Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Q01: Noise-driven Dynamics in Far-from-Equilibrium SystemsFocus
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Sponsoring Units: GSNP Chair: Stephen Teitsworth, Duke University Room: Room 124 |
Wednesday, March 8, 2023 3:00PM - 3:36PM |
Q01.00001: Effective thermal equilibrium induced by cross-linking proteins in polymer chromosome models Invited Speaker: Katherine A Newhall Biological systems are a natural place to find far-from-equilibrium dynamics where ATP-mediated forces are at play. I will discuss one such system, the dynamics of yeast chromatin that displays equilibrium-like self-organized clusters despite the presence of crosslinking condensin proteins pushing the system out of equilibrium. Mathematically, different limits concerning the two sources of noise (randomly switching protein binding forces and thermal noise) produce different predictions for the behavior of the system. The one that accurately describes the results of numerical simulations suggests that the biological system may be taking advantage of the switching noise to produce metastable clusters. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q01.00002: Extreme Diffusion 1: Failure of Classical Diffusion to Characterize Extreme First Passage Times in Correlated Environments Jacob Hass, Eric I Corwin, Ivan Corwin The first passage time for a random diffusing process is essential to the behavior of systems in many disparate fields, such as Biology, Economics, and Ecology. Although the first passage time for a single particle has been studied extensively, the first passage time of a system of multiple particles, which is often the case in physical systems, has received less attention until recently. Random unbiased walks on a 1D lattice are often used to model diffusive systems; however, such a simple model fails to account for any space-time correlations in the system. We study a new framework for diffusion which introduces a space-time random forcing field and characterize the first passage time among many random walkers diffusing in this field. We discover novel scalings of the first passage time, which relate to the KPZ universality class, and numerically verify the asymptotic analytic results across a very wide range of system sizes. Surprisingly, these results hold even for systems with as few as 10 particles. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q01.00003: Extreme Diffusion 2: Experimental Test of a New Model for the Statistics of Extreme Particles in Diffusion Aileen Godfrey, Eric I Corwin In diffusive environments, the classical model of diffusion well describes the bulk behavior of particles, based on individual particles undergoing independent random walks. However, we should expect that particles near one another should be influenced by the shared medium in which they move. Thus, the distributions of outlier particle locations and first passage times should differ from those predicted by the classical diffusion model. Numerical work has already shown that a shared biasing environment will result in markedly different variance for the location and time of first passage for extreme particles. Here, we probe this by studying first passage times in two different diffusive systems. The first system consists of micron-sized colloids diffusing in water, the second of photons diffusing through a scattering medium. We report on the design of experimental apparati as well as the first measurements of the statistics of extreme particles. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q01.00004: Mutual Information Reveals Emergent Effects of Self-Avoidant Memory in Curvature Statistics of Particle Paths. Katherine Daftari Chemically induced swimming of microdroplets motivates a model for self-avoidant particles which exhibit novel trajectory statistics at long timescales. As the particles stochastically explore the self-generated and time-evolving concentration field, they often turn in on their own past history and create concentration "traps" which arrest the overall displacement for a period of time. This transient self-trapping is revealed in the path data as areas of extremely high correlated curvature and it is expressed statistically as suppressed enhanced diffusion when compared to traditional active particle models. We explore the shortcomings of traditional models in explaining this behavior and suggest mutual information as an additional tool can be used to quantify this emergent effect. |
Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q01.00005: Effective Thermal Equilibrium for Switiching Polymer Model of Chromosome Dynamics Anna Coletti How the genome organizes and interacts within the cell can be understood through a polymer-like model of chromosome dynamics that combines Brownian motion with a stochastic switching force. The switching force, which follows a continuous-time Markov chain process, keeps the general overdamped Langevin system out of strict equilibrium. However, an effective energy landscape through the framework of quasipotentials helps us to understand the stability and transitions in the system. We show how this quasipotential changes as a function of switching rate which explains the difference in cluster-lifetimes observed in the large scale simulations of the experimental chromosome system. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q01.00006: Coalescence of limits cycles in the presence of noise Sergei Shmakov, Peter Littlewood In recent studies, pitchfork bifurcation is used to induce bifurcation behavior in dynamical systems with attractors. We model a limit cycle with the normal form of the Hopf oscillator, couple it to the pitchfork, and investigate the resulting dynamical system in the presence of noise. We show that the generating functional for the averages of the dynamical variables factorizes between the pitchfork and the oscillator. The statistical properties of the pitchfork in the presence of noise in its various regimes are investigated and a scaling theory is developed for the correlation and response functions. The analysis is done by perturbative calculations as well as numerical means. Finally, observables illustrating the coupling of a system with a limit cycle to a pitchfork are discussed and the phase-phase correlations are shown to obtain non-diffusive behavior. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q01.00007: Perturbative Field-Theoretical Analysis of Three-Species Cyclic Predator-Prey Models Louie Hong Yao, Mohamed Swailem, Ulrich Dobramysl, Uwe C Tauber We apply a perturbative field-theoretical analysis on the symmetric Rock-Paper-Scissors (RPS) model and the symmetric May-Leonard (ML) model, in which three species compete cyclically. Compared to the two-species Lotka-Volterra predator-prey (LV) model, according to numerical simulations, these cyclical models appear to be less affected by intrinsic stochastic fluctuations. Indeed, we demonstrate that the qualitative features of the ML model are insensitive to intrinsic reaction noise. In contrast, and although as yet not observed in numerical simulations, we find that the RPS model acquires significant fluctuation-induced renormalizations in the perturbative regime, similar to the LV model. We also study the formation of spatio-temporal structures in the framework of stability analysis and provide a clearcut explanation for the absence of spatial patterns in the RPS model, whereas the spontaneous emergence of spatio-temporal structures features prominently in the LV and the ML models. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q01.00008: Exact finite-dimensional reduction for a population of noisy oscillators Arkady Pikovsky A description of complex systems by virtue of a few apposite order parameters is an indispensable tool of the theoretical analysis of nonequilibrium dynamics. In many cases, such a reduction is possible close to a bifurcation point, where a separation of timescales can be employed to derive approximate closed equations for a few order parameters. Here, we report on an exact reduction of the kinetic (generalized Fokker-Planck) equation to three complex variables. The dynamical equations are shown to contain the Ott-Antonsen dynamics as an attracting manifold. We demonstrate, how this finite-dimensional description allows for exact calculation of the effect of resetting of the ensemble. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q01.00009: Irreversibility and heat transfer in closed Hamiltonian systems Stephen W Teitsworth, John C Neu Understanding and quantitatively characterizing irreversibility and related phenomena is a central task in the study of noise-driven non-equilibrium systems. In this talk, we consider a closed Hamiltonian dynamical system consisting of two heat baths, each with many degrees of freedom, coupled to one another via a small number of macroscopic degrees of freedom. Each heat bath is modeled as a network of linearly coupled oscillators [1] initiated so that the effective temperatures of the two baths are different from one another at time t = 0. The macroscopic degrees of freedom are modeled as a mass-spring system consisting of two particles each moving in a bath at different temperature; the particles are coupled to their respective heat bath oscillator networks, and also coupled to each other by a macroscopic spring. An initial temperature difference between the baths drives heat transfer from hot to cold. Strictly speaking, statistics on the full phase space (including all the microscopic degrees of freedom) cannot be stationary. Nonetheless, we find that quasi-stationary statistics representing the steady transfer of heat is achieved asymptotically for sufficiently large baths. Typically, the projected statistics of the full Hamiltonian system settles into this quasi-stationary state for a very long time. Conversely, the lower bound time scale for quasi-stationary behavior is set by transients to decay from arbitrary initial conditions, a time scale that is many of orders of magnitude smaller. Quasi-stationary behavior is also characterized by computing stochastic line integrals [2] corresponding, e.g., to stochastic area or heat transfer. These integrals can be performed using either the macroscopic degrees of freedom or purely microscopic degrees of freedoms associated with either of the heat bath oscillator networks. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q01.00010: Accessing the thermodynamic cost of information in a nano-electromechanical resonator Kushagra Aggarwal, Natalia Ares A piston coupled to a working fluid remains a quintessential example for understanding the laws of thermodynamics. Thermodynamics itself is undergoing a transformation with the emergence of nanoscale and quantum devices, where fluctuations and dissipation play a key role and require a departure from classical description. Here we explore a single electron coupled to a mechanical resonator as a nanoscale working fluid and a piston respectively. We use the back action of the single electron dynamics on the mechanical motion as a possible realisation of an information engine. This system provides a pathway to study the thermodynamic cost of quantum information processing. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q01.00011: Metrics for the violation of detailed balance in microwave circuits: theory and experiment Alexandre Dumont, Pierre FEVRIER, Christian Lupien, Bertrand Reulet We propose a new approach to detailed balance violation in electrical systems by relying on the scattering matrix formalism commonly used in microwave electronics. This allows to include retardation effects which are paramount at high frequencies. We define the spectral densities of phase space angular momentum, heat transfer and cross power, which can serve as criteria for detailed balance violation. We confirm our theory with measurements in the 4-8 GHz frequency range on several two port circuits of varying symmetries, in space and time. This validates our approach, which will allow to treat quantum circuits at ultra-low temperature. |
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