Bulletin of the American Physical Society
85th Annual Meeting of the APS Southeastern Section
Volume 63, Number 19
Thursday–Saturday, November 8–10, 2018; Holiday Inn at World’s Fair Park, Knoxville, Tennessee
Session A04: Statistical and Non-Linear Physics |
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Chair: Michel Pleimling, Virginia Tech Room: World's Fair Park Holiday Inn Parlor |
Thursday, November 8, 2018 8:30AM - 8:42AM |
A04.00001: The effects of inhibitory neuron fraction on the dynamics of an avalanching neural network Jacob A Carroll, Ada Warren, Uwe Claus Tauber The statistical analysis of the collective neural activity known as avalanches provides insight into the proper behavior of brains across many species. In this talk we present a neural network model based on the work of Lombardi, Herrmann, de Arcangelis et al. that captures the relevant dynamics of neural avalanches, and we show how tuning the fraction of inhibitory neurons in this model removes exponential cut-offs present in the distributions of avalanche strength and duration, and transitions the power spectral density of the network into an epileptic regime. We propose that the brain operates away from this regime of low inhibitory fraction to protect itself from the dominating avalanches present in these extended distributions. |
Thursday, November 8, 2018 8:42AM - 8:54AM |
A04.00002: Dynamical properties at Voter critical points Ahmadreza Azizi, James Stidham, Michel Pleimling We discuss the dynamical properties of two non-equilibrium systems that exhibit a critical point belonging to the Voter universality class. At a Voter critical point an order-disorder transition and an absorbing transition take place at the same time. Our extensive numerical simulations reveal a simple aging scaling behavior of two-time quantities with universal dynamic exponents. This corrects earlier claims in the literature. The properties of the time-dependent magnetization at the critical point depend on whether the model is linear or non-linear. |
Thursday, November 8, 2018 8:54AM - 9:06AM |
A04.00003: Evolutionary dynamics of unstable populations invading healthy populations Daniel E Castillo, Maxim Lavrentovich Typical studies of spatial population genetics look at the dynamics of populations as they evolve in an isolated environment. In reality, when a population is evolving and spreading into new territory, it must compete with any other populations who already occupy that space. An invasive animal species, for example, must compete with the species already present in the ecological habitat; similarly, a cancerous tumor which starts out as a small cluster of rapidly growing and mutating cells must compete with surrounding healthy tissue. We look at spatial mutational meltdown models of a mutagenic population in the presence of a neutral bystander species with which it interacts only via competition. In particular we focus on the critical dynamics of the phase transition between the mutagenic population surviving for long times or dying out. We see that the roughness of domain walls between mutagenic and neutral populations becomes enhanced near the phase transition, consistent with the enhancement seen in isolated mutagenic models which have a rough, undulating growth front. Studying how these undulating domain walls couple to the critical dynamics of our model may provide valuable insight into what the shape of a cancerous tumor tells us about its long term survival probability. |
Thursday, November 8, 2018 9:06AM - 9:18AM |
A04.00004: Features of multistability in a system of repulsively coupled Kuramoto oscillators Shadisadat Esmaeili, Darka Labavic, Hildegard Meyer-Ortmanns, Michel Pleimling Coupled oscillators and emergent synchronized patterns are observed in many phenomena in nature. The Kuramoto model is one of the simplest models of coupled oscillators that can explain many such phenomena. A proper choice of (repulsive) coupling constants and topology in this model leads to versatile features of multistability. In particular, by choosing non-homogeneous natural frequencies long period orbits emerge, orders of magnitude longer than the natural frequencies. To understand the characteristics of the phase space we study the effects of tuning parameters like the coupling constant and the width of the frequency distribution. |
Thursday, November 8, 2018 9:18AM - 9:30AM |
A04.00005: Numerical studies on control of surface roughness in the KPZ equation Priyanka ., Michel Pleimling Kardar-Parisi-Zhang (KPZ) equation has been used in determining the growth process in a wide variety of particle interacting systems and experiments. Our objective in this work is to control the surface roughening in one and two dimensions using the KPZ equation. We aim to saturate the surface roughening to the desired value and try to understand its effect on the growth of mean and fluctuations. We perform the numerical simulation of the KPZ equation with and without control using the pseudospectral method. The Family-Vicsek scaling of numerical data shows that the linear feedback control does not affect the underlying process and leaves the system in the same KPZ universality class. |
Thursday, November 8, 2018 9:30AM - 9:42AM |
A04.00006: Non-universal Dynamics of Three-Dimensional Magnetic Systems With Heisenberg Interaction Riya Nandi, Uwe C. Tauber We numerically investigate the non-equilibrium critical dynamics in three-dimensional isotropic Heisenberg antiferromagnets. To account for the reversible terms arising from the microscopic dynamics of the system, we employ a hybrid simulation algorithm that combines reversible spin precession with relaxational Kawasaki spin exchange processes. We verify the dynamic exponent, and obtain a suitable aging scaling window. We observe and thus validate an older renormalization group prediction that, while the critical aging collapse exponent assumes universal value, the temporal decay exponent is found to be non-universal and dependent on the initial distribution of the spins. |
Thursday, November 8, 2018 9:42AM - 9:54AM |
A04.00007: Rare-event extinction phenomena in three species cyclic predation games Shannon Reuben Serrao, Darka Labavic, Hildegard Meyer-Ortmanns In the modified May-Leonard model with cyclically competing three species, we compute the statistics of rare-event two species extinction process from a long lived metastable three-species coexistence state. We employ a master equation based eikonal quasi-stationary approximation of the metastable state effectively reducing the problem to the classical dynamics evolution of a Hamiltonian in six degrees of freedom. We then solve the evolution of this system by applying the Iterative Action Minimization Method(IAMM) and compute the action along the optimal path across the transcritical bifurcation. Our results are compared with action computed from the generating function based Hamiltonian of the said (3,1) game. The results obtained are validated for regions across the transcritical bifurcation in the system and investigated for different values of the system size parameter $V$. |
Thursday, November 8, 2018 9:54AM - 10:06AM |
A04.00008: Transverse Temperature Interfaces in the Katz-Lebowitz-Spohn Driven Lattice Gas Ruslan Mukhamadiarov, Priyanka ., Uwe Claus Täuber We explore the intriguing spatial patterns that emerge in a two-temperature Katz-Lebowitz-Spohn (KLS) model in two dimensions, a driven lattice gas with attractive nearest-neighbor interactions and periodic boundary conditions. The domain is split into two regions with hopping rates governed by different temperatures T > Tc and Tc, respectively, where Tc indicates the critical temperature for phase ordering, and with the temperature boundaries oriented transverse to the drive. In the hotter region, the system behaves like the (totally) asymmetric exclusion processes (T)ASEP, and experiences particle blockage in front of the interface to the critical region. We argue that transport in the subsystem is impeded by the lower current in the cooler region, which tends to set the global stationary particle current value. We observe the density profiles in both high-and low-temperature subsystems to be strikingly similar to the well-characterized coexistence and maximal-current phases in (T)ASEP models with open boundary conditions. If the lower temperature is set equal to Tc, we instead detect the corresponding critical power law density decay. |
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