A11: R.K.P. Zia, Virginia Tech.

"Four Species in Cyclic Competition"
Coauthors: C.H. Durney, S. O. Case and M. Pleimling
Abstract: Generalizing the cyclically competing three-species model (Berr, et. al., PRL 102, 048102 (2009)), we consider a system involving four species (with no spatial structure): A+B -> A+A, ..., D+A -> D+D. Unlike the 3 species case, where the weakest tends to survive, no simple general rule applies here. Instead, the four form alliance pairs, much like in the game of Bridge, so that the end states typically consists of coexisting (but non-interacting) pairs: AC or BD. I will describe the stochastic model, the associated master equation, and the mean-field approximation, i.e., a deterministic set of equations of evolution.

A12: C.H. Durney, Virginia Tech.

"Mean Field Theory (MFT) Predictions for Four Species in Cyclic Competition"
Coauthors: S. Case, M. Pleimling, and R.K.P. Zia
Abstract: Studying the deterministic evolution of four species competing cyclically (A+B -> A+A with rate k_a, ..., D+A -> D+D with rate k_d), we find an intuitively understandable combination of the reaction rates, k_a*k_c-k_b*k_d, which controls whether the AC or BD pair survives. When this combination is zero, MFT predicts closed orbits encircling a fixed line. Limitations and implications of MFT will also be discussed.

A13: S. Case, Virginia Tech

"Surprises from Simulations of Four Species in Cyclic Competition"
Coauthors: M. Pleimling, R.K.P. Zia and C.H. Durney
Abstract:Using Monte Carlo techniques, we investigate a stochastic system with N individuals, consisting of four species and competing cyclically. Letting a randomly chosen pair react by A+B -> A+A, etc., N remains a constant while the fractions of each species evolve non-trivially. Unlike the 3 species case, our system typically ends in absorbing states with coexisting pairs: AC or BD. Thus, the number of absorbing state scales with N, instead of being O(1). Simulation results for N00 are presented, showing some rather unexpected behavior, especially for a system with extremely disparate rates.

A14: E.B. Kaufmann, Purdue University

"Critical exponents in the two-species asymmetric diffusion model"
Abstract: We present a study of the two species totally asymmetric diffusion model using the Bethe Ansatz. The Hamiltonian has $U_q(SU(3))$ symmetry. We derive the nested Bethe Ansatz equations and obtain the dynamical critical exponent from the finite--size scaling properties of the eigenvalue with the smallest real part. The dynamical critical exponent is $\frac{3}{2}$ which is the exponent corresponding to KPZ growth in the single species asymmetric diffusion model.

A15: S. Henkes, Syracuse University

"Elasticity of a cross-linked active bundle"
Coauthors: T.B. Liverpool, M.C. Marchetti, and A.A. Middleton
Abstract: Understanding the effect of motor proteins, such as myosins, on the elasticity of crosslinked actin networks is essential to our understanding of cell mechanics. Both in vivo and in vitro, these active networks have radically different mechanical properties from their equilibrium counterparts, including contractile behavior and higher elastic moduli. Existing theoretical models do not address the relative role of passive and active crosslinkers in controlling the network contractility and stiffening. We construct a one dimensional lattice model with minimal ingredients, that is, rigid polar filaments, spring-like passive crosslinks and active crosslinks with on/off dynamics implemented through non-equilibrium Monte Carlo solution of the corresponding master equations. We find, consistent with experiments, that the network needs to be percolated through the passive crosslinks to be mechanically stable. Contractile behavior is observed for all concentrations of active crosslinks. We study the mechanical properties of the gel in the phase space of motor processivity, crosslink stiffness, and concentration of active crosslinks.

A16: C. Thomas, Texas A & M Univerity

"The specific heat of the two-dimensional Ising spin glass"
Coauthors: A. Alan Middleton, David A. Huse
Abstract: We examine the behavior of the specific heat in the two-dimensional Ising spin glass. At low temperatures, the specific heat is dominated by contributions from excitations at the smallest length scales with nonzero energy. For continuous disorder distributions, this length scale is O(1), which leads to a specific heat C ~ T. For discrete disorder, the smallest excitations with nonzero energy occur at a temperature-dependent length scale which modifies the specific heat exponent. Due to large finite-size effects, this can be seen numerically only in systems with L > 100. In both cases, these small-length scale effects mask the critical behavior due to the spin glass phase transition at zero temperature.

A17: S. Redner, Boston University

"Can Partisan Voting Lead to the Truth"
Coauthors: N. Masuda
Abstract: We study a voter model in which each agent has an innate preference for one of two states --- truth and falsehood. due to interactions with its neighbors, an agent that prefers truth can be in the "false" state (and therefore discordant with its innate preference) or in the internally condordant "true" state, and vice versa for agents that intrinsically prefer falsehood. We determine when the population can ultimately reach a consensus of the truth or get stuck in a partisan state with no consensus.

SESSION B

B1: S. Ji, Rutgers University

"Distances between RNA trajectories are distributed according to Planck's radiation law or the Gaussian distribution law depending on their metabolic functions"
Coauthors: K. So
Abstract:

B2: L. Sperzel, Rutgers University

"Decoding pathway-specific RNA waves of budding yeast undergoing glucose-galactose shift - the sounds of cell language"
Coauthors: S. Ji
Abstract:

B3: A. Shekhawat, Cornell University
"Universal Properties of Fuse Network Fracture Strength Distribution"
Coauthors: C. Manzato, S. Zapperi, J.P. Sethna
Abstract: Fuse networks are a paradigmatic example of brittle fracture. In this talk we show that the fracture strength for Duxbury type fuse networks is in the Gumbel universality class. We contrast this with the widely held belief that fracture statistics are always in the Weibull universality class. We emphasize the connection between fracture and extreme value statistics and explain how the universality class effects the scaling behavior at large length scales. We discuss results of large scale 2-D fuse network simulations and mention some interesting open questions.

B4: M. K. Hawkins, University of Maryland

"Relaxation of Terrace Width Distribution of Vicinal (001) with Zigzag [110] Steps - PART II"
Coauthors: M. Hawkins* and T.L. Einstein
Abstract: We discuss dynamical and steady state results of Kinetic Monte Carlo simulations which show the relaxation of zigzag steps on a vicinal (001) surface. Dynamical results show that the standard deviation of terrace widths of zigzag steps saturates faster than that of straight steps, and its higher level moments are larger (more uctuations). The Arrhenius plots of relaxation times show that 2-atom processes are dominant in attaining a steady state conguration for zigzag steps, in contrast to straight steps where 3-atom processes are dominant. In the steady state, step-step cor- relation functions of zigzag steps further re ect the greater uctuations for zigzag steps compared to straight steps. Also, steady state terrace width distributions for the zigzag system show oscillations in the param- eter P(0), which quanties the amount of step touching. This work was supported by NSF-MRSEC at University of Maryland, DMR 0520471.

B5: A. Gabel, Boston University

"A facilitated asymmetric exclusion process"
Coauthors: S. Redner and P. Krapivsky
Abstract:We study a modified form of the Asymmetric Exclusion Process where hopping rates depend on the local particle arrangement. In our model, particles on a 1-D lattice will move only when pushed from behind by a neigbhor. We find a phase transition from active to absorbing final states as well as the presence of a discontinuity in the rarefaction wave that develops from an initial step function density profile.

B6: H. Kim, University of Notre Dame

"Degree-based graph construction and sampling"
Coauthors: Z. Toroczkai, P.L. Erdos, I. Miklos and L.A Szekely, C.I. Del Genio, K. E. Bassler
Abstract: Network representation and modeling has been one of the most comprehensive ways to study complex systems, ranging from social sciences through chemical compounds to biochemical reaction networks in the cell. However, the network describing the system frequently has to be built from incomplete connectivity data, a typical case being degree-based graph construction, when only the sequence of node degrees is available. In this presentation I will introduce problems and results related to the construction of all the possible graphs and sampling from the class of graphs with fixed degree-sequence. Firstly, for graph construction, we will present necessary and sufficient conditions for a sequence of integers to be realized as a simple graph's degree sequence under the condition that a specific set of connections from an arbitrary node are avoided [1]. Secondly, by using this result, we will show how to provide an efficient, polynomial time algorithm that generates graph samples with a given degree sequence. Unlike other existing algorithms, this method always produces statistically independent samples, without back-tracking or rejections. Also, the algorithm provides the weight associated with each sample, allowing graph observables to be measured uniformly over the graph ensemble [2]. Finally, we will show how these theorems and algorithms can be extended to directed graphs [3].
REFERENCES:

1. Hyunju Kim, Zoltan Toroczkai, Peter L Erdos, István Miklos and Laszlo A Szekely. Degree-based graph construction. J. Phys. A: Math. Theor. (Fast Track Communication) 42, 392001 (2009).
2. Charo I. Del Genio, Hyunju Kim, Zoltán Toroczkai, Kevin E. Bassler. Efficient and exact sampling of simple graphs with given arbitrary degree sequence. PLoS ONE, 5(4), e10012, (2010).
3. Hyunju Kim, Charo I. Del Genio, Kevin E. Bassler, and Zoltán Toroczkai. Constructing and sampling directed graphs with given degree sequence. Preprint, to be submitted.

B7: A. Souslov, University of Pennsylvania

"Constructing Lattice Models with Extraordinary Elasticity"
Coauthors: Xiaoming Mao, Kai Sun, and Tom Lubensky
Abstract:Taking inspiration from jammed systems, we develop isostatic lattice models with unusual and highly tunable elastic properties. A two- (three-) dimensional isostatic lattice has four (six) neighbors, exactly enough to constrain local soft modes, though a sub-extensive number of soft modes remain. We can extend these modes into soft deformations, creating families of lattices with the same connectivity, but different particle configurations. We thus deform the two-dimensional square and kagome and the three-dimensional pyrochlore lattices. Through simple arguments we illustrate the role of symmetry on the long-wavelength elasticity of such systems and gain further insight by examining the full phonon spectrum. We find various models exhibiting negative Poisson ratio and floppy surface modes.

B8: N. Thyagu, Rutgers Univerity

"Competitive cluster growth on networks: complex dynamics and survival strategies"
Coauthors:A. Mehta
Abstract: We extend the study of a model of competitive cluster growth [1-4] in an active medium from a regular topology to a complex network topology; this is done by adding nonlocal connections with probability $p$ to sites on a regular lattice, thus enabling one to interpolate between regularity and full randomness. The model on networks demonstrates high sensitivity to small changes in initial configurations, which we characterize using damage spreading. The main focus of this paper is, however, the devising of survival strategies through selective networking, to alter the fate of an arbitrarily chosen cluster: whether this be to revive a dying cluster to life, or to make a weak survivor into a stronger one. Although such goals are typically achieved by networking with relatively small clusters, our results suggest that it ought to be possible also to network successfully with peers and larger clusters. The main indication of this comes from the probability distributions of mass differences between survivors and their immediate neighbours, which show an interesting universality; they suggest strategies for winning against the odds.

1. J. M. Luck, and A. Mehta, Eur. Phys. J. B 44, 79 (2005)
2. A. Mehta, A. S. Majumdar and J. M. Luck, pp. 199-204 in `Econophysics of Wealth Distributions' edited by A. Chatterjee et al, Springer-Verlag Italia (2005).
3. A. S. Majumdar, Phys. Rev. Lett. 90, 031303 (2003).
4. A. S. Majumdar, A. Mehta and J. M. Luck, Phys. Lett. B 607, 219 (2005).

B9: N. Zimbovskaya, University of Puerto Rico at Humacao

"Nanoparticle shape instability by Coulomb interactions"
Abstract: Metal atoms adsorbed on few-layer graphenes condense to form nanometer-size droplets whose growth in size is limited by a competition between the surface tension and repulsive electrostatic interactions from charge transfer between the metal droplet and the graphene. Under certain conditions a growing droplet can be unstable to a family of shape instabilities. This phenomenon was observed for Yb deposited and annealed on few-layer graphenes. A theoretical model to describe it is developed. The model describes the onset of shape instabilities for nanoparticles where their growth is limited by a generic repulsive potential and provides a good account of the experimentally observed structures for Yb on graphene [1].

1. L. A. Somers, N. A. Zimbovskaya, A. T. Johnson, and E. J. Mele, Phys. Rev. B 82, 115430 (2010).

B10: A. Toom, UFPE, Brazil

"Random Monads"
Abstract: A monad (as suggested by V. Arnold) is a pair (S,M), where S is a finite set having n elements called points and M is a map from S to S. We fix some initial point I and define an infinite sequence I, M(I), M(M(I)),... We denote: by Vis (visited) the number of points which enter this sequence; by Rec (recurrent) the number of points which enter this sequence at least twice; Tra (transient) the number of points which enter this sequence only once. We introduce randomness in the simplest way: M(.) are uniformly distributed in S and independent from each other. Thus Vis, Rec and Tra are integer random variables. We estimate their modes, expectations and standard deviations and some other quantities and in all cases obtain approximatedly square root of n with different coefficients.

B11: S. Jolad, Virginia Tech.

"Contact process on static and adaptive networks"
Coauthors: R. Zia, W. Jia and B. Schmittmann
Abstract: We consider epidemic spreading on an adaptive network where individuals have a fluctuating number of connections around some preferred degree $\kappa$. Using very simple rules for forming such a network, we find some unusual statistical properties which provide an excellent platform to study adaptive contact processes. For example, by letting $\kappa$ depend on the fraction of infected individuals, we can model behavioral changes in response to how the extent of the epidemic is perceived. Specifically, we explore how various simple feedback mechanisms affect transitions between active and inactive states.

B12: Y. Fily, Syracuse University

"Emerging "self propulsion" of a pair of rotors in a viscous liquid"
Coauthors:Y. Fily, A. Baskaran and M.C. Marchetti
Abstract:A particle rotating in a viscous fluid generates an azimuthal flow field felt by other particles present in the fluid. Two such particle of opposite vorticities push each other in the same direction, resulting in a steady motion of the center of mass: the pair becomes self propelled. We study the diffusion of such a "self propelled" pair. As the distance between the two objects varies, the effective self propulsion velocity of the center of mass varies too, leading to non trivial diffusion behavior.

B13: P. Cladis, Advanced LC Tech

"Icosahedral Nematic Liquid Crystal Elastomers"
Coauthors: S. Krause, Y. Yusuf, S.Hashimoto, L. G. Fel, H. Finkelmann, S. Kai, P.E. Cladis
Abstract:A phase transition theory, supported by experiments from a new class of liquid crystal elastomers characterized as a nematic network with smetic C Clusters will be presented.

B14: Y. Liu, Northeastern University

"Controllability of Complex Networks"
Coauthors: J.-J. Slotine, A.-L. Barabasi
Abstract: The ultimate proof of our understanding of natural or technological systems is reflected in our ability to control them. While control theory offers mathematical tools to steer engineered systems towards a desired state, we lack a general framework to control complex self-organized systems, like the regulatory network of a cell or the Internet. Here we develop analytical tools to study the controllability of an arbitrary complex directed network, identifying the set of driver nodes whose time-dependent control can guide the system's dynamics. We apply these tools to real and model networks, finding that sparse inhomogeneous networks, which emerge in many real complex systems, are the most difficult to control. In contrast, dense and homogeneous networks can be controlled via a few driver nodes. Counterintuitively, we find that in both model and real systems the driver nodes tend to avoid the hubs. We show that the robustness of control to link failure is determined by a core percolation problem, helping us understand why many complex systems are relatively insensitive to link deletion. The developed approach offers a framework to address the controllability of an arbitrary network, representing a key step towards the eventual control of complex systems.

SESSION C

C1: Y. Terada, Tohoku University, Japan

"Dynamics and spatial configurations of magnetic colloidal monolayers and chains confined in thin films"
Abstract: We perform extensive Brownian dynamics simulation of dilute magnetic colloidal monolayers and chains confined in thin films. The diffusivity of colloids and chains are controlled by applied external magnetic field, and film thickness. However it is found that all data collapse on a single master curve once the data are rescaled by theoretical singular point. We also discuss the structure of colloidal monolayers and chains.

C2: D. Quint, Syracuse University

"Buckling of Branched Cytoskeletal Filaments "
Coauthors: J.M. Schwartz
Abstract: In vitro experiments of growing dendritic actin networks demonstrate reversible stress-softening at high loads, above some critical load. The transition to the stress-softening regime has been attributed to the elastic buckling of individual actin filaments. To estimate the critical load above which softening should occur, we extend the elastic theory of buckling of individual filaments embedded in a network to include the buckling of branched filaments, a signature trait of growing dendritic actin networks. Under certain assumptions, there will be approximately a seven-fold increase in the classical critical bucking load, when compared to the unbranched filament, which is entirely due to the presence of a branch. Moreover, we go beyond the classical buckling regime to investigate the effect of entropic fluctuations. The result of compressing the filament in this case leads to an increase in these fluctuations and eventually the harmonic approximation breaks down signifying the onset of the buckling transition. We compute corrections to the classical critical buckling load near this breakdown.