Results for "Andrea J. Liu"

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Mechanical signaling via nonlinear wavefront propagation in a mechanically-excitable mediumApr 12 2013Models that invoke nonlinear wavefront propagation in a chemically excitable medium are rife in the biological literature. Indeed, the idea that wavefront propagation can serve as a signaling mechanism has often been invoked to explain synchronization ... More
Jamming Mechanisms and Density Dependence in a Kinetically-Constrained ModelSep 03 2009May 19 2010We add relaxation mechanisms that mimic the effect of temperature and non-equilibrium driving to the recently-proposed spiral model which jams at a critical density rho_c < 1. This enables us to explore unjamming by temperature or driving at rho_c < rho ... More
Direct determination of the size of basins of attraction of jammed solidsJan 31 2011Jun 28 2011We propose a free-energy based Monte-Carlo method to measure the volume of potential-energy basins in configuration space. Using this approach we can estimate the number of distinct potential-energy minima, even when this number is much too large to be ... More
Self-Diffusiophoresis in the Advection Dominated RegimeJul 19 2011In both biological and artificial systems, concentration gradients can serve as a convenient mechanism for manipulating particles and generating motility. Particles that interact with a solute will move along its gradient; if they themselves generate ... More
Activated dynamics and effective temperature in a steady state sheared glassJun 01 2007Oct 02 2007We conduct nonequilibrium molecular dynamics simulations to measure the shear stress, the average inherent structure energy, and the effective temperature $T_{eff}$ of a sheared model glass as a function of bath temperature $T$ and shear strain rate. ... More
Cluster Probability in Bootstrap PercolationSep 27 2006We develop a recursive formula for the probability of a k-cluster in bootstrap percolation.
Why is Random Close Packing Reproducible?Jan 15 2007Aug 27 2007We link the thermodynamics of colloidal suspensions to the statistics of regular and random packings. Random close packing has defied a rigorous definition yet, in three dimensions, there is near universal agreement on the volume fraction at which it ... More
A random matrix definition of the boson peakJul 22 2013May 12 2015The density of vibrational states for glasses and jammed solids exhibits universal features, including an excess of modes above the Debye prediction known as the boson peak located at a frequency $\omega^*$ . We show that the eigenvector statistics for ... More
Physical Questions Posed by DNA CondensationMar 09 2000When multivalent salts are added to dilute DNA solution, the DNA chains condense into bundles of a well-defined size. We explore two physical problems motivated by this phenomenon: the origin of the attractive interactions between the highly-negatively ... More
Vibrational modes identify soft spots in a sheared disordered packingDec 21 2010We analyze low-frequency vibrational modes in a two-dimensional, zero-temperature, quasistatically sheared model glass to identify a population of structural "soft spots" where particle rearrangements are initiated. The population of spots evolves slowly ... More
Far-From-Equilibrium Physics: An OverviewSep 24 2010Isolated systems tend to evolve towards equilibrium, a special state that has been the focus of many-body research for a century. Yet much of the richness of the world around us arises from conditions far from equilibrium. Phenomena such as turbulence, ... More
New Proposed Mechanism of Actin-Polymerization-Driven MotilityJun 04 2008Jun 06 2008We present the first numerical simulation of actin-driven propulsion by elastic filaments. Specifically, we use a Brownian dynamics formulation of the dendritic nucleation model of actin-driven propulsion. We show that the model leads to a self-assembled ... More
Machine Learning Characterization of Structural Defects in Amorphous Packings of Dimers and EllipsesNov 08 2018Jan 26 2019Structural defects within amorphous packings of symmetric particles can be characterized using a machine learning approach that incorporates structure functions of radial distances and angular arrangement. This yields a scalar field, \emph{softness}, ... More
Comment on 'Repulsive Contact Interactions Make Jammed Particulate Systems Inherently Nonharmonic'Jun 06 2013Dec 31 2014In their Letter, Schreck, Bertrand, O'Hern and Shattuck [Phys. Rev. Lett. 107, 078301 (2011)] study nonlinearities in jammed particulate systems that arise when contacts are altered. They conclude that there is "no harmonic regime in the large system ... More
Stability of jammed packings I: the rigidity length scaleJan 29 2013Nov 22 2013In 2005, Wyart et al. (Europhys. Lett., 72 (2005) 486) showed that the low frequency vibrational properties of jammed amorphous sphere packings can be understood in terms of a length scale, called l*, that diverges as the system becomes marginally unstable. ... More
The topological basis of function in flow networksJan 03 2019Feb 05 2019The ability to reroute and control flow is vital to the function of many biological transport networks. By tuning the conductance of edges, many flow networks robustly control the propagation of inputs in order to achieve a wide variety of specific tasks. ... More
Tuning and jamming reduced to their minimaJan 03 2019Feb 05 2019Inspired by protein folding, we introduce funnels into the complex cost function landscapes of two processes, the tuning of networks, and the jamming of ideal spheres. In both processes, geometrical frustration plays a role -- tuning pressure differences ... More
Directed aging, memory and Nature's greedMar 14 2019Disordered materials are often out of equilibrium and evolve very slowly. This allows a memory of the imposed strains or preparation conditions to be encoded in the material. Here we consider "directed aging", where the elastic properties of a material ... More
Role of local response in manipulating the elastic properties of disordered solids by bond removalAug 23 2017We explore the range over which the elasticity of disordered spring networks can be manipulated by the removal of selected bonds. By taking into account the local response of a bond, we demonstrate that the effectiveness of pruning can be improved so ... More
Instabilities of jammed packings of frictionless spheres under compressionApr 04 2017We consider the contribution to the density of vibrational states and the distribution of energy barrier heights of incipient instabilities in a glass modeled by a jammed packing of spheres. On approaching an instability, the frequency of a normal mode ... More
Finite-Size Scaling at the Jamming TransitionApr 22 2012Jun 06 2012We present an analysis of finite-size effects in jammed packings of N soft, frictionless spheres at zero temperature. There is a 1/N correction to the discrete jump in the contact number at the transition so that jammed packings exist only above isostaticity. ... More
Universal Jamming Phase Diagram in the Hard-Sphere LimitNov 30 2010We present a new formulation of the jamming phase diagram for a class of glass-forming fluids consisting of spheres interacting via finite-ranged repulsions at temperature $T$, packing fraction $\phi$ or pressure $p$, and applied shear stress $\Sigma$. ... More
Structural signatures of the unjamming transition at zero temperatureJan 01 2006We study the pair correlation function $g(r)$ for zero-temperature, disordered, soft-sphere packings just above the onset of jamming. We find distinct signatures of the transition in both the first and split second peaks of this function. As the transition ... More
Interference Channels with Correlated Receiver Side InformationOct 14 2008The problem of joint source-channel coding in transmitting independent sources over interference channels with correlated receiver side information is studied. When each receiver has side information correlated with its own desired source, it is shown ... More
Anharmonicity and quasi-localization of the excess low-frequency vibrations in jammed solidsSep 21 2009We compare the harmonic and anharmonic properties of the vibrational modes in 3-dimensional jammed packings of frictionless spheres interacting via repulsive, finite range potentials. A crossover frequency is apparent in the density of states, the diffusivity ... More
Edge Mode Combinations in the Entanglement Spectra of Non-Abelian Fractional Quantum Hall States on the TorusSep 09 2011Jan 19 2012We present a detailed analysis of bi-partite entanglement in the non-Abelian Moore-Read fractional quantum Hall state of bosons and fermions on the torus. In particular, we show that the entanglement spectra can be decomposed into intricate combinations ... More
Fractional Chern Insulators in Topological Flat bands with Higher Chern NumberJun 17 2012Nov 03 2012Lattice models forming bands with higher Chern number offer an intriguing possibility for new phases of matter with no analogue in continuum Landau levels. Here, we establish the existence of a number of new bulk insulating states at fractional filling ... More
Predicting plasticity with soft vibrational modes: from dislocations to glassesMar 04 2014We show that quasi localized low-frequency modes in the vibrational spectrum can be used to construct soft spots, or regions vulnerable to rearrangement, which serve as a universal tool for the identification of flow defects in solids. We show that soft ... More
Spatial structure of states of self stress in jammed systemsJan 13 2016States of self stress, organizations of internal forces in many-body systems that are in equilibrium with an absence of external forces, can be thought of as the constitutive building blocks of the elastic response of a material. In overconstrained disordered ... More
Elasticity and Response in Nearly Isostatic Periodic LatticesJun 15 2009Nov 13 2009The square and kagome lattices with nearest neighbor springs of spring constant $k$ are isostatic with a number of zero-frequency modes that scale with their perimeter. We analytically study the approach to this isostatic limit as the spring constant ... More
Normal Modes in Model Jammed Systems in Three DimensionsMar 18 2008Vibrational spectra and normal modes of mechanically stable particle packings in three dimensions are analyzed over a range of compressions, from near the jamming transition, where the packings lose their rigidity, to far above it. At high frequency, ... More
Two diverging length scales in the structure of jammed packingsOct 19 2017Jun 11 2018At densities higher than the jamming transition for athermal, frictionless repulsive spheres we find two distinct length scales, both of which diverge as a power law as the transition is approached. The first, $\xi_{Z}$, is associated with the two-point ... More
Linking microscopic and macroscopic response in disordered solidsJun 19 2017The modulus of a rigid network of harmonic springs depends on the sum of the energies in each of the bonds due to the applied distortion: compression in the case of the bulk modulus, $B$, or shear in the case of the shear modulus, $\mathcal{G}$. The distortion ... More
Period proliferation in periodic states in cyclically sheared jammed solidsMay 23 2017Athermal disordered systems can exhibit a remarkable response to an applied oscillatory shear: after a relatively few shearing cycles, the system falls into a configuration that had already been visited in a previous cycle. After this point the system ... More
Contact nonlinearities and linear response in jammed particulate packingsFeb 25 2014Dec 31 2014Packings of frictionless athermal particles that interact only when they overlap experience a jamming transition as a function of packing density. Such packings provide the foundation for the theory of jamming. This theory rests on the observation that, ... More
Scaling theory for the jamming transitionOct 12 2015We propose a scaling ansatz for the elastic energy of a system near the critical jamming transition in terms of three relevant fields: the compressive strain $\Delta \phi$ relative to the critical jammed state, the shear strain $\epsilon$, and the inverse ... More
Tuning by pruning: exploiting disorder for global response and the principle of bond-level independenceFeb 10 2015Feb 13 2015We exploit the intrinsic difference between disordered and crystalline solids to create systems with unusual and exquisitely tuned mechanical properties. To demonstrate the power of this approach, we design materials that are either virtually incompressible ... More
Excess Vibrational Modes and the Boson Peak in Model GlassesNov 17 2006The excess low-frequency normal modes for two widely-used models of glasses were studied at zero temperature. The onset frequencies for the anomalous modes for both systems agree well with predictions of a variational argument, which is based on analyzing ... More
Capacity Regions and Bounds for a Class of Z-interference ChannelsAug 06 2008We define a class of Z-interference channels for which we obtain a new upper bound on the capacity region. The bound exploits a technique first introduced by Korner and Marton. A channel in this class has the property that, for the transmitter-receiver ... More
AWECS: A Linear Gyrokinetic Delta-f Particle-in-Cell Simulation Code for the Study of Alfvenic Instabilities in High-Beta Tokamak PlasmasJan 02 2008Jun 27 2008A 1-D linear gyrokinetic code called AWECS is developed to study the kinetic excitation of Alfvenic instabilities in a high-beta tokamak plasma, with beta being the ratio of thermal to magnetic pressure. It is designed to describe physics associated with ... More
On the performance of different mutation operators of a subpopulation-based genetic algorithm for multi-robot task allocation problemsJun 02 2016The performance of different mutation operators is usually evaluated in conjunc-tion with specific parameter settings of genetic algorithms and target problems. Most studies focus on the classical genetic algorithm with different parameters or on solving ... More
Divergence of Voronoi cell anisotropy vector: A threshold-free characterization of local structure in amorphous materialsSep 18 2015Dec 22 2015Characterizing structural inhomogeneity is an essential step in understanding the mechanical response of amorphous materials. We introduce a threshold-free measure based on the field of vectors pointing from the center of each particle to the centroid ... More
Statistics of Shear-induced Rearrangements in a Model FoamApr 07 1999Under steady shear, a foam relaxes stress through intermittent rearrangements of bubbles accompanied by sudden drops in the stored elastic energy. We use a simple model of foam that incorporates both elasticity and dissipation to study the statistics ... More
Deformation-Driven Diffusion and Plastic Flow in Two-Dimensional Amorphous Granular PillarsFeb 04 2015We report a combined experimental and simulation study of deformation-induced diffusion in compacted two-dimensional amorphous granular pillars, in which thermal fluctuations play negligible role. The pillars, consisting of bidisperse cylindrical acetal ... More
Branching, Capping, and Severing in Dynamic Actin StructuresMar 15 2007Branched actin networks at the leading edge of a crawling cell evolve via protein-regulated processes such as polymerization, depolymerization, capping, branching, and severing. A formulation of these processes is presented and analyzed to study steady-state ... More
Effect of Mono- and Multivalent Salts on Angle-dependent Attractions between Charged RodsNov 19 2003Using molecular dynamics simulations we examine the effective interactions between two like-charged rods as a function of angle and separation. In particular, we determine how the competing electrostatic repulsions and multivalent-ion-induced attractions ... More
Rotational and Translational Phonon Modes in Glasses Composed of Ellipsoidal ParticlesDec 01 2010The effects of particle shape on the vibrational properties of colloidal glasses are studied experimentally. 'Ellipsoidal glasses' are created by stretching polystyrene spheres to different aspect ratios and then suspending the resulting ellipsoidal particles ... More
CMB Lensing Beyond the Power Spectrum: Cosmological Constraints from the One-Point PDF and Peak CountsAug 10 2016Nov 01 2016Unprecedentedly precise cosmic microwave background (CMB) data are expected from ongoing and near-future CMB Stage-III and IV surveys, which will yield reconstructed CMB lensing maps with effective resolution approaching several arcminutes. The small-scale ... More
Disconnecting structure and dynamics in glassy thin filmsOct 11 2016Nanometrically thin glassy films depart strikingly from the behavior of their bulk counterparts. We investigate whether the dynamical differences between bulk and thin film glasses can be understood by differences in local microscopic structure. We employ ... More
Emergent SO(3) Symmetry of the Frictionless Shear Jamming TransitionSep 01 2016Mar 23 2017We study the shear jamming of athermal frictionless soft spheres, and find that in the thermodynamic limit, a shear-jammed state exists with different elastic properties from the isotropically-jammed state. For example, shear-jammed states can have a ... More
Mapping the glassy dynamics of soft spheres onto hard-sphere behaviorJul 13 2011We show that the dynamics of soft-sphere systems with purely repulsive interactions can be described by introducing an effective hard-sphere diameter determined using the Andersen-Weeks-Chandler approximation. We find that this approximation, known to ... More
CMB Lensing Beyond the Power Spectrum: Cosmological Constraints from the One-Point PDF and Peak CountsAug 10 2016Unprecedentedly precise cosmic microwave background (CMB) data are expected from ongoing and near-future CMB Stage-III and IV surveys, which will yield reconstructed CMB lensing maps with effective resolution approaching several arcminutes. The small-scale ... More
Strain fluctuations and elastic moduli in disordered solidsMar 25 2015Aug 24 2015Recently there has been a surge in interest in using video-microscopy techniques to infer the local mechanical properties of disordered solids. One common approach is to minimize the difference between particle vibrational displacements in a local coarse-graining ... More
Pinning Susceptibility: The effect of dilute, quenched disorder on jammingSep 02 2015May 18 2016We study the effect of dilute pinning on the jamming transition. Pinning reduces the average contact number needed to jam unpinned particles and shifts the jamming threshold to lower densities, leading to a pinning susceptibility, $\chi_p$. Our main results ... More
Structural Polymorphism of the Cytoskeleton: A Model of Linker-Assisted Filament AggregationApr 27 2005The phase behavior of charged rods in the presence of inter-rod linkers is studied theoretically as a model for the equilibrium behavior underlying the organization of actin filaments by linker proteins in the cytoskeleton. The presence of linkers in ... More
Force distributions near the jamming and glass transitionsMay 02 2000Aug 09 2000We calculate the distribution of interparticle normal forces $P(F)$ near the glass and jamming transitions in model supercooled liquids and foams, respectively. $P(F)$ develops a peak that appears near the glass or jamming transitions, whose height increases ... More
Generalized Retrieval Method for Metamaterial Constitutive Parameters Based on a Physically-Driven Homogenization ApproachMar 23 2013Based on the recently introduced homogenization theory developed in [Phys. Rev. B 84, 075153 (2011)], we propose a generalized retrieval method that allows extracting physically meaningful bulk effective parameters from conventional scattering measurements ... More
Capacity Bounds and Exact Results for the Cognitive Z-interference ChannelDec 12 2011Feb 15 2012We study the discrete memoryless Z-interference channel (ZIC) where the transmitter of the pair that suffers from interference is cognitive. We first provide an upper bound on the capacity of this channel. We then show that, when the channel of the transmitter-receiver ... More
The Relationship Between Local Structure and Relaxation in Out-of-Equilibrium Glassy SystemsJul 23 2016The dynamical glass transition is typically taken to be the temperature at which a glassy liquid is no longer able to equilibrate on experimental timescales. Consequently, the physical properties of these systems just above or below the dynamical glass ... More
A structural approach to relaxation in glassy liquidsJun 25 2015Nov 23 2015When a liquid freezes, a change in the local atomic structure marks the transition to the crystal. When a liquid is cooled to form a glass, however, no noticeable structural change marks the glass transition. Indeed, characteristic features of glassy ... More
Stability of jammed packings II: the transverse length scaleJan 29 2013Nov 22 2013As a function of packing fraction at zero temperature and applied stress, an amorphous packing of spheres exhibits a jamming transition where the system is sensitive to boundary conditions even in the thermodynamic limit. Upon further compression, the ... More
Heat transport in model jammed solidsAug 15 2009We calculate numerically the normal modes of vibrations in 3D jammed packings of soft spheres as a function of the packing fraction and obtain the energy diffusivity, a spectral measure of transport that controls sound propagation and thermal conductivity. ... More
Effect of Ordering on Spinodal Decomposition of Liquid-Crystal/Polymer MixturesOct 14 1998Partially phase-separated liquid-crystal/polymer dispersions display highly fibrillar domain morphologies that are dramatically different from the typical structures found in isotropic mixtures. To explain this, we numerically explore the coupling between ... More
Understanding plastic deformation in thermal glasses from single-soft-spot dynamicsApr 04 2014By considering the low-frequency vibrational modes of amorphous solids, Manning and Liu [Phys. Rev. Lett. 107, 108302 (2011)] showed that a population of "soft spots" can be identified that are intimately related to plasticity at zero temperature under ... More
Equivalence of glass transition and colloidal glass transition in the hard-sphere limitOct 05 2009We show that the slowing of the dynamics in simulations of several model glass-forming liquids is equivalent to the hard-sphere glass transition in the low-pressure limit. In this limit, we find universal behavior of the relaxation time by collapsing ... More
Emergent SO(3) Symmetry of the Frictionless Shear Jamming TransitionSep 01 2016We study the shear jamming of athermal frictionless soft spheres, and find that in the thermodynamic limit, a shear-jammed state exists with different elastic properties from the isotropically-jammed state. For example, shear-jammed states can have a ... More
Optical Backaction-Evading Measurement of a Mechanical OscillatorSep 04 2018Quantum mechanics imposes a limit on the precision of a continuous position measurement of a harmonic oscillator, as a result of quantum backaction arising from quantum fluctuations in the measurement field. A variety of techniques to surpass this standard ... More
The limits of multifunctionality in tunable networksMay 01 2018Oct 05 2018Nature is rife with networks that are functionally optimized to propagate inputs in order to perform specific tasks. Whether via genetic evolution or dynamic adaptation, many networks create functionality by locally tuning interactions between nodes. ... More
Statistical properties of 3D cell geometry from 2D slicesFeb 26 2018Jun 26 2018Although cell shape can reflect the mechanical and biochemical properties of the cell and its environment, quantification of 3D cell shapes within 3D tissues remains difficult, typically requiring digital reconstruction from a stack of 2D images. We investigate ... More
Designing allostery-inspired response in mechanical networksJul 28 2016Recent advances in designing meta-materials have demonstrated that global mechanical properties of disordered spring networks can be tuned by selectively modifying only a small subset of bonds. Here, using a computationally-efficient approach, we extend ... More
Disordered surface vibrations in jammed sphere packingsDec 30 2014We study the vibrational properties near a free surface of disordered spring networks derived from jammed sphere packings. In bulk systems, without surfaces, it is well understood that such systems have a plateau in the density of vibrational modes extending ... More
The jamming scenario - an introduction and outlookJun 11 2010Jan 27 2011The jamming scenario of disordered media, formulated about 10 years ago, has in recent years been advanced by analyzing model systems of granular media. This has led to various new concepts that are increasingly being explored in in a variety of systems. ... More
Energy transport in jammed sphere packingsJun 19 2008Nov 17 2008We calculate the normal modes of vibration in jammed sphere packings to obtain the energy diffusivity, a spectral measure of transport. At the boson peak frequency, we find an Ioffe-Regel crossover from a diffusivity that drops rapidly with frequency ... More
Effective Temperatures of a Driven System Near JammingOct 13 2001Fluctuations in a model of a sheared, zero-temperature foam are studied numerically. Five different quantities that reduce to the true temperature in an equilibrium thermal system are calculated. All five have the same shear-rate dependence, and three ... More
Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glassesMar 11 2011Sep 20 2011We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles which readily permit variation of sample packing fraction. At each packing fraction, ... More
Phonon Dispersion and Elastic Moduli of Two-Dimensional Disordered Colloidal Packings of Soft Particles with Frictional InteractionsJun 13 2013Oct 25 2013Particle tracking and displacement covariance matrix techniques are employed to investigate the phonon dispersion relations of two-dimensional colloidal glasses composed of soft, thermoresponsive microgel particles whose temperature-sensitive size permits ... More
Machine learning determination of atomic dynamics at grain boundariesMar 04 2018Sep 11 2018In polycrystalline materials, grain boundaries are sites of enhanced atomic motion, but the complexity of the atomic structures within a grain boundary network makes it difficult to link the structure and atomic dynamics. Here we use a machine learning ... More
Two-tone optomechanical instability in backaction-evading measurementsDec 28 2018Dec 31 2018While quantum mechanics imposes a fundamental limit on the precision of interferometric measurements of mechanical motion due to measurement backaction, the nonlinear nature of the coupling also leads to parametric instabilities that place practical limits ... More
The syncytial Drosophila embryo as a mechanically excitable mediumApr 15 2013Aug 27 2013Mitosis in the early syncytial Drosophila embryo is highly correlated in space and time, as manifested in mitotic wavefronts that propagate across the embryo. In this paper we investigate the idea that the embryo can be considered a mechanically-excitable ... More
Jamming in finite systems: stability, anisotropy, fluctuations and scalingJun 05 2014Dec 31 2014Athermal packings of soft repulsive spheres exhibit a sharp jamming transition in the thermodynamic limit. Upon further compression, various structural and mechanical properties display clean power-law behavior over many decades in pressure. As with any ... More
Electrostatic cluster formation in lipid monolayersMar 12 2010We study phase separation in mixed monolayers of neutral and highly negatively charged lipids, induced by the addition of divalent positively charged counterions. We find good agreement between experiments on mixtures of pip2 and sopc and simulations ... More
Phonons in two-dimensional soft colloidal crystalsDec 08 2012Sep 11 2013The vibrational modes of pristine and polycrystalline monolayer colloidal crystals composed of thermosensitive microgel particles are measured using video microscopy and covariance matrix analysis. At low frequencies, the Debye relation for two dimensional ... More
Pressure-gradient-induced Alfven eigenmodes: II. Kinetic excitation with ion temperature gradientJul 24 2009Dec 08 2009The kinetic excitation of ideal magnetohydrodynamic (MHD) discrete Alfven eigenmodes in the second MHD ballooning stable domain is studied in the presence of a thermal ion temperature gradient (ITG), using linear gyrokinetic particle-in-cell simulations ... More
High temperature unfolding simulations of a single stranded DNA i-motifMar 30 2011We present the results of high temperature 500 K Molecular Dynamics simulations of the DNA i-motif. The essential dynamics and the main unfolding pathways are compared to a biased metadynamics simulation at 300 K. Our results indicate a remarkable agreement ... More
Pressure-gradient-induced Alfven eigenmodes: I. Ideal MHD and finite ion Larmor radius effectsJul 24 2009Dec 08 2009In the second magnetohydrodynamic (MHD) ballooning stable domain of a high-beta tokamak plasma, the Schroedinger equation for ideal MHD shear Alfven waves has discrete solutions corresponding to standing waves trapped between pressure-gradient-induced ... More
Liapunov Exponents and the Reversibility of Molecular Dynamics AlgorithmsAug 25 1997We study the phenomenon of lack of reversibility in molecular dynamics algorithms for the case of Wilson's lattice QCD. We demonstrate that the classical equations of motion that are employed in these algorithms are chaotic in nature. The leading Liapunov ... More
Knowledge Evolution in Physics Research: An Analysis of Bibliographic Coupling NetworksApr 04 2017Even as we advance the frontiers of physics knowledge, our understanding of how this knowledge evolves remains at the descriptive levels of Popper and Kuhn. Using the APS publications data sets, we ask in this letter how new knowledge is built upon old ... More
A note on commutators in algebras of unbounded operatorsJan 30 2019We show that the identity is the sum of two commutators in the algebra of all operators affiliated with a von Neumann algebra of type II$_1$, settling a question, in the negative, that had puzzled a number of us.
Auxetic metamaterials from disordered networksOct 02 2017Recent theoretical work suggests that systematic pruning of disordered networks consisting of nodes connected by springs can lead to materials that exhibit a host of unusual mechanical properties. In particular, global properties such as the Poisson's ... More
Identifying structural flow defects in disordered solids using machine learning methodsSep 24 2014We use machine learning methods on local structure to identify flow defects - or regions susceptible to rearrangement - in jammed and glassy systems. We apply this method successfully to two disparate systems: a two dimensional experimental realization ... More
The Coannihilation CodexOct 12 2015Jan 04 2016We present a general classification of simplified models that lead to dark matter (DM) coannihilation processes of the form DM + X $\rightarrow$ SM$_1$ + SM$_2$, where X is a coannihilation partner for the DM particle and SM$_1$, SM$_2$ are Standard Model ... More
MassiveNuS: Cosmological Massive Neutrino SimulationsNov 28 2017The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool ... More
Experimentally Generated Randomness Certified by the Impossibility of Superluminal SignalsFeb 22 2018From dice to modern complex circuits, there have been many attempts to build increasingly better devices to generate random numbers. Today, randomness is fundamental to security and cryptographic systems, as well as safeguarding privacy. A key challenge ... More
Single SiV$^-$ centers in low-strain nanodiamonds with bulk-like spectral properties and nano-manipulation capabilitiesFeb 10 2018Nov 23 2018We report on the isolation of single SiV$^-$ centers in nanodiamonds. We observe the fine-structure of single SiV$^-$ center with improved inhomogeneous ensemble linewidth below the excited state splitting, stable optical transitions, good polarization ... More
Low-frequency vibrations of soft colloidal glassesMar 16 2010We conduct experiments on two-dimensional packings of colloidal thermosensitive hydrogel particles whose packing fraction can be tuned above the jamming transition by varying the temperature. By measuring displacement correlations between particles, we ... More
Fractional Calculus and the Evolution of Fractal PhenomenaOct 23 1998It is argued that the evolution of complex phenomena ought to be described by fractional, differential, stochastic equations whose solutions have scaling properties and are therefore random, fractal functions. To support this argument we demonstrate that ... More
A strong maximum principle for the Paneitz operator and a non-local flow for the $Q$-curvatureJan 14 2014Aug 29 2014In this paper we consider Riemannian manifolds $(M^n,g)$ of dimension $n \geq 5$, with semi-positive $Q$-curvature and non-negative scalar curvature. Under these assumptions we prove $(i)$ the Paneitz operator satisfies a strong maximum principle; $(ii)$ ... More
Information Recovery from Pairwise MeasurementsApr 28 2014Aug 02 2016A variety of information processing tasks in practice involve recovering $n$ objects from single-shot graph-based measurements, particularly those taken over the edges of some measurement graph $\mathcal{G}$. This paper concerns the situation where each ... More
A retrodiction paradox in quantum and classical opticsJun 16 2015Apr 07 2016Quantum mechanics represents one of the greatest triumphs of human intellect and, undoubtedly, is the most successful physical theory we have to date. However, since its foundation about a century ago, it has been uninterruptedly the center of harsh debates ... More
The different neighbours around Type-1 and Type-2 active galactic nucleiNov 25 2014One of the most intriguing open issues in galaxy evolution is the structure and evolution of active galactic nuclei (AGN) that emit intense light believed to come from an accretion disk near a super-massive black hole (Rees 1984, Lynden-Bell 1969). To ... More