Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session Q39: Focus Session: Models and Materials Far from Equilibrium 
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Sponsoring Units: GSNP Chair: Michel Pleimling, Virginia Polytechnic Institute and State University Room: Morial Convention Center 231 
Wednesday, March 12, 2008 11:15AM  11:27AM 
Q39.00001: SelfOrganized Porous Nanostructures in Anodized Metal Oxide Liam Stanton, Alexander Golovin We consider the selforganization of porous nanostructures in anodized metal oxide. We have developed a mathematical model which incorporates the electrochemical transport of oxygen anions within the oxide layer and the chemical reactions at the metaloxide and oxideelectrolyte interfaces. It is shown through linear stability analysis, that a shortwave instability exists in certain parameter regimes which leads to the formation of hexagonally ordered pores observed in anodized aluminum oxide. Numerical simulations validate these results. [Preview Abstract] 
Wednesday, March 12, 2008 11:27AM  11:39AM 
Q39.00002: Intercalation of Li Ions into a Graphite Anode Material: Molecular Dynamics Simulations Ibrahim Abou Hamad, Mark Novotny Largescale molecular dynamics simulations of the anode halfcell of a lithiumion battery are presented. The model system is composed of an anode represented by a stack of graphite sheets, an electrolyte of ethylene carbonate and propylene carbonate molecules, and lithium and hexafluorophosphate ions. The simulations are done in the NVT ensemble and at room temperature. One charging scheme explored is normal charging in which intercalation is enhanced by electric charges on the graphitic sheets. The second charging mechanism has an external applied oscillatory electric field of amplitude A and frequency f. The simulations were performed on 2.6 GHz Opteron processors, using 160 processors at a time. Our simulation results show an improvement in the intercalation time of the lithium ions for the second charging mechanism. The dependence of the intercalation time on A and f will be discussed. [Preview Abstract] 
Wednesday, March 12, 2008 11:39AM  11:51AM 
Q39.00003: Aging processes in reversible diffusionlimited reactions Vlad Elgart, Michel Pleimling Reversible diffusionlimited reactions display anomalous (i.e. slow) dynamics characterized by a powerlaw relaxation toward stationarity. In contrast to previous studies that focused on the timedependence of this relaxation, we study here the nonequilibrium behavior of various simple reversible reactiondiffusion models in the aging regime. Starting from the exact Langevin equations describing these models, we derive expressions for twotime autocorrelation and autoresponse functions and obtain a simple aging behavior for these quantities. The autoresponse function is thereby found to depend on the specific nature of the chosen perturbation of the system. [Preview Abstract] 
Wednesday, March 12, 2008 11:51AM  12:03PM 
Q39.00004: Lyapunov modes in coupled map lattices Guenter Radons, Hongliu Yang Hydrodynamic Lyapunov modes, which have recently been observed in many extended systems with translational symmetry, such as hard sphere systems, dynamic XYmodels, or LennardJones fluids, are nowadays regarded as fundamental objects connecting Nonlinear Dynamics and Statistical Physics. A solution to one of the puzzles, the appearance of good and of ``vague'' modes, is presented here for the model system of coupled map lattices: The structural properties of these modes are related to the phase space geometry, especially the angles between Oseledec subspaces, and to fluctuations of local Lyapunov exponents. The numerical calculation of these quantities is achieved with the new algorithm proposed in [1]. In this context we report also on the possible appearance of branches in the Lyapunov spectra of inhomogeneous systems [2], similar to acoustic and optical branches for phonons. \newline [1] F. Ginelli et al., PRL 99, 130601 (2007) \newline [2] H. Yang and G. Radons, PRL 99, 164101 (2007) [Preview Abstract] 
Wednesday, March 12, 2008 12:03PM  12:15PM 
Q39.00005: Simulation of nonlinear pattern formation dynamics in photoinduced structure change Kunio Ishida, Keiichiro Nasu We study the nonlinear dynamics of pattern formation triggered by injection of photoexcited states. In order to describe the nonadiabatic transition during the relaxation process, we employ a model of localized electrons coupled with a fully quantized phonon mode, and the timedependent Schr\"odinger equation for the model is numerically solved. We found that the photoinduced nucleation process is switched on only when certain amount of excitation energy is supplied in a narrow part of the system, i.e., there exists a smallest cluster of excited molecules which makes the nucleation possible. As a result, the portion of the cooperatively converted molecules is nonlinearly dependent on the photoexcitation strength, which has been observed in various materials. [Preview Abstract] 
Wednesday, March 12, 2008 12:15PM  12:27PM 
Q39.00006: A study of some nonequilibrium driven models and their contribution to the understanding of molecular motors Irina Mazilu, Joshua Gonzalez From the point of view of a physicist, a biomolecular motor represents an interesting nonequilibrium system and it is directly amenable to an analysis using standard methods of nonequilibrium statistical physics. We conduct a rigorous Monte Carlo study of three different driven lattice gas models that retain the basic behavior of three types of cytoskeletal molecular motors. Our models incorporate novel features such as realistic dynamics rules and complex motormotor interactions. We are interested to have a deeper understanding of how various parameters influence the macroscopic behavior of these systems, what is the density profile and if the system undergoes a phase transition. On the analytical front, we computed the steadystate probability distributions exactly for the one of the models using the matrix method that was established in 1993 by B. Derrida et al. We also explored the possibilities offered by the ``Bethe ansatz'' method by mapping some well studied spin models into asymmetric simple exclusion models (already analyzed using computer simulations), and to use the results obtained for the spin models in finding an exact solution for our problem. We have exhaustive computational studies of the kinesin and dynein molecular motor models that prove to be very useful in checking our analytical work. [Preview Abstract] 
Wednesday, March 12, 2008 12:27PM  12:39PM 
Q39.00007: Controlling surface morphologies by timedelayed feedback Beate Schmittmann, Michael Block, Eckehard Schoell We propose a new method to control the roughness of a growing surface, via a timedelayed feedback scheme. The method is very general and can be applied to a wide range of nonequilibrium growth phenomena, from solidstate epitaxy to tumor growth. Possible experimental realizations are suggested. As an illustration, we consider the KardarParisiZhang equation in 1+1 dimensions and show that the effective growth exponent of the surface width can be stabilized at any desired value in the interval [0.25,0.33], for a significant length of time. [Preview Abstract] 
Wednesday, March 12, 2008 12:39PM  12:51PM 
Q39.00008: SchwingerKeldysh Formalism for NonHermitian Quantum Problems: A Case Study on NonEquilibrium Steady State Transport Paata Kakashvili, C.J. Bolech Nonunitary quantum mechanics has been used in the past to study irreversibility, dissipation and decay in a variety of physical systems. In this presentation, we propose a general scheme to deal with systems governed by nonHermitian Hamiltonians. We argue that the SchwingerKeldysh formalism gives a natural description for those problems. To be concrete, we study a simple model inspired by mesoscopic physics an asymmetric junction (relevant to spinvalve devices). The system is governed by a nonHermitian Hamiltonian which captures essential aspects of irreversibility. Calculated steady state transport properties show behavior which is anticipated on physical grounds. [Preview Abstract] 

Q39.00009: ABSTRACT WITHDRAWN 
Wednesday, March 12, 2008 1:03PM  1:15PM 
Q39.00010: Caliber approach for nonequilibrium systems with a small number of states Jeremy Schmit, Kingshuk Ghosh, Ken Dill We present a theory for the dynamics of systems with a small number of states based on E.T. Jaynes' principle of Maximum Caliber. We construct the full dynamical partition function using a transfer matrix formalism with the transition rates as input parameters. Using this partition function, we are able to calculate all moments of dynamical quantities, and thus are able to predict fluctuations around the average behavior. We compare our results to single molecule and microfluidics experiments and contrast our results to the predictions of Minimum Entropy Production. [Preview Abstract] 
Wednesday, March 12, 2008 1:15PM  1:27PM 
Q39.00011: Transition rates for a BlumeCapel model coupled to a phonon bath Kyungwha Park In nanoscale systems ranging from semiconductor quantum dots to arrays of magnetic nanoparticles or nanoscale magnetic molecules, dynamic properties play a crucial role in understanding the underlying physics and in designing systems of interest for applications. Dynamic properties are highly sensitive to transition rates used, so it is crucial to use a physically correct stochastic dynamic to examine dynamic properties. However, spin Hamiltonians do not provide generic dynamics, so a dynamic should be determined from microscopic Hamiltonians. As the first step towards deriving a realistic spin dynamic of nanoscale systems, we consider the ferromagnetic S=1 BlumeCapel model on a square lattice in which each spin is weakly coupled to a ddimensional phonon bath, and derive transition rates from a spinphonon coupling Hamiltonian. Based on the derived transition rates, dynamical properties such as metastability and nucleation are studied in the lowtemperature limit using kinetic Monte Carlo simulations. The properties obtained from the phononassisted transition rates are compared with those from the Glauber transition rate. [Preview Abstract] 
Wednesday, March 12, 2008 1:27PM  1:39PM 
Q39.00012: Statistical mechanics far from equilibrium: prediction and test for a sheared system A. Baule, R. M. L. Evans, R. A. Simha, P. D. Olmsted Beginning from a description of the forces of interaction between microscopic particles in motion, equilibrium statistical mechanics can predict both the statistical properties of their resulting configurations and the properties of the fluid (or other material) that they constitute. Despite the existence of statistical steady states of complex fluids under continuous shear flow, with intriguing similarities to equilibrium phase behaviour, a similarly complete statistical solution has hitherto been unobtainable away from thermodynamic equilibrium. Instead, theorists have had to resort to artificial models with simple dynamics (e.g. some invented set of microscopic transition rates) or, alternatively, to use nearequilibrium approximations. We report the first complete statistical treatment of a collection of particles interacting via Newtonian forces in the presence of continuous boundarydriven flow, arbitrarily far from equilibrium [1]. Our investigation is based on a nonequilibrium counterpart to detailed balance [2] which leads to a set of simple constraints for the driven transition rates in our model system. We have tested the predictions in simulations, by numerically solving and timestepping the forcebalance equations. [1] R. M. L. Evans, R. A. Simha, A. Baule and P. D. Olmsted, to be submitted. [2] R. M.L. Evans, Phys. Rev. Lett. 92, 150601 (2004). [Preview Abstract] 
Wednesday, March 12, 2008 1:39PM  2:15PM 
Q39.00013: Dynamic phase transitions in model glass formers Invited Speaker: Fr\'ed\'eric van Wijland Glassy dynamics is identified through a series of signatures, such as aging, slow relaxation and the presence of dynamical heterogeneities. Basing our considerations on kinetically constrained glass formers, we argue that these phenomena are the byproduct of an intrinsically dynamic phase transition. The latter can be unravelled by performing, in the spirit of Ruelle, a Gibbslike statistical mechanics over the set of time realizations of the systems' evolution, rather than over the conventional set of phase space configurations. [Preview Abstract] 
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