanishes due to reflection symmetry. At second order, there are two corrections proportional to $d^2V/dx^2$ and $(dV/dx)^2$, and we propose a method to determine the corresponding coefficients by a perturbative calculation in the Lieb-Liniger model. This leads to an expression for the coefficients in terms of matrix elements of the density operator, which can in principle be evaluated numerically for an arbitrary coupling constant; here we show how to efficiently evaluate the coefficient associated to the curvature of the potential $d^2V/dx^2$, which dominates the deviation to LDA near local minima or maxima of the trapping potential. Both coefficients are evaluated analytically in the limits of infinite repulsion (hard-core bosons) and small repulsion (quasi-condensate).} The corrected LDA density profiles are compared to DMRG calculations, with significant improvement compared to zeroth-order LDA., Comment: accepted version, 17 pages, 8 figures. Substantial revision including a discussion on the validity of the LDA in the introduction and the numerical calculation of the second coefficient in appendix C
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- 2022
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6. Growth of entanglement entropy under local projective measurements
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Michele Coppola, Emanuele Tirrito, Dragi Karevski, and Mario Collura
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Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,FOS: Physical sciences ,Quantum Physics (quant-ph) ,Condensed Matter - Statistical Mechanics ,Settore FIS/03 - Fisica della Materia - Abstract
Non-equilibrium dynamics of many-body quantum systems under the effect of measurement protocols is attracting an increasing amount of attention. It has been recently revealed that measurements may induce an abrupt change in the scaling-law of the bipartite entanglement entropy, thus suggesting the existence of different non-equilibrium regimes. However, our understanding of how these regimes appear and whether they survive in the thermodynamic limit is much less established. Here we investigate these questions on a one-dimensional quadratic fermionic model: this allows us to reach system sizes relevant in the thermodynamic sense. We show that local projective measurements induce a qualitative modification of the time-growth of the entanglement entropy which changes from linear to logarithmic. However, in the stationary regime, the logarithmic behavior of the entanglement entropy do not survive in the thermodynamic limit and, for any finite value of the measurement rate, we numerically show the existence of a single area-law phase for the entanglement entropy. Finally, exploiting the quasi-particle picture, we further support our results analysing the fluctuations of the stationary entanglement entropy and its scaling behavior., Comment: 9 pages, 9 figures
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- 2022
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7. Точные результаты для изотропной цепочки Гейзенберга спина $1/2$ с диссипацией на границах
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Dragi Karevski, Gunter M. Schütz, and Vladislav Popkov
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- 2019
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8. Dynamical phase transitions in annihilating random walks with pair deposition
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Gunter Schütz and Dragi Karevski
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Statistics and Probability ,Modeling and Simulation ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,Mathematical Physics - Abstract
Exact results are presented for conditioned dynamics in a system of interacting random walks in one dimension that annihilate immediately when two particles meet on the same site and where pairs of particles are deposited randomly on neighbouring sites. For an atypical hopping activity one finds dynamical nonequilibrium phase transitions analogous to the zero-temperature equilibrium phase transitions that appear in the spin-1/2 quantum XY spin chain in a transverse magnetic field. Along the critical line the approach of the particle density to its stationary value is algebraic with an unexpected mean field exponent. The time-dependent local stationary density correlations are universal with dynamical exponent z = 1. Inside the disordered phase spatially oscillating correlations appear below the typical activity.
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- 2022
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9. Charge-current correlation equalities for quantum systems far from equilibrium
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Gunter M. Schütz, Dragi Karevski, Laboratoire de Physique et Chimie Théoriques (LPCT), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, and Helmholtz-Gemeinschaft = Helmholtz Association
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Physics ,[PHYS]Physics [physics] ,Current (mathematics) ,Statistical Mechanics (cond-mat.stat-mech) ,82C10 ,Space dimension ,Charge current ,Lattice (group) ,FOS: Physical sciences ,General Physics and Astronomy ,01 natural sciences ,Symmetry (physics) ,lcsh:QC1-999 ,010305 fluids & plasmas ,Correlation ,0103 physical sciences ,ddc:530 ,Autocatalytic reaction ,010306 general physics ,Quantum ,Condensed Matter - Statistical Mechanics ,lcsh:Physics ,Mathematical physics - Abstract
We prove that a recently derived correlation equality between conserved charges and their associated conserved currents for quantum systems far from equilibrium [O.A. Castro-Alvaredo et al., Phys. Rev. X \textbf{6}, 041065 (2016)], is valid under more general conditions than assumed so far. Similar correlation identities, which in generalized Gibbs ensembles give rise to a current symmetry somewhat reminiscent of the Onsager relations, turn out to hold also in the absence of translation invariance, for lattice models, and in any space dimension, and to imply a symmetry of the non-equilibrium linear response functions., 6 pages, major revision with extension to non-translation invariant setting
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- 2019
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10. Exact solution of time-dependent Lindblad equations with closed algebras
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Gabriel T. Landi, Stefano Scopa, Dragi Karevski, Adam Hammoumi, Laboratoire de Physique et Chimie Théoriques (LPCT), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Floquet theory ,Physics ,[PHYS]Physics [physics] ,Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,FOS: Physical sciences ,01 natural sciences ,010305 fluids & plasmas ,Classical mechanics ,Exact solutions in general relativity ,Qubit ,0103 physical sciences ,Master equation ,Dissipative system ,TERMODINÂMICA (FÍSICO-QUÍMICA) ,010306 general physics ,Quantum thermodynamics ,Quantum Physics (quant-ph) ,Quantum ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS ,Quantum computer - Abstract
Time-dependent Lindblad master equations have important applications in areas ranging from quantum thermodynamics to dissipative quantum computing. In this paper we outline a general method for writing down exact solutions of time-dependent Lindblad equations whose superoperators form closed algebras. We focus on the particular case of a single qubit and study the exact solution generated by both coherent and incoherent mechanisms. We also show that if the time-dependence is periodic, the problem may be recast in terms of Floquet theory. As an application, we give an exact solution for a two-levels quantum heat engine operating in a finite-time., Comment: 15 pages, 12 figures
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- 2019
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11. Exact Results for the Isotropic Spin-1/2 Heisenberg Chain With Dissipative Boundary Driving
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V. Yu. Popkov, Gunter M. Schütz, Dragi Karevski, Helmholtz Institute for Radiation and Nuclear Physics, University of Bonn, Institut für Theoretische Physik [Köln], Universität zu Köln, Laboratoire de Physique et Chimie Théoriques (LPCT), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, Institut Jean Lamour (IJL), and Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,Spins ,Isotropy ,Non-equilibrium thermodynamics ,Statistical and Nonlinear Physics ,01 natural sciences ,Magnetization ,Quantum mechanics ,0103 physical sciences ,Dissipative system ,010307 mathematical physics ,010306 general physics ,Spin (physics) ,Mathematical Physics ,Quantum fluctuation ,ComputingMilieux_MISCELLANEOUS ,Ansatz - Abstract
International audience; We consider the open isotropic spin-1/2 Heisenberg quantum spin chain with a finite number N of sites coupled at the ends to a dissipative environment that favors polarization of the boundary spins in different directions. We review the matrix product ansatz (MPA) that yields the exact reduced density matrix of the Heisenberg chain. We develop the matrix algebra coming from the MPA in more detail than in previous work. We hence obtain exact results for the nonequilibrium partition function, about the impact of quantum fluctuations on the targeted boundary states, and for current–magnetization correlations in the steady state. The boundary states turn out to be pure to the order o(N−2). We show that the local magnetization and the local current perpendicular to the plane spanned by the boundary polarizations exhibit long-range correlations while the local magnetization correlations with the local in-plane currents are strongly suppressed.
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- 2019
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12. Lindblad-Floquet description of finite-time quantum heat engines
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Stefano Scopa, Gabriel T. Landi, Dragi Karevski, Laboratoire de Physique et Chimie Théoriques (LPCT), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Universidade de São Paulo (USP)
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Floquet theory ,Physics ,[PHYS]Physics [physics] ,Work (thermodynamics) ,Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,FOS: Physical sciences ,01 natural sciences ,010305 fluids & plasmas ,symbols.namesake ,Limit cycle ,0103 physical sciences ,Master equation ,Convergence (routing) ,symbols ,Statistical physics ,010306 general physics ,Carnot cycle ,Quantum Physics (quant-ph) ,Eigenvalues and eigenvectors ,Harmonic oscillator ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS - Abstract
The operation of autonomous finite-time quantum heat engines rely on the existence of a stable limit cycle in which the dynamics becomes periodic. The two main questions that naturally arise are therefore whether such a limit cycle will eventually be reached and, once it has, what is the state of the system within the limit cycle. In this paper we show that the application of Floquet's theory to Lindblad dynamics offers clear answers to both questions. By moving to a generalized rotating frame, we show that it is possible to identify a single object, the Floquet Liouvillian, which encompasses all operating properties of the engine. First, its spectrum dictates the convergence to a limit cycle. And second, the state within the limit cycle is precisely its zero eigenstate, therefore reducing the problem to that of determining the steady-state of a time-independent master equation. To illustrate the usefulness of this theory, we apply it to a harmonic oscillator subject to a time-periodic work protocol and time-periodic dissipation, an open-system generalization of the Ermakov-Lewis theory. The use of this theory to implement a finite-time Carnot engine subject to continuous frequency modulations is also discussed.
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- 2018
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13. Dynamics of entanglement creation between two spins coupled to a chain
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Pierre Wendenbaum, Dragi Karevski, Giovanna Morigi, Bruno G. Taketani, E. Kajari, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Universität des Saarlandes [Saarbrücken], Departamento de Física [Universidade Federal de Santa Catarina], Universidade Federal de Santa Catarina = Federal University of Santa Catarina [Florianópolis] (UFSC), Laboratoire de Physique et Chimie Théoriques (LPCT), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,Physics ,Density matrix ,Quantum Physics ,Spins ,Thermal reservoir ,Time evolution ,General Physics and Astronomy ,FOS: Physical sciences ,Quantum entanglement ,Coupling (probability) ,01 natural sciences ,010305 fluids & plasmas ,Chain (algebraic topology) ,Quantum mechanics ,0103 physical sciences ,Ising model ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,Quantum Physics (quant-ph) ,ComputingMilieux_MISCELLANEOUS - Abstract
We study the dynamics of entanglement between two spins which is created by the coupling to a common thermal reservoir. The reservoir is a spin-$\frac{1}{2}$ Ising transverse field chain thermally excited, the two defect spins couple to two spins of the chain which can be at a macroscopic distance. In the weak-coupling and low-temperature limit the spin chain is mapped onto a bath of linearly interacting oscillators using the Holstein-Primakoff transformation. We analyse the time evolution of the density matrix of the two defect spins for transient times and deduce the entanglement which is generated by the common reservoir. We discuss several scenarios for different initial states of the two spins and for varying distances., Comment: 16 pages, 5 figures
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- 2018
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14. Conformal Invariance in Driven Diffusive Systems at High Currents
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Dragi Karevski, Gunter M. Schütz, Laboratoire de Physique et Chimie Théoriques (LPCT), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, and Helmholtz-Gemeinschaft = Helmholtz Association
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Physics ,[PHYS]Physics [physics] ,Phase transition ,Statistical Mechanics (cond-mat.stat-mech) ,Conformal field theory ,Probability (math.PR) ,FOS: Physical sciences ,General Physics and Astronomy ,82C26, 82C27, 82C22 ,Invariant (physics) ,Renormalization group ,Asymmetric simple exclusion process ,01 natural sciences ,010305 fluids & plasmas ,Classical mechanics ,Conformal symmetry ,0103 physical sciences ,FOS: Mathematics ,ddc:550 ,Exponent ,010306 general physics ,Central charge ,Condensed Matter - Statistical Mechanics ,Mathematics - Probability ,ComputingMilieux_MISCELLANEOUS - Abstract
We consider space-time correlations in driven diffusive systems which undergo a fluctuation into a regime with an atypically large current or dynamical activity. For a single conserved mass we show that the spatio-temporal density correlations in one space dimension are given by conformally invariant field theories with central charge $c=1$, corresponding to a ballistic universality class with dynamical exponent $z=1$. We derive a phase diagram for atypical behaviour that besides the conformally invariant regime exhibits a regime of phase separation for atypically low current or activity. On the phase transition line, corresponding to typical behaviour, the dynamics belongs to the Kardar-Parisi-Zhang universality class with dynamical exponent $z=3/2$, except for a diffusive point with $z=2$. We demonstrate the validity of the theory for the one-dimensional asymmetric simple exclusion process with both periodic and open boundaries by exact results for the dynamical structure in the limit of maximal current., 5 pages, 2 figures. Revision with typo in Eq. (1) corrected and some cosmetic changes
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- 2017
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15. Matrix Product Ansatz for Non-equilibrium Quantum Steady States
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Gunter M. Schütz, Vladislav Popkov, Dragi Karevski, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Helmholtz-Institut für Strahlen- und Kernphysik (HISKP), Rheinische Friedrich-Wilhelms-Universität Bonn, Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, and Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,Physics ,Quantum discord ,Lindblad equation ,Quantum dynamics ,Density matrix renormalization group ,Quantum entanglement ,01 natural sciences ,010305 fluids & plasmas ,Classical mechanics ,Quantum mechanics ,Quantum process ,0103 physical sciences ,Quantum algorithm ,010306 general physics ,Quantum dissipation ,ComputingMilieux_MISCELLANEOUS - Abstract
We present a general construction of matrix product states for stationary density matrices of one-dimensional quantum spin systems kept out of equilibrium through boundary Lindblad dynamics. As an application we review the isotropic Heisenberg quantum spin chain which is closely related to the generator of the simple symmetric exclusion process. Exact and heuristic results as well as numerical evidence suggest a local quantum equilibrium and long-range correlations reminiscent of similar large-scale properties in classical stochastic interacting particle systems that can be understood in terms of fluctuating hydrodynamics.
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- 2017
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16. Fluctuations of the heat exchanged between two quantum spin chains
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Gabriel T. Landi, Dragi Karevski, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Quantum phase transition ,Coupling ,Physics ,[PHYS]Physics [physics] ,Statistical Mechanics (cond-mat.stat-mech) ,Condensed matter physics ,Characteristic function (probability theory) ,FOS: Physical sciences ,Non-equilibrium thermodynamics ,7. Clean energy ,01 natural sciences ,010305 fluids & plasmas ,Quantum mechanics ,0103 physical sciences ,Thermodynamic limit ,Probability distribution ,010306 general physics ,Quantum ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS ,Spin-½ - Abstract
The statistics of the heat exchanged between two quantum XX spin chains prepared at different temperatures is studied within the assumption of weak coupling. This provides simple formulas for the average heat and its corresponding characteristic function, from which the probability distribu- tion may be computed numerically. These formulas are valid for arbitrary sizes and therefore allow us to analyze the role of the thermodynamic limit in this non-equilibrium setting. It is found that all thermodynamic quantities are extremely sensitive to the quantum phase transition of the XX chain.
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- 2016
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17. Quantum Field Theory and Condensed Matter. An Introduction. By Ramamurti Shankar. Cambridge University Press, 2017. Pp. 450. Price GBP 59.99 (hardback). ISBN 9780521592109
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Dragi Karevski, Laboratoire de Physique et Chimie Théoriques (LPCT), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,Physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,010403 inorganic & nuclear chemistry ,Condensed Matter Physics ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Inorganic Chemistry ,Structural Biology ,General Materials Science ,Physical and Theoretical Chemistry ,Quantum field theory ,0210 nano-technology ,ComputingMilieux_MISCELLANEOUS ,Mathematical physics - Abstract
International audience
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- 2018
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18. Molecular traffic control for a cracking reaction
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Gunter M. Schütz, Dragi Karevski, R. Harish, Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, Indira Gandhi Centre for Atomic Research, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,010405 organic chemistry ,Chemistry ,Monte Carlo method ,Thermodynamics ,010402 general chemistry ,Fluid catalytic cracking ,01 natural sciences ,Catalysis ,Grain size ,0104 chemical sciences ,Reaction rate ,Cracking ,Lattice (order) ,[CHIM]Chemical Sciences ,Physical chemistry ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Porosity ,ComputingMilieux_MISCELLANEOUS - Abstract
We investigate the conditions for reactivity enhancement of a catalytic cracking process in porous crystalline solids using the concept of molecular traffic control (MTC). Using dynamic Monte Carlo simulations we obtain a quantitative description of the MTC effect for a bimodal network of intersecting size-selective channels over a wide range of grain parameters, diffusivities and reaction constants, and external operating conditions. The results are compared with those obtained on a similar network but with only one type of channels, called the reference system. We find significant reactivity enhancement in the MTC system with respect to the reference system. This effect is observed to increase with the grain size, and also with longer segments between lattice intersections. We find that in certain regions of the microscopic reaction rate the reactivity enhancement is up to 68%.
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- 2008
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19. Entanglement replication via quantum repeated interactions
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Dragi Karevski, Thierry Platini, Pierre Wendenbaum, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Coventry University
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Physics ,Length scale ,Quantum Physics ,Quantum decoherence ,FOS: Physical sciences ,Quantum entanglement ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,Atomic and Molecular Physics, and Optics ,Exponential growth ,Quantum mechanics ,Driving current ,Nonequilibrium steady state ,Quantum Physics (quant-ph) ,Quantum - Abstract
International audience; We study entanglement creation between two independent XX chains, which are repeatedly coupled locally to spin-1/2 Bell pairs. We show analytically that in the steady state the entanglement of the Bell pairs is perfectly transferred to the chains, generating large-scale interchain pair correlations. However, before the steady state is reached, within a growing causal region around the interacting locus the chains are found in a current driven nonequilibrium steady state (NESS). In the NESS, the chains cross entanglement decays exponentially with respect to the distance to the boundary sites with a typical length scale which is inversely proportional to the driving current.
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- 2015
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20. Open Heisenberg chain under boundary fields: A magnonic logic gate
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Dragi Karevski, Gabriel T. Landi, Universidade Federal do ABC Santo André, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,Quantum phase transition ,Quantum Physics ,Condensed matter physics ,Statistical Mechanics (cond-mat.stat-mech) ,Boundary (topology) ,FOS: Physical sciences ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Exact solutions in general relativity ,Chain (algebraic topology) ,Quantum mechanics ,Logic gate ,Condensed Matter::Strongly Correlated Electrons ,Quantum Physics (quant-ph) ,Quantum ,Condensed Matter - Statistical Mechanics ,Spin-½ - Abstract
International audience; We study the spin transport in the quantum Heisenberg spin chain subject to boundary magnetic fields and driven out of equilibrium by Lindblad dissipators. An exact solution is given in terms of matrix product states, which allows us to calculate exactly the spin current for any chain size. It is found that the system undergoes a discontinuous spin-valve-like quantum phase transition from ballistic to subdiffusive spin current, depending on the value of the boundary fields. Thus, the chain behaves as an extremely sensitive magnonic logic gate operating with the boundary fields as the base element.
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- 2015
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21. Out of equilibrium process in Ising quantum chains
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Thierry Platini, Dragi Karevski, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,Physics ,History ,Condensed matter physics ,Spins ,Relaxation (NMR) ,01 natural sciences ,010305 fluids & plasmas ,Computer Science Applications ,Education ,Magnetization ,Chain (algebraic topology) ,Quantum mechanics ,0103 physical sciences ,Thermal ,Ising model ,010306 general physics ,Quantum ,Scaling ,ComputingMilieux_MISCELLANEOUS - Abstract
In this paper we present the results obtained concerning the relaxation behaviour of a non equilibrium Ising quantum chain. In particular, we have focues our attention into the transverse magnetization. The out-of-equilibriumness is generated by setting up an initial thermal inhomogeneity. We present two different initial conditions: a completely factorized state, where all the spins are thermalized independently and second a system-bath case, where half of the chain called the system is thermalized at a temperature Ts and the remaining half is at a temperature Tb. In both cases, the magnetization profiles are calculated either analytically or numerically and show a scaling behaviour. It is also found that in the two-temperature case the magnetization relaxes in quantized steps in the strong transverse field region.
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- 2006
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22. One-dimensional Bose gas driven by a slow time-dependent harmonic trap
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Dragi Karevski, Stefano Scopa, Laboratoire de Physique et Chimie Théoriques (LPCT), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Statistics and Probability ,Length scale ,Bose gas ,FOS: Physical sciences ,General Physics and Astronomy ,01 natural sciences ,Power law ,010305 fluids & plasmas ,Trap (computing) ,0103 physical sciences ,010306 general physics ,ComputingMilieux_MISCELLANEOUS ,Condensed Matter - Statistical Mechanics ,Mathematical Physics ,[PHYS]Physics [physics] ,Condensed Matter::Quantum Gases ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Time evolution ,Statistical and Nonlinear Physics ,Mathematical Physics (math-ph) ,Exact solutions in general relativity ,Amplitude ,Quantum Gases (cond-mat.quant-gas) ,Modeling and Simulation ,Quantum electrodynamics ,Harmonic ,Condensed Matter - Quantum Gases - Abstract
We consider the unitary time evolution of a one-dimensional cloud of hard-core bosons loaded on a harmonic trap potential which is slowly released in time with a general ramp $g(t)$. After the identification of a typical length scale $\ell(t)$, related to the time ramp, we focus our attention on the dynamics of the density profile within a first order time-dependent perturbation scheme. In the special case of a linear ramp, we compare the first order predictions to the exact solution obtained through Ermakov-Lewis dynamical invariants. We also obtain an exact analytical solution for a cloud released from a harmonic trap with an amplitude that varies as the inverse of time. In such situation, the typical size of the cloud grows with a power law governed by an exponent that depends continuously on the initial trap frequency. At high enough initial trap amplitude, the exponent acquires an imaginary part that leads to the emergence of a log-periodic modulation of the cloud expansion., 22 pages, 12 figures
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- 2017
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23. Flux rectification in the quantum XXZ chain
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E. Novais, Gabriel T. Landi, Dragi Karevski, Mário J. de Oliveira, Universidade Federal do ABC Santo André, Instituto de Fisica, Universidade de Sao Paulo, Universidade de São Paulo (USP), Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Field (physics) ,Condensed matter physics ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,Thermal conduction ,01 natural sciences ,010305 fluids & plasmas ,Amplitude ,Rectification ,0103 physical sciences ,Master equation ,Thermodynamic limit ,MECÂNICA ESTATÍSTICA ,010306 general physics ,Anisotropy ,Quantum ,Mathematics - Abstract
International audience; Thermal rectification is the phenomenon by which the flux of heat depends on the direction of the flow. It has attracted much interest in recent years due to the possibility of devising thermal diodes. In this paper, we consider the rectification phenomenon in the quantum XXZ chain subject to an inhomogeneous field. The chain is driven out of equilibrium by the contact at its boundaries with two different reservoirs, leading to a constant flow of magnetization from one bath to the other. The nonunitary dynamics of this system, which is modeled by a Lindblad master equation, is treated exactly for small sizes and numerically for larger ones. The functional dependence of the rectification coefficient on the model parameters (anisotropy, field amplitude, and out of equilibrium driving strength) is investigated in full detail. Close to the XX point and at small inhomogeneity and low driving, we have found an explicit expression for the rectification coefficient that is valid at all system sizes. In particular, it shows that the phenomenon of rectification persists even in the thermodynamic limit. Finally, we prove that in the case of the XX chain, there is no rectification.
- Published
- 2014
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24. Quantum quench from a thermal tensor state: Boundary effects and generalized Gibbs ensemble
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Mario Collura, Dragi Karevski, Dipartimento di Fisica dell'Universita di Pisa and INFN,Pisa, University of Pisa - Università di Pisa, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Physics ,Canonical ensemble ,Statistical Mechanics (cond-mat.stat-mech) ,FOS: Physical sciences ,Condensed Matter Physics ,Coupling (probability) ,3. Good health ,Electronic, Optical and Magnetic Materials ,Settore FIS/03 - Fisica della Materia ,Quantum Gases (cond-mat.quant-gas) ,Quantum mechanics ,Thermodynamic limit ,Tensor ,Boundary value problem ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,Condensed Matter - Quantum Gases ,Quantum statistical mechanics ,Condensed Matter - Statistical Mechanics ,Stationary state ,Energy (signal processing) - Abstract
We consider a quantum quench in a non-interacting fermionic one-dimensional field-theory. The system of size $L$ is initially prepared into two halves $\mathcal{L}$ ($[-L/2,0]$) and $\mathcal{R}$ ($[0,L/2]$), each of them thermalized at two different temperatures, ${T_{L}}$ and ${T_{R}}$ respectively. At a given time the two halves are joined together by a local coupling and the whole system is left to evolve unitarily. For an infinitely extended system ($L\rightarrow \infty$), we show that the time evolution of the particle and energy densities is well described via a hydrodynamic approach which allows us to evaluate the correspondent stationary currents. We show, in such a case, that the two-point correlation functions are deduced, at large times, from a simple non-equilibrium steady state. Otherwise, whenever the boundary conditions are retained (in a properly defined thermodynamic limit), any current is suppressed at large times, and the stationary state is described by a generalized Gibbs ensemble, which is diagonal and depends only on the post-quench mode occupation., 12 pages, 9 figures, Fig.6 improved, Sec. IVC largely modified, Sec. V improved, references added
- Published
- 2014
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- View/download PDF
25. Surface and bulk critical behaviour of theXYchain in a transverse field
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Dragi Karevski, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Physics ,Surface (mathematics) ,Statistical Mechanics (cond-mat.stat-mech) ,Condensed matter physics ,Transverse field ,FOS: Physical sciences ,General Physics and Astronomy ,Nearest neighbour ,Statistical and Nonlinear Physics ,01 natural sciences ,010305 fluids & plasmas ,Magnetization ,Chain (algebraic topology) ,Simple (abstract algebra) ,0103 physical sciences ,010306 general physics ,Quantum ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS ,Mathematical Physics ,Phase diagram - Abstract
The surface magnetization of the quantum XY chain in a transverse field is found for arbitrary nearest neighbour interactions in closed form. This allows to derive the bulk phase diagram in a simple way. The magnetic surface behaviour and the bulk correlation length are found exactly., 5 pages, to be published in J. Phys. A
- Published
- 2000
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- View/download PDF
26. Conformal profiles in the Hilhorst-van Leeuwen model
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Loïc Turban, Ferenc Iglói, Dragi Karevski, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Physics ,Statistical Mechanics (cond-mat.stat-mech) ,FOS: Physical sciences ,General Physics and Astronomy ,Perturbation (astronomy) ,Statistical and Nonlinear Physics ,Conformal map ,01 natural sciences ,010305 fluids & plasmas ,Magnetization ,Conformal symmetry ,Critical point (thermodynamics) ,0103 physical sciences ,Ising model ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics ,Quantum ,Scaling ,Condensed Matter - Statistical Mechanics ,Mathematical Physics ,Mathematical physics - Abstract
We study the critical energy and magnetization profiles for the Ising quantum chain with a marginal extended surface perturbation of the form A/y, y being the distance from the surface (Hilhorst-van Leeuwen model). For weak local couplings, AA_c, there is surface order at the bulk critical point. If conformal invariance is assumed to hold with such marginal perturbations, it predicts conformal profiles with the same scaling form as for the unperturbed quantum chain, with marginal surface exponents replacing the unperturbed ones. The results of direct analytical and numerical calculations of the profiles confirm the validity of the conformal expressions in the regimes of second- and first-order surface transitions., Comment: 12 pages, 4 figures, TeX, IOP macros included
- Published
- 2000
- Full Text
- View/download PDF
27. Conformal Invariance: an Introduction to Loops, Interfaces and Stochastic Loewner Evolution
- Author
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Malte Henkel, Dragi Karevski, Malte Henkel, and Dragi Karevski
- Subjects
- System theory, Mathematical physics
- Abstract
Conformal invariance has been a spectacularly successful tool in advancing our understanding of the two-dimensional phase transitions found in classical systems at equilibrium. This volume sharpens our picture of the applications of conformal invariance, introducing non-local observables such as loops and interfaces before explaining how they arise in specific physical contexts. It then shows how to use conformal invariance to determine their properties. Moving on to cover key conceptual developments in conformal invariance, the book devotes much of its space to stochastic Loewner evolution (SLE), detailing SLE's conceptual foundations as well as extensive numerical tests. The chapters then elucidate SLE's use in geometric phase transitions such as percolation or polymer systems, paying particular attention to surface effects. As clear and accessible as it is authoritative, this publication is as suitable for non-specialist readers and graduate students alike.
- Published
- 2012
28. Comparative study of the critical behavior in one-dimensional random and aperiodic environments
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Dragi Karevski, Ferenc Iglói, Heiko Rieger, Research Institute for Solid State Physics and Optics [Budapest], Wigner Research Centre for Physics [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), Laboratoire de physique des matériaux (LPM), Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS), Institut für Theoretische Physik [Köln], and Universität zu Köln
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[PHYS]Physics [physics] ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Universal function ,FOS: Physical sciences ,Disordered Systems and Neural Networks (cond-mat.dis-nn) ,Condensed Matter - Disordered Systems and Neural Networks ,Condensed Matter Physics ,Random walk ,Omega ,Critical point (mathematics) ,Electronic, Optical and Magnetic Materials ,Quantum spin chains ,Aperiodic graph ,Gravitational singularity ,Statistical physics ,Critical exponent ,ComputingMilieux_MISCELLANEOUS ,Condensed Matter - Statistical Mechanics - Abstract
We consider cooperative processes (quantum spin chains and random walks) in one-dimensional fluctuating random and aperiodic environments characterized by fluctuating exponents omega>0. At the critical point the random and aperiodic systems scale essentially anisotropically in a similar fashion: length (L) and time (t) scales are related as t ~ log^{1/omega}. Also some critical exponents, characterizing the singularities of average quantities, are found to be universal functions of omega, whereas some others do depend on details of the distribution of the disorder. In the off-critical region there is an important difference between the two types of environments: in aperiodic systems there are no extra (Griffiths)-singularities., 13 pages RevTeX, 10 eps-figures included
- Published
- 1998
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29. Persistent currents in mesoscopic rings and conformal invariance
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Malte Henkel, Dragi Karevski, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Fibonacci number ,FOS: Physical sciences ,02 engineering and technology ,01 natural sciences ,symbols.namesake ,Conformal symmetry ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,010306 general physics ,Quantum ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS ,[PHYS]Physics [physics] ,Physics ,Mesoscopic physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Condensed matter physics ,Persistent current ,Fermi energy ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Magnetic flux ,Electronic, Optical and Magnetic Materials ,symbols ,0210 nano-technology ,Hamiltonian (quantum mechanics) - Abstract
The effect of point defects on persistent currents in mesoscopic systems is studied in a simple tight-binding model. Using an analogy with the treatment of the critical quantum Ising chain with defects, conformal invariance techniques are employed to relate the persitent current amplitude to the Hamiltonian spectrum jsut above the Fermi energy. From this, the dependence of the current on the magnetic flux is found exactly for a ring with one or two point defects. The effect of an aperiodic modulation of the ring, generated through a binary substitution sequence, on the persistent current is also studied. The flux-dependence of the current is found to vary remarkably between the Fibonacci and the Thue-Morse sequences., Comment: 18 pages, Latex with epsf, including 5 figures
- Published
- 1998
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30. Finite-size effects in layered magnetic systems
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Malte Henkel and Dragi Karevski
- Subjects
High Energy Physics - Theory ,Surface (mathematics) ,Physics ,Phase transition ,Thin layers ,Statistical Mechanics (cond-mat.stat-mech) ,Condensed matter physics ,High Energy Physics - Lattice (hep-lat) ,FOS: Physical sciences ,High Energy Physics - Lattice ,Singularity ,High Energy Physics - Theory (hep-th) ,Conformal symmetry ,Maxima ,Scaling ,Critical exponent ,Condensed Matter - Statistical Mechanics - Abstract
Thermal and magnetic effects in a system consisting of thin layers of coupled Ising spins with $S=1/2$ and $S=1$ are considered. The specific heat and the correlation length display maxima at two different temperatures. It is discussed in what sense these maxima can be interpreted as a finite-size rounding of a thermodynamic singularity associated with a phase transition. The connection with ordinary, extraordinary and special surface phase transitions is made. In $2D$, the surface critical exponents are calculated from conformal invariance. The bulk and surface finite-size scaling of the order parameter profiles at the transition points is discussed. In $2D$, an exact scaling function for the profiles is suggested through conformal invariance arguments for the (extra)ordinary transition., 13 pages, Revtex, with 9 eps figures
- Published
- 1997
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31. Driven isotropic Heisenberg spin chain with arbitrary boundary twisting angle: exact results
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Gunter M. Schütz, Vladislav Popkov, Dragi Karevski, Institut für Theoretische Physik Universität zu Köln, Universität zu Köln, Dipartimento di Fisica e Astronomia [Firenze], Università degli Studi di Firenze = University of Florence [Firenze] (UNIFI), Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institute of Complex Systems (ICS-3), and Institute of Complex Systems
- Subjects
Physics ,Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Condensed matter physics ,Plane (geometry) ,Isotropy ,FOS: Physical sciences ,Boundary (topology) ,Mathematical Physics (math-ph) ,Coupling (probability) ,01 natural sciences ,010305 fluids & plasmas ,Magnetization ,Harmonic function ,Chain (algebraic topology) ,0103 physical sciences ,ddc:530 ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,Quantum Physics (quant-ph) ,010306 general physics ,Condensed Matter - Statistical Mechanics ,Mathematical Physics ,Ansatz - Abstract
We consider an open isotropic Heisenberg quantum spin chain, coupled at the ends to boundary reservoirs polarized in different directions, which sets up a twisting gradient across the chain. Using a matrix product ansatz, we calculate the exact magnetization profiles and magnetization currents in the nonequilibrium steady steady state of a chain with N sites. The magnetization profiles are harmonic functions with a frequency proportional to the twisting angle {\theta}. The currents of the magnetization components lying in the twisting plane and in the orthogonal direction behave qualitatively differently: In-plane steady state currents scale as 1/N^2 for fixed and sufficiently large boundary coupling, and vanish as the coupling increases, while the transversal current increases with the coupling and saturates to 2{\theta}/N., Comment: 12 pages, 5 figures close to published version; misprints corrected, one Figure revised
- Published
- 2013
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- View/download PDF
32. Exact Matrix Product Solution for the Boundary-Driven Lindblad XXZ Chain
- Author
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Dragi Karevski, Vladislav Popkov, Gunter M. Schütz, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut für Theoretische Physik Universität zu Köln, Universität zu Köln, Dipartimento di Fisica e Astronomia [Firenze], Università degli Studi di Firenze = University of Florence [Firenze] (UNIFI), L.D. Landau Institute for Theoretical Physics of RAS, Russian Academy of Sciences [Moscow] (RAS), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Fisica, Universita' di Firenze, Università degli Studi di Firenze = University of Florence [Firenze], Max-Planck-Institut für Physik komplexer Systeme (MPI-PKS), Max-Planck-Gesellschaft, and Forschungszentrum Jülich GmbH
- Subjects
Density matrix ,[PHYS.COND.GAS]Physics [physics]/Condensed Matter [cond-mat]/Quantum Gases [cond-mat.quant-gas] ,FOS: Physical sciences ,General Physics and Astronomy ,Boundary (topology) ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,01 natural sciences ,010305 fluids & plasmas ,Quadratic algebra ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,Quantum mechanics ,0103 physical sciences ,ddc:550 ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,Twist ,010306 general physics ,Condensed Matter - Statistical Mechanics ,Mathematical Physics ,Ansatz ,Physics ,Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Lindblad equation ,Quantum algebra ,Mathematical Physics (math-ph) ,Coherent states ,Quantum Physics (quant-ph) - Abstract
We demonstrate that the exact non-equilibrium steady state of the one-dimensional Heisenberg XXZ spin chain driven by boundary Lindblad operators can be constructed explicitly with a matrix product ansatz for the non-equilibrium density matrix where the matrices satisfy a {\it quadratic algebra}. This algebra turns out to be related to the quantum algebra $U_q[SU(2)]$. Coherent state techniques are introduced for the exact solution of the isotropic Heisenberg chain with and without quantum boundary fields and Lindblad terms that correspond to two different completely polarized boundary states. We show that this boundary twist leads to non-vanishing stationary currents of all spin components. Our results suggest that the matrix product ansatz can be extended to more general quantum systems kept far from equilibrium by Lindblad boundary terms., 4 pages, no figures
- Published
- 2013
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- View/download PDF
33. Hydrodynamic description of hard-core bosons on a Galileo ramp
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Mario Collura, Pierre Wendenbaum, Dragi Karevski, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Dipartimento di Fisica dell'Università di Pisa and INFN
- Subjects
Condensed Matter::Quantum Gases ,Physics ,Quantum Physics ,Optical lattice ,Condensed matter physics ,FOS: Physical sciences ,Non-equilibrium thermodynamics ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Quantum evolution ,010305 fluids & plasmas ,Settore FIS/03 - Fisica della Materia ,Superfluidity ,Quantum Gases (cond-mat.quant-gas) ,Lattice (order) ,Quantum electrodynamics ,0103 physical sciences ,Bloch oscillations ,Quantum Physics (quant-ph) ,Condensed Matter - Quantum Gases ,010306 general physics ,Particle density ,Boson - Abstract
We study the quantum evolution of a cloud of hard-core bosons loaded on a one-dimensional optical lattice after its sudden release from a harmonic trap. Just after the trap has been removed, a linear ramp potential is applied, mimicking the so called Galileo ramp experiment. The non-equilibrium expansion of the bosonic cloud is elucidated through a hydrodynamical description which is compared to the exact numerical evolution obtained by exact diagonalization on finite lattice sizes. The system is found to exhibit a rich behavior showing in particular Bloch oscillations of a self-trapped condensate and an ejected particle density leading to two diverging entangled condensates. Depending on the initial density of the gas different regimes of Josephson-like oscillations are observed. At low densities, the trapped part of the cloud is in a superfluid phase that oscillates in time as a whole. At higher densities, the trapped condensate is in a mixed superfluid-Mott phase that show a breathing regime for steep enough potential ramps., 8 pages, 9 figures
- Published
- 2013
- Full Text
- View/download PDF
34. Defect production in quench from a current-carrying non-equilibrium state
- Author
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Dragi Karevski, Rosemary J. Harris, Institut Jean Lamour (IJL), and Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Statistics and Probability ,Physics ,Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Thermodynamic equilibrium ,FOS: Physical sciences ,Statistical and Nonlinear Physics ,01 natural sciences ,Unitary state ,010305 fluids & plasmas ,Quantum mechanics ,Quantum critical point ,0103 physical sciences ,Quantum system ,Ising model ,Statistics, Probability and Uncertainty ,Current (fluid) ,Quantum Physics (quant-ph) ,010306 general physics ,Quantum ,Scaling ,ComputingMilieux_MISCELLANEOUS ,Condensed Matter - Statistical Mechanics - Abstract
We consider the defect production of a quantum system, initially prepared in a current-carrying non-equilibrium state, during its unitary driving through a quantum critical point. At low values of the initial current, the quantum Kibble-Zurek scaling for the production of defects is recovered. However, at large values of the initial current, i.e., very far from an initial equilibrium situation, a universal scaling of the defect production is obtained which shows an algebraic dependence with respect to the initial current value. These scaling predictions are demonstrated by the exactly solvable Ising quantum chain where the current-carrying state is selected through the imposition of a Dzyaloshinskii-Moriya interaction term., Comment: 13 pages, 3 figures. v2: Minor changes. This is an author-created, un-copyedited version of an article published in JSTAT. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/1742-5468/2016/03/033204
- Published
- 2016
- Full Text
- View/download PDF
35. Local critical behaviour at aperiodic surface extended perturbation in the Ising quantum chain
- Author
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Gábor Palágyi, Lo{ \\'ı}c Turban, Dragi Karevski, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
High Energy Physics - Theory ,Physics ,[PHYS.HTHE]Physics [physics]/High Energy Physics - Theory [hep-th] ,Condensed Matter (cond-mat) ,FOS: Physical sciences ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,Condensed Matter ,Critical value ,01 natural sciences ,Surface energy ,010305 fluids & plasmas ,High Energy Physics - Theory (hep-th) ,Critical point (thermodynamics) ,Aperiodic graph ,[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] ,Quantum mechanics ,0103 physical sciences ,Exponent ,Ising model ,010306 general physics ,Quantum ,Scaling ,Mathematical Physics - Abstract
The surface critical behaviour of the semi--infinite one--dimensional quantum Ising model in a transverse field is studied in the presence of an aperiodic surface extended modulation. The perturbed couplings are distributed according to a generalized Fredholm sequence, leading to a marginal perturbation and varying surface exponents. The surface magnetic exponents are calculated exactly whereas the expression of the surface energy density exponent is conjectured from a finite--size scaling study. The system displays surface order at the bulk critical point, above a critical value of the modulation amplitude. It may be considered as a discrete realization of the Hilhorst--van Leeuwen model., Comment: 13 pages, TeX file + 6 figures, epsf needed
- Published
- 1995
- Full Text
- View/download PDF
36. Conformal invariance: An introduction to loops, interfaces and stochastic Loewner evolution
- Author
-
Dragi Karevski, Malte Henkel, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Schramm–Loewner evolution ,010102 general mathematics ,Mathematical analysis ,Physics::Physics Education ,Boundary (topology) ,01 natural sciences ,Loop (topology) ,immune system diseases ,Conformal symmetry ,0103 physical sciences ,Numerical tests ,0101 mathematics ,skin and connective tissue diseases ,010306 general physics ,General Theoretical Physics ,ComputingMilieux_MISCELLANEOUS ,Mathematics - Abstract
Conformal invariance has been a spectacularly successful tool in advancing our understanding of the two-dimensional phase transitions found in classical systems at equilibrium. This volume sharpens our picture of the applications of conformal invariance, introducing non-local observables such as loops and interfaces before explaining how they arise in specific physical contexts. It then shows how to use conformal invariance to determine their properties. Moving on to cover key conceptual developments in conformal invariance, the book devotes much of its space to stochastic Loewner evolution (SLE), detailing SLE’s conceptual foundations as well as extensive numerical tests. The chapters then elucidate SLE’s use in geometric phase transitions such as percolation or polymer systems, paying particular attention to surface effects. As clear and accessible as it is authoritative, this publication is as suitable for non-specialist readers and graduate students alike.
- Published
- 2012
- Full Text
- View/download PDF
37. A Short Introduction to Conformal Invariance
- Author
-
Malte Henkel, Dragi Karevski, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS]Physics [physics] ,Physics ,010308 nuclear & particles physics ,Conformal field theory ,Conformal map ,01 natural sciences ,Theoretical physics ,Conformal symmetry ,Tensor (intrinsic definition) ,0103 physical sciences ,Lie algebra ,Virasoro algebra ,Operator product expansion ,010306 general physics ,Central charge ,ComputingMilieux_MISCELLANEOUS - Abstract
An easily readable introduction to the main concepts and techniques of conformal invariance is provided. Starting from the global scale-invariance at a critical point, it is argued, through the local conformal Ward identities, that under mild conditions an extension to a local form of scale-invariance, namely conformally invariance, is in general possible. In two space dimensions, the particular role of the infinite-dimensional Lie algebra of conformal transformations is outlined and the main concepts, namely those of a primary scaling operator, the conformal energy-momentum tensor, the Virasoro algebra and the central charge and the main facts of their unitary and/or minimal representations will be presented. Some simple applications for the explicit calculation of two-point functions will be given. The free boson will be used as a paradigmatic illustration and we shall close with an outline of surface critical phenomena and their description in terms of boundary conformal field-theory.
- Published
- 2012
- Full Text
- View/download PDF
38. Entangling many-body bound states with propagative modes in Bose-Hubbard systems
- Author
-
Guillaume Roux, Dragi Karevski, Helge Aufderheide, Mario Collura, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Department Biological Physics [Dresden], Max Planck Institute for the Physics of Complex Systems (MPI-PKS), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS), and Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)
- Subjects
Physics ,Condensed Matter::Quantum Gases ,Optical lattice ,Quantum Physics ,[PHYS.COND.GAS]Physics [physics]/Condensed Matter [cond-mat]/Quantum Gases [cond-mat.quant-gas] ,FOS: Physical sciences ,Observable ,Quantum entanglement ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Quantum evolution ,Settore FIS/03 - Fisica della Materia ,010305 fluids & plasmas ,Coupling (physics) ,Classical mechanics ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,Quantum Gases (cond-mat.quant-gas) ,Quantum mechanics ,0103 physical sciences ,Bound state ,010306 general physics ,Condensed Matter - Quantum Gases ,Quantum Physics (quant-ph) ,Quantum ,Boson - Abstract
The quantum evolution of a cloud of bosons initially localized on part of a one dimensional optical lattice and suddenly subjected to a linear ramp is studied, realizing a quantum analog of the "Galileo ramp" experiment. The main remarkable effects of this realistic setup are revealed using analytical and numerical methods. Only part of the particles are ejected for a high enough ramp, while the others remain self-trapped. Then, the trapped density profile displays rich dynamics with Josephson-like oscillations around a plateau. This setup, by coupling bound states to propagative modes, creates two diverging condensates for which the entanglement is computed and related to the equilibrium one. Further, we address the role of integrability on the entanglement and on the damping and thermalization of simple observables., Comment: 12 pages, 12 figures
- Published
- 2012
39. Nonlinear quenches of power-law confining traps in quantum critical systems
- Author
-
Dragi Karevski, Mario Collura, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut für Theoretische Physik [Leipzig], and Universität Leipzig [Leipzig]
- Subjects
[PHYS]Physics [physics] ,Physics ,Space time ,01 natural sciences ,Power law ,Atomic and Molecular Physics, and Optics ,Settore FIS/03 - Fisica della Materia ,010305 fluids & plasmas ,Many-body problem ,Nonlinear system ,Critical point (thermodynamics) ,Quantum mechanics ,0103 physical sciences ,Ising model ,010306 general physics ,Quantum ,Scaling ,ComputingMilieux_MISCELLANEOUS - Abstract
We describe the coherent quantum evolution of a quantum many-body system with a time-dependent power-law confining potential. The amplitude of the inhomogeneous potential is driven in time along a nonlinear ramp which crosses a critical point. Using Kibble-Zurek-like scaling arguments we derive general scaling laws for the density of excitations and energy excess generated during the nonlinear sweep of the confining potential. It is shown that, with respect to the sweeping rate, the densities follow algebraic laws with exponents that depend on the space-time properties of the potential and on the scaling dimensions of the densities. We support our scaling predictions with both analytical and numerical results on the Ising quantum chain with an inhomogeneous transverse field varying in time.
- Published
- 2011
- Full Text
- View/download PDF
40. Fourier's law on a one-dimensional optical random lattice
- Author
-
Thierry Platini, Rosemary J. Harris, Dragi Karevski, Virginia Tech [Blacksburg], Queen Mary University of London (QMUL), Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Statistics and Probability ,Physics ,[PHYS]Physics [physics] ,Density gradient ,FOS: Physical sciences ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,01 natural sciences ,010305 fluids & plasmas ,symbols.namesake ,Fourier transform ,Quantum Gases (cond-mat.quant-gas) ,Fourier law ,Modeling and Simulation ,Quantum mechanics ,Lattice (order) ,0103 physical sciences ,symbols ,Density of states ,Random lattice ,010306 general physics ,Condensed Matter - Quantum Gases ,Mathematical Physics ,Stationary state ,ComputingMilieux_MISCELLANEOUS - Abstract
We study the transport properties of a one-dimensional hard-core bosonic lattice gas coupled to two particle reservoirs at different chemical potentials which generate a current flow through the system. In particular, the influence of random fluctuations of the underlying lattice on the stationary-state properties is investigated. We show analytically that the steady-state density presents a linear profile. The local steady-state current obeys the Fourier law $j=-\kappa(\tau)\nabla n $ where $\tau$ is a typical timescale of the lattice fluctuations and $\nabla n$ the density gradient imposed by the reservoirs., Comment: 9 pages, 2 figures
- Published
- 2010
- Full Text
- View/download PDF
41. Critical Quench Dynamics in Confined Systems
- Author
-
Dragi Karevski, Mario Collura, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut für Theoretische Physik [Leipzig], and Universität Leipzig [Leipzig]
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Physics ,Quantum phase transition ,[PHYS]Physics [physics] ,Quantum Physics ,Statistical Mechanics (cond-mat.stat-mech) ,General Physics and Astronomy ,FOS: Physical sciences ,16. Peace & justice ,01 natural sciences ,Quantum evolution ,010305 fluids & plasmas ,Settore FIS/03 - Fisica della Materia ,Amplitude ,Classical mechanics ,Critical point (thermodynamics) ,Quantum electrodynamics ,0103 physical sciences ,Ising model ,010306 general physics ,Adiabatic process ,Quantum Physics (quant-ph) ,Quantum ,Excitation ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS - Abstract
We analyze the coherent quantum evolution of a many-particle system after slowly sweeping a power-law confining potential. The amplitude of the confining potential is varied in time along a power-law ramp such that the many-particle system finally reaches or crosses a critical point. Under this protocol we derive general scaling laws for the density of excitations created during the non-adiabatic sweep of the confining potential. It is found that the mean excitation density follows an algebraic law as a function of the sweeping rate with an exponent that depends on the space-time properties of the potential. We confirm our scaling laws by first order adiabatic calculation and exact results on the Ising quantum chain with a varying transverse field., Comment: To appear in Phys. Rev. Lett
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- 2010
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42. Gradient critical phenomena in the Ising quantum chain: surface behaviour
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Loïc Turban, Mario Collura, Dragi Karevski, Institut Jean Lamour (IJL), and Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
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Statistics and Probability ,Length scale ,Critical phenomena ,Pacs: 68.35.Rh, 05.50.+q, 75.10.Pq ,Perturbation (astronomy) ,FOS: Physical sciences ,01 natural sciences ,010305 fluids & plasmas ,Settore FIS/03 - Fisica della Materia ,Quadratic equation ,finite-size scaling ,quantum phase transitions (theory) ,surface effects (theory) ,0103 physical sciences ,Statistical physics ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics ,Quantum ,Scaling ,Condensed Matter - Statistical Mechanics ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Statistical and Nonlinear Physics ,Exact results ,Ising model ,Statistics, Probability and Uncertainty - Abstract
International audience; We consider the influence of a power-law deviation from the critical coupling such that the system is critical at its surface. We develop a scaling theory showing that such a perturbation introduces a new length scale which governs the scaling behaviour of the density profiles as well as the finite-size behaviour of the surface properties. Exact results are obtained for the Ising quantum chain when the perturbation varies linearly whereas the quadratic perturbation is mainly studied numerically. The scaling theory is well confirmed in both cases.
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- 2009
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43. Quantum Nonequilibrium Steady States Induced by Repeated Interactions
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Thierry Platini, Dragi Karevski, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Department of Physics [Blacksburg], and Virginia Tech [Blacksburg]
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Physics ,Quantum decoherence ,Steady state (electronics) ,[PHYS.COND.GAS]Physics [physics]/Condensed Matter [cond-mat]/Quantum Gases [cond-mat.quant-gas] ,Spins ,Condensed matter physics ,Relaxation (NMR) ,General Physics and Astronomy ,Non-equilibrium thermodynamics ,Statistical mechanics ,Gibbs state ,01 natural sciences ,010305 fluids & plasmas ,Open quantum system ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,Quantum mechanics ,0103 physical sciences ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics - Abstract
International audience; We study the steady state of a finite XX chain coupled at its boundaries to quantum reservoirs made of free spins that interact one after the other with the chain. The two-point correlations are calculated exactly, and it is shown that the steady state is completely characterized by the magnetization profile and the associated current. Except at the boundary sites, the magnetization is given by the average of the reservoirs’ magnetizations. The steady-state current, proportional to the difference in the reservoirs’ magnetizations, shows a nonmonotonic behavior with respect to the system-reservoir coupling strength, with an optimal current state for a finite value of the coupling. Moreover, we show that the steady state can be described by a generalized Gibbs state.
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- 2009
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44. Work fluctuations in quantum spin chains
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Dragi Karevski, Sven Dorosz, Thierry Platini, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,Quantum phase transition ,Statistical Mechanics (cond-mat.stat-mech) ,Jarzynski equality ,Quantum dynamics ,FOS: Physical sciences ,PACS.05.30.-d, 05.40.-a ,Quantum phases ,01 natural sciences ,010305 fluids & plasmas ,Quantization (physics) ,Quantum spin chains ,Quantum mechanics ,Quantum electrodynamics ,Quantum process ,0103 physical sciences ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics ,Quantum dissipation ,Quantum statistical mechanics ,Condensed Matter - Statistical Mechanics ,Fluctuation relation - Abstract
We study the work fluctuations of two types of finite quantum spin chains under the application of a time-dependent magnetic field in the context of the fluctuation relation and Jarzynski equality. The two types of quantum chains correspond to the integrable Ising quantum chain and the nonintegrable XX quantum chain in a longitudinal magnetic field. For several magnetic field protocols, the quantum Crooks and Jarzynski relations are numerically tested and fulfilled. As a more interesting situation, we consider the forcing regime where a periodic magnetic field is applied. In the Ising case we give an exact solution in terms of double-confluent Heun functions. We show that the fluctuations of the work performed by the external periodic drift are maximum at a frequency proportional to the amplitude of the field. In the nonintegrable case, we show that depending on the field frequency a sharp transition is observed between a Poisson-limit work distribution at high frequencies toward a normal work distribution at low frequencies., Comment: 10 pages, 13 figures
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- 2008
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45. Entanglement evolution after connecting finite to infinite quantum chains
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Ingo Peschel, Viktor Eisler, Dragi Karevski, Thierry Platini, Freie Universität Berlin, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Statistics and Probability ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,[PHYS.COND.GAS]Physics [physics]/Condensed Matter [cond-mat]/Quantum Gases [cond-mat.quant-gas] ,Conformal field theory ,FOS: Physical sciences ,Statistical and Nonlinear Physics ,Quantum entanglement ,01 natural sciences ,010305 fluids & plasmas ,Transverse plane ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,Homogeneous ,Quantum mechanics ,0103 physical sciences ,Ising model ,Statistics, Probability and Uncertainty ,Remainder ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics ,Quantum ,Entropy (arrow of time) ,Condensed Matter - Statistical Mechanics - Abstract
We study zero-temperature XX chains and transverse Ising chains and join an initially separate finite piece on one or on both sides to an infinite remainder. In both critical and non-critical systems we find a typical increase of the entanglement entropy after the quench, followed by a slow decay towards the value of the homogeneous chain. In the critical case, the predictions of conformal field theory are verified for the first phase of the evolution, while at late times a step structure can be observed., 15 pages, 11 figures
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- 2008
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46. Relaxation in the XX quantum chain
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Dragi Karevski, Thierry Platini, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Statistics and Probability ,[PHYS.COND.GAS]Physics [physics]/Condensed Matter [cond-mat]/Quantum Gases [cond-mat.quant-gas] ,General Physics and Astronomy ,FOS: Physical sciences ,01 natural sciences ,010305 fluids & plasmas ,Magnetization ,Chain (algebraic topology) ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,0103 physical sciences ,Thermal ,Dynamic Properties ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics ,Quantum ,Mathematical Physics ,Condensed Matter - Statistical Mechanics ,Physics ,Condensed matter physics ,Statistical Mechanics (cond-mat.stat-mech) ,Statistical and Nonlinear Physics ,State (functional analysis) ,XX quantum chain ,75.40.Gb, 05.70.Ln ,Magnetic field ,Transverse plane ,Relaxation properties ,Modeling and Simulation ,Relaxation (physics) ,Nonequilibrium properties - Abstract
International audience; We present the results obtained on the magnetization relaxation properties of an XX quantum chain in a transverse magnetic field. We first consider an initial thermal kink-like state where half of the chain is initially thermalized at a very high temperature T b while the remaining half, called the system, is put at a lower temperature T s. From this initial state, we derive analytically the Green function associated with the dynamical behaviour of the transverse magnetization. Depending on the strength of the magnetic field and on the temperature of the system, different regimes are obtained for the magnetic relaxation. In particular, with an initial droplet-like state, that is a cold subsystem of the finite size in contact at both ends with an infinite temperature environment, we derive analytically the behaviour of the time-dependent system magnetization.
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- 2007
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47. Gradient critical phenomena in the Ising quantum chain
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Thierry Platini, Dragi Karevski, Loïc Turban, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Statistics and Probability ,Characteristic length ,Critical phenomena ,FOS: Physical sciences ,General Physics and Astronomy ,01 natural sciences ,010305 fluids & plasmas ,Statistical Mechanics ,symbols.namesake ,Quantum mechanics ,0103 physical sciences ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,010306 general physics ,Quantum ,Scaling ,Condensed Matter - Statistical Mechanics ,Mathematical Physics ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Statistical and Nonlinear Physics ,Condensed Matter - Other Condensed Matter ,Scaling limit ,Quantum harmonic oscillator ,Modeling and Simulation ,[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] ,symbols ,Ising model ,Hamiltonian (quantum mechanics) ,Other Condensed Matter (cond-mat.other) - Abstract
We consider the behaviour of a critical system in the presence of a gradient perturbation of the couplings. In the direction of the gradient an interface region separates the ordered phase from the disordered one. We develop a scaling theory for the density profiles induced by the gradient perturbation which involves a characteristic length given by the width of the interface region. The scaling predictions are tested in the framework of the mean-field Ginzburg-Landau theory. Then we consider the Ising quantum chain in a linearly varying transverse field which corresponds to the extreme anisotropic limit of a classical two-dimensional Ising model. The quantum Hamiltonian can be diagonalized exactly in the scaling limit where the eigenvalue problem is the same as for the quantum harmonic oscillator. The energy density, the magnetization profile and the two-point correlation function are studied either analytically or by exact numerical calculations. Their scaling behaviour are in agreement with the predictions of the scaling theory., Comment: 15 pages, 6 figures, submited to J. Phys. A
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- 2007
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48. Weak universality in inhomogeneous Ising quantum chains
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Dragi Karevski, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,Condensed matter physics ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,01 natural sciences ,010305 fluids & plasmas ,Universality (dynamical systems) ,Magnetization ,Aperiodic graph ,Quantum mechanics ,0103 physical sciences ,Ising model ,010306 general physics ,Anisotropy ,Quantum ,Scaling ,Mathematical Physics ,ComputingMilieux_MISCELLANEOUS - Abstract
The Ising quantum chain with arbitrary coupling distribution {λi} leading to an anisotropic scaling is considered. The smallest gap of the chain is connected to the surface magnetization by the relation Λ1 = ms({λi})ms({λ−1i}). For some aperiodic distribution {λi}, a weak universality of the critical behaviour is found.
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- 2006
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49. Scaling and front dynamics in Ising quantum chains
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Dragi Karevski, Thierry Platini, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS]Physics [physics] ,Statistical Mechanics (cond-mat.stat-mech) ,Spins ,Thermodynamic equilibrium ,Relaxation (NMR) ,FOS: Physical sciences ,State (functional analysis) ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials ,Chain (algebraic topology) ,Quantum mechanics ,0103 physical sciences ,Ising model ,010306 general physics ,Scaling ,Quantum ,Condensed Matter - Statistical Mechanics ,ComputingMilieux_MISCELLANEOUS - Abstract
We study the relaxation dynamics of a quantum Ising chain initially prepared in a product of canonical states corresponding each to an equilibrium state of part of the chain at a given temperature. We focus our attention on the transverse magnetization for which a general expression is given. Explicite results are given for the completely factorized initial state, corresponding to a situation where all the spins are thermalized independently, and for the two-temperatures initial state, where part of the chain called the system is thermalized at a temperature $T_s$ and the remaining part is at a temperature $T_b$., 7 pages, submitted to EPJB
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- 2005
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50. RELAXATION IN QUANTUM SPIN CHAINS: FREE FERMIONIC MODELS
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Dragi Karevski, Laboratoire de physique des matériaux (LPM), and Université Henri Poincaré - Nancy 1 (UHP)-Institut National Polytechnique de Lorraine (INPL)-Centre National de la Recherche Scientifique (CNRS)
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Quantum spin chains ,[PHYS]Physics [physics] ,Condensed matter physics ,Quantum mechanics ,0103 physical sciences ,Relaxation (physics) ,010306 general physics ,01 natural sciences ,ComputingMilieux_MISCELLANEOUS ,Fermionic condensate ,Mathematics - Abstract
International audience
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- 2004
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