Statistical Mechanics Conference

103th Statistical Mechanics Conference

Wednesday, July 14, 2010 at 08:00am -

103rd SMC Program
103rd List of invited talks and abstracts
103rd SMC short talk schedule

List of invited speakers & talk titles

Speaker: Mark Alber, University of Notre Dame
Title: Multiscale modeling in biology
Abstract: A multiscale model of blood clot formation will be described, which combines a detailed tissue factor pathway submodel of blood coagulation, a blood flow submodel and a stochastic discrete cell submodel [1,2]. It will be shown that low levels of FVII in blood result in a significant delay in thrombin production demonstrating that FVII plays an active role in promoting clot development at an early stage. We will also describe a new subcellular element method for simulating cellular blood components. In addition, multiscale models of bacterial swarming will be discussed [3].
1. Xu, Z., J. Lioi, J. Mu, X. Liu, M.M. Kamocka, E.D. Rosen, D.Z. Chen and M.S. Alber [2010], A Multiscale Model of Venous Thrombus Formation with Surface-Mediated Control of Blood Coagulation Cascade, Biophysical Journal 98, 9, 1723-1732.
2. Xu, Z., Chen, N., Shadden, S., Marsden, J.E., Kamocka, M.M., Rosen, E.D., and M.S. Alber [2009], Study of Blood Flow Impact on Growth of Thrombi Using a Multiscale Model, Soft Matter 5, 769-779.
3. Wu, Y., Jiang, Y., Kaiser, D., and M. Alber [2009], Periodic reversal of direction allows Myxobacteria to swarm, Proc. Natl. Acad. Sci. USA 106 4 1222-1227 (featured in the Nature News, January 20th, 2009, doi:10.1038/news.2009.43).
Speaker: Phil Anderson, Princeton University
Title: What is wrong with QMC?
Abstract: It is becoming increasingly clear that the underlying order which changes at a quantum critical point in many of the strong correlation problems--for example, cuprate superconductiivity--is the size and shape of the Fermi surface. The excitations which represent Fermi surface fluctuations are the tomographic Tomonaga bosons invented by Luther, Haldane, and others, which are poorly represented by computational schemes with rigid boundary condiitions and rigidly fixed particle number such as quantum Monte Carlo. Thus such schemes do not faithfully represent just the critical fluctuations around the most relevant quantum critical point.
Speaker: Eva Andrei, Rutgers University
Title:Electronic properties of graphene
Abstract: Graphene, a one-atom thick membrane of crystalline carbon possesses extraordinary electronic properties which make it a prime candidate for novel nano-electronic devices, at the same time raising the prospect to observe phenomena hitherto unseen in bench top experiments. I will present scanning tunneling microscopy^1,2 and transport experiments that provide access to the dynamics of the charge carriers in this material and give new insights their unique world. The findings include direct observation of the Landau level energy spectrum^1,2, observation of the fractional quantum Hall effect³ and a magnetically induced insulating phase.
Speaker: Eli Ben-Naim, Los Alamos
Title: Strong Mobility in Disordered Systems
Abstract: TBA
Speaker: Nihat Berker, Sabanci University
Title: Anisotropy Effects and Impurity Induced Antiferromagnetism: Renormalization-Group Theory of d=3 Electronic Models
Abstract: TBA
Speaker: Lesser Blum, Rutgers University
Title: Hyperscaling theory for charged systems
Abstract
Speaker: Leonid Bunimovich, Georgia Tech.
Title: Which hole is leaking the most: Topological approach to open systems and dynamical networks
Abstract: A natural question on how a process of escape depends on a position of a hole in a phase space seems to be overlooked in the theory of open dynamical systems. An answer to this question allows to reveal a new role of periodic orbits in the evolution of dynamical systems, to classify dynamically the nodes (elements) of dynamical networks and, most surprisingly, to realize that it is possible to make not only traditional (asymptotic in time as time tends to infinity) but finite time predictions of the behavior of dynamical systems.
Speaker: Curtis Callan, Princeton University
Title: Deep sequencing, mutual information and the thermodynamics of gene regulation
Abstract: The regulation of gene expression is thought to be largely governed by the binding thermodynamics of regulatory proteins. I will argue that high-throughput sequencing, combined with a novel analysis technique based on mutual information, can give a precise thermodynamic account of gene regulatory function. I will describe the application of this method to the bacterial lac promoter, showing how one can infer the in vivo interaction energy between two proteins in the cell from sequence data alone.
Speaker: Roberto Car, Princeton University
Title: Quantum protons and hydrogen bonds
Abstract: Near room temperature the momentum distribution of the protons participating in hydrogen bonds is quite different from the classical Boltzmann distribution. Thus the equilibrium structure of systems like liquid water is directly influenced by quantum mechanics. When the proton environment is nearly harmonic semi-classical approximations are possible, but in presence of tunneling, such as e.g. in ice under high pressure, a full quantum treatment is needed. In that case the interplay between quantum tunneling and ice-rule correlations among the protons leads to distinct observable effects.
Speaker: Paul Chaikin, NYU
Title: Self-Replication Without Life
Abstract: We want to make a "non-biological" system which can self-replicate. The idea is to design particles with specific and reversible and irreversible interactions, introduce seed motifs, and cycle the system in such a way that a copy is made. Repeating the cycle would double the number of offspring in each generation leading to exponential growth. Using the chemistry of DNA either on colloids or on DNA tiles makes the specific recognition part easy. In the case of DNA tiles we have in fact replicated the seed at least to the third generation. The DNA linkers can also be self-protected so that particles don't interact unless they are held together for sufficient time-nano-contact glue. We have also designed and produced colloidal particles that use novel "lock and key" geometries to get specific and reversible physical interactions.
Speaker: Arup Chakraborty, MIT
Title: Why people with certain genes can control hiv without therapy: from statistical mechanics to the clinic
Abstract: TBA
Speaker: Lincoln Chayes, UCLA
Title: The McKean-Vlasov Equation in Finite Volume
Abstract: The McK-V system is a nonlinear diffusion equation with a nonlocal nonlinearity provided by convolution. Recently popular in a variety of applications, it enjoys an ancient heritage as a basis for understanding classical fluids in equilibrium and near equilibrium. The model is discussed in finite volume where, on the basis of the physical considerations, the correct scaling (for the model itself) is identified. For dimension two and above and in large volume, the equilibrium phase structure of the model is completely elucidated in (somewhat disturbing) contrast to dynamical results. This is joint work with V. Panferov.
Speaker: Bernard Chazelle, Princeton University
Title: The total S-Energy: An analytical tool for multiagent dynamics
Abstract: I discuss a new analytical device for the study of multiagent agreement systems. The "total s-energy" of an infinite sequence of graphs embedded in Euclidean space is a Dirichlet series encoding all of the edge lengths. It generalizes both the graph Laplacian and the Riesz s-energy of points on a sphere. I will discuss how analytical properties of the total s-energy leads to bounds on the convergence rates of several classical agreement systems, including opinion dynamics, synchronization, and flocking. The total s-energy draws its power from its ability to handle products of stochastic matrices algorithmically "without looking inside the matrices." This work is part of a larger project to explore the benefits of viewing dynamical systems as "natural algorithms."
Speaker: Eugene Chudnovsky, Lehman College
Title: Self-organized tunneling dynamics of molecular nanomagnets
Abstract: Magnetic moments of high-spin molecules can reverse their orientation through quantum tunneling [1]. Many-body quantum dynamics of crystals made of such molecules involves self-organization of magnetic dipoles, aimed at maintaining resonant tunneling condition [2]. Theory and experiments in this field will be reviewed.
1. E. M. Chudnovsky and J. Tejada, Lectures on Magnetism (Rinton Press, Princeton, 2006).
2. D. A. Garanin and E. M. Chudnovsky, Phys. Rev. Lett. 102, 097206 (2009).
Speaker: P. Debenedetti, Princeton University
Title: Thermodynamic and kinetic models of the appearance and amplification of biological chirality
Abstract
Speaker: Robert Ecke, Los Alamos
Title:Unstable diffusion layers: From thermal convection and material dissolution to sequestration of CO2
Abstract: TBA
Speaker: Fereydoon Family, Emory University
Title: Physics of Age-Related Macular Degeneration
Abstract: TBA
Speaker: Jerry Gollub, Haverford College
Title: Statistical Mechanics of Swimming Microorganisms
Abstract: TBA
Speaker: F.D.M. Haldane, Princeton University
Title: Dissipationless "Hall viscosity" and its relation to incompressibility of quantum Hall fluids
Abstract
Speaker: Tom Kennedy, University of Arizona
Title: Renormalization group maps for Ising models in lattice gas variables
Abstract: TBA
Speaker: Michael Kiessling, Rutgers University
Title: On the N dependence of classical and quantum N-body ground state energies
Abstract
Speaker: Paul Krapivsky, Boston University
Title: Kinetics of cell division
Abstract: TBA
Speaker: Robert Kohn, Courant Institute
Title: Surface relaxation below the roughening temperature: steps, pde's, and self-similarity
Abstract:TBA
Speaker: Herbert Levine, University of California,San Diego
Title: Information limits on eukaryotic chemotaxis
Abstract: Many types of eukaryotic cells are able to detect chemical gradients and move accordingly (Parent and Devreotes, 1999). Unlike the case for bacteria, these cells are large enough for the gradient detection to rely on differential receptor binding probabilities on the cell membrane. It is not yet understood how this noisy input data (Rappel and Levine, 2008; Endres and Wingreen, 2008) is processed by the cell to make the motion decision; thus we cannot a priori predict the detection threshold, the response kinetics and the plasticity to changing stimuli. This talk will focus on recent experimental and theoretical work (Fuller et al, submitted) which shows that at small gradients, cell performance is limited primarily by sensor noise.
REFERENCES
Speaker: Mike Lipkin, Columbia University/Katama Trading, LLC
Title: Hard-To-Borrow Stocks. Why restrictions on shorting lead to higher prices, higher volatilities, crashes and bubbles!
Abstract: Restrictions on the shorting of stocks have the paradoxical effect of increasing volatilities and prices. We demonstrate this with a simple but very rich stochastic model which reproduces market prices and allows predictions about asset bubbles as well!
Speaker: Jon Machta, University of Massachussetts
Title:Monte Carlo methods for rough free energy landscapes
Abstract: TBA
Speaker: John Marko, Northwestern University
Title: Linking topology of large DNA molecules
Abstract: Double helix DNA molecules, the carriers of genetic instructions in cells, are strongly affected by their topological properties. Two distinct and biologically important types of linking are associated with double helix DNAs: 'internal' linking of the two strands of individual double helices, and 'external' linking of separate double helix DNAs. Constraint of internal linking gives rise to internal torsional stress and supercoiling of circular DNAs. I will discuss an additional important but often ignored constraint associated with DNA supercoiling as it appears to occur in vivo. I will also discuss 'external' linking of separate double helices, which is a likely outcome of DNA replication, and which must be eliminated by the cell in order to separate duplicated DNAs. I will present an argument based on scaling laws for linking number fluctuations of flexible polymers to address how cells manage to eliminate entanglements (and knots) from their long chromosomal DNAs.
Speaker: Michael Monastyrsky,ITEP,Moscow
Title:Duality transformations for Non-Abelian Spin Systems
Abstract: The Classical Kramers Wannier(KW) Duality is a special Symmetry which relates low-temperature and high-temperature phases in the planar Ising model. Generalization of this transformation to Spin Models with non-Abelian Symmetry is essential for many problems in Statistical Physics and Field theory. In my talk I present new results which solve this problem for finite and compact groups and different two-dimensional lattices,including so called Hecke graphs.
Speaker: David Nelson, Harvard University
Title: Life at Low Reynolds Number
Abstract: As an example of life at high Reynolds number, we investigate the dynamics of the Fisher equation for the spreading of micro-organisms subject to both turbulent advection and diffusion.[1] The effective advecting velocity field turns out to be compressible in a number of important circumstances. For strong enough turbulence, bacteria, for example, track, in a quasilocalized fashion (with remarkably long persistence times), sinks in the turbulent field. An important consequence is a large reduction in the carrying capacity of the fluid medium. We analytically determine the regimes where this quasi-localized behavior occurs and test our predictions by numerical simulations.
Speaker: Charles Newman, Courant Institute
Title: Ground states of the 2D Edwards-Anderson spin glass
Coauthors: Louis-Pierre Arguin, Michael Damron, Chuck Newman*, Dan Stein
Abstract: This is joint work with Louis-Pierre Arguin, Michael Damron and Dan Stein. It is an open problem to determine the number of infinite-volume ground states in the Edwards-Anderson (nearest neighbor) spin glass model on Z^d for d ? 2 (with, say mean zero Gaussian couplings). This is a limiting case of the problem of determining the number of extremal Gibbs states at low temperature. In both cases, there are competing conjectures for d ? 3, but no complete results even for d=2. I report on new results which go some way toward proving that (with zero external field, so that ground states come in pairs, related by a global spin flip) there is only a single ground state pair (GSP). Our result is weaker in two ways: First, it applies not to the full plane Z2, but to a half-plane. Second, rather than showing that with probability one (according to the quenched random coupling realization J) there is a single GSP, we show that there is a natural joint distribution on J and GSP's such that with probability one, the conditional distribution on GSP's given J is supported on only a single GSP. The methods used are a combination of percolation-like geometric arguments together with translation invariance (in one of the two coordinate directions of the half-plane) and employ as a main tool the "excitation metastate" which is a probability measure on GSP's and on how they change as one or more individual couplings vary.
Reference: arXiv:0911.4201
Speaker: Michele Parinello, ETH, Zurich
Title: Advanced sampling methods
Abstract: TBA
Speaker: David Pine, NYU
Title: Non-equilibrium phase transitions and random ordering in driven suspensions of rods
Abstract: TBA
Speaker: Karen Rabe, Rutgers University
Title: Spin-lattice coupling in magnetic perovskite thin films and superlattices
Abstract: In the search for new ferromagnetic-ferroelectric multiferroic materials, one key challenge is to maximize the coupling between the magnetization and the ferroelectric polarization. In this talk, I will briefly review several mechanisms by which such coupling can occur, and present first-principles results for prototypical systems. First, I will discuss the large spin-phonon coupling in SrMnO3. First principles calculations show that this coupling results in an epitaxial-strain-induced ferromagnetic-ferroelectric state. This occurs by the mechanism introduced earlier for EuTiO3, though in SrMnO3, with magnetic ions on the B site, the magnetic and ferroelectric phases persist to much higher temperatures. Next, I will discuss the spinel-structure oxide CdCr2O4 and the perovskite BiMnO3/BiFeO3 nanocheckerboard, in which magnetic frustration in principle allows perturbations that change the structure to drive phase transitions in magnetic ordering. Finally, I will present preliminary results on ferroelectrically-induced weak ferromagnetism in perovskite superlattices identified via the crystal-chemical/symmetry criteria proposed by Craig Fennie.
Speaker: Vered Rom-Kedar, Weizmann Institute
Title: Models of the innate immune system: theory and medical implications
Abstract: Simple models of the innate immune system teach us much about the development of infections when the bone-marrow function is damaged by chemotherapy. The results depend only on robust properties of the underlying modeling assumptions and not on the detailed models. Moreover, such models may lead to improved treatment strategies for neutropenic patients [1,2,3].
1. R. Malka, E. Shochat and V. Rom-Kedar; Bistability and Bacterial Infections. PLoS ONE, 2010, to appear.
2. E. Shochat and V. Rom-Kedar; Novel strategies for G-CSF treatment of high-risk severe neutropenia suggested by mathematical modeling, Clinical Cancer Research 14, 6354-6363, October 15, 2008.
3. E. Shochat, V. Rom-Kedar and L. Segel; G-CSF control of neutrophils dynamics in the blood, Bull. Math. Biology , 69(7), 2299-2338, 2007.
Speaker: James Sethna, Cornell University
Coauthors: Y.S. Chen, W. Choi and S. Papanikolaou
Title: Bending Crystals: The evolution of self-similar dislocation structures
Abstract: TBA
Speaker: Eugene Shaknovich, Harvard University
Title: Dynamics of evolution and adaptation:Insights from ab initio multiscale models
Abstract: TBA
Speaker: David Vanderbilt, Rutgers University
Title: Orbital magnetoelectric effects and topological insulators
Abstract: I will discuss two kinds of topological insulators. First, a "Chern insulator" is one in which the "Chern number," defined in terms of the integral of the Berry curvature over the Brillouin zone, is non-zero. Such a system is also known as a "quantum Hall insulator" because it would exhibit a quantum Hall effect in the absence of a magnetic field (possibly at room temperature). While no examples are yet known to exist in nature, theoretical models of Chern insulators are readily constructed (Haldane first did so two decades ago [1]), and there is no known reason why they should not exist. I shall mention some of our earlier work on the properties of such prospective Chern insulators [2-3], and speculate about prospects for discovering experimental realizations. Second, there has been a great deal of interest recently in another kind of topological insulator, the so-called "Z2-odd" insulator. Such a system can be conceptualized by imagining that a spin-up system of electrons having Chern number $+1$ coexists with a spin-down system having Chern number $-1$ in such a way that the system as a whole has total Chern number zero and obeys time-reversal (T) symmetry. Even when the spin-orbit interaction is turned on, the system carries a topological even-or-odd (Z2) label. Almost all known insulators are Z2-even, but great excitement has surrounded the recent realization that some materials, such as Bi(x)Sb(1-x) [4], Bi2Te3 [5], and related systems, are Z2-odd. We have developed a theory of the orbital contribution to the linear magnetoelectric effect (or equivalently, to the surface Hall conductivity) in magnetoelectric insulators having broken T symmetry [6]. The theory exhibits many attractive analogies to the theory of polarization, and involves a higher-order kind of Chern index than the one discussed above. Interestingly, our theory predicts that an insulator with T symmetry need not have a vanishing magnetoelectric coupling; instead, precisely in the case of a Z2-odd insulator, it must have a half-quantum value (see also [7]). Essentially this means that the surface of a Z2-odd topological insulator, if it is gapped by a T-breaking perturbation, will exhibit a half-integer quantum Hall effect.
1. F.D.M. Haldane, Phys. Rev. Lett. 61, 2015 (1988).
2. T. Thonhauser and D. Vanderbilt, Phys. Rev. B 74, 235111 (2006).
3. S. Coh and D. Vanderbilt, Phys. Rev. Lett. 102, 107603 (2009).
4. D. Hsieh et al., Nature 452, 970 (2008).
5. Y.L. Chen et al., http://arxiv.org/abs/0904.1829.
6. A.M. Essin, J.E. Moore, and D. Vanderbilt, Phys. Rev. Lett. 102, 146805 (2009).
7. X.L. Qi, T.L. Hughes and S.-C. Zhang, Phys. Rev. B 78, 195424 (2008).
Speaker: David Weitz, Harvard University
Title: Fast Crystals and Strong Glasses
Abstract: This talk presents new results for colloidal crystals and glasses. By investigating the morphology of crystal nuclei, we establish the importance of an entropic term in the free energy reflecting the number of morphologies of the nuclei. This modifies the nucleation rate, and accounts for the much faster rate of nucleation observed experimentally when compared to predictions. We also show that the behavior of deformable colloidal particles is reminiscent of molecular glasses with different structures, mimicking the range of fragilities reported for molecular systems.
Speaker: Victor Yakovenko, University of Maryland, College Park
Title: Statistical Mechanics of Money, Income, and Wealth
Abstract: This talk will review the progress in applications of statistical physics to probability distributions of money, income, and wealth in a society [1]. Using analogy between the probability distributions of energy in physics and money in economics, I argue that the distribution of money should follow the exponential Boltzmann-Gibbs law for certain classes of models with interacting economic agents [2]. Analysis of the empirical data shows that income distribution in the USA has a well-defined two-class structure [3]. The majority of the population (about 97%) belongs to the lower class characterized by the exponential ("thermal") distribution [4]. The upper class (about 3% of the population) has the Pareto power-law ("superthermal") distribution, whose share of the total income expands and contracts dramatically following the bubbles and busts in financial markets [5]. When debt is included in the statistical models, it destabilizes the Boltzmann-Gibbs distribution in the absence of an intrinsic mechanism for limiting debt [1]. As a result, the nominal wealth growth of the upper class largely comes from the debt growth of the lower class, until the economy collapses under the burden of excessive debt. I will also briefly discuss the distribution of energy consumption per capita around the world and show that it also follows the exponential Boltzmann-Gibbs law [6]. The data show how globalization of the world economy affects the inequality of energy consumption. More references can be found at the Web site [7].
References
1. V. M. Yakovenko and J. B. Rosser, Jr., "Colloquium: Statistical Mechanics of Money, Wealth, and Income", Reviews of Modern Physics 81 (2009) 1703.
2. A. Dragulescu and V. M. Yakovenko, "Statistical mechanics of money", The European Physical Journal B 17 (2000) 723.
3. A. Dragulescu and V. M. Yakovenko, "Exponential and power-law probability distributions of wealth and income in the United Kingdom and the United States", Physica A 299 (2001) 213.
4. A. Dragulescu and V. M. Yakovenko, "Evidence for the exponential distribution of income in the USA", The European Physical Journal B 20 (2001) 585.
5. A. C. Silva and V. M. Yakovenko, "Temporal evolution of the 'thermal' and 'superthermal' income classes in the USA during 1983-2001", Europhysics Letters 69 (2005) 304.
6. A. Banerjee and V. M. Yakovenko, "Universal patterns of inequality", submitted to New Journal of Physics, arXiv:0912.4898.
7. Econophysics Web page of Victor Yakovenko, http://www2.physics.umd.edu/~yakovenk/econophysics/

Schedule of Short talks

Session A

A1 - Speaker: S. Boettcher, Emory University
Title: Finite-Size Corrections in Mean-Field and Lattice Spin Glasses at T=0
Abstract: Numerical studies of ground states of spin glasses are described pertaining to finite-size corrections for thermodynamic averages and the scaling of energy fluctuations. High-accuracy results for dilute lattices in high dimensions, for sparse graphs, and for the SK model are obtained with the extremal optimization heuristic that allow a few surprising conjectures about scaling relations and connections about seemingly unrelated combinatorial problems. (See, eg, arXiv:0912.4861 and arXiv:0906.1292; more related info at http://www.physics.emory.edu/faculty/boettcher)

A2 - Speaker: S. Burkhardt, University of Massachussets, Amherst
Coauthor: J. Machta
Title: Efficiency of parallel tempering in asymmetric free energy landscapes
Abstract: Using numerical simulations, we compared the efficiency of parallel tempering for the low temperature 2D Ising model with and without an external field. We found that whereas in the absence of an external field, the equilibration time is dominated by the diffusive motion of the replicas, the motion becomes ballistic in the presence of a strong external field, leading to strongly reduced equilibration times.

A3 - Speaker: B. Yucesoy, University of Massachussets, Amherst
Coauthor: H. Katzgraber and J. Machta
Title: Efficiency of parallel tempering for spin glasses
Abstract: We study the efficiency of parallel tempering for the 3D Ising spin glass at low temperatures. We investigate correlations between the overlap distribution and the equilibration time. We find that overlap distributions having weight near zero, equilibrate significantly more slowly than those with no weight near zero.

A4 - Speaker: H. Castillo, Ohio University
Coauthor: A. Parsaeian
Title: Fluctuations in the relaxation of glasses
Abstract: Glass transitions are associated with a rapid increase of the relaxation time in a system as a function of an external parameter, usually temperature or volume fraction. When the relaxation time becomes longer than the typical experimental timescale, phenomena associated with the absence of thermodynamic equilibrium start to become evident. Additionally, it has been recently observed that in the regime near the glass transition, materials exhibit "dynamical heterogeneity", i.e., correlated fluctuations in the dynamical behavior of small regions of the system. At the present time, our understanding of the origin of dynamical heterogeneity is rather limited. One possible theoretical approach to explain the origin of these fluctuations involves the presence of local fluctuations in the time variable. I will present Molecular Dynamics simulations characterizing the statistical properties of the fluctuations in models of structural glasses, both in equilibrium and out of equilibrium. The results of these simulations exhibit evidence for scaling behavior and universality, and for the presence of a dynamic correlation length that grows as the system relaxes; all of which is consistent with the predictions of the theory.

A5 - Speaker: E. Vedmedenko, University of Hamburg, Germany
Coauthors: N. Mikuszeit, T. Stapelfeldt, R. Wieser, M. Potthoff, A. Lichtenstein, and R. Wiesendanger
Title:Crossover temperature of finite samples at finite observation times
Abstract: Motivated by an effective Landau free-energy functional, a simple analytical form for the twopoint magnetic correlation function is suggested for magnetic nanoparticles and shown to excellently fit Ising and numerically exact Monte-Carlo data of finite anisotropic spin models. A complex phenomenology governed by different temperature scales emerges and is traced back to the enhancement of fluctuations at the system's boundary and to an incomplete statistical average corresponding to a finite observation time. Unambiguous definitions of crossover temperatures for finite systems and an effective method to estimate the critical temperature of corresponding infinite systems are given.

A6 - Speaker:S. Huntsman, Equilibrium Networks & US Naval Postgraduate School
Title: Limiting effective temperature of 2D hyperbolic toral automorphisms
Abstract: The chaotic hypothesis of Gallavotti and Cohen is that the time evolution map of a many-particle system can be regarded (for the purposes of statistical physics) as a mixing Anosov map. The natural coarse-grainings (Markov partitions) admitted by Anosov maps on their domains may be used in concert with the SRB measure to provide a discretized picture of dynamics. We discuss evidence for nontrivial limiting behavior of an effective temperature when applied to the Arnol'd cat map and more generally of two-dimensional hyperbolic toral automorphisms. Time permitting, we will also discuss possible connections with a generalized Gibbs paradox and preliminary numerical results for the effective temperature of the geodesic flow on surfaces of constant negative curvature.

A7 - Speaker: V. Tkachenko, Ben-Gurion University of the Negev
Title: An inverse problem for 1d periodic differential operator of high order
Abstract

A8 - Speaker: R. Batten, Princeton University
Coauthor:F.H. Stillinger, S. Torquato
Title: Novel Low Temperature Behavior in Classical Many Particle Systems
Abstract: We show that classical many-particle systems interacting with certain soft pair interactions in two dimensions exhibit novel low-temperature behaviors. Ground states span from disordered to crystalline. At certain densities, many of the normal-mode frequencies vanish. Lattice ground-state configurations have more vanishing frequencies than disordered ground states at the same density and exhibit vanishing shear moduli. For the melting transition from a crystal, the thermal expansion coefficient is negative. These unusual results are attributed to the topography of the energy landscape.

A9 - Speaker: Y. Jiao, Princeton University
Title: Dense packings of regular tetrahedra
Abstract: Dense packings of regular tetrahedra obtained from both theoretical considerations and numerical simulations will be discussed, which include Welsh packing, icosahedral packing, wagon-wheel packings, and dimer-uniform packings. The dimer-uniform packings contains the densest known tetrahedron packing with $phi = 4000/4671 = 0.856347...$.

A10 - Speaker: A. Hopkins, Princeton University
Coauthors: F.H. Stillinger and S. Torquato
Title: Spherical codes, maximal local packing density, and the golden ratio
Abstract:The densest local packing (DLP) problem in d-dimensional Euclidean space Rd seeks to find the minimal radius (optimal) Rmin(N) of a larger sphere within which the centers of N identical nonoverlapping smaller spheres placed near a (additional) fixed same-size central sphere can be packed. Knowledge of Rmin(N) for any N can be used to form a useful realizability condition on pair correlation functions for sphere packings in any dimension. A simple proof relates DLP packings for N spheres of unit diameter to spherical codes, or packings of N spheres with centers restricted to the surface of a (d-1)-sphere in Rd. Specifically, the optimal spherical codes for N spheres, formulated to minimize the radius of a (d-1)-sphere onto which the centers of N identical nonoverlapping d-dimensional spheres of unit diameter can be placed, are also DLP optimal packings when Rmin(N) ranges between unity and the golden ratio.

A11 - Speaker: C. Zachary, Princeton University
Coauthor: S. Torquato
Title: Hyperuniformity in point patterns and heterogeneous media
Abstract: Hyperuniform point patterns are characterized by a variance in the local number density that grows more slowly than the volume for large observation windows. We extend this concept to the more general case of two-phase heterogeneous media by considering the decay of local volume fraction fluctuations. Hyperuniformity in this context involves a local volume fraction variance decaying faster than the volume of an observation window. We also discuss the number variance problem for point patterns in high Euclidean dimensions with applications to number theory. Our results indicate that hyperuniformity can be used as a quantitative order metric characterizing the extent of randomness in a system.

A12 - Speaker: N. Maric, University of Missouri
Coauthors: T. Cox and R. Schinazi
Title: Contact process in a wedge
Abstract: We prove that the supercritical one-dimensional contact process survives in certain wedge-like space-time regions, and that when it survives it couples with the unrestricted contact process started from its upper invariant measure. As an application we show that a type of weak coexistence is possible in the nearest-neighbor "grass-bushes-trees" successional model introduced in Durrett and Swindle (1991).

A13 - Speaker: B. Daniels, Cornell University
Coauthor: J.P. Sethna
Title: Nucleation at the DNA supercoiling transition
Abstract: When overtwisted, DNA forms supercoiled structures called plectonemes. At the transition where a plectoneme is first nucleated, experiments have observed thermal hopping between states with and without a plectoneme. Reaction-rate theory predicts a rate of hopping related to the energy barrier between the states, which appears too small to explain the slow measured rate. We therefore perform a full calculation of the prefactor, including hydrodynamics, entropic factors, and sequence-dependent intrinsic bend disorder, to find which effects may be responsible for the slow rate.

A14 - Speaker: O.S. Sariyer, Koc University
Coauthor: C. Guven
Title: Amino acid sequence alignment using simulated annealing
Abstract: The simulated annealing algorithm reveals connections between statistical mechanics and combinatorial optimization by introducing a temperature-like variable that gives rise to efficient search for global optimum. Some main problems of bioinformatics, onto which the simulated annealing methods have been applied during the last two decades, include phylogenetic tree search, homology modeling, improvement of threading-based protein models, secondary structure alignment, tertiary structure prediction emph{etc}. We investigated if and how simulated annealing can be applied onto amino acid sequence alignment, a problem particularly relevant to evolution, for which the widely accepted method of solution is an application of dynamic programming, namely the Needleman-Wunsch algorithm of time complexity $mathcal{O}(N2)$ for aligning two sequences both of length $N$. We studied the case of equal sequence lengths for simplicity, while the procedure can be well generalized to different sequence lengths. Our time complexity analysis suggests simulated annealing being better than the Needleman-Wunsch algorithm for sequences of lengths longer than median protein lengths, for which the optimal alignment cost deviation per residue saturates to a fair value. It should be noted that although the Needleman-Wunsch algorithm yields the exact optimal alignment, it cannot be extended to multiple sequence alignment, while this extension can be easily implemented for simulated annealing.

A15 - Speaker: L. Chayes, UCLA
Title: Ballistic Behavior for Biased SAW
Abstract: The following (obvious) contention is demonstrated mathematically: For the SAW measure defined with a (strictly) positive bias, there is a (strictly) positive drift.

A16 - Speaker: C.N. Kaplan, Brandeis University
Coauthors: H. Tu, R. Pelcovits and R.B. Meyer
Title: Theory of depletion induced phase transition from chiral smectic A twisted ribbons to semi-infinite flat membranes
Abstract: Smectic A layers expel twist and bend deformations, just as magnetic field is expelled from bulk superconductors. In analogy with the London penetration length, the typical distance to which a magnetic field penetrates into a superconductor, twist and bend deformations can penetrate at the edges or around isolated defects of smectic A layers composed of chiral molecules. These deformations appear intrinsically due to the competition of molecular chirality with the tendency of the molecules to build a perfect twist-free smectic layer. We consider single smectic A layers in the form of twisted ribbons composed of chiral molecules. By allowing local tilting, we evaluate their equilibrium free energy and obtain the twist penetration profile across the width of the twisted ribbon. Furthermore, we calculate the phase diagrams in terms of the line tension, which corresponds to experimentally inducing an attractive depletion interaction, and K24, the saddle-play constant. We find a first-order phase transition from isolated chiral smectic A twisted ribbons to chiral smectic A semi-infinite flat layers.

A17 - Speaker: H. Lei, UCLA
Coauthors: I. Binder and L. Chayes
Title: Cardy's Formula and Convergence to SLE$_6$ for a (Correlated) Percolation Model
Abstract: A 2D percolation model defined on the bond-triangular lattice with local correlations is demonstrated to have a conformally invariant scaling limit. 1) Cardy's Formula holds in (quite) general domains. 2) The law of the interface converges to SLE$_6$. The above provides a non-trivial example of universality.

A18 - Speaker: M. Drake, University of Massachussetts
Coauthor: J. Machta, D. Abraham and C. Newman
Title: Monte Carlo Simulations of an Equilibrium Random Surface Model
Abstract: We present results of Monte Carlo simulations of the equilibrium random surface model proposed in [1]. The model includes both the Volmer-Weber and Stranski-Krastanow growth regimes. In one limit, the model reduces to the two-dimensional Ising model in the height representation. We find that the critical temperature is reduced when the Ising model constraint of a single height steps is relaxed. The critical properties of the model are explored using a variant of the worm algorithm.
[1] C. Newman and D. B. Abraham, Equilibrium Stranski-Krastanow and Volmer-Weber models, Europhys. Lett., 86, 16002 (2009).

Session B

B1 - Speaker: S. Ji, Rutgers University
Title: Are There Three More Laws of Thermodynamics?
Abstract

B2 - Speaker: A. Shekhawat, Cornell University
Coauthors: S. Papanikolaou, S. Zapperi, and J.P. Sethna
Title:Theory of phase transition and avalanches in non-equlibrium Mott transition
Abstract: We present a dielectric-breakdown model for resistance jumps and avalanches in materials driven through the Mott transition by temperature. The model consists of dielectric elements at finite resistance contrast with temperature and voltage-dependent breakdown thresholds. We discover numerical evidence for a continuous phase transition separating a 'bolt-like' phase from a 'percolative' phase. The model duplicates the resistance jump distribution exponents observed in several recent experiments.

B3 - Speaker: M. Novotny, Mississippi University
Coauthors: J. Yancey, S. Gwaltney, C. Varghese, L. Solomon, X. Zhang and S. Boettcher
Title: Are social-network-based nanomaterials possible?
Abstract: The statistical mechanics of models on networks inspired by social structures, such as small-world networks, exhibit interesting behavior. One example is (modified) mean-field critical behavior in Ising models on small-world networks. Another is the existence of an edge from complete reflection to complete transmission at a particular energy for (spinless, single-band) electron transport through a Hanoi network. The question to address is whether nanomaterials based on social-inspired networks can be synthesized and what materials properties they would possess. Using density-functional theory calculations, we have demonstrated that all-carbon nanomaterials inspired by small-world networks can be stable.

B4 - Speaker: M. Keskin, Erciyes University
Coauthors: B. Devirenb, and Y. Kocakaplan
Title:Topology of the correlation networks among major currencies using hierarchical structure methods
Abstract: We study the topology of the correlation networks among 34 major currencies by using the concept of a minimal-spanning tree (MST) and hierarchical tree (HT) for the full years of 2007-2008 periods in which very important turbulences were occurred. We use the USD (US dollar) as numeraire that is a major currency. We derive a hierarchical organization, and construct the minimal-spanning and hierarchical trees in the full years of 2007, 2008 and 2007-2008 periods. The trees are known as useful tools to perceive and detect the global structure, taxonomy and hierarchy in financial data. We illustrate how the MSTs and their related HTs develop over time. From these trees we detect different clusters of currencies according to their proximity and economics ties. Clustered structure of the currencies and the key currency in each cluster is obtained and it is found that the clusters match nicely with the geographical regions of corresponding countries in the world such as Asia or Europe. The key currencies are generally given by major economic activities as expected. We also found that the MST in 2007-2008 periods is very similar to the MST in the full year of 2008 and this implies that the global financial crisis is dominant.

B5 - Speaker: R. Fisch, Princeton University
Title: From collective pinning to dilute strong pinning: glassy freezing in the 3D random-field XY model
Abstract: Monte Carlo simulations on the 3D random-field XY model have been performed on a sequence of random-field distributions. These start from distributions where the magnitude of the random field is the same on every site. The distribution is then diluted, and the strength of the field on the remaining sites is increased so that the freezing temperature, T_g, remains approximately unchanged. For all these distributions, the structure factor, S(k,T), at small nonzero k displays Arrhenius behavior in a range above T_g, but then flattens out and has a maximum at or near T_g. The sharpness of this maximum at T_g decreases as the dilution is increased.

B6 - Speaker: G. Gor, Rutgers University
Coauthor: A.V. Neimark
Title: Coupling Adsorption and Deformation: Thermodynamic Approach
Abstract: We suggest a theoretical model of hysteretic deformation of mesoporous solids during adsorption-desorption processes. The proposed description exploits the notions of classical thermodynamics (Derjaguin - Broekhoff - de Boer theory for capillary condensation) and provides an analytical expression for the solvation pressure which determines the strain of the solid framework. We reveal a non-monotonic variation of solvation pressure during adsorption prior to capillary condensation. We derive analytical expressions for the pressure drops at the equilibrium and capillary condensation transitions. The obtained results are in semi-quantitative agreement with recent experiments on adsorption deformation of mesoporous solids with alternating stages of expansion and contraction.

B7 - Speaker: M. Krüger, MIT
Coauthors: M. Fuchs
Title: Fluctuation Dissipation Relations for Brownian Particles under Shear
Abstract: We present the theoretical study of the Fluctuation Dissipation Theorem (FDT) under shear. The FDT connects response and correlation functions in equilibrium and is violated in the considered out-of-equilibrium situation. This violation is often interpreted in terms of an effective temperature. We derive an approximate relation for sheared systems at high density (glassy systems) building on mode coupling theory. The interesting result is that the ratio of response and correlation function takes half the value as expected from the equilibrium FDT in the simplest approximation. B8 - Speaker: B. Machta, Cornell University
Coauthors: S. Papanikolaou, J.P. Sethna, S.L. Veatch
Title: Why Are Cell Membranes Near Criticality?
Abstract: Recent work [1] suggests that the plasma membranes of living cells are tuned close to a liquid liquid miscibility critical point in the 2D Ising class. Here we discuss some reasons why cells might want to tune to this non-generic region of phase space. The Ising order parameter can mediate long ranged effective forces and provide a channel for communication between membrane bound proteins. It can also increase the collective sensitivity of membrane bound receptors to ligand if those receptors change their liquid preference on ligand binding. [1]Veatch SL, et al. (2008) Critical fluctuations in plasma membrane vesicles. ACS Chem Biol 3(5):287-293.

B9 - Speaker: A. Kosmrlj, MIT
Coauthors: A. Chakraborty and M. Kardar
Title: Thymic selection of T cells as a diffusion with intermittent traps
Abstract: T cells orchestrate adaptive immune responses by recognizing peptides from pathogens, and distinguishing them from self-peptides. To ensure the latter, immature T-cells (thymocytes) diffusive around the thymus gland, where they encounter an ensemble of self-peptides presented on (immobile) antigen presenting cells (APC). If a thymocyte binds strongly to such an APC, it is eliminated; i.e. the APC acts as a trap for the diffusing thymocyte. Since the peptides presented by APCs are recycled, the traps are not permanent, but intermittently turn on and off.
We model this process by the diffusion of a particle in a field of immobile, but intermittent traps. Diffusion of a particle in a static field of randomly distributed traps has been studied extensively in the last 100 years. We discuss the effects of switching the traps between 'on' and 'off' states on the survival probability of a diffusing particle.

B9¹ - Speaker: S.J. Rahi, MIT
Coauthors: S. Zaheer, T. Emig, R. Jaffe, M. Kardar
Title:Casimir interaction of an object with a cavity
Abstract:We analyze the electrodynamic Casimir force and torque on an object inside a sphere or a spheroid. Whether the center of the cavity is a point of stable or unstable equilibrium depends on the material properties of the medium and the walls in a simple way. The direction of the torque on the object inside the cavity, however, has a varied dependence on the permittivities of the medium and the walls.

B10 - Speaker: R. Kerr, Univerity of Warwick
Title: Numerical generation of a vortex ring cascade in quantum turbulence
Abstract: A symmetric anti-parallel pair of quantum vortices is simulated using the three-dimensional Gross-Pitaevski equations. The initial development demonstrates vortex dynamics of stretching, curvature and torsion consistent with a filament calculation and simulations of the classical, ideal Euler equations. How a vacuum mediates reconnection between the pair is illustrated. Out of the reconnection, vortex waves are emitted with properties similar to waves in the local induction approximation. These waves propagate down the initial vortex and deepen. When they deepen far enough, sec$, spectra form a $k^{-3}$ regime, while at the final time simulated spectra in two directions are closer to the classical -5/3 iner.

B11 - Speaker: M. F. Maghrebi, MIT
Title:Feynman graphs for computing the Casimir energy in a multiple- reflection expansion
Abstract: The Casimir interaction between several objects can be organized in a Feynman diagrammatic fashion in orders of multiple reflections from the objects. While for perturbative QFTs, the coupling constant is a small parameter that justifies the expansion, there is no corresponding a priori small parameter in computing Casimir interactions. Nonetheless, higher order terms are in practice smaller due to geometrical, and other, reasons. We shall demonstrate this for a variety of different shapes and geometries.

B12 - Speaker: D. Gonzalez, University of Maryland
Coauthors: A. Pimpinelli and T.L. Einstein
Title:Statistical distribution of many-particle systems: Multi-neighbors spacings
Abstract: The nearest-neighbor spacing distribution function $p^{(0)}(s)$ is often used to describe the statistical behavior of many particle systems. In the standard approach, the system is characterized based on the information extracted from $p^{(0)}(s)$. However, the information contained in it about the system is very limited; the finer details are in the multi-neighbor spacing distributions $p^{(n)}(s)$. These distributions allow one to describe the many-particle interactions through an effective pair potential and facilitate the interpretation of the physical properties of the systems. We show how systems with different $p^{(n)}(s)$ can share the same $p^{(0)}(s)$.

B13 - Speaker: P. Patrone, University of Maryland
Coauthors: T. Einstein and D. Margetis
Title:Vicinal Surfaces with Singular Step Interactions: 1D Stochastic Model

B14 - Speaker: M. Hawkins, University of Maryland-College Park
Coauthor: T.L. Einstein
Title: Relaxation of Terrace Width Distribution of Vicinal (001) with zigzag [110] steps
Abstract: We discuss preliminary results of Kinetic Monte Carlo Simulations which show the relaxation of zigzag steps of a vicinal (001) surface towards equilibrium. At equilibrium the distribution of terrace widths can be fit to a generalized wigner surmise.

B15 - Speaker: S. Muir, University of North Texas
Coauthor: M. Urbanski
Title: Local Energy vs Interaction Approach to Gibbs/Equilibrium States
Abstract: We introduce interactions and local energy functions on classical lattice models and show how they produce equivalent sets of Gibbs/equilibrium measures. We show how to represent "exp-summable d-regular" local energy functions by interactions for which Georgii has shown that Gibbs/equilibrium states exist. Our recent work shows that in the case of a countably infinite single spin space the local energy approach applies to all "exp-summable (d-1)-regular" local energy functions, a slightly larger class.

B16 - Speaker: M. Schmiedeberg, University of Pennsylvania
Coauthors: A. Liu
Title: Dynamics of soft spheres beyond the hard-sphere limit Abstract: In the limit of low pressures the dynamics of model glass-forming liquids with finite-ranged repulsive interactions are universal. In that limit, where the product of the pressure and the particle volume is small compared to the interaction energy, soft sphere systems behave as hard spheres, so that the dynamics correspond to those of the hard-sphere glass transition and depend only on the ratio of temperature to the product of pressure and the particle volume. However, at higher pressures relative to the interaction energy, there are deviations from this universal behavior that depend on the inter-particle potential. We consider a bidisperse system consisting of soft spheres that repel each other according to a power law potential $delta^{alpha}$ where $delta$ is the particle overlap. By using molecular-dynamics simulations, we determine relaxation times as a function of temperature and pressure. We find that the dynamics of soft spheres can be mapped on hard spheres with a smaller diameter and therefore a reduced effective volume fraction.

B17 - Speaker: R. Ziff, University of Michigan
Title: Explosive percolation on lattices
Abstract: Explosive percolation by the "Achlioptas" product-rule process on regular lattices is studied. The resulting transition is shown to be first-order, as evidenced by some quantities (such as the susceptibility) being discontinuous at the transition. In this process, two prospective bonds are tested, and the one that minimizes the product of the cluster masses is chosen. Simulation is very efficient using the algorithm of Newman and Ziff.

Session C

C1 - Speaker: M. Kardar, MIT
Coauthor: Y. Kantor
Title: Universality in the jamming limit for elongated hard particles in one dimension
Abstract: We study thermodynamics properties of a one dimensional gas of hard elongated particles. The particle centers are restricted to a line, while they can rotate in two-dimensional space. Correlations between orientations of the objects are studied (by transfer matrix method) as a function of density and aspect ratio. The behavior in the extreme high-density (jamming) limit is described by a few universality classes depending on the object's shape. In particular, there is a diverging correlation length when the contact point of adjacent objects is far from the line along which their centers move, as for needles and rectangles.

C2 - Speaker: D. Blair, University of Massachusetts Amherst
Coauthors: J. Machta
Title: Diameter of random clusters in potts models
Abstract: We report measurements of cluster diameter -- the maximum over all pairs of connected vertices of the minimum path length between the vertices in numerical simulations of random clusters in q-state Potts models in two, three, and four dimensions. Although the diameter is not a thermodynamic quantity, it is expected to display critical behavior for Potts models models as the size of the largest cluster diverges at the critical point. We have developed an efficient algorithm for measuring the diameter, and have obtained results using the Swendsen-Wang algorithm both for equilibrating the model and for identifying clusters.

C3 - Speaker: L. Lafuerza, IFISC
Coauthors: P. Colet and R. Toral

Title: Non-equilibrium transition in a model of coupled active rotators
Abstract: We consider a variant of the Kuramoto model where the elements are active rotators near the excitable regime. It is shown that, for some distributions of the natural frequencies, there is a non-equilibrium transition which leads to a regime where the system exhibits coherent oscillations. We investigate the influence of the type of distribution and we derive expressions for the phase space of the system.

C4 - Speaker: M. Damron, Princeton University
Coauthor: A. Sapozhnikov and B. Vagvolgyi
Title: Invasion percolation and the incipient infinite cluster in 2D
Abstract: In this talk, we consider invasion percolation on two-dimensional lattices. We give some basic relations between invasion percolation and critical Bernoulli percolation. We use these relations to compare connectivity properties of the IPC to those of Kesten's incipient infinite cluster.

C5 - Speaker: W. Choi, Cornell University
Coauthors: Y.S. Chen, S. Papanikolaou, and J.P. Sethna
Title:Linear stability analysis of turbulent behaviors in plastic flow
Abstract: Simulations of a continuum dislocation dynamics theory exhibit complicated structures when climb is forbidden, even with a smooth initial condition. The physics of this fractal structure formation has many similarities to turbulence in fluid flow modelled with Euler and Navier-Stokes equations. In light of the well understood linear instabilities in turbulence, we study the linear stability problem of the dislocation dynamics theory, both analytically and numerically.

C6 - Y. Chen, Cornell University
Coauthors: W. Choi, S. Papanikolaou, and J.P. Sethna
Title:Scaling theory of continuum dislocation dynamics
Abstract: We present a scaling theory for continuum dislocation dynamics. When dislocations are forbidden to climb, we observe the self-similar cellular dislocation structures. We analyze them in terms of critical exponents for correlation functions of dislocation density, orientation, and plastic distortion. We show the exponent relations in agreement with numerical simulations. In view of previous experimental studies of cell structure, we find that both average cell sizes and average misorientations show power-law behaviors depending upon the loading strain, and still explore how they are related to these critical exponents of correlation functions.

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Statistical Mechanics Conference

103th Statistical Mechanics Conference

List of invited speakers & talk titles

Schedule of Short talks