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Results for "Sebastian J. R. Lee"

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Analytical Gradients for Projection-Based Wavefunction-in-DFT EmbeddingMar 14 2019Projection-based embedding provides a simple, robust, and accurate approach for describing a small part of a chemical system at the level of a correlated wavefunction method while the remainder of the system is described at the level of density functional ... More
Conformal and projection diagrams in LaTeXMay 09 2013In general relativity, the causal structure of space-time may sometimes be depicted by conformal Carter-Penrose diagrams or a recent extension of these - the projection diagrams. The introduction of conformal diagrams in the sixties was one of the progenitors ... More
Toward a Science of Autonomy for Physical Systems: TransportationSep 19 2016Transportation systems are currently being transformed by advances in information and communication technologies. The development of autonomous transportation holds the promise of providing revolutionary improvements in speed, efficiency, safety and reliability ... More
Embedding the diamond graph in $L_p$ and dimension reduction in $L_1$Jul 30 2004We show that any embedding of the level-k diamond graph of Newman and Rabinovich into $L_p$, $1 < p \le 2$, requires distortion at least $\sqrt{k(p-1) + 1}$. An immediate consequence is that there exist arbitrarily large n-point sets $X \subseteq L_1$ ... More
Why, when, and how fast innovations are adoptedAug 10 2012When the full stock of a new product is quickly sold in a few days or weeks, one has the impression that new technologies develop and conquer the market in a very easy way. This may be true for some new technologies, for example the cell phone, but not ... More
A Geometric Approach for Computing Tolerance Bounds for Elastic Functional DataMay 29 2018In this paper, we develop a method for constructing tolerance bounds for functional data with random warping variability. In particular, we present a general technique that is able to appropriately model both amplitude and phase variabilities. In particular, ... More
Space-time diagrammaticsNov 07 2012Jan 20 2013We introduce a new class of two-dimensional diagrams, the \emph{projection diagrams}, as a tool to visualize the global structure of space-times. We construct the diagrams for several metrics of interest, including the Kerr-Newman - (anti) de Sitter family, ... More
A Geometric Approach for Computing Tolerance Bounds for Elastic Functional DataMay 29 2018Apr 25 2019We develop a method for constructing tolerance bounds for functional data with random warping variability. In particular, we define a generative, probabilistic model for the amplitude and phase components of such observations, which parsimoniously characterizes ... More
Flavour Physics in the Soft Wall ModelAug 06 2011Nov 18 2011We extend the description of flavour that exists in the Randall-Sundrum (RS) model to the soft wall (SW) model in which the IR brane is removed and the Higgs is free to propagate in the bulk. It is demonstrated that, like the RS model, one can generate ... More
Real Space Imaging of One-Dimensional Standing Waves: Direct Evidence for a Luttinger LiquidNov 30 2004Electronic standing waves with two different wavelengths were directly mapped near one end of a single-wall carbon nanotube as a function of the tip position and the sample bias voltage with highresolution position-resolved scanning tunneling spectroscopy. ... More
Functional Schroedinger and BRST Quantization of (1+1)--Dimensional GravityJul 08 1996We discuss the quantization of pure string--inspired dilaton--gravity in $(1+1)$--dimensions, and of the same theory coupled to scalar matter. We perform the quantization using the functional Schroedinger and BRST formalisms. We find, both for pure gravity ... More
New analytic results for electroweak baryon number violationOct 25 2001Real-time anomalous fermion number violation has been investigated for massless chiral fermions in spherically symmetric SU(2) Yang-Mills gauge field backgrounds which can be weakly dissipative or even nondissipative. Restricting consideration to spherically ... More
Spectral flow of chiral fermions in nondissipative Yang-Mills gauge field backgroundsApr 10 2001Sep 06 2001Real-time anomalous fermion number violation is investigated for massless chiral fermions in spherically symmetric SU(2) Yang-Mills gauge field backgrounds which can be weakly dissipative or even nondissipative. Restricting consideration to spherically ... More
Structure of exciton condensates in imbalanced electron-hole bilayersNov 29 2016We investigate the possibility of excitonic superfluidity in electron-hole bilayers. We calculate the phase diagram of the system for the whole range of electron-hole density imbalance and for different degrees of electrostatic screening, using mean-field ... More
CP Violating Asymmetries Induced by SupersymmetrySep 22 2009In the Minimal Supersymmetric Standard Model (MSSM) with complex parameters, one-loop corrections to the decay of a stop into a bottom-quark and a chargino can lead to a CP violating decay rate asymmetry. We perform a detailed numerical analysis of this ... More
Quenched Cold Accretion of a Large Scale Metal-Poor Filament due to Virial Shocking in the Halo of a Massive z=0.7 GalaxyMay 03 2012Using HST/COS/STIS and HIRES/Keck high-resolution spectra, we have studied a remarkable HI absorbing complex at z=0.672 toward the quasar Q1317+277. The HI absorption has a velocity spread of 1600 km/s, comprises 21 Voigt profile components, and resides ... More
On light propagation in Swiss-Cheese cosmologiesDec 23 2010Mar 26 2011We study the effect of inhomogeneities on light propagation. The Sachs equations are solved numerically in the Swiss-Cheese models with inhomogeneities modelled by the Lemaitre-Tolman solutions. Our results imply that, within the models we study, inhomogeneities ... More
A dynamical trichotomy for structured populations experiencing positive density-dependence in stochastic environmentsJan 29 2017Positive density-dependence occurs when individuals experience increased survivorship, growth, or reproduction with increased population densities. Mechanisms leading to these positive relationships include mate limitation, saturating predation risk, ... More
ZNN - A Fast and Scalable Algorithm for Training 3D Convolutional Networks on Multi-Core and Many-Core Shared Memory MachinesOct 22 2015Convolutional networks (ConvNets) have become a popular approach to computer vision. It is important to accelerate ConvNet training, which is computationally costly. We propose a novel parallel algorithm based on decomposition into a set of tasks, most ... More
ZNNi - Maximizing the Inference Throughput of 3D Convolutional Networks on Multi-Core CPUs and GPUsJun 17 2016Sliding window convolutional networks (ConvNets) have become a popular approach to computer vision problems such as image segmentation, and object detection and localization. Here we consider the problem of inference, the application of a previously trained ... More
Causality constraints for charged particlesOct 31 2012Mar 12 2013In quantum systems with short-range interactions, causality imposes nontrivial constraints on low-energy scattering parameters. We investigate these causality constraints for systems where a long-range Coulomb potential is present in addition to a short-range ... More
Orbifold Reduction and 2d (0,2) Gauge TheoriesSep 22 2016We introduce Orbifold Reduction, a new method for generating $2d$ $(0,2)$ gauge theories associated to D1-branes probing singular toric Calabi-Yau 4-folds starting from $4d$ $\mathcal{N}=1$ gauge theories on D3-branes probing toric Calabi-Yau 3-folds. ... More
Volume Dependence of Bound States with Angular MomentumMar 23 2011Sep 09 2011We derive general results for the mass shift of bound states with angular momentum l >= 1 in a finite periodic volume. Our results have direct applications to lattice simulations of hadronic molecules as well as atomic nuclei. While the binding of S-wave ... More
Posterior Consistency for Bayesian Inverse Problems through Stability and Regression ResultsFeb 17 2013Jul 16 2013In the Bayesian approach, the a priori knowledge about the input of a mathematical model is described via a probability measure. The joint distribution of the unknown input and the data is then conditioned, using Bayes' formula, giving rise to the posterior ... More
Magnetic domain-wall motion by propagating spin wavesFeb 02 2009We found by micromagnetic simulations that the motion of a transverse wall (TW) type domain wall in magnetic thin-film nanostripes can be manipulated via interaction with spin waves (SWs) propagating through the TW. The velocity of the TW motion can be ... More
Stable causality of Black SaturnsFeb 19 2011We prove that the Black Saturns are stably causal on the closure of the domain of outer communications.
Persistence for stochastic difference equations: A mini-reviewSep 27 2011Understanding under what conditions populations, whether they be plants, animals, or viral particles, persist is an issue of theoretical and practical importance in population biology. Both biotic interactions and environmental fluctuations are key factors ... More
When do factors promoting balanced selection also promote population persistence? A demographic perspective on Gillespie's SAS-CFF modelFeb 09 2019Classical stochasticity demography predicts that environmental stochasticity reduces population growth rates and, thereby, can increase extinction risk. In contrast, the SAS-CFF model demonstrates that environmental stochasticity can promote genetic diversity. ... More
Dimension-Independent MCMC Sampling for Inverse Problems with Non-Gaussian PriorsFeb 09 2013Oct 22 2014The computational complexity of MCMC methods for the exploration of complex probability measures is a challenging and important problem. A challenge of particular importance arises in Bayesian inverse problems where the target distribution may be supported ... More
Brane Brick Models, Toric Calabi-Yau 4-Folds and 2d (0,2) QuiversOct 06 2015Feb 03 2016We introduce brane brick models, a novel type of Type IIA brane configurations consisting of D4-branes ending on an NS5-brane. Brane brick models are T-dual to D1-branes over singular toric Calabi-Yau 4-folds. They fully encode the infinite class of 2d ... More
Brane Brick Models and 2d (0,2) TrialityFeb 04 2016Feb 21 2016We provide a brane realization of 2d (0,2) Gadde-Gukov-Putrov triality in terms of brane brick models. These are Type IIA brane configurations that are T-dual to D1-branes over singular toric Calabi-Yau 4-folds. Triality translates into a local transformation ... More
Non-relativistic bound states in a finite volumeSep 21 2011We derive general results for the mass shift of bound states with angular momentum l >= 1 in a periodic cubic box in two and three spatial dimensions. Our results have applications to lattice simulations of hadronic molecules, halo nuclei, and Feshbach ... More
Chaotic self-similar wave maps coupled to gravityOct 08 2003Oct 08 2003We continue our studies of spherically symmetric self-similar solutions in the SU(2) sigma model coupled to gravity. For some values of the coupling constant we present numerical evidence for the chaotic solution and the fractal threshold behavior. We ... More
On gravitational interactions between two bodiesSep 03 2014Sep 13 2015Many physicists, following Einstein, believe that the ultimate aim of theoretical physics is to find a unified theory of all interactions which would not depend on any free dimensionless constant, i.e., a dimensionless constant that is only empirically ... More
Coexistence in the face of uncertaintyDec 12 2015Sep 23 2016Over the past century, nonlinear difference and differential equations have been used to understand conditions for species coexistence. However, these models fail to account for random fluctuations due to demographic and environmental stochasticity which ... More
Measurement and analysis of the Hall effect of A-Fe$_2$As$_2$ single crystals with A = Ba, Ca or SrNov 06 2009We report measurements of the Hall coefficient $R_H$ for single crystals of AFe$_2$As$_2$ with $A = Ba, Ca$ or $Sr$ which are the anti-ferromagnetic parent compounds of some high temperature pnictide superconductors. We show that $R_H$ of Sr-122 is consistent ... More
Exciton-exciton interaction and biexciton formation in bilayer systemsNov 20 2008We report quantum Monte Carlo calculations of biexciton binding energies in ideal two-dimensional bilayer systems with isotropic electron and hole masses. We have also calculated exciton-exciton interaction potentials, and pair distribution functions ... More
Elastic constants and volume changes associated with two high-pressure rhombohedral phase transformations in vanadiumNov 27 2007Jan 18 2008We present results from ab initio calculations of the mechanical properties of the rhombohedral phase (beta) of vanadium metal reported in recent experiments, and other predicted high-pressure phases (gamma and bcc), focusing on properties relevant to ... More
Fermion Condensation Quantum Phase Transition versus Conventional Quantum Phase TransitionsMay 03 2004Jun 18 2004The main features of fermion condensation quantum phase transition (FCQPT), which are distinctive in several aspects from that of conventional quantum phase transition (CQPT), are considered. We show that in contrast to CQPT, whose physics in quantum ... More
Pulsars and Gravitational WavesSep 05 2011Sep 13 2011The relationship between pulsar-like compact stars and gravitational waves is briefly reviewed. Due to regular spins, pulsars could be useful tools for us to detect ~nano-Hz low-frequency gravitational waves by pulsar-timing array technique; besides, ... More
Finite Temperature Time-Dependent Effective Theory For The Goldstone Field In A BCS-Type SuperfluidMay 02 1999Oct 11 1999We extend to finite temperature the time-dependent effective theory for the Goldstone field (the phase of the pair field) $ \theta $ which is appropriate for a superfluid containing one species of fermions with s-wave interactions, described by the BCS ... More
Obtaining Communities with a Fitness Growth ProcessJun 06 2012The study of community structure has been a hot topic of research over the last years. But, while successfully applied in several areas, the concept lacks of a general and precise notion. Facts like the hierarchical structure and heterogeneity of complex ... More
The lightest visible-sector supersymmetric particle is likely to be unstableApr 18 2016We argue, based on typical properties of known solutions of string/$M$-theory, that the lightest supersymmetric particle of the visible sector will not be stable. In other words, dark matter is {\em not} a particle with Standard Model quantum numbers, ... More
Apsidal motions of 90 eccentric binary systems in the Small Magellanic CloudApr 08 2016We examined light curves of 1138 stars brighter than 18.0 mag in the $I$ band and less than a mean magnitude error of 0.1 mag in the $V$ band from the OGLE-III eclipsing binary catalogue, and found 90 new binary systems exhibiting apsidal motion. In this ... More
Characterizing the Cool KOIs III. KOI-961: A Small Star with Large Proper Motion and Three Small PlanetsJan 10 2012We present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission. We proceed by comparing KOI 961 to Barnard's Star, a nearby, well-characterized ... More
Coulomb Gas Representation of Low Energy QCDApr 17 1999Jun 22 2000A novel Coulomb gas (CG) description of low energy $QCD_4$, based on the dual transformation of the QCD effective chiral Lagrangian, is constructed. The CG is found to contain several species of charges, one of which is fractionally charged and can be ... More
Two Higgs Doublets and a Complex Singlet: Disentangling the Decay Topologies and Associated PhenomenologyAug 08 2018Dec 17 2018We present a systematic study of an extension of the Standard Model (SM) with two Higgs doublets and one complex singlet (2HDM+S). In order to gain analytical understanding of the parameter space, we re-parameterize the 27 parameters in the Lagrangian ... More
Neutrino and gravitational wave signal of a delayed-detonation model of Type Ia supernovaeNov 08 2015Jan 25 2016The progenitor system(s) and the explosion mechanism(s) of Type Ia supernovae (SNe Ia) are still under debate. Non-electromagnetic observables, in particular gravitational waves and neutrino emission, of thermonuclear supernovae are a complementary window ... More
Atomic-resolution imaging of carbonyl sulfide by laser-induced electron diffractionMay 09 2019Measurements on the strong-field ionization of carbonyl sulfide molecules by short, intense, 2~\um wavelength laser pulses are presented from experiments where angle-resolved photoelectron distributions were recorded with a high-energy velocity map imaging ... More
Near-infrared imaging and spectroscopy of the nuclear region of the disturbed Virgo cluster spiral NGC 4438Aug 24 2009Oct 21 2009We present near-infrared VLT ISAAC imaging and spectroscopy of the peculiar Virgo galaxy NGC 4438, whose nucleus has been classified as a LINER. The data are supplemented by mid-infrared imaging, and compared to previous WFPC2 HST broadband images. Images ... More
Constraint-Based Qualitative SimulationApr 07 2005We consider qualitative simulation involving a finite set of qualitative relations in presence of complete knowledge about their interrelationship. We show how it can be naturally captured by means of constraints expressed in temporal logic and constraint ... More
The massless string spectrum on AdS_3 x S^3 from the supergroupJul 13 2011Oct 11 2011String theory on AdS_3 x S^3 is studied in the hybrid formulation. We give a detailed description of the PSL(2|2) supergroup WZW model that underlies the background with pure NS-NS flux, and determine the BRST-cohomology corresponding to the massless ... More
Infinite Qualitative Simulations by Means of Constraint ProgrammingAug 03 2006We introduce a constraint-based framework for studying infinite qualitative simulations concerned with contingencies such as time, space, shape, size, abstracted into a finite set of qualitative relations. To define the simulations, we combine constraints ... More
Benchmark Suggestions for Resonant Double Higgs Production at the LHC for Extended Higgs SectorsApr 23 2019In this note we present benchmark scenarios for resonant double Higgs production at the $13\,$TeV LHC in the 2HDM+S model and the $Z_3$ Next-to-Minimal Supersymmetric Standard Model (NMSSM), which may be accessible with 300 fb$^{-1}$ of data. The NMSSM ... More
Structure and superconductivity of LiFeAsJul 14 2008Jul 15 2008The lithium ions in Lithium iron arsenide phases with compositions close to LiFeAs have been located using powder neutron diffraction. These phases exhibit superconductivity at temperatures at least as high as 16 K demonstrating that superconductivity ... More
Bringing "The Moth" to Light: A Planet-Sculpting Scenario for the HD 61005 Debris DiskMay 19 2016Sep 16 2016The HD 61005 debris disk ("The Moth") stands out from the growing collection of spatially resolved circumstellar disks by virtue of its unusual swept-back morphology, brightness asymmetries, and dust ring offset. Despite several suggestions for the physical ... More
Schedulers and Redundancy for a Class of Constraint Propagation RulesMar 23 2004Nov 02 2004We study here schedulers for a class of rules that naturally arise in the context of rule-based constraint programming. We systematically derive a scheduler for them from a generic iteration algorithm of [Apt 2000]. We apply this study to so-called membership ... More
Schedulers for Rule-based Constraint ProgrammingNov 15 2002We study here schedulers for a class of rules that naturally arise in the context of rule-based constraint programming. We systematically derive a scheduler for them from a generic iteration algorithm of Apt [2000]. We apply this study to so-called membership ... More
Monopoles and Coulomb Gas Representation of the QCD Effective LagrangianMay 28 1999A novel Coulomb gas (CG) description of low energy QCD_4(N_c) is constructed. The construction is based on the dual transformation of the QCD effective Lagrangian. By considering a large gauge transformation, the charges of this statistical system are ... More
Factoring semi-primes with (quantum) SAT-solversFeb 04 2019The assumed computationally difficulty of factoring large integers forms the basis of security for RSA public-key cryptography, which specifically relies on products of two large primes or semi-primes. The best-known factoring algorithms for classical ... More
Virtual Representations for Iterative IoT DeploymentMar 02 2019A central vision of the Internet of Things is the representation of the physical world in a consistent virtual environment. Especially in the context of smart factories the connection of the different, heterogeneous production modules through a digital ... More
On the Interstellar Medium and Star Formation Demographics of Galaxies in the Local UniverseAug 07 2009We present a demographic analysis of integrated star formation and gas properties for a sample of galaxies representative of the overall population at z~0. This research was undertaken in order to characterise the nature of star formation and interstellar ... More
Spintronic properties of one-dimensional electron gas in graphene armchair ribbonsApr 02 2012Sep 17 2012We have investigated, using effective mass approach (EMA), magnetic properties of a one-dimensional electron gas in graphene armchair ribbons when the electrons of occupy only the lowest conduction subband. We find that magnetic properties of the one-dimensional ... More
Hole concentration dependence of the magnetic moment in superconducting and insulating La2-xSrxCuO4Nov 22 2000Mar 05 2001Recent neutron scattering measurements on the La2-xSrxCuO4 system have revealed a drastic change of the incommensurate static spin correlations from diagonal in the insulating region to parallel in the superconducting region. We report the doping dependence ... More
Dynamics of the molecular orientation field coupled to ions in two-dimensional ferroelectric liquid crystalsAug 15 2007Molecular orientation fluctuations in ferroelectric smectic liquid crystals produce space charges, due to the divergence of the spontaneous polarization. These space charges interact with mobile ions, so that one must consider the coupled dynamics of ... More
Disorder and superfluid density in overdoped cuprate superconductorsApr 16 2017Jun 15 2018We calculate superfluid density for a dirty d-wave superconductor. The effects of impurity scattering are treated within the self-consistent t-matrix approximation, in weak-coupling BCS theory. Working from a realistic tight-binding parameterization of ... More
Synthesis and characterisation of nanomaterials of the topological crystalline insulator SnTeApr 03 2014A new class of materials, Topological Crystalline Insulators (TCIs) have been shown to possess exotic surface state properties that are protected by mirror symmetry. These surface features can be enhanced if the surface-area-to-volume ratio of the material ... More
Extraction of the proton radius from electron-proton scattering dataMay 06 2015Jul 28 2015We perform a new analysis of electron-proton scattering data to determine the proton electric and magnetic radii, enforcing model-independent constraints from form factor analyticity. A wide-ranging study of possible systematic effects is performed. An ... More
Recognizing recurrent neural networks (rRNN): Bayesian inference for recurrent neural networksJan 20 2012Recurrent neural networks (RNNs) are widely used in computational neuroscience and machine learning applications. In an RNN, each neuron computes its output as a nonlinear function of its integrated input. While the importance of RNNs, especially as models ... More
The Brain Uses Reliability of Stimulus Information when Making Perceptual DecisionsSep 07 2015In simple perceptual decisions the brain has to identify a stimulus based on noisy sensory samples from the stimulus. Basic statistical considerations state that the reliability of the stimulus information, i.e., the amount of noise in the samples, should ... More
Spell Once, Summon Anywhere: A Two-Level Open-Vocabulary Language ModelApr 23 2018Nov 23 2018We show how the spellings of known words can help us deal with unknown words in open-vocabulary NLP tasks. The method we propose can be used to extend any closed-vocabulary generative model, but in this paper we specifically consider the case of neural ... More
Einstein clusters as models of inhomogeneous spacetimesDec 28 2018We study the effect of small-scale inhomogeneities for Einstein clusters. We construct a spherically symmetric stationary spacetime with small-scale radial inhomogeneities and propose the Gedankenexperiment. An hypothetical observer at the center constructs, ... More
A Deep Radio Limit for the TRAPPIST-1 SystemJun 01 2018Sep 10 2018The first nearby very-low mass star planet-host discovered, TRAPPIST-1, presents not only a unique opportunity for studying a system of multiple terrestrial planets, but a means to probe magnetospheric interactions between a star at the end of the main ... More
On standing waves in general relativityJan 29 2019We propose a covariant definition of standing gravitational waves in general relativity.
The magnetic field and pressure dependence of the magnetic ordering transition in NaxCoO2 (0.6<x<0.72)Oct 26 2005Apr 27 2006We have measured the magnetic field (H<90 kOe) and pressure (P<10 kbar) dependence of the magnetic ordering temperature, Tmag, in single crystal samples of NaxCoO2 for a range of Na concentrations (0.60<x<0.72). We show that in zero field, Tmag remains ... More
Scattering Amplitudes for Multi-indexed Extensions of Solvable PotentialsSep 21 2013Sep 25 2013New solvable one-dimensional quantum mechanical scattering problems are presented. They are obtained from known solvable potentials by multiple Darboux transformations in terms of virtual and pseudo virtual wavefunctions. The same method applied to confining ... More
Investigation of the Spin Density Wave in NaxCoO2Jun 22 2004Oct 04 2004Magnetic susceptibility, transport and heat capacity measurements of single crystal NaxCoO2 (x=0.71) are reported. A transition to a spin density wave (SDW) state at Tmag = 22 K is observable in all measurements, except chi(ac) data in which a cusp is ... More
Resonant, non-resonant, and anomalous states of Dirac electrons in a parabolic well in the presence of magnetic fieldsOct 08 2012Nov 12 2012We report on several new basic properties of a parabolic dot in the presence of a magnetic field. The ratio between the potential strength and the Landau level (LL) energy spacing serves as the coupling constant of this problem. In the weak coupling limit ... More
Neutron-scattering studies of arsenic sulphide glassesFeb 24 2004High-resolution neutron-scattering measurements have been performed on bulk glasses of As2S3 and As2S3I1.65 at a spallation neutron source. For the case of As2S3, an isotopic-substitution experiment involving the S isotope has allowed some of the various ... More
Fractal Threshold Behavior in Vacuum Gravitational CollapseNov 28 2007Apr 02 2008We present the numerical evidence for fractal threshold behavior in the five dimensional vacuum Einstein equations satisfying the cohomogeneity-two triaxial Bianchi type-IX ansatz. In other words, we show that a flip of the wings of a butterfly may influence ... More
Semi-geostrophic particle motion and exponentially accurate normal formsOct 21 2005Mar 27 2006We give an exponentially-accurate normal form for a Lagrangian particle moving in a rotating shallow-water system in the semi-geostrophic limit, which describes the motion in the region of an exponentially-accurate slow manifold (a region of phase space ... More
Persistence and extinction for stochastic ecological difference equations with feedbacksAug 23 2018Sep 13 2018Species' densities experience both internal frequency-dependent feedbacks due to population structure and external feedbacks from abiotic factors. These feedbacks can determine whether populations persist or go extinct, and may be subject to stochastic ... More
On continuum modeling of sputter erosion under normal incidence: interplay between nonlocality and nonlinearityJan 04 2005Apr 05 2005Under specific experimental circumstances, sputter erosion on semiconductor materials exhibits highly ordered hexagonal dot-like nanostructures. In a recent attempt to theoretically understand this pattern forming process, Facsko et al. [Phys. Rev. B ... More
Entropy Trees and Range-Minimum Queries In Optimal Average-Case SpaceMar 06 2019The range-minimum query (RMQ) problem is a fundamental data structuring task with numerous applications. Despite the fact that succinct solutions with worst-case optimal $2n+o(n)$ bits of space and constant query time are known, it has been unknown whether ... More
Robust permanence for ecological equations with internal and external feedbacksDec 20 2016Species experience both internal feedbacks with endogenous factors such as trait evolution and external feedbacks with exogenous factors such as weather. These feedbacks can play an important role in determining whether populations persist or communities ... More
Persistence in fluctuating environments for interacting structured populationsApr 06 2013Nov 02 2013Individuals within any species exhibit differences in size, developmental state, or spatial location. These differences coupled with environmental fluctuations in demographic rates can have subtle effects on population persistence and species coexistence. ... More
Quasi-stationary distributions for randomly perturbed dynamical systemsJan 18 2011Apr 15 2014We analyze quasi-stationary distributions $\{\mu^{\varepsilon}\}_{\varepsilon>0}$ of a family of Markov chains $\{X^{\varepsilon}\}_{\varepsilon>0}$ that are random perturbations of a bounded, continuous map $F:M\to M$, where $M$ is a closed subset of ... More
How ripples turn into dots: modeling ion-beam erosion under oblique incidenceSep 16 2005May 12 2006Pattern formation on semiconductor surfaces induced by low energetic ion-beam erosion under normal and oblique incidence is theoretically investigated using a continuum model in form of a stochastic, nonlocal, anisotropic Kuramoto-Sivashinsky equation. ... More
Robust permanence for interacting structured populationsMay 22 2010The dynamics of interacting structured populations can be modeled by $\frac{dx_i}{dt}= A_i (x)x_i$ where $x_i\in \R^{n_i}$, $x=(x_1,\dots,x_k)$, and $A_i(x)$ are matrices with non-negative off-diagonal entries. These models are permanent if there exists ... More
Nearly-Optimal Mergesorts: Fast, Practical Sorting Methods That Optimally Adapt to Existing RunsMay 10 2018We present two stable mergesort variants, "peeksort" and "powersort", that exploit existing runs and find nearly-optimal merging orders with practically negligible overhead. Previous methods either require substantial effort for determining the merging ... More
Persistence and extinction for stochastic ecological models with internal and external variablesAug 23 2018Mar 26 2019The dynamics of species' densities depend both on internal and external variables. Internal variables include frequencies of individuals exhibiting different phenotypes or living in different spatial locations. External variables include abiotic factors ... More
Ensemble filter techniques for intermittent data assimilation - a surveyAug 31 2012This survey paper is written with the intention of giving a mathematical introduction to filtering techniques for intermittent data assimilation, and to survey some recent advances in the field. The paper is divided into three parts. The first part introduces ... More
Evolutionarily induced alternative states and coexistence in systems with apparent competitionApr 03 2015Predators often consume multiple prey and by mutually subsidizing a shared predator, the prey may reciprocally harm each other. When predation levels are high, this apparent competition can culminate in a prey species being displaced. Coupling quantitative ... More
Exploring the Variable Sky with the Sloan Digital Sky SurveyApr 04 2007We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS Stripe 82, and contains 58 million photometric observations in the SDSS ugriz system for 1.4 million unresolved ... More
Solving First Order Autonomous Algebraic Ordinary Differential Equations by PlacesMar 13 2018Nov 14 2018Given a first-order autonomous algebraic ordinary differential equation, we present a method for computing formal power series solutions by means of places. We provide an algorithm for computing a full characterization of possible initial values, classified ... More
Reproducible $k$-means clustering in galaxy feature data from the GAMA surveyOct 01 2018A fundamental bimodality of galaxies in the local Universe is apparent in many of the features used to describe them. Multiple sub-populations exist within this framework, each representing galaxies following distinct evolutionary pathways. Accurately ... More
The mass of the b-quark from lattice NRQCD and lattice perturbation theoryFeb 15 2013Mar 26 2013We present a determination of the b-quark mass accurate through O(\alpha_s^2) in perturbation theory and including partial contributions at O(\alpha_s^3). Nonperturbative input comes from the calculation of the Upsilon and B_s energies in lattice QCD ... More
Recursive Training of 2D-3D Convolutional Networks for Neuronal Boundary DetectionAug 20 2015Efforts to automate the reconstruction of neural circuits from 3D electron microscopic (EM) brain images are critical for the field of connectomics. An important computation for reconstruction is the detection of neuronal boundaries. Images acquired by ... More
An Error Detection and Correction Framework for ConnectomicsAug 08 2017Dec 03 2017We define and study error detection and correction tasks that are useful for 3D reconstruction of neurons from electron microscopic imagery, and for image segmentation more generally. Both tasks take as input the raw image and a binary mask representing ... More
A Spitzer view of protoplanetary disks in the gamma Velorum clusterJun 16 2008We present new Spitzer Space Telescope observations of stars in the young ~5 Myr gamma Velorum stellar cluster. Combining optical and 2MASS photometry, we have selected 579 stars as candidate members of the cluster. With the addition of the Spitzer mid-infrared ... More