Results for "Alexander T. Holmes"

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A Simple Bayesian Method for Improved Analysis of Quasi-2D Scattering DataApr 03 2014Apr 24 2014A new method is presented for the analysis of small angle neutron scattering data from quasi-2D systems such as flux lattices, Skyrmion lattices, and aligned liquid crystals. A significant increase in signal to noise ratio, and a natural application of ... More
Valence fluctuation mediated superconductivity in CeCu2Si2Sep 30 2005It has been proposed that there are two types of superconductivity in CeCu2Si2, mediated by spin fluctuations at ambient pressure, and by critical valence fluctuations around a charge instability at a pressure P_v \simeq 4.5 GPa. We present in detail ... More
Spin and Valence-Fluctuation Mediated Superconductivity in Pressurized Fe and CeCu2(Si/Ge)2Oct 06 2004We review the evidence supporting valence-fluctuation mediated superconductivity in CeCu2Si2 and CeCu2Ge2, where Tc reaches 2.4 K at high pressure. In these systems the valence and magnetic critical points, at p_V and p_c respectively, are well separated. ... More
Valence Instability and Superconductivity in Heavy Fermion SystemsNov 16 2006Many cerium-based heavy fermion (HF) compounds have pressure-temperature phase diagrams in which a superconducting region extends far from a magnetic quantum critical point. In at least two compounds, CeCu2Si2 and CeCu2Ge2, an enhancement of the superconducting ... More
A 17 T horizontal field cryomagnet with rapid sample change designed for beamline useAug 30 2011Dec 20 2011We describe a new 17 T cryomagnet for neutron, x-ray or optical experiments with rapid in-situ sample change. Sample temperatures are controllable from < 2 K to 300 K in vacuum. Alternatively a room temperature bore insert can be used for experiments ... More
A comparison of box and Carleson conditions on bi-treesMar 06 2019In this note we give an example of measure satisfying the box condition on certain sub-bi-trees (see below) but not satisfying Carleson condition on those sub-bi-trees. This can be considered as a certain counterexample for two weight bi-parameter embedding ... More
The Sharp Constant in the Weak (1,1) Inequality for the Square Function: A New ProofOct 03 2017Dec 20 2018In this note we give a new proof of the sharp constant $C = e^{-1/2} + \int_0^1 e^{-x^2/2}\,dx$ in the weak (1, 1) inequality for the dyadic square function. The proof makes use of two Bellman functions $\mathbb{L}$ and $\mathbb{M}$ related to the problem, ... More
A comparison of box and Carleson conditions on bi-treesMar 06 2019Mar 18 2019In this note we give an example of measure satisfying the box condition on certain sub-bi-trees (see below) but not satisfying Carleson condition on those sub-bi-trees. This can be considered as a certain counterexample for two weight bi-parameter embedding ... More
A comparison of box and Carleson conditions on bi-treesMar 06 2019Mar 07 2019In this note we give an example of measure satisfying the box condition on certain sub-bi-trees (see below) but not satisfying Carleson condition on those sub-bi-trees. This can be considered as a certain counterexample for two weight bi-parameter embedding ... More
An ion species model for positive ion sources - part II analysis of hydrogen isotope effectsMar 24 2014A one dimensional model of the magnetic multipole volume plasma source has been developed for application to intense ion/neutral atom beam injectors. The model uses plasma transport coefficients for particle and energy flow to create a detailed description ... More
Strain enhancement of superconductivity in CePd2Si2 under pressureFeb 22 2002We report resistivity and calorimetric measurements on two single crystals of CePd2Si2 pressurized up to 7.4 GPa. A weak uniaxial stress induced in the pressure cell demonstrates the sensitivity of the physics to anisotropy. Stress applied along the c-axis ... More
An ion species model for positive ion sources - part I description of the modelMar 24 2014A one dimensional model of the magnetic multipole volume plasma source has been developed for use in intense ion/neutral atom beam injectors. The model uses plasma transport coefficients for particle and energy flow to create a detailed description of ... More
Signatures of valence fluctuations in CeCu2Si2 under high pressureJun 03 2003Simultaneous resistivity and a.c.-specific heat measurements have been performed under pressure on single crystalline CeCu2Si2 to over 6 GPa in a hydrostatic helium pressure medium. A series of anomalies were observed around the pressure coinciding with ... More
Bi-parameter embedding and measures with restriction energy conditionNov 02 2018Dec 18 2018Nicola Arcozzi, Pavel Mozolyako, Karl-Mikael Perfekt, Giulia Sarfatti \cite{AMPS} recently gave the proof of a bi-parameter Carleson embedding theorem. Their proof uses heavily the notion of capacity on bi-tree. In this note we give one more proof of ... More
Bounds on Spectral Dispersion from Fermi-detected Gamma Ray BurstsSep 23 2011Apr 18 2012Data from four Fermi-detected gamma-ray bursts (GRBs) is used to set limits on spectral dispersion of electromagnetic radiation across the universe. The analysis focuses on photons recorded above 1 GeV for Fermi detected GRB 080916C, GRB 090510A, GRB ... More
Bi-parameter embedding and measures with restriction energy conditionNov 02 2018Feb 28 2019Nicola Arcozzi, Pavel Mozolyako, Karl-Mikael Perfekt, Giulia Sarfatti \cite{AMPS} recently gave the proof of a bi-parameter Carleson embedding theorem. Their proof uses heavily the notion of capacity on bi-tree. In this note we give one more proof of ... More
Bi-parameter embedding and measures with restriction energy conditionNov 02 2018Mar 13 2019Nicola Arcozzi, Pavel Mozolyako, Karl-Mikael Perfekt, Giulia Sarfatti \cite{AMPS} recently gave the proof of a bi-parameter Carleson embedding theorem. Their proof uses heavily the notion of capacity on bi-tree. In this note we give one more proof of ... More
Bi-parameter embedding and measures with restriction energy conditionNov 02 2018Apr 15 2019Nicola Arcozzi, Pavel Mozolyako, Karl-Mikael Perfekt, Giulia Sarfatti \cite{AMPS} recently gave the proof of a bi-parameter Carleson embedding theorem. Their proof uses heavily the notion of capacity on bi-tree. In this note we give one more proof of ... More
Disentangling Improves VAEs' Robustness to Adversarial AttacksJun 01 2019This paper is concerned with the robustness of VAEs to adversarial attacks. We highlight that conventional VAEs are brittle under attack but that methods recently introduced for disentanglement such as $\beta$-TCVAE (Chen et al., 2018) improve robustness, ... More
Bi-parameter embedding and measures with restriction energy conditionNov 02 2018Mar 07 2019Nicola Arcozzi, Pavel Mozolyako, Karl-Mikael Perfekt, Giulia Sarfatti \cite{AMPS} recently gave the proof of a bi-parameter Carleson embedding theorem. Their proof uses heavily the notion of capacity on bi-tree. In this note we give one more proof of ... More
Fast Nonparametric Conditional Density EstimationJun 20 2012Conditional density estimation generalizes regression by modeling a full density f(yjx) rather than only the expected value E(yjx). This is important for many tasks, including handling multi-modality and generating prediction intervals. Though fundamental ... More
Bellman function sitting on a treeSep 10 2018Dec 18 2018In this note we give a proof-by-formula of certain important embedding inequalities on dyadic tree. This is done with the help of Bellman function. We also consider the case of a bi-tree, where a different approach is explained.
The First Orbital Flight of the ELROI Optical Satellite License PlateJul 29 2019Space Object Identification is one of the cornerstones of Space Traffic Control and a requirement for successful operation of a spacecraft. ELROI, the Extremely Low Resource Optical Identifier, is a new concept that can provide a self-powered satellite ... More
Commutators in the Two-Weight SettingJun 18 2015Jan 04 2016Let $R$ be the vector of Riesz transforms on $\mathbb{R}^n$, and let $\mu,\lambda \in A_p$ be two weights on $\mathbb{R}^n$, $1 < p < \infty$. The two-weight norm inequality for the commutator $[b, R] : L^p(\mathbb{R}^n;\mu) \to L^p(\mathbb{R}^n;\lambda)$ ... More
Molecular diffusion of stable water isotopes in polar firn as a proxy for past temperaturesFeb 05 2018Polar precipitation archived in ice caps contains information on past temperature conditions. Such information can be retrieved by measuring the water isotopic signals of $\delta{}^{18}\mathrm{O}$ and $\delta\mathrm{D}$ in ice cores. These signals have ... More
Bloom's Inequality: Commutators in a Two-Weight SettingMay 29 2015Oct 19 2015In 1985, Bloom characterized the boundedness of the commutator $[b,H]$ as a map between a pair of weighted $L^{p}$ spaces, where both weights are in $A_p$. The characterization is in terms of a novel $BMO$ condition. We give a 'modern' proof of this result, ... More
Influence of the Fermi Surface Morphology on the Magnetic Field-Driven Vortex Lattice Structure Transitions in YBa$_{2}$Cu$_{3}$O$_{7-δ}:δ=$0, 0.15Mar 13 2015We report small-angle neutron scattering measurements of the vortex lattice (VL) structure in single crystals of the lightly underdoped cuprate superconductor YBa2Cu3O6.85. At 2 K, and for fields of up to 16 T applied parallel to the crystal c-axis, we ... More
Colloidomers: freely-jointed polymers made of dropletsMay 09 2018An important goal of self-assembly is to achieve a preprogrammed structure with high fidelity. Here, we control the valence of DNA-functionalized emulsions to make linear and branched model polymers, or `colloidomers'. The distribution of cluster sizes ... More
The unusual phase diagram of CeNiGe2Jan 30 2009Feb 02 2009The heavy fermion antiferromagnet CeNiGe2 was investigated under pressure by resistivity and ac calorimetry up to 4 GPa and down to 40 mK. The two magnetic transitions found in both resistivity and specific heat at 0.1 GPa at T_N1=3.95 and T_{N2}=3.21 ... More
Epidemiologically optimal static networks from temporal network dataFeb 04 2013Network epidemiology's most important assumption is that the contact structure over which infectious diseases propagate can be represented as a static network. However, contacts are highly dynamic, changing at many time scales. In this paper, we investigate ... More
Metabolic robustness and network modularity: A model studyDec 20 2010[Background] Several studies have mentioned network modularity -- that a network can easily be decomposed into subgraphs that are densely connected within and weakly connected between each other -- as a factor affecting metabolic robustness. In this paper ... More
Model validation of simple-graph representations of metabolismDec 16 2008The large-scale properties of chemical reaction systems, such as the metabolism, can be studied with graph-based methods. To do this, one needs to reduce the information -- lists of chemical reactions -- available in databases. Even for the simplest type ... More
Network dynamics of ongoing social relationshipsAug 26 2003Many recent large-scale studies of interaction networks have focused on networks of accumulated contacts. In this paper we explore social networks of ongoing relationships with an emphasis on dynamical aspects. We find a distribution of response times ... More
Computing Néron-Tate heights of points on hyperelliptic JacobiansApr 26 2010Jun 03 2011It was shown by Faltings and Hriljac that the N\'eron-Tate height of a point on the Jacobian of a curve can be expressed as the self-intersection of a corresponding divisor on a regular model of the curve. We make this explicit and use it to give an algorithm ... More
Objective measures for sentinel surveillance in network epidemiologyMar 28 2018May 23 2018Assume one has the capability of determining whether a node in a network is infectious or not by probing them. Then problem of optimizing sentinel surveillance in networks is to identify the nodes to probe such that an emerging disease outbreak can be ... More
Probing empirical contact networks by simulation of spreading dynamicsJun 28 2017Disease, opinions, ideas, gossip, etc. all spread on social networks. How these networks are connected (the network structure) influences the dynamics of the spreading processes. By investigating these relationships one gains understanding both of the ... More
Quasi-compactness of Néron models, and an application to torsion pointsApr 05 2016Apr 07 2016We prove that N\'eron models of jacobians of generically-smooth nodal curves over bases of arbitrary dimension are quasi-compact (hence of finite type) whenever they exist. We give a simple application to the orders of torsion subgroups of jacobians over ... More
An Arakelov-Theoretic Approach to Naïve Heights on Hyperelliptic JacobiansJul 25 2012Oct 28 2014We use Arakelov theory to define a height on divisors of degree zero on a hyperelliptic curve over a global field, and show that this height has computably bounded difference from the N\'eron-Tate height of the corresponding point on the Jacobian. We ... More
Multivariate data analysis: The French wayMay 19 2008This paper presents exploratory techniques for multivariate data, many of them well known to French statisticians and ecologists, but few well understood in North American culture. We present the general framework of duality diagrams which encompasses ... More
Information content of contact-pattern representations and predictability of epidemic outbreaksMar 23 2015To understand the contact patterns of a population -- who is in contact with whom, and when the contacts happen -- is crucial for modeling outbreaks of infectious disease. Traditional theoretical epidemiology assumes that any individual can meet any with ... More
Modern temporal network theory: A colloquiumAug 06 2015Aug 31 2015The power of any kind of network approach lies in the ability to simplify a complex system so that one can better understand its function as a whole. Sometimes it is beneficial, however, to include more information than in a simple graph of only nodes ... More
Model versions and fast algorithms for network epidemiologyMar 05 2014Network epidemiology has become a core framework for investigating the role of human contact patterns in the spreading of infectious diseases. In network epidemiology represents the contact structure as a network of nodes (individuals) connected by links ... More
Extinction times of epidemic outbreaks in networksOct 15 2013In the Susceptible-Infectious-Recovered (SIR) model of disease spreading, the time to extinction of the epidemics happens at an intermediate value of the per-contact transmission probability. Too contagious infections burn out fast in the population. ... More
Congestion and centrality in traffic flow on complex networksJan 02 2003The central points of communication network flow has often been identified using graph theoretical centrality measures. In real networks, the state of traffic density arises from an interplay between the dynamics of the flow and the underlying network ... More
Excited against the tide: A random walk with competing driftsJan 28 2009We study a random walk that has a drift $\frac{\beta}{d}$ to the right when located at a previously unvisited vertex and a drift $\frac{\mu}{d}$ to the left otherwise. We prove that in high dimensions, for every $\mu$, the drift to the right is a strictly ... More
Edge overload breakdown in evolving networksJul 18 2002We investigate growing networks based on Barabasi and Albert's algorithm for generating scale-free networks, but with edges sensitive to overload breakdown. the load is defined through edge betweenness centrality. We focus on the situation where the average ... More
On the diameter of Hochster-Huneke graphs of Stanley-Reisner rings with Serre $(S_2)$ property and Hirsch type bounds on abstractions of polytopesNov 22 2016Let $R$ be a Noetherian commutative ring of positive dimension. The Hochster-Huneke graph of $R$ (sometimes called the dual graph of Spec $R$ and denoted by $\mathcal{G} (R)$) is defined as follows: the vertices are the minimal prime ideals of $R$, and ... More
The Coherent Crooks EqualityDec 26 2018This chapter reviews an information theoretic approach to deriving quantum fluctuation theorems. When a thermal system is driven from equilibrium, random quantities of work are required or produced: the Crooks equality is a classical fluctuation theorem ... More
Modular non-repeating codes for DNA storageJun 06 2016Jun 08 2016We describe a strategy for constructing codes for DNA-based information storage by serial composition of weighted finite-state transducers. The resulting state machines can integrate correction of substitution errors; synchronization by interleaving watermark ... More
Temporal network structures controlling disease spreadingMay 03 2016We investigate disease spreading on eight empirical data sets of human contacts (mostly proximity networks recording who is close to whom, at what time). We compare three levels of representations of these data sets: temporal networks, static networks ... More
Dark matter signals in deflected mirage mediationSep 18 2009We investigate the parameter space of a specific class of model within the deflected mirage mediation (DMM) scenario. We look at neutralino properties and compute the thermal relic density as well as interaction rates with xenon direct detection experiments. ... More
On strict monotonicity of the speed for excited random walks in one dimensionFeb 24 2015We give a "direct" coupling proof of strict monotonicity of the speed for 1-dimensional multi-excited random walks with positive speed. This reproves (and extends) a recent result of Peterson without using branching processes.
Efficiency of navigation in indexed networksJul 07 2007We investigate efficient methods for packets to navigate in complex networks. The packets are assumed to have memory, but no previous knowledge of the graph. We assume the graph to be indexed, i.e. every vertex is associated with a number (accessible ... More
Network reachability of real-world contact sequencesOct 13 2004Nov 12 2004We use real-world contact sequences, time-ordered lists of contacts from one person to another, to study how fast information or disease can spread across network of contacts. Specifically we measure the reachability time -- the average shortest time ... More
Signatures of currency verticesDec 18 2008Many real-world networks have broad degree distributions. For some systems, this means that the functional significance of the vertices is also broadly distributed, in other cases the vertices are equally significant, but in different ways. One example ... More
Extending the double ramification cycle by resolving the Abel-Jacobi mapJul 07 2017Oct 18 2017Over the moduli space of smooth curves, the double ramification cycle can be defined by pulling back the unit section of the universal jacobian along the Abel-Jacobi map. This breaks down over the boundary since the Abel-Jacobi map fails to extend. We ... More
The norm of the saturation of a binomial ideal, and applications to Markov basesJul 24 2019Given a pure binomial ideal I in variables x_i, we define a new measure of the complexity of the saturation of I with respect to the product of the variables x_i, which we call the norm. We give a bound on the norm in terms of easily-computed invariants ... More
A Néron model of the universal jacobianDec 06 2014Sep 07 2015The jacobian of the universal curve over $\mathcal{M}_{g,n}$ is an abelian scheme over $\mathcal{M}_{g,n}$. Our main result is the construction of an algebraic space $\beta\colon \tilde{\mathcal{M}}_{g,n} \rightarrow \bar{\mathcal{M}}_{g,n}$ over which ... More
Superconductivity of epsilon-Fe: complete resistive transitionMay 27 2002Last year, iron was reported to become superconducting at temperatures below 2K and pressures between 15 and 30 GPa. The evidence presented was a weak resistivity drop, suppressed by a magnetic field above 0.2 T, and a small Meissner signal. However, ... More
Resource Optimized Quantum Architectures for Surface Code Implementations of Magic-State DistillationApr 25 2019Quantum computers capable of solving classically intractable problems are under construction, and intermediate-scale devices are approaching completion. Current efforts to design large-scale devices require allocating immense resources to error correction, ... More
Shadows of the SIS immortality transition in small networksMar 06 2015May 13 2015Much of the research on the behavior of the SIS model on networks has concerned the infinite size limit; in particular the phase transition between a state where outbreaks can reach a finite fraction of the population, and a state where only a finite ... More
Detecting degree symmetries in networksMay 03 2006The surrounding of a vertex in a network can be more or less symmetric. We derive measures of a specific kind of symmetry of a vertex which we call degree symmetry -- the property that many paths going out from a vertex have overlapping degree sequences. ... More
Core-periphery organization of complex networksJun 06 2005Networks may, or may not, be wired to have a core that is both itself densely connected and central in terms of graph distance. In this study we propose a coefficient to measure if the network has such a clear-cut core-periphery dichotomy. We measure ... More
Efficient local strategies for vaccination and network attackMar 16 2004We study how a fraction of a population should be vaccinated to most efficiently top epidemics. We argue that only local information (about the neighborhood of specific vertices) is usable in practice, and hence we consider only local vaccination strategies. ... More
Local symmetries in complex networksAug 30 2006Sep 06 2006Symmetry -- invariance to certain operators -- is a fundamental concept in many branches of physics. We propose ways to measure symmetric properties of vertices, and their surroundings, in networks. To be stable to the randomness inherent in many complex ... More
Scale-free networks with a large- to hypersmall-world transitionJul 05 2006Nov 07 2006Recently there have been a tremendous interest in models of networks with a power-law distribution of degree -- so called "scale-free networks." It has been observed that such networks, normally, have extremely short path-lengths, scaling logarithmically ... More
Remembering the Tevatron: The Machine(s)Sep 13 2011For 25 years the Tevatron proton-antiproton collider was the highest energy collider in the world. This presentation will trace the origins of the Tevatron, the challenges that were overcome in creating high luminosity collisions of protons and antiprotons, ... More
An Inversion Formula for the Gaussian Radon Transform for Banach SpacesAug 06 2013We provide a disintegration theorem for the Gaussian Radon transform Gf on Banach spaces and use the Segal-Bargmann transform on abstract Wiener spaces to find a procedure to obtain f from its Gaussian Radon transform Gf.
A Generalized Serre's ConditionOct 07 2017Oct 10 2018Throughout, let $R$ be a commutative Noetherian ring. A ring $R$ satisfies Serre's condition $(S_{\ell})$ if for all $P \in \Spec R,$ $\depth R_P \geq \min \{ \ell , \dim R_P \}$. Serre's condition has been a topic of expanding interest. In this paper, ... More
Three faces of node importance in network epidemiology: Exact results for small graphsAug 22 2017Oct 14 2017We investigate three aspects of the importance of nodes with respect to Susceptible-Infectious-Removed (SIR) disease dynamics: influence maximization (the expected outbreak size given a set of seed nodes), the effect of vaccination (how much deleting ... More
Computing Néron-Tate heights of points on hyperelliptic JacobiansApr 26 2010May 02 2017It was shown by Faltings and Hriljac that the N\'eron-Tate height of a point on the Jacobian of a curve can be expressed as the self-intersection of a corresponding divisor on a regular model of the curve. We make this explicit and use it to give an algorithm ... More
Torsion points and height jumping in higher-dimensional families of abelian varietiesApr 15 2016In 1983 Silverman and Tate showed that the set of points in a 1-dimensional family of abelian varieties where a section of infinite order has `small height' is finite. We conjecture a generalisation to higher-dimensional families, where we replace `finite' ... More
Néron models of jacobians over base schemes of dimension greater than 1Feb 04 2014Feb 26 2016We investigate to what extent the theory of N\'eron models of jacobians and of abel-jacobi maps extends to relative curves over base schemes of dimension greater than 1. We give a necessary and sufficient criterion for the existence of a N\'eron model. ... More
On the diameter of dual graphs of Stanley-Reisner rings with Serre $(S_2)$ property and Hirsch type bounds on abstractions of polytopesNov 22 2016Dec 07 2017Let $R$ be a Noetherian commutative ring of positive dimension. The Hochster-Huneke graph of $R$ (sometimes called the dual graph of Spec $R$ and denoted by $\mathcal{G} (R)$) is defined as follows: the vertices are the minimal prime ideals of $R$, and ... More
Cheap and near exact CASSCF with large active spacesAug 24 2017Aug 29 2017We use the recently-developed Heat-bath Configuration Interaction (HCI) algorithm as an efficient active-space solver to perform multi-configuration self-consistent field calculations (HCISCF) with large active spaces. We give a detailed derivation of ... More
Anisotropy, disorder, and superconductivity in CeCu2Si2 under high pressureMay 25 2005Resistivity measurements were carried out up to 8 GPa on single crystal and polycrystalline samples of CeCu2Si2 from differing sources in the homogeneity range. The anisotropic response to current direction and small uniaxial stresses was explored, taking ... More
Unconventional superconductivity and normal state properties of epsilon-iron at high pressureOct 22 2003Following the discovery of superconductivity in epsilon-iron, subsequent experiments hinted at non-Fermi liquid behaviour of the normal phase and sensitive dependence of the superconducting state on disorder, both signatures of unconventional pairing. ... More
The intersection of two vertex coloring problemsApr 17 2019A hole is an induced cycle with at least four vertices. A hole is even if its number of vertices is even. Given a set L of graphs, a graph G is L-free if G does not contain any graph in L as an induced subgraph. Currently, the following two problems are ... More
Microscopic theory of the Andreev gapJan 20 2009Jul 16 2009We present a microscopic theory of the Andreev gap, i.e. the phenomenon that the density of states (DoS) of normal chaotic cavities attached to superconductors displays a hard gap centered around the Fermi energy. Our approach is based on a solution of ... More
Magic-State Functional Units: Mapping and Scheduling Multi-Level Distillation Circuits for Fault-Tolerant Quantum ArchitecturesSep 05 2018Quantum computers have recently made great strides and are on a long-term path towards useful fault-tolerant computation. A dominant overhead in fault-tolerant quantum computation is the production of high-fidelity encoded qubits, called magic states, ... More
Optimized Surface Code Communication in Superconducting Quantum ComputersAug 30 2017Quantum computing (QC) is at the cusp of a revolution. Machines with 100 quantum bits (qubits) are anticipated to be operational by 2020 [googlemachine,gambetta2015building], and several-hundred-qubit machines are around the corner. Machines of this scale ... More
Robust surface plasmon polaritons on gyrotropic interfacesFeb 24 2019Unidirectional surface plasmon polaritons (SPPs) at the interface between a gyrotropic medium and a simple medium are studied in a newly-recognized frequency regime wherein the SPPs form narrow, beam-like patterns due to hyperbolic dispersion. The SPP ... More
Dipolar Spin Ice Under Uniaxial PressureJul 08 2019The magnetically frustrated spin ice family of materials is host to numerous exotic phenomena such as magnetic monopole excitations and macroscopic residual entropy extending to low temperature. A finite-temperature ordering transition in the absence ... More
The diplomat's dilemma: Maximal power for minimal effort in social networksMay 26 2008Closeness is a global measure of centrality in networks, and a proxy for how influential actors are in social networks. In most network models, and many empirical networks, closeness is strongly correlated with degree. However, in social networks there ... More
A network-based threshold model for the spreading of fads in society and marketsMay 06 2005We investigate the behavior of a threshold model for the spreading of fads and similar phenomena in society. The model is giving the fad dynamics and is intended to be confined to an underlying network structure. We investigate the whole parameter space ... More
A Zero-Temperature Study of Vortex Mobility in Two-Dimensional Vortex Glass ModelsNov 29 2001Three different vortex glass models are studied by examining the energy barrier against vortex motion across the system. In the two-dimensional gauge glass this energy barrier is found to increase logarithmically with system size which is interpreted ... More
Time evolution of predictability of epidemics on networksDec 16 2014May 05 2015Epidemic outbreaks of new pathogens, or known pathogens in new populations, cause a great deal of fear because they are hard to predict. For theoretical models of disease spreading, on the other hand, quantities characterizing the outbreak converge to ... More
Computational Tools for Evaluating Phylogenetic and Hierarchical Clustering TreesJun 05 2010Inferential summaries of tree estimates are useful in the setting of evolutionary biology, where phylogenetic trees have been built from DNA data since the 1960's. In bioinformatics, psychometrics and data mining, hierarchical clustering techniques output ... More
An Exposition of Götze's Estimation of the Rate of Convergence in the Multivariate Central Limit TheoremMar 22 2010We provide an explanation of the main ideas underlying G\"otze's main result in using Stein's method. We also provide detailed derivations of various intermediate estimates. Curiously, we are led to a different dimensional dependence of the constant than ... More
Provenance and Pseudo-Provenance for Seeded Learning-Based Automated Test GenerationNov 05 2017Nov 15 2017Many methods for automated software test generation, including some that explicitly use machine learning (and some that use ML more broadly conceived) derive new tests from existing tests (often referred to as seeds). Often, the seed tests from which ... More
The Brauer-Manin obstruction on Kummer varieties and ranks of twists of abelian varietiesApr 14 2014Aug 18 2015Let r > 0 be an integer. We present a sufficient condition for an abelian variety A over a number field k to have infinitely many quadratic twists of rank at least r, in terms of density properties of rational points on the Kummer variety Km(A^r) of the ... More
Substance graphs are optimal simple-graph representations of metabolismJun 17 2008Dec 03 2008One approach to studying the system-wide organization of biochemistry is to use statistical graph theory. Even in such a heavily simplified method, which disregards most of the dynamic aspects of biochemistry, one is faced with fundamental questions, ... More
Currency and commodity metabolites: Their identification and relation to the modularity of metabolic networksMar 31 2006The large-scale shape and function of metabolic networks are intriguing topics of systems biology. Such networks are on one hand commonly regarded as modular (i.e. built by a number of relatively independent subsystems), but on the other hand they are ... More
Rank Selection and Depth Conditions for Balanced Simplicial ComplexesFeb 09 2018Feb 22 2019We prove some new rank selection theorems for balanced simplicial complexes. Specifically, we prove that rank selected subcomplexes of balanced simplicial complexes satisfying Serre's condition $(S_{\ell})$ retain $(S_{\ell})$. We also provide a formula ... More
Heterogeneous inputs to central pattern generators can shape insect gaitsJul 13 2018In our previous work, we studied an interconnected bursting neuron model for insect locomotion, and its corresponding phase oscillator model, which at high speed can generate stable tripod gaits with three legs off the ground simultaneously in swing, ... More
Stablizing oscillating universes against quantum decayJul 21 2014We investigate the effect of vacuum corrections, due to the trace anomaly and Casimir effect, on the stability of an oscillating universe with respect to decay by tunneling to the singularity. We find that these corrections do not generally stabilize ... More
Instability of an emergent universeMar 04 2014Mar 20 2014Oscillating solutions to the effective equations of Loop Quantum Cosmology have been suggested for the role of an `eternal seed', providing a possible starting point for the emergent universe scenario. We investigate the stability of a particular model, ... More
Tunneling decay rate in quantum cosmologyMar 02 2015In canonical quantum cosmology, the wave function of the universe lacks explicit time dependence. However, time evolution may be present implicitly through the semiclassical superspace variables, which themselves depend on time in classical dynamics. ... More
Collapse of simple harmonic universeOct 18 2011Dec 16 2011In a recent paper Graham et al constructed oscillating and static universe models which are stable with respect to all classical perturbations. Here we show that such universes are quantum-mechanically unstable and can collapse by quantum tunneling to ... More
Dynamics of networking agents competing for high centrality and low degreeDec 06 2005Dec 08 2005We model a system of networking agents that seek to optimize their centrality in the network while keeping their cost, the number of connections they are participating in, low. Unlike other game-theory based models for network evolution, the success of ... More