Buendia, Gloria M., Rikvold, Per Arne
We study the dynamical response of a two-dimensional Ising model subject to a square-wave oscillating external field. In contrast to earlier studies, the system evolves under a so-called soft Glauber...
Effects of stochastic population fluctuations in two models of biological macroevolution (2008)
Murase, Yohsuke, Shimada, Takashi, Ito, Nobuyasu, Rikvold, Per Arne
Two mathematical models of macroevolution are studied. These models have population dynamics at the species level, and mutations and extinction of species are also included. The population dynamics...
Chaotic Gene Regulatory Networks Can Be Robust Against Mutations and Noise (2007)
Sevim, Volkan, Rikvold, Per Arne
Robustness to mutations and noise has been shown to evolve through stabilizing selection for optimal phenotypes in model gene regulatory networks. The ability to evolve robust mutants is known to...
Realization of the mean-field universality class in spin-crossover materials (2007)
Miyashita, Seiji, Konishi, Yusuké, Nishino, Masamichi, Tokoro, Hiroko, Rikvold, Per Arne
In spin-crossover materials, the volume of a molecule changes depending on whether it is in the high-spin (HS) or low-spin (LS) state. This change causes distortion of the lattice. Elastic...
Unbiased Random Threshold Networks Are Chaotic or Critical (2007)
Sevim, Volkan, Rikvold, Per Arne
This paper has been withdrawn.
Hamad, Ibrahim Abou, Robb, Daniel T., Novotny, Mark A., Rikvold, Per Arne
We propose a new, cyclic-voltammetry based experimental technique that can not only differentiate between discontinuous and continuous phase transitions in an adsorbate layer, but also quite...
Network Growth with Preferential Attachment for High Indegree and Low Outdegree (2007)
Sevim, Volkan, Rikvold, Per Arne
We study the growth of a directed transportation network, such as a food web, in which links carry resources. We propose a growth process in which new nodes (or species) preferentially attach to...
Community-driven dispersal in an individual-based predator-prey model (2007)
Filotas, Elise, Grant, Martin, Parrott, Lael, Rikvold, Per Arne
We present a spatial, individual-based predator-prey model in which dispersal is dependent on the local community. We determine species suitability to the biotic conditions of their local environment...
Are Genetically Robust Regulatory Networks Dynamically Different from Random Ones? (2007)
Sevim, Volkan, Rikvold, Per Arne
We study a genetic regulatory network model developed to demonstrate that genetic robustness can evolve through stabilizing selection for optimal phenotypes. We report preliminary results on whether...
Rikvold, Per Arne, Sevim, Volkan
We study an individual-based predator-prey model of biological coevolution, using linear stability analysis and large-scale kinetic Monte Carlo simulations. The model exhibits approximate 1/f noise...
Complex Behavior in Simple Models of Biological Coevolution (2006)
We explore the complex dynamical behavior of simple predator-prey models of biological coevolution that account for interspecific and intraspecific competition for resources, as well as adaptive...
Frank, Stefan, Rikvold, Per Arne
The influence of lateral adsorbate diffusion on the dynamics of the first-order phase transition in a two-dimensional Ising lattice gas with attractive nearest-neighbor interactions is investigated...
Sevim, Volkan, Rikvold, Per Arne
We study the growth of a directed network, in which the growth is constrained by the cost of adding links to the existing nodes. We propose a new preferential-attachment scheme, in which a new node...
Waiting-time distribution for a stock-market index (2005)
Lee, Jae Woo, Lee, Kyoung Eun, Rikvold, Per Arne
We investigate the waiting-time distribution of the absolute return in the Korean stock-market index KOSPI. We define the waiting time as a time interval during which the normalized absolute return...
We compare and contrast the long-time dynamical properties of two individual-based models of biological coevolution. Selection occurs via multispecies, stochastic population dynamics with...
Sevim, Volkan, Rikvold, Per Arne
Models of coevolution have recently been studied, in which a species is defined by a genome in the form of a bitstring, and the interactions between species i and j are given by a fixed matrix with...
Fluctuations in models of biological macroevolution (2005)
Fluctuations in diversity and extinction sizes are discussed and compared for two different, individual-based models of biological coevolution. Both models display power-law distributions for various...
Multifractal Behavior of the Korean Stock-market Index KOSPI (2004)
Lee, Jae Woo, Lee, Kyuoung Eun, Rikvold, Per Arne
We investigate multifractality in the Korean stock-market index KOSPI. The generalized $q$th order height-height correlation function shows multiscaling properties. There are two scaling regimes with...
Frank, Stefan, Roberts, Daniel E., Rikvold, Per Arne
The influence of nearest-neighbor diffusion on the decay of a metastable low-coverage phase (monolayer adsorption) in a square lattice-gas model of electrochemical metal deposition is investigated by...
Machado, Erik, Buendia, Gloria M., Rikvold, Per Arne, Ziff, Robert M.
We present a kinetic Monte Carlo study of the dynamical response of a Ziff-Gulari-Barshad model for CO oxidation with CO desorption to periodic variation of the CO presure. We use a square-wave...
A Biological Coevolution Model with Correlated Individual-Based Dynamics (2004)
Sevim, Volkan, Rikvold, Per Arne
We study the effects of interspecific correlations in a biological coevolution model in which organisms are represented by genomes of bitstrings. We present preliminary results for this model,...
Buendia, Gloria M., Rikvold, Per Arne, Park, Kyungwha, Novotny, M. A.
Using both analytical and simulational methods, we study low-temperature nucleation rates in kinetic Ising lattice-gas models that evolve under two different Arrhenius dynamics that interpose between...
Fluctuations and correlations in an individual-based model of biological coevolution (2004)
Zia, R. K. P., Rikvold, Per Arne
We extend our study of a simple model of biological coevolution to its statistical properties. Staring with a complete description in terms of a master equation, we provide its relation to the...
Low-temperature nucleation in a kinetic Ising model with soft stochastic dynamics (2003)
Park, Kyungwha, Rikvold, Per Arne, Buendia, Gloria M., Novotny, M. A.
We study low-temperature nucleation in kinetic Ising models by analytical and simulational methods, confirming the general result for the average metastable lifetime, = A*exp(beta*Gamma) (beta =...
Rikvold, Per Arne, Zia, R. K. P.
We present a study by linear stability analysis and large-scale Monte Carlo simulations of a simple model of biological coevolution. Selection is provided through a reproduction probability that...
Update statistics in conservative parallel discrete event simulations of asynchronous systems (2003)
Kolakowska, A., Novotny, M. A., Rikvold, Per Arne
We model the performance of an ideal closed chain of L processing elements that work in parallel in an asynchronous manner. Their state updates follow a generic conservative algorithm. The...
Flicker Noise in a Model of Coevolving Biological Populations (2003)
Rikvold, Per Arne, Zia, R. K. P.
We present long Monte Carlo simulations of a simple model of biological macroevolution in which births, deaths, and mutational changes in the genome take place at the level of individual organisms....
Rikvold, Per Arne, Kolesik, M.
We present theoretical and dynamic Monte Carlo simulation results for the mobility and microscopic structure of 1+1-dimensional Ising interfaces moving far from equilibrium in an applied field under...
Wang, Sanwu, Mitchell, Steven J., Rikvold, Per Arne
Ab initio Monte Carlo simulations have been performed to determine the equilibrium properties of liquid lithium and lithium clusters at different temperatures. First-principles density-functional...
Extreme Long-time Dynamic Monte Carlo Simulations (2002)
Kolesik, Miroslav, Novotny, M. A., Rikvold, Per Arne
We study the extreme long-time behavior of the metastable phase of the three-dimensional Ising model with Glauber dynamics in an applied magnetic field and at a temperature below the critical...
Determining the Saddle Point in Micromagnetic Models of Magnetization Switching (2002)
Brown, Gregory, Novotny, M. A., Rikvold, Per Arne
A numerical model of single-domain nanoscale iron magnets fabricated using scanning-microscope-assisted chemical vapor deposition is simulated using finite-temperature micromagnetics. A...
Fine-grid Simulations of Thermally Activated (2002)
Per Arne Rikvold, Gregory Brown
Numerical integration of the Landau-Lifshitz-Gilbert equation with thermal fluctuations is used to study the dynamic response of single-domain nanomagnets to rapid changes in the applied magnetic...
Dynamics of Magnetization Reversal in Models (2001)
Per Arne Rikvold, Gregory Brown, M. A. Novotny
We discuss numerical and theoretical results for models of magnetization switching in nanoparticles and ultrathin films. The models and computational methods include kinetic Ising and classical...
Dynamics of Magnetization Reversal in Models of Magnetic Nanoparticles and Ultrathin Films (2001)
Rikvold, Per Arne, Brown, Gregory, Mitchell, Steven J., Novotny, M. A.
We discuss numerical and theoretical results for models of magnetization switching in nanoparticles and ultrathin films. The models and computational methods include kinetic Ising and classical...
Soft versus Hard Dynamics for Field-driven Solid-on-Solid Interfaces (2001)
Rikvold, Per Arne, Kolesik, Miroslav
Analytical arguments and dynamic Monte Carlo simulations show that the microstructure of field-driven Solid-on-Solid interfaces depends strongly on the dynamics. For nonconservative dynamics with...
Numerical Confirmation of Late-time t^{1/2} Growth in Three-dimensional Phase Ordering (2001)
Brown, Gregory, Rikvold, Per Arne
Results for the late-time regime of phase ordering in three dimensions are reported, based on numerical integration of the time-dependent Ginzburg-Landau equation with nonconserved order parameter at...
Wang, Sanwu, Rikvold, Per Arne
Ab initio total-energy density-functional methods with supercell models have been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and Au(100) surfaces. The atomic geometries of...
Langevin Simulation of Thermally Activated Magnetization Reversal in Nanoscale Pillars (2001)
Brown, Gregory, Novotny, M. A., Rikvold, Per Arne
Numerical solutions of the Landau-Lifshitz-Gilbert micromagnetic model incorporating thermal fluctuations and dipole-dipole interactions (calculated by the Fast Multipole Method) are presented for...
Statistical Mechanics of Lattice Models of Electrochemical Interfaces (2001)
Per Arne Rikvold, Gregory Brown, Steven J. Mitchell
Introduction The interfac between a solidelecM ode and a liquid elec4 olyte is ac omplic==+ multicM ponent system, in whic h the ions andc onduc tion elec trons of the elec trode interac t with...
Thermal Magnetization Reversal in Arrays of Nanoparticles (2000)
Brown, Gregory, Novotny, M. A., Rikvold, Per Arne
The results of large-scale simulations investigating the dynamics of magnetization reversal in arrays of single-domain nanomagnets after a rapid reversal of the applied field at nonzero temperature...
Analytic Approximations for the Velocity of Field-Driven Ising Interfaces (1999)
Rikvold, Per Arne, Kolesik, M.
We present analytic approximations for the field, temperature, and orientation dependences of the interface velocity in a two-dimensional kinetic Ising model in a nonzero field. The model, which has...
Micromagnetic simulations of thermally activated magnetization reversal of nanoscale magnets (1999)
Brown, Gregory, Novotny, M. A., Rikvold, Per Arne
Numerical integration of a stochastic Landau-Lifshitz-Gilbert equation is used to study dynamic processes in single-domain nanoscale magnets at nonzero temperatures. Special attention is given to...
Evolution of speckle during spinodal decomposition (1999)
Brown, Gregory, Rikvold, Per Arne, Sutton, Mark, Grant, Martin
Time-dependent properties of the speckled intensity patterns created by scattering coherent radiation from materials undergoing spinodal decomposition are investigated by numerical integration of the...
Simulation of Magnetization Switching in Biaxial Single-Domain Ferromagnetic Particles (1998)
Kou, Xuekun, Novotny, M. A., Rikvold, Per Arne
The magnetization switching dynamics of biaxial single-domain homogeneous ferromagnetic particles, in which the two easy axes are perpendicular to each other, is simulated using a 4-state clock...
Ramos, Raphael A., Rikvold, Per Arne, Novotny, M. A.
The Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory for the time evolution of the order parameter in systems undergoing first-order phase transformations has been extended by Sekimoto to the level of...
Universality and Scaling for the Structure Factor in Dynamic Order-Disorder Transitions (1998)
Brown, Gregory, Rikvold, Per Arne, Grant, Martin
The universal form for the average scattering intensity from systems undergoing order-disorder transitions is found by numerical integration of the Langevin dynamics. The result is nearly identical...
Gregory Brown, Per Arne Rikvold
We present a tutorial discussion of Monte Carlo methods for equilibrium and nonequilibrium problems in interfacial electrochemistry. The discussion is illustrated with results from simulations of...
Brown, Gregory, Rikvold, Per Arne, Mitchell, S. J., Novotny, M. A.
We present a tutorial discussion of Monte Carlo methods for equilibrium and nonequilibrium problems in interfacial electrochemistry. The discussion is illustrated with results from simulations of...
Kolesik, M., Novotny, M. A., Rikvold, Per Arne
Iron sesquilayers are ultrathin films with coverages between one and two atomic monolayers. They consist of an almost defect-free monolayer with compact islands of a second atomic layer on top. This...
Simulated Dynamics of Underpotential Deposition of Cu with Sulfate on Au(111) (1997)
Gregory Brown, Per Arne Rikvold, M. A. Novotny, Andrzej Wieckowski
Numerical studies of lattice-gas models are well suited to describe multi-adsorbate systems. One example is the underpotential deposition of Cu on Au(111) in the presence of sulfuric acid....
Simulated Dynamics of Underpotential Deposition of Cu with Sulfate on Au(111) (1997)
Brown, Gregory, Rikvold, Per Arne, Novotny, M. A., Wieckowski, Andrzej
Numerical studies of lattice-gas models are well suited to describe multi-adsorbate systems. One example is the underpotential deposition of Cu on Au(111) in the presence of sulfuric acid....
Speckle from phase ordering systems (1997)
Brown, Gregory, Rikvold, Per Arne, Sutton, Mark, Grant, Martin
The statistical properties of coherent radiation scattered from phase-ordering materials are studied in detail using large-scale computer simulations and analytic arguments. Specifically, we consider...
Equilibrium and nonequilibrium applications of lattice-gas models in electrochemistry (1997)
Rikvold, Per Arne, Brown, Gregory, Novotny, M. A., Wieckowski, Andrzej
We discuss applications of statistical-mechanical lattice-gas models to study static and dynamic aspects of electrochemical adsorption. The strategy developed to describe specific systems includes...
Richards, Howard L., Kolesik, M., Lindgard, Per-Anker, Rikvold, Per Arne, Novotny, M. A.
Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of...
Kolesik, M., Richards, H. L., Novotny, M. A., Rikvold, Per Arne, Lindgard, Per-Anker
We present results obtained with various types of heterogeneous nucleation in a kinetic Ising model of magnetization switching in single-domain ferromagnetic nanoparticles. We investigate the effect...
Numerical simulations of scattering speckle from phase ordering systems (1996)
Brown, Gregory, Rikvold, Per Arne, Grant, Martin
The scattering of coherent X-rays from dynamically evolving systems is currently becoming experimentally feasible. The scattered beam produces a pattern of bright and dark speckles, which fluctuate...
Richards, Howard L., Novotny, Mark A., Rikvold, Per Arne
An important aspect of real ferromagnetic particles is the demagnetizing field resulting from magnetostatic dipole-dipole interaction, which causes large particles to break up into domains....
Kinetic Ising Systems as Models of Magnetization Switching in Submicron Ferromagnets (1995)
Richards, Howard L., Sides, Scott W., Novotny, Mark A., Rikvold, Per Arne
Recently experimental techniques, such as magnetic force microscopy (MFM), have enabled the magnetic state of individual sub-micron particles to be resolved. Motivated by these experimental...
Richards, Howard L., Sides, Scott W., Novotny, M. A., Rikvold, Per Arne
The magnetic relaxation of ferromagnetic powders has been studied for many years, largely due to its importance to recording technologies. However, only recently have experiments been performed that...
Finite-range-scaling analysis of metastability in an Ising model with long-range interactions (1994)
Gorman, Bryan M., Rikvold, Per Arne, Novotny, M. A.
We apply both a scalar field theory and a recently developed transfer-matrix method to study the stationary properties of metastability in a two-state model with weak, long-range interactions: the...
Metastable lifetimes in a kinetic Ising model: Dependence on field and system size (1994)
Rikvold, Per Arne, Tomita, H., Miyashita, S., Sides, Scott W.
The lifetimes of metastable states in kinetic Ising ferromagnets are studied by droplet theory and Monte Carlo simulation, in order to determine their dependences on applied field and system size....
Numerical Transfer-Matrix Study of Metastability in the d=2 Ising Model (1993)
Guenther, C. C. A., Rikvold, Per Arne, Novotny, M. A.
We apply a generalized numerical transfer-matrix method to the 2-d Ising ferro- magnet in a nonzero field to obtain complex constrained free energies. Below $T_c$ certain eigenstates of the transfer...
Richards, Howard L., Novotny, M. A., Rikvold, Per Arne
We compute by numerical transfer-matrix methods the surface free energy $\tau(T),$ the surface stiffness coefficient $\kappa(T),$ and the single-step free energy $s(T)$ for Ising ferromagnets with...
Scaling analysis of pattern formation in some equilibrium and non-equilibrium systems / (1983)
Thesis (Ph.D.)--Temple University, 1984.
A Projection Method for Lattice Spin Systems (1970)
M. A. Novotny, Per Arne Rikvold
Recently, the projection method was proposed for computer simulation of dynamic and static properties of lattice spin systems. This talk describes the basic ideas, justification, practical...