Browsing by Author "Henkel, M."

Now showing 1 - 3 of 3
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    Field-theory approaches to nonequilibrium dynamics
    Täuber, Uwe C. (Springer-Verlag Berlin, 2007-01-01)
    It is explained how field-theoretic methods and the dynamic renormalisation group (RG) can be applied to study the universal scaling properties of systems that either undergo a continuous phase transition or display generic scale invariance, both near and far from thermal equilibrium. Part 1 introduces the response functional field theory representation of (nonlinear) Langevin equations. The RG is employed to compute the scaling exponents for several universality classes governing the critical dynamics near second-order phase transitions in equilibrium. The effects of reversible mode-coupling terms, quenching from random initial conditions to the critical point, and violating the detailed balance constraints are briefly discussed. It is shown how the same formalism can be applied to nonequilibrium systems such as driven diffusive lattice gases. Part 2 describes how the master equation for stochastic particle reaction processes can be mapped onto a field theory action. The RG is then used to analyse simple diffusion-limited annihilation reactions as well as generic continuous transitions from active to inactive, absorbing states, which are characterised by the power laws of (critical) directed percolation. Certain other important universality classes are mentioned, and some open issues are listed.
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    Phenomenology of aging in the Kardar-Parisi-Zhang equation
    Henkel, M.; Noh, J. D.; Pleimling, Michel J. (American Physical Society, 2012-03-27)
    We study aging during surface growth processes described by the one-dimensional Kardar-Parisi-Zhang equation. Starting from a flat initial state, the systems undergo simple aging in both correlators and linear responses, and its dynamical scaling is characterized by the aging exponents a = -1/3, b = -2/3, lambda(C) = lambda(R) = 1, and z = 3/2. The form of the autoresponse scaling function is well described by the recently constructed logarithmic extension of local scale invariance.
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    Superuniversality in phase-ordering disordered ferromagnets
    Henkel, M.; Pleimling, Michel J. (American Physical Society, 2008-12)
    The phase-ordering kinetics of the ferromagnetic two-dimensional Ising model with uniform bond disorder is investigated by intensive Monte Carlo simulations. Simple aging behavior is observed in the single-time correlator and the two-time responses and correlators. The dynamical exponent z and the autocorrelation exponent lambda(C) only depend on the ratio epsilon/T, where epsilon describes the width of the distribution of the disorder, whereas a more complicated behavior is found for the nonequilibrium exponent a of the two-time response as well as for the autoresponse exponent lambda(R). The scaling functions are observed to depend only on the dimensionless ratio epsilon/T. If the length scales are measured in terms of the time-dependent domain size L(t), the form of the scaling functions is in general independent of both epsilon and T. Conditions limiting the validity of this "superuniversality" are discussed.