Results for "Gregory R. Brady"

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Phase-Retrieval-Based Wavefront Metrology for High Contrast CoronagraphyMar 05 2019We discuss the use of parametric phase-diverse phase retrieval as an in-situ high-fidelity wavefront measurement method to characterize and optimize the transmitted wavefront of a high-contrast coronagraphic instrument. We apply our method to correct ... More
Searching for periodic sources with LIGO. II: Hierarchical searchesDec 04 1998The detection of quasi-periodic sources of gravitational waves requires the accumulation of signal-to-noise over long observation times. If not removed, Earth-motion induced Doppler modulations, and intrinsic variations of the gravitational-wave frequency ... More
Critical phenomena in gravitational collapseDec 21 1998This article reviews classical and quantum aspects of critical phenomena in gravitational collapse. We pay special attention to the origin of the scaling law for black hole mass, and to phase transitions in which black hole formation turns on at finite ... More
Cauchy horizon singularity without mass inflationNov 20 1992A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the nature of the singularity along the Cauchy horizon of a charged spherically symmetric black hole. For these solutions, conditions may prevail under which the mass function is ... More
Integration of fluorescence collection optics with a microfabricated surface electrode ion trapAug 17 2010Sep 23 2010We have successfully demonstrated an integrated optical system for collecting the fluorescence from a trapped ion. The system, consisting of an array of transmissive, dielectric micro-optics and an optical fiber array, has been intimately incorporated ... More
A note on the affine-invariant plank problemApr 02 2016Suppose that $C$ is a bounded convex subset of $\mathbb{R}^n$, and that $P_1, \dots, P_k$ are planks which cover $C$ in respective directions $v_1, \dots, v_k$ and with widths $w_1, \dots, w_k$. In 1951, Bang conjectured that $$\sum_{i=1}^k \frac{w_i}{w_{v_i}(C)} ... More
Convolutional Neural Networks for Histopathology Image Classification: Training vs. Using Pre-Trained NetworksOct 11 2017We explore the problem of classification within a medical image data-set based on a feature vector extracted from the deepest layer of pre-trained Convolution Neural Networks. We have used feature vectors from several pre-trained structures, including ... More
Gaia Shows That Messier 40 is Definitely Not a Binary StarDec 02 2016M40 has always been something of an oddity in the Messier Catalogue, since it is just a pair of stars rather than an extended object. Doubts have also been expressed as to whether it is even a physical binary. Here, we note that the Hipparcos/Gaia parallaxes ... More
Computing the merger of black-hole binaries: the IBBH problemApr 22 1998Gravitational radiation arising from the inspiral and merger of binary black holes (BBH's) is a promising candidate for detection by kilometer-scale interferometric gravitational wave observatories. This paper discusses a serious obstacle to searches ... More
The New Eclipsing Cataclysmic Variable SDSS 154453+2553Jan 07 2011The cataclysmic variable SDSS154453+2553 was recently identified in the Sloan Digital Sky Survey. We obtained spectra and photometry at the MDM Observatory, which revealed an eclipse with a 6.03 hour period. The H{\alpha} emission line exhibits a strong ... More
Proof of the Log-Convex Density ConjectureNov 16 2013Mar 15 2015We completely characterize isoperimetric regions in R^n with density e^h, where h is convex, smooth, and radially symmetric. In particular, balls around the origin constitute isoperimetric regions of any given volume, proving the Log-Convex Density Conjecture ... More
On the Classification of Legendrian Rational TanglesNov 12 2014We show that under certain conditions the flyping operation on rational tangles, which produces topologically isotopic tangles, may also produce tangles which are not Legendrian isotopic when viewed in the standard contact structure on $\mathbb{R}^3$. ... More
A constitutive model for brittle granular materials considering the competition between breakage and dilationFeb 20 2019A constitutive model is presented for brittle granular materials based on a recent reformulation of the breakage mechanics theory. Compared with previous breakage mechanics-based models, the proposed model is improved to capture strain softening towards ... More
Geometric stability of the Coulomb energyJul 08 2014Jul 06 2015The Coulomb energy of a charge that is uniformly distributed on some set is maximized (among sets of given volume) by balls. It is shown here that near-maximizers are close to balls.
Cohomology of One-dimensional Mixed Substitution Tiling SpacesDec 07 2011Mar 06 2012We compute the Cech cohomology with integer coefficients of one-dimensional tiling spaces arising from not just one, but several different substitutions, all acting on the same set of tiles. These calculations involve the introduction of a universal version ... More
Ends of iterated function systemsMar 06 2014Guided by classical concepts, we define the notion of \emph{ends} of an iterated function system and prove that the number of ends is an upper bound for the number of nondegenerate components of its attractor. The remaining isolated points are then linked ... More
Optimal sweepouts of a Riemannian 2-sphereNov 24 2014Jun 25 2016Given a sweepout of a Riemannian 2-sphere which is composed of curves of length less than L, we construct a second sweepout composed of curves of length less than L which are either constant curves or simple curves. This result, and the methods used to ... More
Sums of seven octahedral numbersSep 14 2015Sep 16 2015We show that for a large class of cubic polynomials $f$, every sufficiently large number can be written as a sum of seven positive values of $f$. As a special case, we show that every number greater than $e^{10^7}$ is a sum of seven positive octahedral ... More
General divisor function inequalities and the third cumulantSep 14 2015We extend a lower bound of Munshi on sums over divisors of a number $n$ which are less than a fixed power of $n$ from the squarefree case to the general case. In the process we prove a lower bound on the entropy of a geometric distribution with finite ... More
Beyond primitivity for one-dimensional substitution tiling spacesApr 05 2016We study the topology and dynamics of subshifts and tiling spaces associated to non-primitive substitutions in one dimension. We identify a property of a substitution, which we call tameness, in the presence of which most of the possible pathological ... More
Beyond primitivity for one-dimensional substitution subshifts and tiling spacesApr 05 2016Jul 17 2017We study the topology and dynamics of subshifts and tiling spaces associated to non-primitive substitutions in one dimension. We identify a property of a substitution, which we call tameness, in the presence of which most of the possible pathological ... More
Splitting a contraction of a simple curve traversed $m$ timesOct 12 2015Suppose that $M$ is a $2$-dimensional oriented Riemannian manifold, and let $\gamma$ be a simple closed curve on $M$. Let $m \gamma$ denote the curve formed by tracing $\gamma$ $m$ times. We prove that if $m \gamma$ is contractible through curves of length ... More
High-contrast imager for complex aperture telescopes (HiCAT): 5. first results with segmented-aperture coronagraph and wavefront controlMar 13 2019Segmented telescopes are a possibility to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the complexity of their aperture geometry, due to the central obstruction, support structures and segment ... More
Monotone homotopies and contracting discs on Riemannian surfacesNov 13 2013Oct 05 2016We prove a "gluing" theorem for monotone homotopies; a monotone homotopy is a homotopy through simple contractible closed curves which themselves are pairwise disjoint. We show that two monotone homotopies which have appropriate overlap can be replaced ... More
Existence of minimal hypersurfaces in complete manifolds of finite volumeSep 13 2016We prove that every complete non-compact manifold of finite volume contains a (possibly non-compact) minimal hypersurface of finite volume.
Existence of minimal hypersurfaces in complete manifolds of finite volumeSep 13 2016Nov 11 2016We prove that every complete non-compact manifold of finite volume contains a (possibly non-compact) minimal hypersurface of finite volume.
Converting homotopies to isotopies and dividing homotopies in half in an effective wayNov 04 2013Jan 09 2014We prove two theorems about homotopies of curves on 2-dimensional Riemannian manifolds. We show that, for any epsilon > 0, if two simple closed curves are homotopic through curves of bounded length L, then they are also isotopic through curves of length ... More
Perimeter under multiple Steiner symmetrizationsSep 20 2012Steiner symmetrization along n linearly independent directions transforms every compact subset of R^n into a set of finite perimeter.
The spectrum of large unitarily invariant models with increasingly many spikesMar 29 2019Apr 02 2019In this paper we study random matrix models where the matrices in question contain infinitely many spikes. Recent work has characterized the possible outliers in the spectrum of large deformed unitarily invariant models when the number of spikes in the ... More
Inequalities and higher order convexityAug 26 2011We study the following problem: given n real arguments a1, ..., an and n real weights w1, ..., wn, under what conditions does the inequality w1 f(a1) + w2 f(a2) + ... + wn f(an) >= 0 hold for all functions f with nonnegative kth derivative for some given ... More
Chromatic numbers of directed hypergraphs with no "bad" cyclesJun 03 2018Imagine that you are handed a rule for determining whether a cycle in a digraph is "good" or "bad", based on which edges of the cycle are traversed in the forward direction and which edges are traversed in the backward direction. Can you then construct ... More
Hunting electromagnetic counterparts of gravitational-wave events using the Zwicky Transient FacilityAug 22 2017Detections of coalescing binary black holes by LIGO have opened a new window of transient astronomy. With increasing sensitivity of LIGO and participation of the Virgo detector in Cascina, Italy, we expect to soon detect coalescence of compact binary ... More
The Loudest Event Statistic: General Formulation, Properties and ApplicationsOct 02 2007The use of the loudest observed event to generate statistical statements about rate and strength has become standard in searches for gravitational waves from compact binaries and pulsars. The Bayesian formulation of the method is generalized in this paper ... More
Extracting equation of state parameters from black hole-neutron star mergers: aligned-spin black holes and a preliminary waveform modelMar 25 2013Information about the neutron-star equation of state is encoded in the waveform of a black hole-neutron star system through tidal interactions and the possible tidal disruption of the neutron star. During the inspiral this information depends on the tidal ... More
Quantum Effects in Black Hole InteriorsOct 23 1992The Weyl curvature inside a black hole formed in a generic collapse grows, classically without bound, near to the inner horizon, due to partial absorption and blueshifting of the radiative tail of the collapse. Using a spherical model, we examine how ... More
Sequential decision problems, dependent types and generic solutionsOct 23 2016Mar 22 2017We present a computer-checked generic implementation for solving finite-horizon sequential decision problems. This is a wide class of problems, including inter-temporal optimizations, knapsack, optimal bracketing, scheduling, etc. The implementation can ... More
A Critical Look At Massive Scalar Field CollapseOct 02 1997We present the findings of an investigation of critical behavior in the collapse of spherically symmetric distributions of massive scalar field. Two distinct types of phase transition are observed at the verge of black hole formation and a criterion for ... More
Extracting equation of state parameters from black hole-neutron star mergers. I. Nonspinning black holesSep 15 2011The late inspiral, merger, and ringdown of a black hole-neutron star (BHNS) system can provide information about the neutron-star equation of state (EOS). Candidate EOSs can be approximated by a parametrized piecewise-polytropic EOS above nuclear density, ... More
The Intrinsic Fractions and Radio Properties of Low Ionization Broad Absorption Line QuasarsApr 05 2010Apr 12 2011Low-ionization (MgII, FeII, FeIII) broad absorption line quasars (LoBALs) probe a relatively obscured quasar population, and could be at an early evolutionary stage for quasars. We study the intrinsic fractions of LoBALs using the SDSS, 2MASS, and FIRST ... More
A note on automatic continuityOct 13 2017We present new results regarding automatic continuity, unifying some diagonalization concepts that have been developed over the years. For example, any homomorphism from a completely metrizable topological group to Thompson's group $F$ has open kernel. ... More
Derivative-free optimization of rate parameters of capsid assembly models from bulk in vitro dataJul 07 2015The assembly of virus capsids from free coat proteins proceeds by a complicated cascade of association and dissociation steps, the great majority of which cannot be directly experimentally observed. This has made capsid assembly a rich field for computational ... More
Some anomalous examples of lifting spacesAug 02 2017An inverse limit of a sequence of covering spaces over a given space $X$ is not, in general, a covering space over $X$ but is still a lifting space, i.e. a Hurewicz fibration with unique path lifting property. Of particular interest are inverse limits ... More
Self-affine ManifoldsFeb 12 2014Nov 09 2015This paper studies closed 3-manifolds which are the attractors of a system of finitely many affine contractions that tile $\mathbb{R}^3$. Such attractors are called self-affine tiles. Effective characterization and recognition theorems for these 3-manifolds ... More
2MASS Reveals a Large Intrinsic Fraction of BALQSOsApr 22 2007Sep 18 2007The intrinsic fraction of broad absorption line quasars (BALQSOs) is important in constraining geometric and evolutionary models of quasars. We present the fraction of BALQSOs in 2MASS detected quasars within the SDSS DR3 sample in the redshift range ... More
Archipelago groupsOct 30 2014The classical archipelago is a non-contractible subset of $\mathbb{R}^3$ which is homeomorphic to a disk except at one non-manifold point. Its fundamental group, $\mathcal{A}$, is the quotient of the topologist's product of $\mathbb Z$, the fundamental ... More
Quantitative nullhomotopy and rational homotopy typeNov 10 2016Mar 14 2018In \cite{GrOrang}, Gromov asks the following question: given a nullhomotopic map $f:S^m \to S^n$ of Lipschitz constant $L$, how does the Lipschitz constant of an optimal nullhomotopy of $f$ depend on $L$, $m$, and $n$? We establish that for fixed $m$ ... More
Ergodic properties of folding maps on spheresSep 08 2015Nov 13 2016We consider the trajectories of points on $\mathbb{S}^{d - 1}$ under sequences of certain folding maps associated with reflections. The main result characterizes collections of folding maps that produce dense trajectories. The minimal number of maps in ... More
On Boundary -- Value Problems for the Laplacian in Boundedand in Unbounded Domains Withperforated BoundariesMar 04 2003In the paper we consider boundary -- value problems with rapidly alternating type of boundary conditions, including problems in domains with perforated boundaries. We present the classification of homogenized (limit) problems depending on the ratio of ... More
Dependence of the BALQSO fraction on Radio LuminosityJan 28 2008Jul 01 2008We find that the fraction of classical Broad Absorption Line quasars (BALQSOs) among the FIRST radio sources in the Sloan Data Release 3, is 20.5^{+7.3}_{-5.9}% at the faintest radio powers detected (L_{\rm 1.4 GHz}~10^{32} erg/s), and rapidly drops to ... More
On the First Homology of Peano ContinuaSep 23 2015We show that the first homology group of a locally connected compact metric space is either uncountable or is finitely generated. This is related to Shelah's well-known result which shows that the fundamental group of such a space satisfies a similar ... More
Geometry of compact lifting spacesJan 07 2019We study a natural generalization of inverse systems of finite regular covering spaces. A limit of such a system is a fibration whose fibres are profinite topological groups. However, as shown in a previous paper (Conner-Herfort-Pavesic: Some anomalous ... More
Host Galaxies Catalog Used in LIGO Searches for Compact Binary Coalescence EventsJun 09 2007Feb 07 2008An up-to-date catalog of nearby galaxies considered as hosts of binary compact objects is provided with complete information about sky position, distance, extinction-corrected blue luminosity and error estimates. With our current understanding of binary ... More
Snowflake geometry in CAT(0) groupsFeb 26 2016Aug 15 2017We construct CAT(0) groups containing subgroups whose Dehn functions are given by $x^s$, for a dense set of numbers $s \in [2, \infty)$. This significantly expands the known geometric behavior of subgroups of CAT(0) groups.
Violation of Bell's inequality in fluid mechanicsMay 28 2013We show that a classical fluid mechanical system can violate Bell's inequality because the fluid motion is correlated over large distances.
Lattices in finite real reflection groupsJan 28 2005For a finite real reflection group $W$ with Coxeter element $\gamma$ we give a uniform proof that the closed interval, $[I, \gamma]$ forms a lattice in the partial order on $W$ induced by reflection length. The proof involves the construction of a simplicial ... More
From Permutahedron to AssociahedronApr 15 2008For each finite real reflection group $W$, we identify a copy of the type-$W$ simplicial generalised associahedron inside the corresponding simplicial permutahedron. This defines a bijection between the facets of the generalised associahedron and the ... More
Braids, posets and orthoschemesSep 25 2009In this article we study the curvature properties of the order complex of a graded poset under a metric that we call the ``orthoscheme metric''. In addition to other results, we characterize which rank 4 posets have CAT(0) orthoscheme complexes and by ... More
Dehn functions of subgroups of right-angled Artin groupsSep 12 2017We show that for each positive integer $k$ there exist right-angled Artin groups containing free-by-cyclic subgroups whose monodromy automorphisms grow as $n^k$. As a consequence we produce examples of right-angled Artin groups containing finitely presented ... More
A fast multigrid-based electromagnetic eigensolver for curved metal boundaries on the Yee meshJan 16 2013For embedded boundary electromagnetics using the Dey-Mittra algorithm, a special grad-div matrix constructed in this work allows use of multigrid methods for efficient inversion of Maxwell's curl-curl matrix. Efficient curl-curl inversions are demonstrated ... More
A More Accurate, Stable, FDTD Algorithm for Electromagnetics in Anisotropic DielectricsDec 19 2012Sep 04 2013A more accurate, stable, finite-difference time-domain (FDTD) algorithm is developed for simulating Maxwell's equations with isotropic or anisotropic dielectric materials. This algorithm is in many cases more accurate than previous algorithms (G. R. Werner ... More
Unsupervised Machine Learning of Open Source Russian Twitter Data Reveals Global Scope and Operational CharacteristicsOct 02 2018We developed and used a collection of statistical methods (unsupervised machine learning) to extract relevant information from a Twitter supplied data set consisting of alleged Russian trolls who (allegedly) attempted to influence the 2016 US Presidential ... More
Factoring euclidean isometriesDec 30 2013Every isometry of a finite dimensional euclidean space is a product of reflections and the minimum length of a reflection factorization defines a metric on its full isometry group. In this article we identify the structure of intervals in this metric ... More
Why quantum computing is hard - and quantum cryptography is not provably secureJan 30 2013Despite high hopes for quantum computation in the 1990s, progress in the past decade has been slow; we still cannot perform computation with more than about three qubits and are no closer to solving problems of real interest than a decade ago. Separately, ... More
Origin and reduction of wakefields in photonic crystal accelerator cavitiesSep 04 2013Sep 09 2013Photonic crystal (PhC) defect cavities that support an accelerating mode tend to trap unwanted higher-order modes (HOMs) corresponding to zero-group-velocity PhC lattice modes at the top of the bandgap. The effect is explained quite generally from photonic ... More
The Eclipsing Cataclysmic Variable Lanning 386: Dwarf Nova, SW Sextantis Star, or Both?Jan 24 2008We present photometry and spectroscopy of the suspected cataclysmic variable (CV) Lanning 386. We confirm that it is a CV, and observe deep eclipses, from which we determine the orbital period Porb to be 0.1640517 +- 0.0000001 d (= 3.94 h). Photometric ... More
A Super-Earth Orbiting the Nearby Sun-like Star HD 1461Dec 14 2009We present precision radial velocity data that reveal a Super-Earth mass planet and two probable additional planets orbiting the bright nearby G0V star HD 1461. Our 12.8 years of Keck HIRES precision radial velocities indicate the presence of a 7.4M_Earth ... More
How well does your sampler really work?Dec 16 2017We present a new data-driven benchmark system to evaluate the performance of new MCMC samplers. Taking inspiration from the COCO benchmark in optimization, we view this task as having critical importance to machine learning and statistics given the rate ... More
Density of isoperimetric spectraDec 04 2008We show that the set of k-dimensional isoperimetric exponents of finitely presented groups is dense in the interval [1, \infty) for k > 1. Hence there is no higher-dimensional analogue of Gromov's gap (1,2) in the isoperimetric spectrum.
Two-dimensional Artin groups with CAT(0) dimension threeDec 13 2000Mar 08 2002We exhibit 3-generator Artin groups which have finite 2-dimensional Eilenberg-Mac Lane spaces, but which do not act properly discontinuously by semi-simple isometries on a 2-dimensional CAT(0) complex. We prove that infinitely many of these groups are ... More
Is Your Load Generator Launching Web Requests in Bunches?Sep 27 2018Feb 14 2019One problem with load test quality, almost always overlooked, is the potential for the load generator's user thread pool to sync up and dispatch queries in bunches rather than independently from each other like real users initiate their requests. A spiky ... More
Why bouncing droplets are a pretty good model of quantum mechanicsJan 16 2014In 2005, Couder, Protiere, Fort and Badouad showed that oil droplets bouncing on a vibrating tray of oil can display nonlocal interactions reminiscent of the particle-wave associations in quantum mechanics; in particular they can move, attract, repel ... More
Maxwell's fluid model of magnetismFeb 20 2015In 1861, Maxwell derived two of his equations of electromagnetism by modelling a magnetic line of force as a `molecular vortex' in a fluid-like medium. Later, in 1980, Berry and colleagues conducted experiments on a `phase vortex', a wave geometry in ... More
Luminous X-ray Flares from Low Mass X-ray Binary Candidates in the Early-Type Galaxy NGC 4697Mar 08 2005We report results of the first search specifically targeting short-timescale X-ray flares from low-mass X-ray binaries in an early-type galaxy. A new method for flare detection is presented. In NGC 4697, the nearest, optically luminous, X-ray faint elliptical ... More
Young Planetary Nebulae: Hubble Space Telescope Imaging and a New Morphological Classification SystemJan 11 2011Using Hubble Space Telescope images of 119 young planetary nebulae, most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system ... More
Generative Modeling with Conditional Autoencoders: Building an Integrated CellApr 28 2017We present a conditional generative model to learn variation in cell and nuclear morphology and the location of subcellular structures from microscopy images. Our model generalizes to a wide range of subcellular localization and allows for a probabilistic ... More
DarkHistory: A code package for calculating modified cosmic ionization and thermal histories with dark matter and other exotic energy injectionsApr 19 2019We present a new public Python package, DarkHistory, for computing the effects of dark matter annihilation and decay on the temperature and ionization history of the early universe. DarkHistory simultaneously solves for the evolution of the free electron ... More
The relative growth of Optical and Radio Quasars in SDSSSep 23 2009We cross-correlate the SDSS DR3 quasar sample with FIRST and the Vestergaard et al. black hole (BH) mass sample to compare the mean accretion histories of optical and radio quasars. We find significant statistical evidence that radio quasars have a higher ... More
Fragmentation in Dusty Low-Metallicity Star Forming HalosSep 16 2013The first stars in the universe, termed Population III, are thought to have been very massive compared to the stars that form in the present epoch. As feedback from the first generation of stars altered the contents of the interstellar medium, the universe ... More
Chandra Observations of Low Mass X-ray Binaries and Diffuse Gas in the Early-Type Galaxies NGC 4365 and NGC 4382 (M85)Aug 18 2003(Abridged) We used the Chandra X-ray Observatory ACIS S3 to image the X-ray faint elliptical galaxy NGC 4365 and lenticular galaxy NGC 4382. The observations resolve much of the X-ray emission into 99 and 58 sources, respectively, most of which are low-mass ... More
Asymptotics of Eigenvalues and Eigenfunctions for the Laplace Operator in a Domain with Oscillating Boundary. Multiple Eigenvalue CaseDec 26 2006We study the asymptotic behavior of the solutions of a spectral problem for the Laplacian in a domain with rapidly oscillating boundary. We consider the case where the eigenvalue of the limit problem is multiple. We construct the leading terms of the ... More
Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian backgroundJan 13 2012Jan 17 2012We describe a general approach to detection of transient gravitational-wave signals in the presence of non-Gaussian background noise. We prove that under quite general conditions, the ratio of the likelihood of observed data to contain a signal to the ... More
Detecting transient gravitational waves in non-Gaussian noise with partially redundant analysis methodsJan 13 2012Apr 25 2012There is a broad class of astrophysical sources that produce detectable, transient, gravitational waves. Some searches for transient gravitational waves are tailored to known features of these sources. Other searches make few assumptions about the sources. ... More
Education and Outreach for the Pierre Auger ObservatoryJul 25 2007The scale and scope of the physics studied at the Auger Observatory offer significant opportunities for original outreach work. Education, outreach, and public relations of the Auger collaboration are coordinated in a task of its own whose goals are to ... More
Chandra Observations of Diffuse Gas and Luminous X-ray Sources Around the X-ray Bright Elliptical NGC 1600Aug 23 2004(Abridged) We observed the X-ray bright E3 galaxy NGC 1600 and nearby group members with the Chandra X-ray Observatory ACIS S3. Unresolved emission dominates the observation; however, we resolved some emission into 71 sources, most of which are low-mass ... More
Quantitative null-cobordismOct 16 2016Jul 24 2017For a given null-cobordant Riemannian $n$-manifold, how does the minimal geometric complexity of a null-cobordism depend on the geometric complexity of the manifold? In [Gro99], Gromov conjectured that this dependence should be linear. We show that it ... More
Investigation of the Vertical Movement of an Isothermal Line at the Density Maximum in H2O and D2OMar 05 2008We studied the cooling of a column of water, primarily in a freezer, and analyzed the development and movement of an isothermal line at ~4 degC in H2O and ~11 degC in D2O. Our experiments show that the vertical velocity of the symmetrical isothermal line ... More
Quantum optical neural networksAug 29 2018Sep 20 2018Physically motivated quantum algorithms for specific near-term quantum hardware will likely be the next frontier in quantum information science. Here, we show how many of the features of neural networks for machine learning can naturally be mapped into ... More
Area of convex disksJan 23 2017This paper considers metric balls $B(p,R)$ in two dimensional Riemannian manifolds when $R$ is less than half the convexity radius. We prove that $Area(B(p,R)) \geq \frac{8}{\pi}R^2$. This inequality has long been conjectured for $R$ less than half the ... More
MLtuner: System Support for Automatic Machine Learning TuningMar 20 2018MLtuner automatically tunes settings for training tunables (such as the learning rate, the momentum, the mini-batch size, and the data staleness bound) that have a significant impact on large-scale machine learning (ML) performance. Traditionally, these ... More
Two dimensional heteroclinic attractor in the generalized Lotka-Volterra systemSep 15 2015We study a simple dynamical model exhibiting sequential dynamics. We show that in this model there exist sets of parameter values for which a cyclic chain of saddle equilibria, $O_k$, $k=1, \ldots, p$, have two dimensional unstable manifolds that contain ... More
Computing arithmetic invariants for hyperbolic reflection groupsAug 15 2007We describe a collection of computer scripts written in PARI/GP to compute, for reflection groups determined by finite-volume polyhedra in $\mathbb{H}^3$, the commensurability invariants known as the invariant trace field and invariant quaternion algebra. ... More
The force on a body in active matterOct 27 2015We present a general theory for determining the force (and torque) exerted on a boundary (or body) in active matter. The theory extends the description of passive Brownian colloids to self-propelled active particles and applies for all ratios of the thermal ... More
Direct sampling of optical coherence using quantum interferenceDec 15 2008We describe a detector that measures the mutual coherence of two optical fields directly using quantum interference, free from photon noise of the individual irradiances. Our approach utilizes Raman transition in an atomic system where the state evolution ... More
An efficient adaptive sparse grid collocation method through derivative estimationSep 13 2017Nov 30 2017For uncertainty propagation of highly complex and/or nonlinear problems, one must resort to sample-based non-intrusive approaches [1]. In such cases, minimizing the number of function evaluations required to evaluate the response surface is of paramount ... More
Evolution-Time Dependence in Near-Adiabatic Quantum EvolutionsJan 12 2018May 03 2018We expand upon the standard quantum adiabatic theorem, examining the time-dependence of quantum evolution in the near-adiabatic limit. We examine a Hamiltonian that evolves along some fixed trajectory from $\hat{H}_0$ to $\hat{H}_1$ in a total evolution-time ... More
Anti-Swarming: Structure and Dynamics of Repulsive Chemically Active ParticlesNov 04 2017Chemically active Brownian particles with surface catalytic reactions may repel each other due to diffusiophoretic interactions in the reaction and product concentration fields. The system behavior can be described by a `chemical' coupling parameter $\Gamma_c$ ... More
Short-time transport properties of bidisperse suspensions and porous media: a Stokesian Dynamics studyDec 28 2014We present a comprehensive computational study of the short-time transport properties of bidisperse neutral colloidal suspensions and the corresponding porous media. Our study covers bidisperse particle size ratios up to $4$, and total volume fractions ... More
Formal Concept Analysis with Many-sorted AttributesOct 12 2018This paper unites two problem-solving traditions in computer science: (1) constraint-based reasoning, and (2) formal concept analysis. For basic definitions and properties of networks of constraints, we follow the foundational approach of Montanari and ... More
The curved kinetic boundary layer of active matterNov 04 2017The finite reorient-time of swimmers leads to a finite run length $\ell$ and the kinetic accumulation boundary layer on the microscopic length scale $\delta$ on a non-penetrating wall. That boundary layer is the microscopic origin of the swim pressure, ... More
Orbital periods of cataclysmic variables identified by the SDSS. III. Time-series photometry obtained during the 2004/5 International Time Project on La PalmaFeb 29 2008We present time resolved CCD photometry of 15 cataclysmic variables (CVs) identified by the Sloan Digital Sky Survey (SDSS). The data were obtained as part of the 2004/05 International Time Programme on La Palma. We discuss the morphology of the light ... More