Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session S40: Systems with Large Fluctuations and Strong Correlations IIFocus

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Sponsoring Units: GSNP Chair: Uwe Tauber, Virginia Tech Room: 343 
Thursday, March 17, 2016 11:15AM  11:51AM 
S40.00001: FirstPassage Statistics of Extreme Values Invited Speaker: Eli BenNaim Theoretical concepts from nonequilibrium statistical physics such as scaling and correlations are used to analyze firstpassage processes involving extreme values. The focus of this talk is statistics of the running maxima, defined as the largest variable in a sequence of random variables. In particular, the running maxima of multiple independent sequences of stochastic variables are compared. The probability that these maxima remain perfectly ordered decays algebraically with the number of random variables, and the decay exponent characterizing this decay is nontrivial. Exact solutions for the scaling exponents will be discussed for uncorrelated variables as well as Brownian trajectories which are correlated. Relevance of such statistical measures for analysis of empirical data will be discussed as well. [Preview Abstract] 
Thursday, March 17, 2016 11:51AM  12:03PM 
S40.00002: Emergence of universal statistics from conserved topological features of underlying network dynamics Srividya IyerBiswas In this talk I will discuss how universal statistics emerge from conserved topological features of underlying network dynamics. I will indicate how dynamical phase transitions between different network structures also encode universal signatures. I will connect these results with our singlecell experiments on C. crescentus cells. [Preview Abstract] 
Thursday, March 17, 2016 12:03PM  12:15PM 
S40.00003: Anomalous Dimension in a TwoSpecies ReactionDiffusion Model Joshua Hellerick , Benjamin VollmayrLee We consider particles ($A$) diffusing in the presence of traps ($B$), which themselves are diffusing and reacting, i.e. the twospecies reaction diffusion model $A+B\to B$ and $B+B\to(0,B)$. We introduce a simulation technique that provides the full probability distribution of particles for a given realization of the trap dynamics. Previous renormalization group analysis predicted that the density of $A$ particles decays as $a~t^{\theta}$ where $\theta$ is a nontrivial, universal exponent for $d<2$. We compare our results with these predictions, and also demonstrate the scaling of the correlation functions. We discover an anomalous dimension in the particleparticle correlation function, described by $G_{AA}(0)\sim t^\phi$, and we report our measurements for this new exponent. [Preview Abstract] 
Thursday, March 17, 2016 12:15PM  12:27PM 
S40.00004: Nonequilibrium steady states of stochastic processes with intermittent resetting Stephan Eule , Jakob Metzger Stochastic processes that are randomly reset to an initial condition serve as a showcase to analytically investigate nonequilibrium steady states. Here we study such processes for which the time between the resets is random and drawn from a generic waiting time distribution. We obtain the general solution for the stationary state and quantify the temporal relaxation of the process in terms of its moments. Our results are applied to analyze the efficiency of constrained random search processes. For a fixed mean reset time, we show that the search efficiency can be optimized by adapting the shape of the waiting time distribution. [Preview Abstract] 
Thursday, March 17, 2016 12:27PM  12:39PM 
S40.00005: Persistent Probability Currents in Nonequilibrium Steady States Royce Zia , Andrew Mellor , Mauro Mobilia , Baylor FoxKemper , Jeffrey Weiss For many interesting phenomena in nature, from all life forms to the global climate, the fundamental hypothesis of equilibrium statistical mechanics does not apply. Instead, they are perhaps better characterized by nonequilibrium steady states, evolving with dynamical rules which violate detailed balance. In particular, such dynamics leads to the existence of nontrivial, persistent probability currents  a principal characteristic of nonequilibrium steady states. In turn, they give rise to the notion of 'probability angular momentum'. Observable manifestations of such abstract concepts will be illustrated in two distinct contexts: a heterogeneous nonlinear voter model and our ocean heat content. [Preview Abstract] 
Thursday, March 17, 2016 12:39PM  12:51PM 
S40.00006: From randomly accelerated particles to L\'{e}vy walks: nonergodic behavior and aging Guenter Radons , Tony Albers For randomly accelerated particles we detected, and were able to analyze in detail (PRL 113, 184101 (2014)), the phenomenon of weakergodicity breaking (WEB), i.e. the inequivalence of ensemble and timeaveraged meansquared displacements (MSD). These results, including their aging time dependence, are relevant for anomalous chaotic diffusion in Hamiltonian systems, for passive tracer transport in turbulent flows, and many other systems showing momentum diffusion. There are, however, several related models, such as the integrated random excursion model, or, spacetime correlated L\'{e}vy walks and flights, with similar statistical behavior. We compare the WEB related properties of these models and find surprising differences although, for equivalent parameters, all of them are supposed to lead to the same ensembleaveraged MSD. Our findings are relevant for distinguishing possible models for the anomalous diffusion occurring in experimental situations. [Preview Abstract] 
Thursday, March 17, 2016 12:51PM  1:03PM 
S40.00007: Disordered confinement and anomalous diffusion Gerald Lapeyre We discuss the effect of disordered confinement on anomalous diffusion. We treat confinement in conjunction with ordinary diffusion and with anomalous diffusions associated with aging and with correlated displacements. In particular, we compute the altered anomalous exponents. Finally, we relate these results to previous work and show that they shed light on the nature of diffusion on percolation clusters. [Preview Abstract] 
Thursday, March 17, 2016 1:03PM  1:15PM 
S40.00008: Nonequilibrium dynamics of the complex GinzburgLandau equation Weigang Liu , Uwe Tauber The complex GinzburgLandau equation combines the quantum manyparticle nonlinear SchrÃ¶dinger equation with the timedependent GinzburgLandau equation or model A relaxational dynamics. It arises in quite diverse contexts that include spontaneous pattern formation out of equilibrium, chemical oscillations, multimode lasers, thermal convection in binary fluids, cyclic population dynamics, and drivendissipative BoseEinstein condensates. Indeed, the complex GinzburgLandau equation exhibits a remarkably rich phase diagram with intriguing dynamics. We employ detailed numerical studies as well as analytical tools such as the perturbative renormalization group and the spherical model limit to study the nonequilibrium coarsening and critical aging scaling for the complex GinzburgLandau equation following quenches from an initial disordered configuration to either one of the ordered phases or the critical point. [Preview Abstract] 
Thursday, March 17, 2016 1:15PM  1:27PM 
S40.00009: Multiscale phenomena and crossover in fluctuations in nonequilibrium systems A. Surjalal Sharma , Venkat Anurag Setty Fluctuations in multiscale phenomena in natural systems, e. g., Earth's magnetosphere, exhibit crossover behavior in the scaling exponents. These exponents represent the nature of correlation in the system and the crossover shows the presence of more than one type of correlation. An accurate characterization of the crossover behavior is thus needed for a better understanding of the inherent correlations in the system. A multistep process is developed for accurate computation of the crossover behavior. First the detrended fluctuation analysis is used to remove the trends in the data and the scaling exponents are computed. The crossover point is then computed by a Hyperbolic regression technique, with no prior assumptions. The time series data of the magnetic field variations in the Earth's magnetosphere is analyzed with these techniques and yields a crossover behavior with a time scale of ~ 4 hrs. A Langevin model of the magnetospheric dynamics yields an excellent fit to the crossover in the scaling exponents and thus provide a model of the nonequilibrium system. [Preview Abstract] 
Thursday, March 17, 2016 1:27PM  1:39PM 
S40.00010: Ligand binding kinetics in surface plasmon resonance devices: A Monte Carlo simulation analysis Jacob Carroll , Uwe Tauber Surface plasmon resonance (SPR) chips are widely used to measure association and dissociation rates for the binding kinetics between two species of chemicals, e.g., cell receptors and ligands. It is commonly assumed that ligands are spatially well mixed in the SPR region, and hence a meanfield rate equation description is appropriate. This approximation however ignores the spatial fluctuations as well as temporal correlations induced by multiple local rebinding events, which become prominent for slow diffusion rates. We report detailed Monte Carlo simulations of ligand binding kinetics in an SPR cell subject to laminar flow. We extract the binding and dissociation rates by means of the techniques frequently employed in experimental analysis that are motivated by the meanfield approximation. We find major discrepancies in a wide parameter regime between the thus extracted rates and the input simulation values. These results underscore the crucial quantitative importance of spatiotemporal correlations in binary reaction kinetics in SPR cell geometries. [Preview Abstract] 
Thursday, March 17, 2016 1:39PM  1:51PM 
S40.00011: Thermodynamic and Information Entropy in Electroconvection John Cressman , Marcus Daum , David Patrick , Rory Cerbus , Walter Goldburg Transitions in driven systems often produce wild fluctuations that can be both detrimental and beneficial. Our fundamental understanding of these transients is inadequate to permit optimal interactions with systems ranging from biology, to energy generation, to finance. Here we report on experiments performed in electroconvecting liquid crystals where we abruptly change the electrical forcing across the sample from a state below defect turbulence into a state of defect turbulence. We simultaneously measure the electrical power flow through the liquid crystal as well as image the structure in the sample. These measurements enable us to simultaneously track the evolution of the thermodynamic and information entropies. Our experiments demonstrate that there are strong correlations between the fluctuations in these two entropic measures however they are not exact. We will discuss these discrepancies as well as the relevance of large transient fluctuations in nonequilibrium transitions in general. [Preview Abstract] 
Thursday, March 17, 2016 1:51PM  2:03PM 
S40.00012: Low dissipation in nonequilibrium control: sampling the ensemble of efficient protocols. Grant Rotskoff , Todd Gingrich , Gavin Crooks , Phillip Geissler Designing schemes to efficiently control fluctuating, nonequilibrium systems is problem of fundamental importance and tremendous practical interest. A number of optimization techniques have proven fruitful in the pursuit of optimal control, but these approaches focus on the singular goal of finding the exact, optimal protocol. Here, we investigate the diversity of protocols that achieve low dissipation with a Monte Carlo path sampling algorithm. Akin to Boltzmann weighting configurations in Metropolis Monte Carlo, each protocol is exponentially biased by its mean dissipation. We show that the ensemble of low dissipation protocols can be sampled exactly in the Gaussian limit and that the method continues to robustly generate low dissipation protocols, even as the external control drives the system far from equilibrium. [Preview Abstract] 
Thursday, March 17, 2016 2:03PM  2:15PM 
S40.00013: Geometry of dissipative evolution equations Celia Reina The modeling of continuum dissipative evolution equations remains a challenge and is primarily based on phenomenological constitutive relations. In this talk we present some connections between the geometry of dissipative gradient flows, the principle of maximum entropy production, large deviation principles for stochastically augmented evolution equations and fluctuationdissipation relations. [Preview Abstract] 
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