29 research outputs found
Non-universal disordered Glauber dynamics
We consider the one-dimensional Glauber dynamics with coupling disorder in
terms of bilinear fermion Hamiltonians. Dynamic exponents embodied in the
spectrum gap of these latter are evaluated numerically by averaging over both
binary and Gaussian disorder realizations. In the first case, these exponents
are found to follow the non-universal values of those of plain dimerized
chains. In the second situation their values are still non-universal and
sub-diffusive below a critical variance above which, however, the relaxation
time is suggested to grow as a stretched exponential of the equilibrium
correlation length.Comment: 11 pages, 5 figures, brief addition
Logarithmic coarsening and glassy behavior in a polymer model with mass-dependent diffusion
We present a model of polymer growth and diffusion with frustration
mechanisms for density increase and with diffusion rates of Arrhenius form with
mass-dependent energy barriers Gamma(m) ~ (m-1)^gamma. It shows non-universal
logarithmic coarsening involving the exponent gamma. Strong-glass behavior is
found in the typical times for disappearance of all polymers up to a given
length, without reference to the equilibrium states of the macroscopic system.
These features are predicted by numerical simulations, scaling theories and an
analytic solution of the master equation within an independent interval
approximation, which also provides the cluster size distribution.Comment: 16 pages, including 7 figures. To be published in Phys. Rev.
Diffusion-annihilation dynamics in one spatial dimension
We discuss a reaction-diffusion model in one dimension subjected to an
external driving force. Each lattice site may be occupied by at most one
particle. The particles hop with asymmetric rates (the sum of which is one) to
the right or left nearest neighbour site if it is vacant, and annihilate with
rate one if it is occupied.
We compute the long time behaviour of the space dependent average density in
states where the initial density profiles are step functions. We also compute
the exact time dependence of the particle density for uncorrelated random
initial conditions. The representation of the uncorrelated random initial state
and also of the step function profile in terms of free fermions allows the
calculation of time-dependent higher order correlation functions. We outline
the procedure using a field theoretic approach.Comment: 26 pages, 1 Postscript figure, uses epsf.st
Nonuniversal disordered Glauber dynamics
We consider the one-dimensional Glauber dynamics with coupling disorder in terms of bilinear fermion Hamiltonians. Dynamic exponents embodied in the spectrum gap of these latter are evaluated numerically by averaging over both binary and Gaussian disorder realizations. In the first case, these exponents are found to follow the nonuniversal values of those of plain dimerized chains. In the second situation their values are still nonuniversal and subdiffusive below a critical variance above which, however, the relaxation time is suggested to grow as a stretched exponential of the equilibrium correlation length.Facultad de Ciencias Exacta
Quantum Annealing in a Kinetically Constrained System
Classical and quantum annealing is discussed for a kinetically constrained
chain of non-interacting asymmetric double wells, represented by Ising
spins in a longitudinal field . It is shown that in certain cases, where the
kinetic constraints may arise from infinitely high but vanishingly narrow
barriers appearing in the relaxation path of the system, quantum annealing
exploiting the quantum-mechanical penetration of sufficiently narrow barriers
may be far more efficient than its thermal counterpart.
We have used a semiclassical picture of scattering dynamics to do our
simulation for the quantum system.Comment: 5 pages, 3 figure
Stick-slip statistics for two fractal surfaces: A model for earthquakes
Following the observations of the self-similarity in various length scales in
the roughness of the fractured solid surfaces, we propose here a new model for
the earthquake. We demonstrate rigorously that the contact area distribution
between two fractal surfaces follows an unique power law. This is then utilised
to show that the elastic energy releases for slips between two rough fractal
surfaces indeed follow a Guttenberg-Richter like power law.Comment: 9 pages (Latex), 4 figures (postscript
Exact joint density-current probability function for the asymmetric exclusion process
We study the asymmetric exclusion process with open boundaries and derive the
exact form of the joint probability function for the occupation number and the
current through the system. We further consider the thermodynamic limit,
showing that the resulting distribution is non-Gaussian and that the density
fluctuations have a discontinuity at the continuous phase transition, while the
current fluctuations are continuous. The derivations are performed by using the
standard operator algebraic approach, and by the introduction of new operators
satisfying a modified version of the original algebra.Comment: 4 pages, 3 figure
Directed diffusion of reconstituting dimers
We discuss dynamical aspects of an asymmetric version of assisted diffusion
of hard core particles on a ring studied by G. I. Menon {\it et al.} in J. Stat
Phys. {\bf 86}, 1237 (1997). The asymmetry brings in phenomena like kinematic
waves and effects of the Kardar-Parisi-Zhang nonlinearity, which combine with
the feature of strongly broken ergodicity, a characteristic of the model. A
central role is played by a single nonlocal invariant, the irreducible string,
whose interplay with the driven motion of reconstituting dimers, arising from
the assisted hopping, determines the asymptotic dynamics and scaling regimes.
These are investigated both analytically and numerically through
sector-dependent mappings to the asymmetric simple exclusion process.Comment: 10 pages, 6 figures. Slight corrections, one added reference. To
appear in J. Phys. Cond. Matt. (2007). Special issue on chemical kinetic
The function of fear in institutional maintenance: Feeling frightened as an essential ingredient in haute cuisine
Fear is a common and powerful emotion that can regulate behaviour. Yet institutional scholars have paid limited attention to the function of fear in processes of institutional reproduction and stability. Drawing on an empirical study of elite chefs within the institution of haute cuisine, this article finds that the multifaceted emotion of fear characterised their experiences and served to sustain their institution. Chefs’ individual feelings of fear prompted conformity and a cognitive constriction, which narrowed their focus on to the precise reproduction of traditional practices whilst also limiting challenges to the norms underpinning the institution. Through fear work, chefs used threats and violence to connect individual experiences of fear to the violation of institutionalized rules, sustaining the conditions in which fear-driven maintenance work thrived. The study also suggests that fear is a normative element of haute cuisine in its own right, where the very experience and eliciting of fear preserved an essential institutional ingredient. In this way, emotions such as fear do not just accompany processes of institutionalization but can be intimately involved in the maintenance of institutions