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A dynamical magnetic field accompanying the motion of ferroelectric domain wallsApr 12 2019The recently proposed dynamical multiferroic effect describes the generation of magnetization from temporally varying electric polarization. Here, we show that the effect can lead to a magnetic field at moving ferroelectric domain walls, where the rearrangement ... More

The Aligned z ~ 1 Radio Galaxy 3C 280Oct 03 2003The z~1 radio galaxy 3C280 has a striking rest-frame UV morphology, with multiple line and continuum components precisely aligned with the radio structure, including an obvious semi-circular arc. We explore the nature of these various components by bringing ... More

Deconvolving the Input to Random Abstract Parabolic Systems; A Population Model-Based Approach to Estimating Blood/Breath Alcohol Concentration from Transdermal Alcohol Biosensor DataJul 13 2018The distribution of random parameters in, and the input signal to, a distributed parameter model with unbounded input and output operators for the transdermal transport of ethanol are estimated. The model takes the form of a diffusion equation with the ... More

Non-Hamiltonian actions with isolated fixed pointsOct 09 2015We construct a non-Hamiltonian symplectic circle action on a closed, connected, six-dimensional symplectic manifold with exactly 32 fixed points.

Studies of inflation and dark energy with coupled scalar fieldsFeb 03 2015Currently there is no definitive description for the accelerated expansion of the Universe at both early and late times; we know these two periods as the epochs of inflation and dark energy. Contained within this Thesis are two studies of inflation and ... More

Optical spectroscopy of two overlapping, flux-density-limited samples of radio sources in the North Ecliptic Cap, selected at 38 MHz and 151 MHzMay 27 1999We present the results of optical spectroscopy of two flux-density-limited samples of radio sources selected at frequencies of 38 and 151 MHz in the same region around the North Ecliptic Cap, the 8C-NEC and 7C-III samples respectively. Both samples are ... More

Depth and regularity of monomial ideals via polarization and combinatorial optimizationMar 06 2018Oct 18 2018In this paper we use polarization to study the behavior of the depth and regularity of a monomial ideal $I$, locally at a variable $x_i$, when we lower the degree of all the highest powers of the variable $x_i$ occurring in the minimal generating set ... More

Depths of Powers of the Edge Ideal of a TreeAug 04 2009Lower bounds are given for the depths of R/I^t for t at least one when I is the edge ideal of a tree or forest. The bounds are given in terms of the diameter of the tree, or in case of a forest, the largest diameter of a connected component and the number ... More

The Glueing Construction and Double CategoriesDec 06 2011We introduce Artin-Wraith glueing and locally closed inclusions in double categories. Examples include locales, toposes, topological spaces, categories, and posets. With appropriate assumptions, we show that locally closed inclusions are exponentiable, ... More

Exponentiability via Double CategoriesDec 06 2011Apr 24 2012We use double categories to obtain a single theorem characterizing certain exponentiable morphisms of small categories, topological spaces, locales, and posets.

Si-compatible candidates for high-K dielectrics with the Pbnm perovskite structureMay 16 2010Aug 03 2010We analyze both experimentally (where possible) and theoretically from first-principles the dielectric tensor components and crystal structure of five classes of Pbnm perovskites. All of these materials are believed to be stable on silicon and are therefore ... More

Yarkovsky Drift Detections for 159 Near-Earth AsteroidsAug 18 2017Aug 26 2017The Yarkovsky effect is a thermal process acting upon the orbits of small celestial bodies, which can cause these orbits to slowly expand or contract with time. The effect is subtle -- typical drift rates lie near $10^{-4}$ au/My for a $\sim$1 km diameter ... More

On nearly semifree circle actionsMar 22 2005Recall that an effective circle action is semifree if the stabilizer subgroup of each point is connected. We show that if $(M, \om)$ is a coadjoint orbit of a compact Lie group $G$ then every element of $\pi_1(G)$ may be represented by a semifree $S^1$-action. ... More

Two globally convergent nonmonotone trust-region methods for unconstrained optimizationJan 09 2015This paper addresses some trust-region methods equipped with nonmonotone strategies for solving nonlinear unconstrained optimization problems. More specifically, the importance of using nonmonotone techniques in nonlinear optimization is motivated, then ... More

Reduction of twisted generalized Kähler structureOct 01 2005Oct 11 2005We show that our earlier work in \cite{LT05} extends to the twisted case, that is, we defined a notion of moment map and reduction in both twisted generalized complex geometry and twisted generalized K\"ahler geometry.

Estimating the Distribution of Random Parameters in a Diffusion Equation Forward Model for a Transdermal Alcohol BiosensorAug 13 2018We estimate the distribution of random parameters in a distributed parameter model with unbounded input and output for the transdermal transport of ethanol in humans. The model takes the form of a diffusion equation with the input being the blood alcohol ... More

Effect of time of day on reward circuitry: Further thoughts on methods, prompted by Steel et al 2018Nov 14 2018Dec 11 2018The interplay between circadian and reward function is well understood in animal models, and is of growing interest as an aetiological explanation in psychopathologies. Circadian modulation of reward function has been demonstrated in human behavioural ... More

Complete invariants for Hamiltonian torus actions with two dimensional quotientsFeb 18 2002Dec 14 2003We study torus actions on symplectic manifolds with proper moment maps in the case that each reduced space is two-dimensional. We provide a complete set of invariants for such spaces. Our proof uses sheaves of groupoids of Hamiltonian spaces.

Topology of complexity one quotientsOct 02 2018We describe of the topology of the geometric quotients of 2n dimensional compact connected symplectic manifolds with n-1 dimensional torus actions. When the isotropy weights at each fixed point are in general position, the quotient is homeomorphic to ... More

Processes that break baryon number by two units and the Majorana nature of the neutrinoAug 15 2018Jan 31 2019We employ the simplest possible models of scalar-fermion interactions that are consistent with the gauge symmetries of the Standard Model and permit no proton decay to analyze the connections possible among processes that break baryon number by two units. ... More

No positive cone in a free product is regularSep 20 2016Nov 15 2017We show that there exists no left order on the free product of two nontrivial, finitely generated, left-orderable groups such that the corresponding positive cone is represented by a regular language. Since there are orders on free groups of rank at least ... More

A counterexample to the Bernhard-Jablan unknotting conjectureMay 17 2017Dec 31 2017We show that there is a knot satisfying the property that for each minimal crossing number diagram of the knot and each single crossing of the diagram, changing the crossing results in a diagram for a knot whose unknotting number is at least that of the ... More

Charge density wave behavior and order-disorder in the antiferromagnetic metallic series Eu(Ga_1-xAl_x)_4Apr 05 2018The solid solution Eu(Ga_1-xAl_x)_4 was grown in single crystal form to reveal a rich variety of crystallographic, magnetic, and electronic properties that differ from the isostructural end compounds EuGa_4 and EuAl_4, despite the similar covalent radii ... More

Hamiltonian circle actions on eight dimensional manifolds with minimal fixed setsAug 27 2014Feb 11 2016Consider a Hamiltonian circle action on a closed $8$-dimensional symplectic manifold $M$ with exactly five fixed points, which is the smallest possible fixed set. In their paper, L. Godinho and S. Sabatini show that if $M$ satisfies an extra "positivity ... More

The unstable spectrum of the Navier-Stokes operator in the limit of vanishing viscositySep 23 2005A general class of linear advective PDEs, whose leading order term is of viscous dissipative type, is considered. It is proved that beyond the limit of the essential spectrum of the underlying inviscid operator, the eigenvalues of the viscous operator, ... More

A Lower Bound For Depths of Powers of Edge IdealsSep 24 2014May 20 2015Let $G$ be a graph and let $I$ be the edge ideal of $G$. Our main results in this article provide lower bounds for the depth of the first three powers of $I$ in terms of the diameter of $G$. More precisely, we show that $\depth R/I^t \geq \left\lceil{\frac{d-4t+5}{3}} ... More

Tame Circle ActionsOct 06 2015Sep 07 2017In this paper, we consider Sjamaar's holomorphic slice theorem, the birational equivalence theorem of Guillemin and Sternberg, and a number of important standard constructions that work for Hamiltonian circle actions in both the symplectic category and ... More

Geometric algebras on projective surfacesOct 27 2009Jun 17 2010Let X be a projective surface, let \sigma be an automorphism of X, and let L be a \sigma-ample invertible sheaf on X. We study the properties of a family of subrings, parameterized by geometric data, of the twisted homogeneous coordinate ring B(X, L, ... More

Symmetries in generalized Kähler geometrySep 04 2005We define the notion of a moment map and reduction in both generalized complex geometry and generalized K\"{a}hler geometry. As an application, we give very simple explicit constructions of bi-Hermitian structures on $\C\P^n$, Hirzebruch surfaces, the ... More

G-algebras, twistings, and equivalences of graded categoriesAug 31 2006Jul 23 2007Given Z-graded rings A and B, we study when the categories gr-A and gr-B are equivalent. We relate the Morita-type results of Ahn-Marki and del Rio to the twisting systems introduced by Zhang. Using Z-algebras, we obtain a simple proof of Zhang's main ... More

Rings graded equivalent to the Weyl algebraNov 09 2007Dec 16 2008We consider the first Weyl algebra, A, in the Euler gradation, and completely classify graded rings B that are graded equivalent to A: that is, the categories gr-A and gr-B are equivalent. This includes some surprising examples: in particular, we show ... More

SDSS 1355+0856: A detached white dwarf + M star binary in the period gap discovered by the SWARMS surveyOct 24 2012SDSS 1355+0856 was identified as a hot white dwarf (WD) with a binary companion from time-resolved SDSS spectroscopy as part of the ongoing SWARMS survey. Follow-up observations with the ARC 3.5m telescope and the MMT revealed weak emission lines in the ... More

TRIPPy: Trailed Image Photometry in PythonMar 31 2016Photometry of moving sources typically suffers from reduced signal-to-noise (SNR) or flux measurements biased to incorrect low values through the use of circular apertures. To address this issue we present the software package, TRIPPy: TRailed Image Photometry ... More

Discovery and Vetting of Exoplanets I: Benchmarking K2 Vetting ToolsJan 22 2019We have adapted the algorithmic tools developed during the Kepler mission to vet the quality of transit-like signals for use on the K2 mission data. Using the four sets of publicly-available lightcurves on MAST, we produced a uniformly-vetted catalog ... More

Regina Lectures on Fat PointsOct 14 2013These notes are a record of lectures given in the Workshop on Connections Between Algebra and Geometry at the University of Regina, May 29--June 1, 2012. The lectures were meant as an introduction to current research problems related to fat points for ... More

Spatially Localized Atlas Network Tiles Enables 3D Whole Brain Segmentation from Limited DataJun 01 2018Jun 05 2018Whole brain segmentation on a structural magnetic resonance imaging (MRI) is essential in non-invasive investigation for neuroanatomy. Historically, multi-atlas segmentation (MAS) has been regarded as the de facto standard method for whole brain segmentation. ... More

3D Whole Brain Segmentation using Spatially Localized Atlas Network TilesMar 28 2019Detailed whole brain segmentation is an essential quantitative technique, which provides a non-invasive way of measuring brain regions from a structural magnetic resonance imaging (MRI). Recently, deep convolution neural network (CNN) has been applied ... More

A Spitzer Study of Comets 2P/Encke, 67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT)Jul 18 2006We present infrared images and spectra of comets 2P/Encke, 67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT) as part of a larger program to observe comets inside of 5 AU from the sun with the Spitzer Space Telescope. The nucleus of comet 2P/Encke ... More

Edge ideals: algebraic and combinatorial propertiesDec 24 2010Mar 29 2011Let C be a clutter and let I(C) be its edge ideal. This is a survey paper on the algebraic and combinatorial properties of R/I(C) and C, respectively. We give a criterion to estimate the regularity of R/I(C) and apply this criterion to give new proofs ... More

HNN extensions and stackable groupsMay 19 2016Stackability for finitely presented groups consists of a dynamical system that iteratively moves paths into a maximal tree in the Cayley graph. Combining with formal language theoretic restrictions yields auto- or algorithmic stackability, which implies ... More

Maximal Hamiltonian tori for polygon spacesJul 06 2002We study the poset of Hamiltonian tori for polygon spaces. We determine some maximal elements and give examples where maximal Hamiltonian tori are not all of the same dimension.

A First and Second Law for Nonequilibrium Thermodynamics: Maximum Entropy Derivation of the Fluctuation-Dissipation Theorem and Entropy Production FunctionalsMay 27 2011A theory for non-equilibrium systems is derived from a maximum entropy approach similar in spirit to the equilibrium theory given by Gibbs. Requiring Hamilton's principle of stationary action to be satisfied on average during a trajectory, we add constraints ... More

Nonlinear Instability for the Critically Dissipative Quasi-Geostrophic EquationMar 08 2009Apr 23 2009We prove that linear instability implies non-linear instability in the energy norm for the critically dissipative quasi-geostrophic equation.

Switching the structural force in ionic liquid-solvent mixtures by varying compositionFeb 10 2017Feb 13 2017The structure and interactions in electrolytes at high concentration have implications from energy storage to biomolecular interactions. However many experimental observations are yet to be explained in these mixtures, which are far beyond the regime ... More

Representation, Justification and Explanation in a Value Driven Agent: An Argumentation-Based ApproachDec 13 2018For an autonomous system, the ability to justify and explain its decision making is crucial to improve its transparency and trustworthiness. This paper proposes an argumentation-based approach to represent, justify and explain the decision making of a ... More

Group gradings on simple Lie algebras of type A in positive characteristicJun 07 2007In this paper we consider gradings by a finite abelian group $G$ on the Lie algebra $\mathfrak{sl}_n(F)$ over an algebraically closed field $F$ of characteristic different from 2 and not dividing $n$.

A Constant Introduction of Additional Food Does Not Yield Pest Eradication in Finite TimeOct 01 2018Biological control, the use of predators and pathogens to control target pests, is a promising alternative to chemical control. It is hypothesized that the introduced predators efficacy can be boosted by providing them with an additional food source. ... More

Spanning Trees and Mahler MeasureFeb 08 2016The complexity of a finite connected graph is its number of spanning trees; for a non-connected graph it is the product of complexities of its connected components. If $G$ is an infinite graph with cofinite free ${\mathbb Z}^d$-symmetry, then the logarithmic ... More

Twisted Alexander Invariants of Twisted LinksFeb 07 2012Let L be an oriented (d+1)-component link in the 3-sphere, and let L(q) be the d-component link in a homology 3-sphere that results from performing 1/q-surgery on the last component. Results about the Alexander polynomial and twisted Alexander polynomials ... More

An Algorithmic Approach to Forecasting Rare Violent Events: An Illustration Based in IPV PerpetrationMar 02 2019Mass violence, almost no matter how defined, is (thankfully) rare. Rare events are very difficult to study in a systematic manner. Standard statistical procedures can fail badly and usefully accurate forecasts of rare events often are little more than ... More

Threshold graph limits and random threshold graphsAug 17 2009We study the limit theory of large threshold graphs and apply this to a variety of models for random threshold graphs. The results give a nice set of examples for the emerging theory of graph limits.

On Eigenvalues of Free Group EndomorphismsJun 21 2012Jun 25 2012Let \phi be an endomorphism of a finitely generated free group F, and let H be a finite-index subgroup of F that is invariant under \phi. The nonzero eigenvalues of \phi are contained in the eigenvalues of \phi restricted to H.

Twisting Alexander Invariants with Periodic RepresentationsJun 21 2010Dec 21 2010Twisted Alexander invariants have been defined for any knot and linear representation of its group. The invariants are generalized for any periodic representation of the commutator subgroup of the knot group. Properties of the new twisted invariants are ... More

Interval graph limitsFeb 14 2011We work out the graph limit theory for dense interval graphs. The theory developed departs from the usual description of a graph limit as a symmetric function $W(x,y)$ on the unit square, with $x$ and $y$ uniform on the interval $(0,1)$. Instead, we fix ... More

Trapping Penguins with Entangled B MesonsSep 24 2014Jan 12 2016The first direct observation of time-reversal (T) violation in the $B\bar{B}$ system has been reported by the BaBar collaboration, employing the method of Ba$\tilde {\rm n}\!$uls and Bernab\'eu. Given this, we generalize their analysis of the time-dependent ... More

$FSZ$-groups and Frobenius-Schur Indicators of Quantum DoublesAug 21 2012We study the higher Frobenius-Schur indicators of the representations of the Drinfel'd double of a finite group G, in particular the question as to when all the indicators are integers. This turns out to be an interesting group-theoretic question. We ... More

Cohen-Macaulay, Shellable and unmixed clutters with a perfect matching of König typeAug 22 2007Nov 06 2007Let $\mathcal{C}$ be a clutter with a perfect matching $e_1,...,e_g$ of K\"onig type and let $\Delta_\mathcal{C}$ be the Stanley-Reisner complex of the edge ideal of $\mathcal{C}$. If all c-minors of $\mathcal{C}$ have a free vertex and $\mathcal{C}$ ... More

Hopf Powers and Orders for Some Bismash ProductsMay 21 2004The Hopf order of an element $h$ of a Hopf algebra $H$ is the least $n$ such that the $n$-th Hopf power of $h$ is trivial. For some bismash product Hopf algebras obtained from factorizable groups (including Drinfeld doubles of some groups) we compute ... More

Virtual Genus of Satellite LinksFeb 01 2013The virtual genus of a virtual satellite link is equal to that of its companion.

The Alpha Problem & Line Count ConfigurationsDec 15 2013Mar 30 2014Motivated by the work of Chudnovsky and the Eisenbud-Mazur Conjecture on evolutions, Harbourne and Huneke give a series of conjectures that relate symbolic and regular powers of ideals of fat points in $\mathbb P^n$. The conjectures involve both containment ... More

Initially regular sequences and depths of idealsOct 02 2018For an arbitrary ideal $I$ in a polynomial ring $R$ and any term order, we define a new notion of initially regular sequences on $R/I$. These sequences share properties with regular sequences, and are relatively easy to construct using information obtained ... More

Ideals in the enveloping algebra of the positive Witt algebraOct 27 2017Let $W_+$ be the positive Witt algebra, which has a $C$-basis $\{e_n: n \in Z_{\geq 1}\}$, with Lie bracket $[ e_i, e_j] = (j-i) e_{i+j}$. We study the two-sided ideal structure of the universal enveloping algebra $U(W_+)$ of $W_+$. We show that if $I$ ... More

A Class of Eccentric Binaries with Dynamic Tidal Distortions Discovered with KeplerMar 27 2012We have discovered a class of eccentric binary systems within the Kepler data archive that have dynamic tidal distortions and tidally-induced pulsations. Each has a uniquely shaped light curve that is characterized by periodic brightening or variability ... More

Horseshoes in multidimensional scaling and local kernel methodsNov 10 2008Classical multidimensional scaling (MDS) is a method for visualizing high-dimensional point clouds by mapping to low-dimensional Euclidean space. This mapping is defined in terms of eigenfunctions of a matrix of interpoint dissimilarities. In this paper ... More

Computing Severi Degrees with Long-edge GraphsMar 21 2013Nov 03 2013We study a class of graphs with finitely many edges in order to understand the nature of the formal logarithm of the generating series for Severi degrees in elementary combinatorial terms. These graphs are related to floor diagrams associated to plane ... More

Algorithms and topology for Cayley graphs of groupsJul 18 2013Autostackability for finitely generated groups is defined via a topological property of the associated Cayley graph which can be encoded in a finite state automaton. Autostackable groups have solvable word problem and an effective inductive procedure ... More

Containment results for ideals of various configurations of points in P^NSep 09 2011Jun 16 2013Guided by evidence coming from a few key examples and attempting to unify previous work of Chudnovsky, Esnault-Viehweg, Eisenbud-Mazur, Ein-Lazarsfeld-Smith, Hochster-Huneke and Bocci-Harbourne, Harbourne and Huneke recently formulated a series of conjectures ... More

Knots Connected by Wide RibbonsAug 01 2018A ribbon is, intuitively, a smooth mapping of an annulus $S^1 \times I$ in 3-space having constant width $\varepsilon$. This can be formalized as a triple $(x,\varepsilon, \mathbf{u})$ where $x$ is smooth curve in 3-space and $\mathbf{u}$ is a unit vector ... More

Tangles and links: a view with treesOct 30 2017Mar 02 2018A result about spanning forests for graphs yields a short proof of Krebes's theorem concerning embedded tangles in links.

Graph complexity and Mahler measureJan 21 2017The (torsion) complexity of a finite edge-weighted graph is defined to be the order of the torsion subgroup of the abelian group presented by its Laplacian matrix. When G is d-periodic (i.e., G has a free action of the rank-d free abelian group by graph ... More

Decoding dynamic brain patterns from evoked responses: A tutorial on multivariate pattern analysis applied to time-series neuroimaging dataJun 09 2016Multivariate pattern analysis (MVPA) or brain decoding methods have become standard practice in analysing fMRI data. Although decoding methods have been extensively applied in Brain Computing Interfaces (BCI), these methods have only recently been applied ... More

Micro-Randomized Trials in mHealthApr 01 2015The use and development of mobile interventions is experiencing rapid growth. In "just-in-time" mobile interventions, treatments are provided via a mobile device that are intended to help an individual make healthy decisions" in the moment," and thus ... More

Approximate word matches between two random sequencesJan 21 2008Given two sequences over a finite alphabet $\mathcal{L}$, the $D_2$ statistic is the number of $m$-letter word matches between the two sequences. This statistic is used in bioinformatics for expressed sequence tag database searches. Here we study a generalization ... More

Knot Groups with Many KillersSep 17 2009The group of any nontrivial torus knot, hyperbolic 2-bridge knot, or hyperbolic knot with unknotting number one contains infinitely many elements, none the automorphic image of another, such that each normally generates the group.

Stable Prediction across Unknown EnvironmentsJun 16 2018Jul 10 2018In many important machine learning applications, the training distribution used to learn a probabilistic classifier differs from the testing distribution on which the classifier will be used to make predictions. Traditional methods correct the distribution ... More

Estimating Heterogeneous Consumer Preferences for Restaurants and Travel Time Using Mobile Location DataJan 22 2018This paper analyzes consumer choices over lunchtime restaurants using data from a sample of several thousand anonymous mobile phone users in the San Francisco Bay Area. The data is used to identify users' approximate typical morning location, as well ... More

The Triple Helix of University-Industry-Government Relations at the Country Level, and Its Dynamic Evolution under the Pressures of GlobalizationSep 06 2012Jan 03 2013Using data from the Web of Science (WoS), we analyze the mutual information among university, industrial, and governmental addresses (U-I-G) at the country level for a number of countries. The dynamic evolution of the Triple Helix can thus be compared ... More

Col-OSSOS: The Colours of the Outer Solar System Origins SurveySep 22 2018Apr 12 2019The Colours of the Outer Solar System Origins Survey (Col-OSSOS) is acquiring near-simultaneous $g$, $r$, and $J$ photometry of unprecedented precision with the Gemini North Telescope, targeting nearly a hundred trans-Neptunian objects (TNOs) brighter ... More

Twelve Decades: Probing the Interstellar Medium from kiloparsec to sub-AU scalesMar 18 2019After a decade of great progress in understanding gas flow into, out of, and through the Milky Way, we are poised to merge observations with simulations to build a comprehensive picture of the multi-scale magnetized interstellar medium (ISM). These insights ... More

Pathway to the PiezoElectronic Transduction Logic DeviceMar 25 2015The information age challenges computer technology to process an exponentially increasing computational load on a limited energy budget - a requirement that demands an exponential reduction in energy per operation. In digital logic circuits, the switching ... More

High-Dimensional Density Estimation via SCA: An Example in the Modelling of Hurricane TracksJul 01 2009We present nonparametric techniques for constructing and verifying density estimates from high-dimensional data whose irregular dependence structure cannot be modelled by parametric multivariate distributions. A low-dimensional representation of the data ... More

Conjugacy languages in groupsJan 28 2014We study the regularity of several languages derived from conjugacy classes in a finitely generated group G for a variety of examples including word hyperbolic, virtually abelian, Artin, and Garside groups. We also determine the rationality of the growth ... More

On a Dynamical Mordell-Lang Conjecture for Coherent SheavesNov 17 2016May 05 2017We introduce a dynamical Mordell-Lang-type conjecture for coherent sheaves. When the sheaves are structure sheaves of closed subschemes, our conjecture becomes a statement about unlikely intersections. We prove an analogue of this conjecture for affinoid ... More

Vertex-Colored Graphs, Bicycle Spaces and Mahler MeasureAug 27 2014Oct 13 2015The space C of conservative vertex colorings (over a field F) of a countable, locally finite graph G is introduced. The subspace of based colorings is shown to be isomorphic to the bicycle space of the graph. For graphs G with a free Z^d-action by automorphisms, ... More

An Optimization-Based Sum-of-Squares Approach to Vizing's ConjectureJan 29 2019Feb 04 2019Vizing's conjecture (open since 1968) relates the sizes of dominating sets in two graphs to the size of a dominating set in their Cartesian product graph. In this paper, we formulate Vizing's conjecture itself as a Positivstellensatz existence question. ... More

All planetesimals born near the Kuiper Belt formed as binariesMay 01 2017The cold classical Kuiper belt objects have low inclinations and eccentricities and are the only Kuiper belt population suspected to have formed in situ. Compared with the dynamically excited populations, which exhibit a broad range of colours and a low ... More

The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud observed with IRAC and MIPSFeb 25 2014We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70 and 160 micron observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 sq-deg with IRAC ... More

Division and the Giambelli IdentityApr 24 2005Given two polynomials f(x) and g(x), we extend the formula expressing the remainder in terms of the roots of these two polynomials to the case where f(x) is a Laurent polynomial. This allows us to give new expressions of a Schur function, which generalize ... More

Associated primes of powers of edge idealsMar 04 2011May 20 2011Let G be a graph and let I be its edge ideal. Our main result shows that the sets of associated primes of the powers of I form an ascending chain. It is known that the sets of associated primes of I(i) and intcl(I(i)) stabilize for large i, where "intcl" ... More

Effect of transitions in the Planck mass during inflation on primordial power spectraJun 20 2014Oct 23 2014We study the effect of sudden transitions in the effective Planck mass during inflation on primordial power spectra. Specifically, we consider models in which this variation results from the non-minimal coupling of a Brans-Dicke type scalar field. We ... More

Assessing Time-Varying Causal Effect Moderation in Mobile HealthJan 03 2016Aug 17 2016In mobile health interventions aimed at behavior change and maintenance, treatments are provided in real time to manage current or impending high risk situations or promote healthy behaviors in near real time. Currently there is great scientific interest ... More

CH 3 GHz Observations of the Galactic CenterAug 24 2005A 3 $\times$ 3 map of the Galactic Center was made at 9$\arcmin$ resolution and 10$\arcmin$ spacing in the CH $^2\Pi_{1/2}$, J=1/2, F=1-1 transition at 3335 MHz. The CH emission shows a velocity extent that is nearly that of the CO(1-0) line, but the ... More

On a singular incompressible porous media equationMar 05 2012May 15 2012In this paper we study a singularly modified version of the incompressible porous media equation. We investigate the implications for the local well-posedness of the equations by modifying, with a fractional derivative, the constitutive relation between ... More

Safely Abstracting Memory LayoutsJan 23 2019Modern architectures require applications to make effective use of caches to achieve high performance and hide memory latency. This in turn requires careful consideration of placement of data in memory to exploit spatial locality, leverage hardware prefetching ... More

Autostackability of Thompson's group $F$Nov 28 2018The word problem for Thompson's group $F$ has a solution, but it remains unknown whether $F$ is automatic or has a finite or regular convergent (terminating and confluent) rewriting system. We show that the group $F$ admits a natural extension of these ... More

Observational prospects for gravitational waves from hidden or dark chiral phase transitionsApr 16 2019We study the gravitational wave (GW) signature of first-order chiral phase transitions ($\chi$PT) in strongly interacting hidden or dark sectors. We do so using several effective models in order to reliably capture the relevant non-perturbative dynamics. ... More

Flint for Safer Smart ContractsApr 13 2019The Ethereum blockchain platform supports the execution of decentralised applications or smart contracts. These typically hold and transfer digital currency to other parties on the platform; however, they have been subject to numerous attacks due to the ... More

Invariants of Links in Thickened SurfacesApr 17 2013A group invariant for links in thickened closed orientable surfaces is studied. Associated polynomial invariants are defined. The group detects nontriviality of a virtual link and determines its virtual genus.

Hosts and Alignment Effect in 0.5 < z < 1 radio sourcesSep 11 1998R- and I- band images with good seeing at the NOT of the hosts of a sample of 7C radio galaxies at z ~ 0.7 (with mean radio flux 20 times fainter than the 3C sample) show some evidence of radio-optical alignment. A quantitative analysis of the alignment ... More

EmptyHeaded: A Relational Engine for Graph ProcessingMar 09 2015Jan 05 2017There are two types of high-performance graph processing engines: low- and high-level engines. Low-level engines (Galois, PowerGraph, Snap) provide optimized data structures and computation models but require users to write low-level imperative code, ... More