Results for "Graham M. Harper"

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Science with an ngVLA: Stellar Activity on Red Giant and Supergiant Stars: Mass Loss and the Evolution of the Stellar DynamoOct 22 2018In this Chapter we examine the role of the ngVLA to further our understanding of the different manifestations of convective or turbulence-driven stellar activity on red giant and supergiant stars. The combination of high spatial resolution and high sensitivity ... More
Astro2020: Molecular Masers as Probes of the Dynamic Atmospheres of Dying StarsMar 13 2019More than half of the dust and heavy element enrichment in galaxies originates from the winds and outflows of evolved, low-to-intermediate mass stars on the asymptotic giant branch (AGB). However, numerous details of the physics of late-stage stellar ... More
Astro2020: Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss through Radio Wavelength ImagingMar 13 2019During the late phases of evolution, low-to-intermediate mass stars like our Sun undergo periods of extensive mass loss, returning up to 80% of their initial mass to the interstellar medium. This mass loss profoundly affects the stellar evolutionary history, ... More
Multi-wavelength Radio Continuum Emission Studies of Dust-free Red GiantsSep 03 2013Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths however, and previous observations ... More
CARMA CO(J = 2 - 1) Observations of the Circumstellar Envelope of BetelgeuseJun 19 2012We report radio interferometric observations of the 12C16O 1.3 mm J = 2-1 emission line in the circumstellar envelope of the M supergiant Alpha Ori and have detected and separated both the S1 and S2 flow components for the first time. Observations were ... More
Temporal Evolution of the Size and Temperature of Betelgeuse's Extended AtmosphereJun 24 2015We use the Very Large Array (VLA) in the A configuration with the Pie Town (PT) Very Long Baseline Array (VLBA) antenna to spatially resolve the extended atmosphere of Betelgeuse over multiple epochs at 0.7, 1.3, 2.0, 3.5, and 6.1 cm. The extended atmosphere ... More
MUSE CSP: An Extension to the Constraint Satisfaction ProblemNov 01 1996This paper describes an extension to the constraint satisfaction problem (CSP) called MUSE CSP (MUltiply SEgmented Constraint Satisfaction Problem). This extension is especially useful for those problems which segment into multiple sets of partially shared ... More
The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and AbsorptionApr 04 2011We exploit the high sensitivity and moderate spectral resolution of the $HST$-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present ... More
Mass Transport Processes and their Roles in the Formation, Structure, and Evolution of Stars and Stellar SystemsMar 13 2009We summarize some of the compelling new scientific opportunities for understanding stars and stellar systems that can be enabled by sub-mas angular resolution, UV/Optical spectral imaging observations, which can reveal the details of the many dynamic ... More
Approximate Convex Hulls: sketching the convex hull using curvatureFeb 27 2017Jun 14 2017Convex hulls are fundamental objects in computational geometry. In moderate dimensions or for large numbers of vertices, computing the convex hull can be impractical due to the computational complexity of convex hull algorithms. In this article we approximate ... More
On instanton homology of corks W_nApr 18 2013We consider a family of corks, denoted $W_n$, constructed by Akbulut and Yasui. Each cork gives rise to an exotic structure on a smooth 4-manifold via a twist $\tau$ on its boundary $\Sigma_n = \partial W_n$. We compute the instanton Floer homology of ... More
Entropy Rates of the Multidimensional Moran Processes and GeneralizationsJan 13 2014The interrelationships of the fundamental biological processes natural selection, mutation, and stochastic drift are quantified by the entropy rate of Moran processes with mutation, measuring the long-run variation of a Markov process. The entropy rate ... More
A Population-centric Approach to the Beauty Contest GameMay 07 2010Dec 13 2014An population-centric analysis for a version of the p-beauty contest game is given for the two-player, finite population, and infinite population cases. Winning strategies are characterized in terms of iterative thinking relative to the population. To ... More
The Inherent Randomness of Evolving PopulationsMar 08 2013Mar 27 2013The entropy rates of the Wright-Fisher process, the Moran process, and generalizations are computed and used to compare these processes and their dependence on standard evolutionary parameters. Entropy rates are measures of the variation dependent on ... More
Escort Evolutionary Game TheoryNov 09 2009Feb 24 2012A family of replicator-like dynamics, called the escort replicator equation, is constructed using information-geometric concepts and generalized information entropies and diverenges from statistical thermodynamics. Lyapunov functions and escort generalizations ... More
Fundamental Stellar Properties from Optical InterferometryDec 06 2010High-resolution observations by visible and near-infrared interferometers of both single stars and binaries have made significant contributions to the foundations that underpin many aspects of our knowledge of stellar structure and evolution for cool ... More
Optimizing the domain wall fermion Dirac operator using the R-Stream source-to-source compilerDec 04 2015The application of the Dirac operator on a spinor field, the Dslash operation, is the most computation-intensive part of the lattice QCD simulations. It is often the key kernel to optimize to achieve maximum performance on various platforms. Here we report ... More
A novel approach for using programming exercises in electromagnetism courseworkJul 01 2017While there exists a significant number of web interactives for introductory physics, students are almost never shown the computer code that generates these interactives even when the physics parts of these programs are relatively simple. Building off ... More
Metastability in the dilute Ising modelSep 02 2011Consider Glauber dynamics for the Ising model on the hypercubic lattice with a positive magnetic field. Starting from the minus configuration, the system initially settles into a metastable state with negative magnetization. Slowly the system relaxes ... More
Detection of thermal radio emission from a single coronal giantNov 25 2016We report the detection of thermal continuum radio emission from the K0 III coronal giant Pollux ($\beta$ Gem) with the Karl G. Jansky Very Large Array (VLA). The star was detected at 21 and 9 GHz with flux density values of $150\pm21$ and $43\pm8\,\mu$Jy, ... More
Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant StarsJul 26 2016We report on an ultraviolet spectroscopic survey of red giants observed by the Hubble Space Telescope, focusing on spectra of the Mg II h & k lines near 2800 A in order to study stellar chromospheric emission, winds, and astrospheric absorption. We focus ... More
Far-UV Emissions of the Sun in Time: Probing Solar Magnetic Activity and Effects on Evolution of Paleo-Planetary AtmospheresMay 15 2003We present and analyze FUSE observations of six solar analogs. These are single, main-sequence G0-5 strs selected as proxies for the Sun at several stages of its main-sequence lifetime. The emission features in the FUSE 920-1180 A wavelength range allow ... More
A Unified Term for Directed and Undirected Motility in Collective Cell InvasionMar 22 2012In this paper we develop mathematical models for collective cell motility. Initially we develop a model using a linear diffusion-advection type equation and fit the parameters to data from cell motility assays. This approach is helpful in classifying ... More
Graphic Processing Unit Simulation of Axon Growth and Guidance through Cue Diffusion on Massively Parallel ProcessorsMay 13 2014Neural development represents not only an exciting and complex field of study, with ongoing progress, but it also became the epicentre of neuroscience and developmental biology, as it strives to describe the underlying cellular and molecular mechanisms ... More
On geometric quantization of the Dirac magnetic monopoleMar 31 2011Jul 24 2013We give a simple derivation of the spectrum of the Dirac magnetic monopole on a unit sphere based on geometric quantization and the Frobenius reciprocity formula. We also briefly discuss the generalisations of Dirac magnetic monopole to any coadjoint ... More
Constraints on discrete symmetries from anomaly cancellation in compactified superstring theoriesJul 14 1993Compactified string theories give rise to discrete symmetries which are essential if they are to provide a realistic low energy theory. We find that in a class of four dimensional string theories these symmetries are constrained by similar conditions ... More
Computational Higher Type Theory II: Dependent Cubical RealizabilityJun 30 2016This is the second in a series of papers extending Martin-L\"{o}f's meaning explanation of dependent type theory to account for higher-dimensional types. We build on the cubical realizability framework for simple types developed in Part I, and extend ... More
The scissors mode from a different perspectiveJan 05 2015Apr 09 2015The scissors mode, a magnetic dipole excitation-mainly orbital is usually discussed in terms of a transition from a J=0^{+} ground state to a J=1^{+} excited state. This is understandable because it follows from the way the experiment is performed-e.g. ... More
Wave functions of the Q.Q interaction in terms of unitary 9-j coefficientsJun 19 2013Mar 20 2015We obtain wave functions for 2 protons and 2 neutrons in the g_{9/2} shell expressed as column vectors with amplitudes D(J_{p},J_{n}). When we use a quadrupole-quadrupole interaction (Q.Q) we get, in many cases, a very strong overlap with wave functions ... More
Normal Form for Edge MetricsJul 05 2012A normal form for edge metrics is derived under the necessary conditions that the metric be normalized and exact. The normal forms for such an edge metric are shown to be in 1-1 correspondence with representative metrics for a reduced conformal infinity ... More
The Chemical Evolution of Fluorine in the Bulge - High-resolution K-band spectra of giants in three fieldsMar 11 2014Possible main formation sites of F in the Universe include AGB stars, the {\nu}-process in Type II SNe, and/or W-R stars. The importance of the W-R stars has theoretically been questioned and they are probably not needed in the modelling of the chemical ... More
A Casson-Lin type invariant for linksJul 06 2009Nov 23 2009We define an integer valued invariant for two-component links in S^3 by counting projective SU(2) representations of the link group having non-trivial second Stiefel-Whitney class. We show that our invariant is, up to sign, the linking number of the link. ... More
Homotopy theory of modules over operads in symmetric spectraDec 31 2007May 15 2014We establish model category structures on algebras and modules over operads in symmetric spectra, and study when a morphism of operads induces a Quillen equivalence between corresponding categories of algebras (resp. modules) over operads.
Parametric Cubical Type TheoryJan 02 2019We exhibit a computational type theory which combines the higher-dimensional structure of cartesian cubical type theory with the internal parametricity primitives of parametric type theory, drawing out the similarities and distinctions between the two ... More
From Radio to X-ray: The Quiescent Atmosphere of the dMe Flare Star EV LacertaeApr 11 2006We report on multi-wavelength observations spanning radio to X-ray wavelengths of the M dwarf flare star, EV Lacertae, probing the characteristics of the outer atmospheric plasma from the upper chromosphere to the corona. We detect the star at a wavelength ... More
Small-N collisional dynamics III: The battle for the realm of not-so-small-NJul 06 2017In this paper, the third in the series, we continue our study of combinatorics in chaotic Newtonian dynamics. We study the chaotic four-body problem in Newtonian gravity assuming finite-sized particles, and we focus on interactions that produce direct ... More
An Updated 2017 Astrometric Solution for BetelgeuseJun 19 2017We provide an update for the astrometric solution for the Type II supernova progenitor Betelgeuse using the revised Hipparcos Intermediate Astrometric Data (HIAD) of van Leeuwen, combined with existing VLA and new e-MERLIN and ALMA positions. The 2007 ... More
Instanton Floer homology for two-component linksJan 22 2010Sep 25 2011For any link of two components in an integral homology sphere, we define an instanton Floer homology whose Euler characteristic is the linking number between the components of the link. We relate this Floer homology to the Kronheimer-Mrowka instanton ... More
The edge-isorperimetric problem on Sierpinski graphsOct 06 2016Some families of graphs, such as the n-cubes and Sierpinski gaskets, are self-similar. In this paper we show how such recursive structure can be used systematically to prove isoperimetric theorems.
Stability of Anomalous Floquet Edge UnitariesSep 20 2016It has recently been shown that periodically driven noninteracting systems may exhibit anomalous chiral edge modes, despite hosting bands with trivial topology. We obtain many-body versions of such drives, corresponding to class A, which exhibit anomalous ... More
The Range of a Steiner OperationAug 27 2016This paper answers a fundamental question in the theory of Steiner operations (StOps) as defined and studied in the monograph, "Global Methods for Combinatorial Isoperimetric Problems" (GMCIP). StOps are morphisms for combinatorial isoperimetric problems, ... More
Guarded Computational Type TheoryApr 24 2018Nakano's later modality can be used to specify and define recursive functions which are causal or synchronous; in concert with a notion of clock variable, it is possible to also capture the broader class of productive (co)programs. Until now, it has been ... More
Homotopy theory of modules over operads and non-Sigma operads in monoidal model categoriesDec 31 2007Jun 03 2009This paper studies the existence of model category structures on algebras and modules over operads in monoidal model categories.
TEXES Observations of M Supergiants: Dynamics and Thermodynamics of Wind AccelerationJun 25 2009We have detected [Fe II] 17.94 um and 24.52 um emission from a sample of M supergiants using TEXES on the IRTF. These low opacity emission lines are resolved at R = 50, 000 and provide new diagnostics of the dynamics and thermodynamics of the stellar ... 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
Homotopy completion and topological Quillen homology of structured ring spectraFeb 07 2011Feb 06 2013Working in the context of symmetric spectra, we describe and study a homotopy completion tower for algebras and left modules over operads in the category of modules over a commutative ring spectrum (e.g., structured ring spectra). We prove a strong convergence ... More
Higher homotopy excision and Blakers-Massey theorems for structured ring spectraFeb 19 2014May 05 2016Working in the context of symmetric spectra, we prove higher homotopy excision and higher Blakers-Massey theorems, and their duals, for algebras and left modules over operads in the category of modules over a commutative ring spectrum (e.g., structured ... More
The SU(N) Casson-Lin invariants for linksJun 11 2015Dec 03 2015We introduce the $SU(N)$ Casson-Lin invariants for links $L$ in $S^3$ with more than one component. Writing $L = \ell_1 \cup \cdots \cup \ell_n$, we require as input an $n$-tuple $(a_1,\ldots, a_n) \in {\mathbb Z}^n$ of labels, where $a_j$ is associated ... More
Longitudinal spin diffusion in a nondegenerate trapped $^{87}$Rb gasJan 16 2015May 30 2015Longitudinal spin diffusion of two pseudo-spin domains is studied in a trapped $^{87}$Rb sample above quantum degeneracy, and the effect of coherence in the domain wall on the dynamics of the system is investigated. Coherence in a domain wall leads to ... More
A nilpotent Whitehead theorem for TQ-homology of structured ring spectraJun 26 2018Oct 12 2018The aim of this short paper is to prove a TQ-Whitehead theorem for nilpotent structured ring spectra. We work in the framework of symmetric spectra and algebras over operads in modules over a commutative ring spectrum. Our main result can be thought of ... More
On H-Spaces and a Congruence of Catalan NumbersDec 12 2016Jul 09 2017For $p$ an odd prime and $F$ the cyclic group of order $p$, we show that the number of conjugacy classes of embeddings of $F$ in $SU(p)$ such that no element of $F$ has 1 as an eigenvalue is $(1+C_{p-1})/p$, where $C_{p-1}$ is a Catalan number. We prove ... More
Derived Koszul duality and TQ-homology completion of structured ring spectraFeb 24 2015Jul 23 2015Working in the context of symmetric spectra, we consider any higher algebraic structures that can be described as algebras over an operad O. We prove that the fundamental adjunction comparing O-algebra spectra with coalgebra spectra over the associated ... More
Basic Experiment Planning via Information Metrics: the RoboMendel ProblemOct 17 2012In this paper we outline some mathematical questions that emerge from trying to "turn the scientific method into math". Specifically, we consider the problem of experiment planning (choosing the best experiment to do next) in explicit probabilistic and ... More
Detecting Concepts Crucial for Success in Mathematics Courses from Knowledge State-based Placement DataDec 02 2013We show that individual topics and skills can have a dramatic effect on the outcomes of students in various mathematics courses at the University of Illinois. Data from the placement program at Illinois associates a knowledge state, a subset of 182 items ... More
Damage Spreading During Domain GrowthApr 07 1994We study damage spreading in models of two-dimensional systems undergoing first order phase transitions. We consider several models from the same non-conserved order parameter universality class, and find unexpected differences between them. An exact ... More
Braid moves in commutation classes of the symmetric groupJul 02 2015Nov 01 2016We prove that the expected number of braid moves in the commutation class of the reduced word $(s_1 s_2 \cdots s_{n-1})(s_1 s_2 \cdots s_{n-2}) \cdots (s_1 s_2)(s_1)$ for the long element in the symmetric group $\mathfrak{S}_n$ is one. This is a variant ... More
Investigating a Possible Spectral Signature of the Wind-ISM Interaction Region of Alpha TauSep 04 2002Ultraviolet spectra from the GHRS instrument on board the Hubble Space Telescope reveal the presence of a mysterious absorption feature in the Mg II h & k lines of the nearby (d=20.0 pc) K5 III star Alpha Tau. The narrow absorption looks like an interstellar ... More
The Secret Lives of Cepheids: Evolutionary Changes and Pulsation-Induced Shock Heating in the Prototype Classical Cepheid δ CepSep 30 2014Over the past decade, the Secret Lives of Cepheids (SLiC) program has been carried out at Villanova University to study aspects and behaviors of classical Cepheids that are still not well-understood. In this, the first of several planned papers on program ... More
A Game-Centered, Interactive Approach for Using Programming Exercises in Introductory PhysicsJan 07 2017Jun 01 2017Incorporating computer programming exercises in introductory physics is a delicate task that involves a number of choices that may have a strong affect on student learning. We present an approach that speaks to a number of common concerns that arise when ... More
Performance Impact of Lock-Free Algorithms on Multicore Communication APIsJan 09 2014Data race conditions in multi-tasking software applications are prevented by serializing access to shared memory resources, ensuring data consistency and deterministic behavior. Traditionally tasks acquire and release locks to synchronize operations on ... More
Symmetric Function Theory at the Border of A_n and C_nSep 10 2018We relate the type $A_n$ and type $C_n$ Stanley symmetric functions, by producing a new symmetric function: Our double Stanley symmetric function gives the type $A$ case at $(\mathbf{x},\mathbf{0})$ and gives the type $C$ case at $(\mathbf{x},\mathbf{x})$ ... More
A binary deletion channel with a fixed number of deletionsSep 05 2013Suppose a binary string x = x_1...x_n is being broadcast repeatedly over a faulty communication channel. Each time, the channel delivers a fixed number m of the digits (m<n) with the lost digits chosen uniformly at random, and the order of the surviving ... More
Higher resonance varieties of matroidsMar 17 2015May 22 2015We present some new results about the resonance varieties of matroids and hyperplane arrangements. Though these have been the objects of ongoing study, most work so far has focussed on cohomological degree 1. We show that certain phenomena become apparent ... More
A special class of congruences on $κ$-framesMay 19 2017Madden has shown that in contrast to the situation with frames, the smallest dense quotient of a $\kappa$-frame need not be Boolean. We characterise these so-called d-reduced $\kappa$-frames as those which may be embedded as a generating sub-$\kappa$-frame ... More
The non-linear Plateau problem in non-positively curved manifoldsApr 02 2010Using the Perron method, we prove the existence of hypersurfaces of prescribed special Lagrangian curvature with prescribed boundary inside complete Riemannian manifolds of non-positive curvature.
Compactness for immersions of prescribed Gaussian curvature II - geometric aspectsFeb 16 2010Mar 16 2011We develop a compactness result near the boundary for families of locally convex immersions. We also develop a mod 2 degree theory for immersion of constant (and prescribed) Gaussian curvature with prescribed boundary. These are then used to solve the ... More
Eternal forced mean curvature flows I - A compactness resultMar 02 2012With a view to constructing a Morse/Floer homology theory for CMC hypersurfaces, we prove a compactness result modulo broken trajectories for eternal mean curvature flows with forcing term in compact, hyperbolic manifolds.
On additive complexity of infinite wordsSep 21 2012We consider questions related to the structure of infinite words (over an integer alphabet) with bounded additive complexity, i.e., words with the property that the number of distinct sums exhibited by factors of the same length is bounded by a constant ... More
Global Singularity Theory for the Gauss Curvature EquationJun 24 2012Jun 02 2015Lecture notes for a minicourse to given in the XVII Brazilian School of Geometry, UFAM (Amazonas), Brazil, July 2012.
Pointed k-surfacesJun 13 2005Following on from ``Hyperbolic Plateau problems'' (by the same author), we provide a complete geometric description of solutions to the Plateau problem $(S,\phi)$ when $S$ is a compact Riemann surface with a finite number of points removed.
An Arzela-Ascoli Theorem for Immersed SubmanifoldsOct 11 2005Oct 12 2005The classical Arzela-Ascoli theorem is a compactness result for families of functions depending on bounds on the derivatives of the functions, and is of invaluable use in many fields of mathemathics. In this paper, inspired by a result of Corlette, we ... More
Is the Symmetric Group Sperner?Jan 01 2019Jan 03 2019An antichain $\mathcal{A}$ in a poset $\mathcal{P}$ is a subset of $\mathcal{P}$ in which no two elements are comparable. Sperner showed that the maximal antichain in the Boolean lattice, $\mathcal{B}_n = \left\{ 0 < 1 \right\}^n$, is the largest rank ... More
Eigenvectors for a random walk on a hyperplane arrangementOct 01 2010Oct 13 2011We find explicit eigenvectors for the transition matrix of a random walk due to Bidegare, Hanlon and Rockmore. This is accomplished by using Brown and Diaconis' analysis of its stationary distribution, together with some combinatorics of functions on ... More
Strictly zero-dimensional biframes and a characterisation of congruence framesOct 30 2017Strictly zero-dimensional biframes were introduced by Banaschewski and Br\"{u}mmer as a class of strongly zero-dimensional biframes including the congruence biframes. We consider the category of strictly zero-dimensional biframes and show it is both complete ... More
On an Enneper-Weierstrass-type representation of constant Gaussian curvature surfaces in $3$-dimensional hyperbolic spaceApr 20 2014For all $k\in]0,1[$, we construct a canonical bijection between the space of ramified coverings of the sphere and the space of complete immersed surfaces in $3$-dimensional hyperbolic space of finite area and of constant extrinsic curvature equal to $k$. ... More
Precise asymptotics for Fisher-KPP frontsDec 07 2017We consider the one-dimensional Fisher-KPP equation with step-like initial data. Nolen, Roquejoffre, and Ryzhik showed that the solution $u$ converges at long time to a traveling wave $\phi$ at a position $\tilde \sigma(t) = 2t - (3/2)\log t + \alpha_0- ... More
Bit Threads in Higher Curvature GravityJul 11 2018Dec 01 2018We generalize holographic bit threads to bulk theories with a gravitational action containing higher-curvature terms. Bit threads are a reformulation of holographic entanglement entropy, where the entropy is given by the maximum number of threads emanating ... More
Causality, Modality and ExplanationJan 27 2008We present a sequent calculus system for a modal reformulation of a system of nonmonotonic logic due to McCain and Turner: we prove cut elimination for our system. The proof system is in general infinitary: because we can prove cut elimination, many applications ... More
A functional central limit theorem in equilibrium for a large network in which customers join the shortest of several queuesDec 17 2003Mar 31 2004We consider N single server infinite buffer queues with service rate beta. Customers arrive at rate N times alpha,choose L queues uniformly, and join the shortest one. The stability condition is alpha strictly less than beta. We study in equilibrium the ... More
Automorphisms of geometric structures associated to Coxeter groupsFeb 29 2012In this paper, we consider the automorphism groups of the Cayley graph with respect to the Coxeter generators and the Davis complex of an arbitrary Coxeter group. We determine for which Coxeter groups these automorphism groups are discrete. In the case ... More
Crippling Crypto-RansomwareSep 26 2018This research seeks to expose a major weakness in Crypto-ransomware by modeling it as four integral sub-systems consisting of: An Agent, a Command and Control Service (CNC), an anonymous payment channel (APC) and an obfuscated command channel (OCC). We ... More
Convergence of multi-class systems of fixed possibly infinite sizesFeb 03 2009Multi-class systems having possibly both finite and infinite classes are investigated under a natural partial exchangeability assumption. It is proved that the conditional law of such a system, given the vector of the empirical measures of its finite ... More
Reasoning about Unreliable ActionsFeb 01 2012May 03 2012We analyse the philosopher Davidson's semantics of actions, using a strongly typed logic with contexts given by sets of partial equations between the outcomes of actions. This provides a perspicuous and elegant treatment of reasoning about action, analogous ... More
On complete embedded translating solitons of the mean curvature flow that are of finite genusJan 17 2015Mar 21 2017We desingularise the union of $3$ Grim paraboloids along Costa-Hoffman-Meeks surfaces in order to obtain what we believe to be the first examples in $\Bbb{R}^3$ of complete embedded translating solitons of the mean curvature flow of arbitrary non-trivial ... More
Bifurcation of Solutions to the Allen-Cahn EquationNov 10 2013We use Morse Homology to study bifurcation of the solution sets of the Allen-Cahn Equation.
Special Lagrangian CurvatureJun 13 2005Jul 16 2008We define the notion of special Lagrangian curvature, showing how it may be interpreted as an alternative higher dimensional generalisation of two dimensional Gaussian curvature. We obtain first a local rigidity result for this curvature when the ambiant ... More
The Non-Liner Dirichlet Problem in Hadamard ManifoldsAug 25 2009We proof existence theorems for the Dirichlet problem for hypersurfaces of constant special Lagrangian curvature in Hadamard manifolds. The first results are obtained using the continuity method and approximation and then refined using two iterations ... More
A Brief Note on Foliations of Constant Gaussian CurvatureFeb 15 2008This note provides an alternative proof of a result of Labourie. We show that the two complements of the convex core of a three dimensional quasi-fuchsian hyperbolic manifold may be foliated by embedded hypersurfaces of constant Gaussian curvature.
Hyperbolic Plateau problemsJun 13 2005May 23 2011We consider surfaces of constant Gaussian curvature immersed in 3-dimensional manifolds, and we strengthen the compactness result of Labourie in the case where the ambient manifold is 3-dimensional hyperbolic space. This allows us to prove results of ... More
The response of self-graviting protostellar discs to slow reduction in cooling timescale: the fragmentation boundary revisitedAug 06 2007A number of previous studies of the fragmentation of self-gravitating protostellar discs have modeled radiative cooling with a cooling timescale (t_{cool}) parameterised as a simple multiple (beta_{cool}) of the local dynamical timescale. Such studies ... More
Perturbative Approach to Flat Chern Bands in the Hofstadter ModelApr 21 2014Aug 18 2014We present a perturbative approach to the study of the Hofstadter model for when the amount of flux per plaquette is close to a rational fraction. Within this approximation certain eigenstates of the system are shown to be multi-component wavefunctions ... More
Controlled Experimentation in Naturalistic Mobile SettingsJun 17 2013Jun 18 2013Performing controlled user experiments on small devices in naturalistic mobile settings has always proved to be a difficult undertaking for many Human Factors researchers. Difficulties exist, not least, because mimicking natural small device usage suffers ... More
e-MERLIN resolves Betelgeuse at wavelength 5 cmMar 12 2013Convection, pulsation and magnetic fields have all been suggested as mechanisms for the transport of mass and energy from the optical photosphere of red supergiants, out to the region where the stellar wind is launched. We imaged the red supergiant Betelgeuse ... More
NOEMA maps the CO $J = 2-1$ environment of the red supergiant $μ$ CepMar 17 2019Red supergiant stars are surrounded by a gaseous and dusty circumstellar environment created by their mass loss which spreads heavy elements into the interstellar medium. The structure and the dynamics of this envelope are crucial to understand the processes ... More
Gamma-rays from SS433: evidence for periodicityMar 01 2019In this paper we present our study of the gamma-ray emission from the microquasar SS433. Integrating over 9 years of Fermi-LAT \textsc{pass8} data, we detect SS433 with a significance of ~13$\sigma$ in the 200 to 500 MeV photon energy range, with evidence ... More
Non-Kondo zero-bias anomaly in quantum wiresMar 18 2009Apr 17 2009It has been suggested that a zero-bias conductance peak in quantum wires signifies the presence of Kondo spin-correlations, which might also relate to an intriguing 1D spin-effect known as the 0.7 structure. These zero-bias anomalies (ZBA) are strongly ... More
Phase preparation by atom counting of Bose-Einstein condensates in mixed statesApr 18 1997We study the build up of quantum coherence between two Bose-Einstein condensates which are initially in mixed states. We consider in detail the two cases where each condensate is initially in a thermal or a Poisson distribution of atom number. Although ... More
A note on De Concini and Procesi's curious identityMay 16 2007We give a short, case-free and combinatorial proof of de Concini and Procesi's formula for the volume of the simplicial cone spanned by the simple roots of any finite root system. The argument presented here also extends their formula to include the non-crystallographic ... More
The congruence biframe as a quasi-uniform bicompletionFeb 17 2019K\"unzi and Ferrario have shown that a $T_0$ space is sober if and only if it is bicomplete in the well-monotone quasi-uniformity. We prove a pointfree version of this result: a strictly zero-dimensional biframe is a congruence biframe if and only if ... More
A smooth foliation of convex hypersurfaces for quasi-hyper-Fuchsian manifoldsNov 14 2007Jul 16 2008This submission has been withdrawn by the author and superseded by arXiv:0804.0744.