1,258 research outputs found

    Spatially heterogeneous dynamics in granular compaction

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    We prove the emergence of spatially correlated dynamics in slowly compacting dense granular media by analyzing analytically and numerically multi-point correlation functions in a simple particle model characterized by slow non-equilibrium dynamics. We show that the logarithmically slow dynamics at large times is accompanied by spatially extended dynamic structures that resemble the ones observed in glass-forming liquids and dense colloidal suspensions. This suggests that dynamic heterogeneity is another key common feature present in very different jamming materials.Comment: 4 pages, 3 figure

    Domain scaling and marginality breaking in the random field Ising model

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    A scaling description is obtained for the dd--dimensional random field Ising model from domains in a bar geometry. Wall roughening removes the marginality of the d=2d=2 case, giving the T=0T=0 correlation length ξexp(Ahγ)\xi \sim \exp\left(A h^{-\gamma}\right) in d=2d=2, and for d=2+ϵd=2+\epsilon power law behaviour with ν=2/ϵγ\nu = 2/\epsilon \gamma, hϵ1/γh^\star \sim \epsilon^{1/\gamma}. Here, γ=2,4/3\gamma = 2,4/3 (lattice, continuum) is one of four rough wall exponents provided by the theory. The analysis is substantiated by three different numerical techniques (transfer matrix, Monte Carlo, ground state algorithm). These provide for strips up to width L=11L=11 basic ingredients of the theory, namely free energy, domain size, and roughening data and exponents.Comment: ReVTeX v3.0, 19 pages plus 19 figures uuencoded in a separate file. These are self-unpacking via a shell scrip

    Second-Line Therapy for Advanced NSCLC

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    Most patients with lung cancer have non-small cell lung cancer (NSCLC) subtype and have advanced disease at the time of diagnosis. Improvements in both first-line and subsequent therapies are allowing longer survival and enhanced quality of life for these patients. The median overall survival observed in many second-line trials is approximately 9 months, and many patients receive further therapy after second-line therapy. The cytotoxic agents pemetrexed and docetaxel and the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib are standard second-line therapies. For patients with EGFR mutation, a TKI is the favored second-line therapy if not already used in first-line therapy. For patients without the EGFR mutation, TKIs are an option, but many oncologists favor cytotoxic therapy. The inhibitor of the EML4/ALK fusion protein, crizotinib, has recently become a standard second-line treatment for patients with the gene rearrangement and has promise for patients with the ROS1 rearrangement

    Random manifolds in non-linear resistor networks: Applications to varistors and superconductors

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    We show that current localization in polycrystalline varistors occurs on paths which are, usually, in the universality class of the directed polymer in a random medium. We also show that in ceramic superconductors, voltage localizes on a surface which maps to an Ising domain wall. The emergence of these manifolds is explained and their structure is illustrated using direct solution of non-linear resistor networks

    Classical evolution of fractal measures on the lattice

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    We consider the classical evolution of a lattice of non-linear coupled oscillators for a special case of initial conditions resembling the equilibrium state of a macroscopic thermal system at the critical point. The displacements of the oscillators define initially a fractal measure on the lattice associated with the scaling properties of the order parameter fluctuations in the corresponding critical system. Assuming a sudden symmetry breaking (quench), leading to a change in the equilibrium position of each oscillator, we investigate in some detail the deformation of the initial fractal geometry as time evolves. In particular we show that traces of the critical fractal measure can sustain for large times and we extract the properties of the chain which determine the associated time-scales. Our analysis applies generally to critical systems for which, after a slow developing phase where equilibrium conditions are justified, a rapid evolution, induced by a sudden symmetry breaking, emerges in time scales much shorter than the corresponding relaxation or observation time. In particular, it can be used in the fireball evolution in a heavy-ion collision experiment, where the QCD critical point emerges, or in the study of evolving fractals of astrophysical and cosmological scales, and may lead to determination of the initial critical properties of the Universe through observations in the symmetry broken phase.Comment: 15 pages, 15 figures, version publiced at Physical Review

    Exact time-dependent correlation functions for the symmetric exclusion process with open boundary

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    As a simple model for single-file diffusion of hard core particles we investigate the one-dimensional symmetric exclusion process. We consider an open semi-infinite system where one end is coupled to an external reservoir of constant density ρ\rho^\ast and which initially is in an non-equilibrium state with bulk density ρ0\rho_0. We calculate the exact time-dependent two-point density correlation function Ck,l(t)C_{k,l}(t)\equiv - and the mean and variance of the integrated average net flux of particles N(t)N(0)N(t)-N(0) that have entered (or left) the system up to time tt. We find that the boundary region of the semi-infinite relaxing system is in a state similar to the bulk state of a finite stationary system driven by a boundary gradient. The symmetric exclusion model provides a rare example where such behavior can be proved rigorously on the level of equal-time two-point correlation functions. Some implications for the relaxational dynamics of entangled polymers and for single-file diffusion in colloidal systems are discussed.Comment: 11 pages, uses REVTEX, 2 figures. Minor typos corrected and reference 17 adde

    First- and second-order phase transitions in a driven lattice gas with nearest-neighbor exclusion

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    A lattice gas with infinite repulsion between particles separated by 1\leq 1 lattice spacing, and nearest-neighbor hopping dynamics, is subject to a drive favoring movement along one axis of the square lattice. The equilibrium (zero drive) transition to a phase with sublattice ordering, known to be continuous, shifts to lower density, and becomes discontinuous for large bias. In the ordered nonequilibrium steady state, both the particle and order-parameter densities are nonuniform, with a large fraction of the particles occupying a jammed strip oriented along the drive. The relaxation exhibits features reminiscent of models of granular and glassy materials.Comment: 8 pages, 5 figures; results due to bad random number generator corrected; significantly revised conclusion

    Lee-Yang zeros and phase transitions in nonequilibrium steady states

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    We consider how the Lee-Yang description of phase transitions in terms of partition function zeros applies to nonequilibrium systems. Here one does not have a partition function, instead we consider the zeros of a steady-state normalization factor in the complex plane of the transition rates. We obtain the exact distribution of zeros in the thermodynamic limit for a specific model, the boundary-driven asymmetric simple exclusion process. We show that the distributions of zeros at the first and second order nonequilibrium phase transitions of this model follow the patterns known in the Lee-Yang equilibrium theory.Comment: 4 pages RevTeX4 with 4 figures; revised version to appear in Phys. Rev. Let

    A sufficient criterion for integrability of stochastic many-body dynamics and quantum spin chains

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    We propose a dynamical matrix product ansatz describing the stochastic dynamics of two species of particles with excluded-volume interaction and the quantum mechanics of the associated quantum spin chains respectively. Analyzing consistency of the time-dependent algebra which is obtained from the action of the corresponding Markov generator, we obtain sufficient conditions on the hopping rates for identifing the integrable models. From the dynamical algebra we construct the quadratic algebra of Zamolodchikov type, associativity of which is a Yang Baxter equation. The Bethe ansatz equations for the spectra are obtained directly from the dynamical matrix product ansatz.Comment: 19 pages Late
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