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Results for "A. Nicholas Black"

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Quantum, Nonlocal Aberration CancellationJun 11 2019Phase distortions, or aberrations, can negatively influence the performance of an optical imaging system. Through the use of position-momentum entangled photons, we nonlocally correct for aberrations in one photon's optical path by intentionally introducing ... More
Topological Superconductivity in Two Dimensions with Mixed ChiralityMar 09 2015Nov 02 2015We find a mixed chirality $d$-wave superconducting state in the coexistence region between antiferromagnetism and interaction-driven superconductivity in lightly doped honeycomb materials. This state has a topological chiral $d+id$-wave symmetry in one ... More
Filling of magnetic-impurity-induced gap in topological insulators by potential scatteringFeb 23 2015May 27 2015We show that the energy gap induced by ferromagnetically aligned magnetic impurities on the surface of a topological insulator can be filled, due to scattering off the non-magnetic potential of the impurities. In both a continuum surface model and a three-dimensional ... More
Magnon Dirac materialsDec 15 2015Aug 15 2016We demonstrate how a Dirac-like magnon spectrum is generated for localized magnetic moments forming a two-dimensional honeycomb lattice. The Dirac crossing point is proven to be robust against magnon-magnon interactions, as these only shift the spectrum. ... More
The Scalar Sector and the Eta -> 3 Pi ProblemApr 17 2003First, recent work on light scalar mesons, which is of possible interest in connection with the strong coupling region of QCD is briefly discussed. Then a very short highlighting of a paper concerned with an application to the eta -> 3 pi problem is presented. ... More
Lower bounds for the smallest singular value of structured random matricesAug 26 2016May 18 2018We obtain lower tail estimates for the smallest singular value of random matrices with independent but non-identically distributed entries. Specifically, we consider $n\times n$ matrices with complex entries of the form \[ M = A\circ X + B = (a_{ij}\xi_{ij} ... More
The circular law for random regular digraphsMar 16 2017Aug 07 2017Let $\log^Cn\le d\le n/2$ for a sufficiently large constant $C>0$ and let $A_n$ denote the adjacency matrix of a uniform random $d$-regular directed graph on $n$ vertices. We prove that as $n$ tends to infinity, the empirical spectral distribution of ... More
Dense random regular digraphs: singularity of the adjacency matrixMar 24 2014Aug 02 2015Fix $c\in (0,1)$ and let $\Gamma$ be a $\lfloor c n\rfloor$-regular digraph on $n$ vertices drawn uniformly at random. We prove that when $n$ is large, the (non-symmetric) adjacency matrix $M$ of $\Gamma$ is invertible with high probability. The proof ... More
Discrepancy properties for random regular digraphsOct 21 2014Oct 26 2015For the uniform random regular directed graph we prove concentration inequalities for (1) codegrees and (2) the number of edges passing from one set of vertices to another. As a consequence, we can deduce discrepancy properties for the distribution of ... More
Fluid-Structure Interaction for the Classroom: Interpolation, Hearts, and Swimming!Aug 23 2018While students may find spline interpolation easily digestible, based on their familiarity with continuity of a function and its derivatives, some of its inherent value may be missed when students only see it applied to standard data interpolation exercises. ... More
Supercurrent detection of topologically trivial zero-energy states in nanowire junctionsApr 08 2019We report the emergence of zero-energy states in the trivial phase of a short nanowire junction with strong spin-orbit coupling and magnetic field, formed by strong coupling between the nanowire and two superconductors. The zero-energy states appear in ... More
The circular law for random regular digraphs with random edge weightsAug 02 2015Sep 08 2017We consider random $n\times n$ matrices of the form $Y_n=\frac1{\sqrt{d}}A_n\circ X_n$, where $A_n$ is the adjacency matrix of a uniform random $d$-regular directed graph on $n$ vertices, with $d=\lfloor p n\rfloor$ for some fixed $p \in (0,1)$, and $X_n$ ... More
Eventual smoothness of generalized solutions to a singular chemotaxis-Stokes systemMay 17 2017We study the chemotaxis-fluid system \begin{align*} \left\{ \begin{array}{r@{\,}c@{\,}c@{\ }l@{\quad}l@{\quad}l@{\,}c} n_{t}&+&u\cdot\!\nabla n&=\Delta n-\nabla\!\cdot(\frac{n}{c}\nabla c),\ &x\in\Omega,& t>0, c_{t}&+&u\cdot\!\nabla c&=\Delta c-nc,\ &x\in\Omega,& ... More
Global very weak solutions to a chemotaxis-fluid system with nonlinear diffusionDec 01 2017Jun 06 2018We consider the chemotaxis-fluid system \begin{align}\label{star}\tag{$\diamondsuit$} \left\{ \begin{array}{r@{\,}c@{\,}c@{\ }l@{\quad}l@{\quad}l@{\,}c} n_{t}&+&u\cdot\!\nabla n&=\Delta n^m-\nabla\!\cdot(n\nabla c),\ &x\in\Omega,& t>0,\\ c_{t}&+&u\cdot\!\nabla ... More
The Stokes limit in a three-dimensional chemotaxis-Navier-Stokes systemFeb 17 2019We consider initial-boundary value problems for the $\kappa$-dependent family of chemotaxis-(Navier--)Stokes systems \begin{align*} \left\{ \begin{array}{r@{\,}c@{\,}c@{\ }l@{\quad}l@{\quad}l@{\,}c} n_{t}&+&u\cdot\!\nabla n&=\Delta n-\nabla\!\cdot(n\nabla ... More
Global solvability of chemotaxis-fluid systems with nonlinear diffusion and matrix-valued sensitivities in three dimensionsJul 06 2018In this work we extend a recent result to chemotaxis fluid systems which include matrix-valued sensitivity functions $S(x,n,c):\Omega\times[0,\infty)^2\to\mathbb{R}^{3\times3}$ in addition to the porous medium type diffusion, which were discussed in the ... More
Global generalized solutions to a parabolic-elliptic Keller-Segel system with singular sensitivityMay 18 2017May 19 2017We investigate the parabolic-elliptic Keller-Segel model \begin{align*}\left\{\begin{array}{r@{\,}l@{\quad}l@{\quad}l@{\,}c} u_{t}&=\Delta u-\,\chi\nabla\!\cdot(\frac{u}{v}\nabla v),\ &x\in\Omega,& t>0,\\ 0&=\Delta v-\,v+u,\ &x\in\Omega,& t>0,\\ \frac{\partial ... More
Zero Cycles of Degree One on Principal Homogeneous SpacesSep 23 2010Let $k$ be a field of characteristic different from 2. Let $G$ be a simply connected or adjoint semisimple algebraic $k$-group which does not contain a simple factor of type $E_8$ and such that every exceptional simple factor of type other than $G_2$ ... More
Implications of the Hasse Principle for Zero Cycles of Degree One on Principal Homogeneous SpacesOct 08 2010Let $k$ be a perfect field of virtual cohomological dimension $\leq 2$. Let $G$ be a connected linear algebraic group over $k$ such that $G^{sc}$ satisfies a Hasse principle over $k$. Let $X$ be a principal homogeneous space under $G$ over $k$. We show ... More
Sublinear signal production in a two-dimensional Keller-Segel-Stokes systemFeb 01 2016We study the chemotaxis-fluid system \begin{align*} \left\{\begin{array}{r@{\,}l@{\quad}l@{\,}c} n_{t}&=\Delta n-\nabla\!\cdot(n\nabla c)-u\cdot\!\nabla n,\ &x\in\Omega,& t>0,\\ c_{t}&=\Delta c-c+f(n)-u\cdot\!\nabla c,\ &x\in\Omega,& t>0,\\ u_{t}&=\Delta ... More
Neural networks as a tool for parameter estimation in astrophysical dataDec 14 2001We present a neural net algorithm for parameter estimation in the context of large cosmological data sets. Cosmological data sets present a particular challenge to pattern-recognition algorithms since the input patterns (galaxy redshift surveys, maps ... More
Neural Networks as a tool for parameter estimation in mega-pixel data setsAug 14 2001We present a neural net algorithm for parameter estimation in the context of large cosmological data sets. Cosmological data sets present a particular challenge to pattern-recognition algorithms since the input patterns (galaxy redshift surveys, maps ... More
Boundedness in a Keller-Segel system with external signal productionJul 27 2015We study the Neumann initial-boundary problem for the chemotaxis system \begin{align*} \left\{\begin{array}{c@{\,}l@{\quad}l@{\,}c} u_{t}&=\Delta u-\nabla\!\cdot(u\nabla v),\ &x\in\Omega,& t>0,\\ v_{t}&=\Delta v-v+u+f(x,t),\ &x\in\Omega,& t>0,\\ \frac{\partial ... More
Blow-up of weak solutions to a chemotaxis system under influence of an external chemoattractantOct 24 2015We study nonnnegative radially symmetric solutions of the parabolic-elliptic Keller-Segel whole space system \begin{align*} \left\{\begin{array}{c@{\,}l@{\quad}l@{\,}c} u_{t}&=\Delta u-\nabla\!\cdot(u\nabla v),\ &x\in\mathbb{R}^n,& t>0,\\ 0 &=\Delta v+u+f(x),\ ... More
Large deviations of subgraph counts for sparse Erdős--Rényi graphsSep 28 2018Dec 10 2018For any fixed, connected graph $H=(V,E)$ of maximum degree $\Delta$ and any fixed $u>0$, we establish the leading order of the exponential rate function for the probability that the number of copies of $H$ in the Erd\H{o}s--R\'enyi graph $G(N,p)$ exceeds ... More
On the automorphism group of the Morse complexApr 24 2019Let $K$ be a finite, connected, abstract simplicial complex. The Morse complex of $K$, first introduced by Chari and Joswig, is the simplicial complex constructed from all gradient vector fields on $K$. We show that if $K$ is neither the boundary of the ... More
The realization problem for discrete Morse functions on treesJul 24 2018We introduce a new notion of equivalence of discrete Morse functions on graphs called persistence equivalence. Two functions are considered persistence equivalent if and only if they induce the same persistence diagram. We compare this notion of equivalence ... More
A dynamic network approach for the study of human phenotypesSep 22 2009The use of networks to integrate different genetic, proteomic, and metabolic datasets has been proposed as a viable path toward elucidating the origins of specific diseases. Here we introduce a new phenotypic database summarizing correlations obtained ... More
Interfacial Effects of Al-Termination on Spin Transport in Magnetic Tunnel JunctionsOct 23 2009Experiments have shown that the tunneling current in a Co/Al$_2$O$_3$ magnetic tunneling junction (MTJ) is positively spin polarized, opposite to what is intuitively expected from standard tunneling theory which gives the spin polarization as exclusively ... More
The Transition of a Type IIL Supernova into a Supernova Remnant: Late-time Observations of SN 2013bySep 05 2017Sep 11 2017We present early-time Swift and Chandra X-ray data along with late-time optical and near-infrared observations of SN 2013by, a Type IIL supernova (SN) that occurred in the nearby spiral galaxy ESO 138$-$G10 (D $\sim 14.8$ Mpc). Optical and NIR photometry ... More
The imaging X-ray detector for Lobster-ISSMay 07 2003Lobster-ISS is a revolutionary astrophysical X-ray all-sky monitor scheduled for deployment as an attached payload on the International Space Station (ISS) in 2009. Using a new wide field-of-view focusing optic, Lobster-ISS provides an order-of-magnitude ... More
Bifurcations in valveless pumping techniques from a coupled fluid-structure-electrophysiology model in heart developmentSep 14 2017We explore an embryonic heart model that couples electrophysiology and muscle-force generation to flow induced using a $2D$ fluid-structure interaction framework based on the immersed boundary method. The propagation of action potentials are coupled to ... More
A Distance Estimate to the Cygnus Loop Based on the Distances to Two Stars Located Within the RemnantNov 06 2017Nov 25 2017Underlying nearly every quantitative discussion of the Cygnus Loop supernova remnant is uncertainty about its distance. Here we present optical images and spectra of nebulosities around two stars whose mass-loss material appears to have interacted with ... More
Learning and Tracking the 3D Body Shape of Freely Moving Infants from RGB-D sequencesOct 17 2018Statistical models of the human body surface are generally learned from thousands of high-quality 3D scans in predefined poses to cover the wide variety of human body shapes and articulations. Acquisition of such data requires expensive equipment, calibration ... More
Unitarized pseudoscalar meson scattering amplitudes in three flavor linear sigma modelsDec 21 2000The three flavor linear sigma model is studied as a ``toy model'' for understanding the role of possible light scalar mesons in the \pi \pi, \pi K and \pi \eta scattering channels. The approach involves computing the tree level partial wave amplitude ... More
Combinatorics of certain higher $q,t$-Catalan polynomials: chains, joint symmetry, and the Garsia-Haiman formulaNov 09 2012Jun 22 2013The higher $q,t$-Catalan polynomial $C^{(m)}_n(q,t)$ can be defined combinatorially as a weighted sum of lattice paths contained in certain triangles, or algebraically as a complicated sum of rational functions indexed by partitions of $n$. This paper ... More
Kinetic limitations of cooperativity based drug delivery systemsAug 17 2007Mar 07 2008We study theoretically a novel drug delivery system that utilizes the overexpression of certain proteins in cancerous cells for cell specific chemotherapy. The system consists of dendrimers conjugated with "keys" (ex: folic acid) which "key-lock" bind ... More
Subdivision of Maps of Digital ImagesJun 07 2019With a view towards providing tools for analyzing and understanding digitized images, various notions from algebraic topology have been introduced into the setting of digital topology. In the ordinary topological setting, invariants such as the fundamental ... More
A Combinatorial Approach to the Symmetry of $q,t$-Catalan NumbersFeb 02 2016The \emph{$q,t$-Catalan numbers} $C_n(q,t)$ are polynomials in $q$ and $t$ that reduce to the ordinary Catalan numbers when $q=t=1$. These polynomials have important connections to representation theory, algebraic geometry, and symmetric functions. Haglund ... More
A test for dependence between two point processes on the real lineAug 17 2014Dec 20 2014Many scientific questions rely on determining whether two sequences of event times are associated. This article introduces a likelihood ratio test which can be parameterised in several ways to detect different forms of dependence. A common finite-sample ... More
Nested quantum Dyck paths and nabla(s_lambda)May 31 2007We conjecture a combinatorial formula for the monomial expansion of the image of any Schur function under the Bergeron-Garsia nabla operator. The formula involves nested labeled Dyck paths weighted by area and a suitable "diagonal inversion" statistic. ... More
A Zero Knowledge Sumcheck and its ApplicationsApr 07 2017Many seminal results in Interactive Proofs (IPs) use algebraic techniques based on low-degree polynomials, the study of which is pervasive in theoretical computer science. Unfortunately, known methods for endowing such proofs with zero knowledge guarantees ... More
Atom laser dynamicsMar 29 2001An ideal atom laser would produce an atomic beam with highly stable flux and energy. In practice the stability is likely to be limited by technical noise and nonlinear dynamical effects. We investigate the dynamics of an atom laser using a comprehensive ... More
Direct Extragalactic Distance Determination Using X-Ray ScatteringJul 20 2004We examine the feasibility of using dust-scattered X-rays for direct determination of distances to nearby galaxies with bright background AGNs, QSOs, or GRBs. We show how the Chandra X-Ray Observatory could be used to determine the distance to M31 to ... More
Pairwise balanced designs covered by bounded flatsOct 27 2014We prove that for any $K$ and $d$, there exist, for all sufficiently large admissible $v$, a pairwise balanced design PBD$(v,K)$ of dimension $d$ for which all $d$-point-generated flats are bounded by a constant independent of $v$. We also tighten a prior ... More
Size biased couplings and the spectral gap for random regular graphsOct 20 2015Mar 08 2017Let $\lambda$ be the second largest eigenvalue in absolute value of a uniform random $d$-regular graph on $n$ vertices. It was famously conjectured by Alon and proved by Friedman that if $d$ is fixed independent of $n$, then $\lambda=2\sqrt{d-1} +o(1)$ ... More
Feynman-Kac Formulas for Regime-Switching Jump Diffusions and their ApplicationsFeb 06 2017This work develops Feynman-Kac formulas for a class of regime-switching jump diffusion processes, in which the jump part is driven by a Poisson random measure associated to a general L\'evy process and the switching part depends on the jump diffusion ... More
Direct measurements reveal non-Markovian fluctuations of DNA threading through a solid-state nanoporeJul 15 2016The threading of a polymer chain through a small pore is a classic problem in polymer dynamics and underlies nanopore sensing technology. However important experimental aspects of the polymer motion in a solid-state nanopore, such as an accurate measurement ... More
Don't be jelly: Exploring effective jellyfish locomotionApr 19 2019Jellyfish have been called one of the most energy-efficient animals in the world due to the ease in which they move through their fluid environment, by product of their morphological, muscular, and material properties. We investigated jellyfish locomotion ... More
Effects of the non-uniform initial environment and the guide field on the plasmoid instabilityJul 08 2013Effects of non-uniform initial mass density and temperature on the plasmoid instability are studied via 2.5-dimensional resistive magnetohydrodynamic(MHD) simulations. Our results indicate that the development of the plasmoid instability is apparently ... More
Possible Observational Criteria for Distinguishing Brown Dwarfs from PlanetsOct 14 1997The difference in formation process between binary stars and planetary systems is reflected in their composition as well as their orbital architecture, particularly orbital eccentricity as a function of orbital period. It is suggested here that this difference ... More
RKKY coupling in grapheneJan 22 2010May 12 2010We study the carrier-mediated exchange interaction, the so-called RKKY coupling, between two magnetic moments in graphene using exact diagonalization on the honeycomb lattice. By using the tight-binding nearest neighbor band structure of graphene we avoid ... More
Near-integrable behaviour in a family of discretised rotationsMay 30 2014We consider a one-parameter family of invertible maps of a two-dimensional lattice, obtained by applying round-off to planar rotations. All orbits of these maps are conjectured to be periodic. We let the angle of rotation approach pi/2, and show that ... More
Expressive Body Capture: 3D Hands, Face, and Body from a Single ImageApr 11 2019To facilitate the analysis of human actions, interactions and emotions, we compute a 3D model of human body pose, hand pose, and facial expression from a single monocular image. To achieve this, we use thousands of 3D scans to train a new, unified, 3D ... More
A toolkit to describe and interactively display three-manifolds embedded in four-spaceJan 25 2012A data structure and toolkit are presented here that allow for the description and manipulation of mathematical models of three-manifolds and their interactive display from multiple viewpoints via the OpenGL 3D graphics package. The data structure and ... More
Chemical Analysis of a Diffuse Cloud along a Line of Sight Toward W51: Molecular Fraction and Cosmic-Ray Ionization RateAug 15 2012Absorption lines from the molecules OH+, H2O+, and H3+ have been observed in a diffuse molecular cloud along a line of sight near W51 IRS2. We present the first chemical analysis that combines the information provided by all three of these species. Together, ... More
Far field imaging by a planar lens: diffraction versus superresolutionMay 22 2007We resolve the long standing controversy regarding the imaging by a planar lens made of left-handed media and demonstrate theoretically that its far field image has a fundamentally different origin depending on the relationship between losses {inside} ... More
IB2d: a Python and MATLAB implementation of the immersed boundary methodOct 24 2016The development of fluid-structure interaction (FSI) software involves trade-offs between ease of use, generality, performance, and cost. Typically there are large learning curves when using low-level software to model the interaction of an elastic structure ... More
A Comparative Study of Velocity Statistics of Hydrodynamic and Magnetohydrodynamic TurbulenceNov 15 2006Turbulence in an incompressible fluid with and without a magnetic field as well as moderately compressible MHD turbulence are compared. For the magnetohydrodynamic (MHD) models the probability distribution functions of the velocity components perpendicular ... More
Magnetic reconnection in the low solar chromosphere with a more realistic radiative cooling modelApr 16 2018Oct 25 2018Magnetic reconnection is the most likely mechanism responsible for the high temperature events that are observed in strongly magnetized locations around the temperature minimum in the low solar chromosphere. This work improves upon our previous work ["Magnetic ... More
Transition matrices for symmetric and quasisymmetric Hall-Littlewood polynomialsFeb 15 2012Jun 19 2013We introduce explicit combinatorial interpretations for the coefficients in some of the transition matrices relating to skew Hall-Littlewood polynomials P_lambda/mu(x;t) and Hivert's quasisymmetric Hall-Littlewood polynomials G_gamma(x;t). More specifically, ... More
Spatial Isolation Implies Zero Knowledge Even in a Quantum WorldMar 05 2018Zero knowledge plays a central role in cryptography and complexity. The seminal work of Ben-Or et al. (STOC 1988) shows that zero knowledge can be achieved unconditionally for any language in NEXP, as long as one is willing to make a suitable physical ... More
Translocation frequency of double-stranded DNA through a solid-state nanoporeAug 18 2015Jan 15 2016Solid-state nanopores are single molecule sensors that measure changes in ionic current as charged polymers such as DNA pass through. Here, we present comprehensive experiments on the length, voltage and salt dependence of the frequency of double-stranded ... More
Obstacle and predator avoidance by a flockJun 19 2009The modeling and investigation of the dynamics and configurations of animal groups is a subject of growing attention. In this paper, we present a continuum model of flocking and use it to investigate the reaction of a flock to an obstacle or an attacking ... More
Alignment of vorticity and rods with Lagrangian fluid stretching in turbulenceNov 04 2013Stretching in continuum mechanics is naturally described using the Cauchy-Green strain tensors. These tensors quantify the Lagrangian stretching experienced by a material element, and provide a powerful way to study processes in turbulent fluid flows ... More
On the structure of proten-protein interaction networksSep 23 2003We present a simple model for the underlying structure of protein-protein pairwise interaction graphs that is based on the way in which proteins attach to each other in experiments such as yeast two-hybrid assays. We show that data on the interactions ... More
The appearance, motion, and disappearance of three-dimensional magnetic null pointsSep 19 2015While theoretical models and simulations of magnetic reconnection often assume symmetry such that the magnetic null point when present is co-located with a flow stagnation point, the introduction of asymmetry typically leads to non-ideal flows across ... More
Theory of plasmon-enhanced Foerster energy transfer in optically-excited semiconductor and metal nanoparticlesDec 12 2006May 23 2007We describe the process of Foerster transfer between semiconductor nanoparticles in the presence of a metal subsystem (metal nanocrystals). In the presence of metal nanocrystals, the Foerster process can become faster and more long-range. The enhancement ... More
Tight Analyses for Non-Smooth Stochastic Gradient DescentDec 13 2018Consider the problem of minimizing functions that are Lipschitz and strongly convex, but not necessarily differentiable. We prove that after $T$ steps of stochastic gradient descent, the error of the final iterate is $O(\log(T)/T)$ with high probability. ... More
Modeling Hierarchical Usage Context for Software Exceptions based on Interaction DataApr 15 2019Traces of user interactions with a software system, captured in production, are commonly used as an input source for user experience testing. In this paper, we present an alternative use, introducing a novel approach of modeling user interaction traces ... More
Meta-analysis of mid-p-values: some new results based on the convex orderMay 19 2015May 31 2017The mid-p-value is a proposed improvement on the ordinary p-value for the case where the test statistic is partially or completely discrete. In this case, the ordinary p-value is conservative, meaning that its null distribution is larger than a uniform ... More
Rational parking functions and Catalan numbersMar 07 2014The classical parking functions, counted by the Cayley number (n+1)^(n-1), carry a natural permutation representation of the symmetric group S_n in which the number of orbits is the n'th Catalan number. In this paper, we will generalize this setup to ... More
Physical Combinatorics and QuasiparticlesMar 03 2009Oct 16 2009We consider the physical combinatorics of critical lattice models and their associated conformal field theories arising in the continuum scaling limit. As examples, we consider A-type unitary minimal models and the level-1 sl(2) Wess-Zumino-Witten (WZW) ... More
Density of States for Warped Energy BandsJul 14 2015An angular effective mass formalism previously introduced is used to study the density of states in warped and non-warped energy bands. Band warping may or may not increase the density-of-states effective mass. Band "corrugation," referring to energy ... More
The Evolution of Post-Starburst Galaxies from $z\sim1$ to the PresentOct 27 2014Aug 15 2016Post-starburst galaxies are in the transitional stage between blue, star-forming galaxies and red, quiescent galaxies, and therefore hold important clues for our understanding of galaxy evolution. In this paper, we systematically searched for and identified ... More
A Scalable Blocked Gibbs Sampling Algorithm For Gaussian And Poisson Regression ModelsJan 30 2016Markov Chain Monte Carlo (MCMC) methods are a popular technique in Bayesian statistical modeling. They have long been used to obtain samples from posterior distributions, but recent research has focused on the scalability of these techniques for large ... More
Modeling the prescription opioid epidemicNov 10 2017Jun 02 2018Opioid addiction has become a global epidemic and a national health crisis in recent years, with the number of opioid overdose fatalities steadily increasing since the 1990s. In contrast to the dynamics of a typical illicit drug or disease epidemic, opioid ... More
On the Amplitude of Convective Velocities in the Deep Solar InteriorMay 07 2012Aug 09 2012We obtain lower limits on the amplitude of convective velocities in the deep solar convection zone based only on the observed properties of the differential rotation and meridional circulation together with simple and robust dynamical balances obtained ... More
Greedy and Local Ratio Algorithms in the MapReduce ModelJun 17 2018MapReduce has become the de facto standard model for designing distributed algorithms to process big data on a cluster. There has been considerable research on designing efficient MapReduce algorithms for clustering, graph optimization, and submodular ... More
Magnetic reconnection in strongly magnetized regions of the low solar chromosphereDec 02 2017Dec 22 2017Magnetic reconnection in strongly magnetized regions around the temperature minimum region of the low solar atmosphere is studied by employing MHD-based simulations of a partially ionized plasma within a reactive 2.5D multi-fluid model. It is shown that ... More
Blob formation and ejection in coronal jets due to the plasmoid and Kelvin-Helmholtz instabilitiesApr 29 2017We perform two-dimensional resistive magnetohydrodynamic simulations of coronal jets driven by flux emergence along the lower boundary. The reconnection layers are susceptible the formation of blobs that are ejected in the jet. Our simulation with low ... More
Algebraic and geometric aspects of rational $Γ$-inner functionsFeb 14 2015Dec 22 2017The set \[ \Gamma {\stackrel{\rm def}{=}} \{(z+w,zw):|z|\leq 1,|w|\leq 1\} \subset {\mathbb{C}}^2 \] has intriguing complex-geometric properties; it has a 3-parameter group of automorphisms, its distinguished boundary is a ruled surface homeomorphic to ... More
Large $N$ expansions for the Laguerre and Jacobi $β$ ensembles from the loop equationsJul 16 2017The $\beta$-ensembles of random matrix theory with classical weights have many special properties. One is that the loop equations specifying the resolvent and corresponding multipoint correlators permit a derivation at general order of the correlator ... More
Diverse Large-Scale ITS Dataset Created from Continuous Learning for Real-Time Vehicle DetectionOct 07 2015In traffic engineering, vehicle detectors are trained on limited datasets resulting in poor accuracy when deployed in real world applications. Annotating large-scale high quality datasets is challenging. Typically, these datasets have limited diversity; ... More
Near-integrable behaviour in a family of discretised rotationsAug 06 2012Apr 09 2013We consider a one-parameter family of invertible maps of a two-dimensional lattice, obtained by discretising the space of planar rotations. We let the angle of rotation approach $\pi/2$, and show that the limit of vanishing discretisation is described ... More
Generating Mandarin and Cantonese F0 Contours with Decision Trees and BLSTMsJul 04 2018This paper models the fundamental frequency contours on both Mandarin and Cantonese speech with decision trees and DNNs (deep neural networks). Different kinds of f0 representations and model architectures are tested for decision trees and DNNs. A new ... More
Data Augmentation for Neural Online Chat Response SelectionSep 03 2018Data augmentation seeks to manipulate the available data for training to improve the generalization ability of models. We investigate two data augmentation proxies, permutation and flipping, for neural dialog response selection task on various models ... More
The ALMA view of UV irradiated cloud edges: unexpected structures and processesJul 27 2017Far-UV photons (E<13.6 eV) from hot massive stars regulate, or at least influence, the heating, ionization, and chemistry of most of the neutral interstellar medium. Investigating the interaction between FUV radiation and interstellar matter thus plays ... More
Modeling the Dynamics of PDE Systems with Physics-Constrained Deep Auto-Regressive NetworksJun 13 2019In recent years, deep learning has proven to be a viable methodology for surrogate modeling and uncertainty quantification for a vast number of physical systems. However, in their traditional form, such models require a large amount of training data. ... More
Neutron interferometric measurement of the scattering length difference between the triplet and singlet states of n-$^3$HeSep 30 2014We report a determination of the n-$^3$He scattering length difference $\Delta b^{\prime} = b_{1}^{\prime}-b_{0}^{\prime} = $ ($-5.411$ $\pm$ $0.031$ (statistical) $\pm$ $0.039$ (systematic)) fm between the triplet and singlet states using a neutron interferometer. ... More
Majorana fermions at odd junctions in a wire network of ferromagnetic impuritiesMay 02 2016We consider a wire network of ferromagnetic impurities on the surface of an $s$-wave superconductor with strong Rashba spin-orbit interaction. Within the topological phase, zero-energy Majorana fermions appear at wire end-points as well as at junctions ... More
Majorana fermions in spin-orbit coupled ferromagnetic Josephson junctionsJun 09 2011Nov 17 2011We study all possible Majorana modes in two-dimensional spin-orbit coupled ferromagnetic superconductor-normal state-superconductor (SNS) Josephson junctions and propose experiments to detect them. With the S region in a non-trivial topological phase ... More
Odd-frequency superconducting pairing and subgap density of states at the edge of a two-dimensional topological insulator without magnetismJul 26 2017Oct 10 2017We investigate the emergence and consequences of odd-frequency spin-triplet s-wave pairing in superconducting hybrid junctions at the edge of a two-dimensional topological insulator without any magnetism. More specifically, we consider several different ... More
Random Field Induced Order in Low DimensionMar 26 2012Oct 22 2012Consider the behavior of a classical O(n) model in a weak random external field acting along some $k$-dimensional subspace in $\R^n$ with $k<n$. We show rigorously that if $k=n-1$, for the model defined on $\Z^d$, $d ={2, 3}$ there is residual magnetic ... More
On the one-endedness of graphs of groupsMar 25 2014Mar 25 2015We give a technical result that implies a straightforward necessary and sufficient conditions for a graph of groups with virtually cyclic edge groups to be one ended. For arbitrary graphs of groups, we show that if their fundamental group is not one-ended, ... More
Fluxoid fluctuations in mesoscopic superconducting ringsAug 27 2010Rings are a model system for studying phase coherence in one dimension. Superconducting rings have states with uniform phase windings that are integer multiples of 2$\pi$ called fluxoid states. When the energy difference between these fluxoid states is ... More
Odin observations of H2O in the Galactic CentreMay 21 2003The Odin satellite has been used to detect emission and absorption in the 557-GHz H2O line in the Galactic Centre towards the Sgr A* Circumnuclear Disk (CND), and the Sgr A +20 km/s and +50 km/s molecular clouds. Strong broad H2O emission lines have been ... More
Meson-Meson Scattering in the Quark Model: Spin Dependence and Exotic ChannelsJul 11 2000We apply a quark interchange model to spin-dependent and exotic meson-meson scattering. The model includes the complete set of standard quark model forces, including OGE spin-orbit and tensor and scalar confinement spin-orbit. Scattering amplitudes derived ... More
Chiral approach to phi radiative decaysJan 06 2006The radiative decays of the phi meson are known to be a good source of information about the a0(980) and f0(980) scalar mesons. We discuss these decays starting from a non-linear model Lagrangian which maintains the (broken) chiral symmetry for the pseudoscalar ... More
Radiative Decays involving a0(980) and f0(980) in the Vector Meson Dominance ModelJun 07 2003We summarize some features of the vector meson dominance model which was recently proposed for studying radiative decays involving the scalar mesons. Using the experimental values of $\Gamma(a_0 \to \gamma\gamma)$, $\Gamma(f_0 \to \gamma\gamma)$ and $\Gamma(\phi ... More