Results for "Hannah M. Price"

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The 6D quantum Hall effect and 3D topological pumpsApr 05 2018Oct 23 2018Modern technological advances allow for the study of systems with additional synthetic dimensions. Using such approaches, higher-dimensional physics that was previously deemed to be of purely theoretical interest has now become an active field of research. ... More
Artificial Magnetic Fields in Momentum Space in Spin-Orbit Coupled SystemsDec 11 2014Apr 01 2015The Berry curvature is a geometrical property of an energy band which can act as a momentum space magnetic field in the effective Hamiltonian of a wide range of systems. We apply the effective Hamiltonian to a spin-1/2 particle in two dimensions with ... More
Constraining stochastic parametrisation schemes using high-resolution simulationsApr 09 2019Stochastic parametrisations are used in weather and climate models to improve the representation of unpredictable unresolved processes. When compared to a deterministic model, a stochastic model represents `model uncertainty', i.e., sources of error in ... More
Topological PhotonicsFeb 12 2018Apr 02 2019Topological photonics is a rapidly emerging field of research in which geometrical and topological ideas are exploited to design and control the behavior of light. Drawing inspiration from the discovery of the quantum Hall effects and topological insulators ... More
Leaf segmentation through the classification of edgesApr 05 2019We present an approach to leaf level segmentation of images of Arabidopsis thaliana plants based upon detected edges. We introduce a novel approach to edge classification, which forms an important part of a method to both count the leaves and establish ... More
Predictive Accuracy of Dynamic Mode DecompositionMay 05 2019Dynamic mode decomposition (DMD), which the family of singular-value decompositions (SVD), is a popular tool of data-driven regression. While multiple numerical tests demonstrated the power and efficiency of DMD in representing data (i.e., in the interpolation ... More
Numerical CohomologySep 18 2015May 07 2016We develop a numerical approach to cohomology. Essentially, vector spaces and linear maps are replaced by real numbers, which represent dimensions of vector spaces and ranks of linear maps. We use this to refine ideas of Van der Geer and Schoof about ... More
Soft Extragalactic X-Ray Binaries at the Eddington ThresholdFeb 01 2017The luminosity range at and just below the 10^39 erg/s cut-off for defining ultraluminous X-ray sources (ULXs) is a little-explored regime. It none-the-less hosts a large number of X-ray sources, and has great potential for improving our understanding ... More
Ionized and molecular gas kinematics in a z=1.4 star-forming galaxyFeb 06 2018We present deep observations of a $z=1.4$ massive, star-forming galaxy in molecular and ionized gas at comparable spatial resolution (CO 3-2, NOEMA; H$\alpha$, LBT). The kinematic tracers agree well, indicating that both gas phases are subject to the ... More
The MOSDEF Survey: Kinematic and Structural Evolution of Star-Forming Galaxies at $1.4\leq z\leq 3.8$Feb 25 2019We present ionized gas kinematics for 708 galaxies at $z\sim 1.4-3.8$ from the MOSFIRE Deep Evolution Field survey, measured using models which account for random galaxy-slit misalignments together with structural parameters derived from CANDELS Hubble ... More
Synthetic Dimensions for Cold Atoms from Shaking a Harmonic TrapMay 30 2016Jun 23 2016We introduce a simple scheme to implement synthetic dimensions and gauge fields in ultracold atomic gases, which only requires two basic and ubiquitous ingredients: the harmonic trap, which confines the atoms, combined with a periodic shaking. In our ... More
Quantum Hall effect in momentum spaceFeb 24 2016May 04 2016We theoretically discuss a momentum-space analog of the quantum Hall effect, which could be observed in topologically nontrivial lattice models subject to an external harmonic trapping potential. In our proposal, the Niu-Thouless-Wu formulation of the ... More
Transferable neural networks for enhanced sampling of protein dynamicsJan 02 2018Variational auto-encoder frameworks have demonstrated success in reducing complex nonlinear dynamics in molecular simulation to a single non-linear embedding. In this work, we illustrate how this non-linear latent embedding can be used as a collective ... More
Quantum Mechanics with a Momentum-Space Artificial Magnetic FieldMar 24 2014Nov 19 2014The Berry curvature is a geometrical property of an energy band which acts as a momentum space magnetic field in the effective Hamiltonian describing single-particle quantum dynamics. We show how this perspective may be exploited to study systems directly ... More
Momentum-space Harper-Hofstadter modelNov 05 2014Aug 14 2015We show how the weakly trapped Harper-Hofstadter model can be mapped onto a Harper-Hofstadter model in momentum space. In this momentum-space model, the band dispersion plays the role of the periodic potential, the Berry curvature plays the role of an ... More
Effects of Berry Curvature on the Collective Modes of Ultracold GasesJun 20 2013Nov 28 2013Topological energy bands have important geometrical properties described by the Berry curvature. We show that the Berry curvature changes the hydrodynamic equations of motion for a trapped Bose-Einstein condensate, and causes significant modifications ... More
Black hole collisions from Brill-Lindquist initial data: predictions of perturbation theorySep 09 1995The Misner initial value solution for two momentarily stationary black holes has been the focus of much numerical study. We report here analytic results for an astrophysically similar initial solution, that of Brill and Lindquist (BL). Results are given ... More
Applying black hole perturbation theory to numerically generated spacetimesAug 29 1995Nonspherical perturbation theory has been necessary to understand the meaning of radiation in spacetimes generated through fully nonlinear numerical relativity. Recently, perturbation techniques have been found to be successful for the time evolution ... More
Coefficients of McKay-Thompson series and distributions of the moonshine moduleAug 15 2015Jan 03 2016In a recent paper, Duncan, Griffin and Ono provide exact formulas for the coefficients of McKay-Thompson series and use them to find asymptotic expressions for the distribution of irreducible representations in the moonshine module $V^\natural = \bigoplus_n ... More
Semidualizing DG Modules over Tensor ProductsNov 25 2014We study the existence of nontrivial semidualizing DG modules over tensor products of DG algebras over a field. In particular, this gives a lower bound on the number of semidualizing DG modules over the tensor product.
Macroscopic stability and simplicial norms of hypersurfacesDec 12 2017We introduce a $\mathbb{Z}$--coefficient version of Guth's macroscopic stability inequality for almost-minimizing hypersurfaces. In manifolds with a lower bound on macroscopic scalar curvature, we use the inequality to prove a lower bound on areas of ... More
Using simplicial volume to count maximally broken Morse trajectoriesJun 15 2015Given a closed Riemannian manifold of dimension $n$ and a Morse-Smale function, there are finitely many $n$-part broken trajectories of the negative gradient flow. We show that if the manifold admits a hyperbolic metric, then the number of $n$-part broken ... More
Discrete configuration spaces of squares and hexagonsApr 20 2017We consider generalizations of the familiar fifteen-piece sliding puzzle on the 4 by 4 square grid. On larger grids with more pieces and more holes, asymptotically how fast can we move the puzzle into the solved state? We also give a variation with sliding ... More
How to directly observe Landau levels in driven-dissipative strained honeycomb latticesApr 15 2015Sep 24 2015We study the driven-dissipative steady-state of a coherently-driven Bose field in a honeycomb lattice geometry. In the presence of a suitable spatial modulation of the hopping amplitudes, a valley-dependent artificial magnetic field appears and the low-energy ... More
Floquet topological system based on frequency-modulated classical coupled harmonic oscillatorsOct 15 2015Feb 03 2016We theoretically propose how to observe topological effects in a generic classical system of coupled harmonic oscillators, such as classical pendula or lumped-element electric circuits, whose oscillation frequency is modulated fast in time. Making use ... More
Momentum-space Landau levels in driven-dissipative cavity arraysOct 11 2015Jan 21 2016We theoretically study the driven-dissipative Harper-Hofstadter model on a 2D square lattice in the presence of a weak harmonic trap. Without pumping and loss, the eigenstates of this system can be understood, in certain limits, as momentum-space toroidal ... More
Experimental Measurement of the Berry Curvature from Anomalous TransportSep 29 2016Geometrical properties of energy bands underlie fascinating phenomena in a wide-range of systems, including solid-state materials, ultracold gases and photonics. Most famously, local geometrical characteristics like the Berry curvature can be related ... More
Sleepless in Seoul: `The Ant and the Metrohopper'Oct 06 2010One of Aesop's (La Fontain's) famous fables `The Ant and the Grasshopper' is widely known to give a moral lesson through comparison between the hard working ant and the party-loving grasshopper. Here we show a slightly different version of this fable, ... More
Sensitivity of codispersion to noise and error in ecological and environmental dataJan 24 2018Codispersion analysis is a new statistical method developed to assess spatial covariation between two spatial processes that may not be isotropic or stationary. Its application to anisotropic ecological datasets have provided new insights into mechanisms ... More
Why stellar feedback promotes disc formation in simulated galaxiesMar 24 2014Jul 04 2014We study how feedback influences baryon infall onto galaxies using cosmological, zoom-in simulations of haloes with present mass $M_{vir}=6.9\times10^{11} M_{\odot}$ to $1.7\times10^{12} M_{\odot}$. Starting at z=4 from identical initial conditions, implementations ... More
Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion CollisionsFeb 20 2019In this work, the production of photons through binary scattering processes is investigated for equilibrated hadronic systems. More precisely, a non-equilibrium hadronic transport approach to describe relativistic heavy-ion collisions is benchmarked with ... More
The density variance -- Mach number relation in supersonic, isothermal turbulenceOct 18 2010Dec 13 2010We examine the relation between the density variance and the mean-square Mach number in supersonic, isothermal turbulence, assumed in several recent analytic models of the star formation process. From a series of calculations of supersonic, hydrodynamic ... More
Congruence properties of Taylor coefficients of modular formsJun 11 2014In their work, Serre and Swinnerton-Dyer study the congruence properties of the Fourier coefficients of modular forms. We examine similar congruence properties, but for the coefficients of a modified Taylor expansion about a CM point $\tau$. These coefficients ... More
Sieved Enumeration of Interval Orders and Other Fishburn StructuresFeb 18 2015Mar 10 2015Following a result of Eriksen and Sj\"{o}strand (2014) we detail a technique to construct structures following the Fishburn distribution from appropriate Mahonian structures. This technique is introduced on a bivincular pattern of Bousquet-M\'elou et ... More
Hyperbolicity of the partition Jensen polynomialsApr 29 2019Given an arithmetic function $a: \mathbb{N} \rightarrow \mathbb{R}$, one can associate a naturally defined, doubly infinite family of Jensen polynomials. Recent work of Griffin, Ono, Rolen, and Zagier shows that for certain families of functions $a: \mathbb{N} ... More
Tropical Real Hurwitz numbersDec 13 2014Aug 25 2015In this paper, we define tropical analogues of real Hurwitz numbers, i.e. numbers of covers of surfaces with compatible involutions satisfying prescribed ramification properties. We prove a correspondence theorem stating the equality of the tropical numbers ... More
Intersecting Psi-classes on tropical M_{0,n}Sep 25 2007Jul 01 2009We apply the tropical intersection theory developed by L. Allermann and J. Rau to compute intersection products of tropical Psi-classes on the moduli space of rational tropical curves. We show that in the case of zero-dimensional (stable) intersections, ... More
The Eternal Game Chromatic Number of a GraphNov 06 2018Apr 16 2019Game coloring is a well-studied two-player game in which each player properly colors one vertex of a graph at a time until all the vertices are colored. An `eternal' version of game coloring is introduced in this paper in which the vertices are colored ... More
Macroscopic scalar curvature and areas of cyclesMay 08 2017Jun 20 2017In this paper we prove the following. Let $\Sigma$ be an $n$--dimensional closed hyperbolic manifold and let $g$ be a Riemannian metric on $\Sigma \times \mathbb{S}^1$. Given an upper bound on the volumes of unit balls in the Riemannian universal cover ... More
Traces of singular values of HauptmodulnJul 16 2014Sep 01 2014In an important paper, Zagier proved that certain half-integral weight modular forms are generating functions for traces of polynomials in the $j$-function. It turns out that Zagier's work makes it possible to algorithmically compute Hilbert class polynomials ... More
Tropical covers of curves and their moduli spacesMar 26 2013We define the tropical moduli space of covers of a tropical line in the plane as weighted abstract polyhedral complex, and the tropical branch map recording the images of the simple ramifications. Our main result is the invariance of the degree of the ... More
Tropical descendant Gromov-Witten invariantsSep 08 2008Nov 29 2009We define tropical Psi-classes on the moduli space of rational tropical curves in R^2 and consider intersection products of Psi-classes and pull-backs of evaluations on this space. We show a certain WDVV equation which is sufficient to prove that tropical ... More
Using APOGEE Wide Binaries to Test Chemical Tagging with Dwarf StarsNov 29 2018Stars of a common origin are thought to have similar, if not nearly identical, chemistry. Chemical tagging seeks to exploit this fact to identify Milky Way subpopulations through their unique chemical fingerprints. In this work, we compare the chemical ... More
A conditional strong large deviation result and a functional central limit theorem for the rate functionNov 21 2014Dec 04 2014We study the large deviation behaviour of $S_n=\sum_{j=1}^n W_jZ_j$, where $(W_j)_{j \in \mathbb N}$ and $(Z_j)_{j \in \mathbb N}$ are sequences of real-valued, independent and identically distributed random variables satisfying certain moment conditions, ... More
Spin-orbit coupling in a hexagonal ring of pendulaSep 30 2016May 24 2017We consider the mechanical motion of a system of six macroscopic pendula which are connected with springs and arranged in a hexagonal geometry. When the springs are pre-tensioned, the coupling between neighbouring pendula along the longitudinal (L) and ... More
Spin-orbit coupling in a hexagonal ring of pendulaSep 30 2016We consider the mechanical motion of a system of six macroscopic pendula which are connected with springs and arranged in a hexagonal geometry. When the springs are pre-tensioned, the coupling between neighbouring pendula along the longitudinal (L) and ... More
Spreadsheet Risk - A New Direction for HMRC?Nov 28 2007Her Majestys Revenue & Customs (HMRC) was born out of the need to create a UK tax authority by merging both the Inland Revenue and HM Customs & Excise into one department. HMRC encounters spreadsheets in tax-payers systems on a very regular basis as well ... More
Pointwise Schauder estimates of parabolic equations in Carnot groupsJan 13 2016Schauder estimates were a historical stepping stone for establishing uniqueness and smoothness of solutions for certain classes of partial differential equations. Since that time, they have remained an essential tool in the field. Roughly speaking, the ... More
Four-Dimensional Quantum Hall Effect with Ultracold AtomsMay 17 2015Jan 29 2016We propose a realistic scheme to detect the 4D quantum Hall effect using ultracold atoms. Based on contemporary technology, motion along a synthetic fourth dimension can be accomplished through controlled transitions between internal states of atoms arranged ... More
Synthetic dimensions in integrated photonics: From optical isolation to 4D quantum Hall physicsOct 13 2015Apr 23 2016Recent technological advances in integrated photonics have spurred on the study of topological phenomena in engineered bosonic systems. Indeed, the controllability of silicon ring-resonator arrays has opened up new perspectives for building lattices for ... More
Smoothed Particle HydrodynamicsJul 20 2005Smoothed Particle Hydrodynamics (SPH) is a unique numerical method widely used for astrophysical problems since it involves no spatial grid. Rather, fluid quantities are carried by a set of Lagrangian `particles' which move with the flow, meaning that ... More
Recent star formation in the inner Galactic Bulge seen by ISOGAL. I - Classification of bright mid-IR sources in a test fieldMar 21 2006Context: The stellar populations in the central region of the Galaxy are poorly known because of the high visual extinction and very great source density in this direction. Aims: To use recent infrared surveys for studying the dusty stellar objects in ... More
Experimental Estimation of Number of Clusters Based on Cluster QualityMar 10 2015Text Clustering is a text mining technique which divides the given set of text documents into significant clusters. It is used for organizing a huge number of text documents into a well-organized form. In the majority of the clustering algorithms, the ... More
Giant Magnons of String Theory in the Lambda BackgroundApr 18 2017Jul 10 2017The analogues of giant magnon configurations are studied on the string world sheet in the lambda background. This is a discrete deformation of the AdS(5)xS(5) background that preserves the integrability of the world sheet theory. Giant magnon solutions ... More
Optimizing performance per watt on GPUs in High Performance Computing: temperature, frequency and voltage effectsJul 30 2014Oct 20 2015The magnitude of the real-time digital signal processing challenge attached to large radio astronomical antenna arrays motivates use of high performance computing (HPC) systems. The need for high power efficiency (performance per watt) at remote observatory ... More
Photoproduction of the doubly-strange Xi HyperonsFeb 05 2004We report on the first measurement of exclusive Xi- and Xi0 photoproduction. The Xi- states are produced in the reaction gamma p --> K+ K+ Xi-, and the Xi0 states in gamma p --> K+ K+ pi- Xi0. Identification is made by the unique mass measured as the ... More
Optimally focused cold atom systems obtained using density-density correlationsSep 19 2013Jan 26 2014Resonant absorption imaging is a common technique for detecting the two-dimensional column density of ultracold atom systems. In many cases, the system's thickness along the imaging direction greatly exceeds the imaging system's depth of field, making ... More
Localized and intense energy conversion in the diffusion region of asymmetric magnetic reconnectionOct 12 2017May 14 2018We analyze a high-resolution simulation of magnetopause reconnection observed by the Magnetospheric Multiscale (MMS) mission and explain the occurrence of strongly localized dissipation with an amplitude more than an order of magnitude larger than expected. ... More
The Effects of Turbulence on Three-Dimensional Magnetic Reconnection at the MagnetopauseApr 27 2016Jun 07 2016Two- and three-dimensional particle-in-cell simulations of a recent encounter of the Magnetospheric Multiscale Mission (MMS) with an electron diffusion region at the magnetopause are presented. While the two-dimensional simulation is laminar, turbulence ... More
Predicting Language Recovery after Stroke with Convolutional Networks on Stitched MRINov 26 2018One third of stroke survivors have language difficulties. Emerging evidence suggests that their likelihood of recovery depends mainly on the damage to language centers. Thus previous research for predicting language recovery post-stroke has focused on ... More
Multiple periods in the variability of the supermassive black hole binary candidate quasar PG1302-102?Feb 10 2015Graham et al. (2015) discovered a supermassive black hole binary (SMBHB) candidate and identified the detected 5.2 yr period of the optical variability as the orbital period of the binary. Hydrodynamical simulations predict multiple periodic components ... More
Radiation tails and boundary conditions for black hole evolutionsJan 21 2004In numerical computations of Einstein's equations for black hole spacetimes, it will be necessary to use approximate boundary conditions at a finite distance from the holes. We point out here that ``tails,'' the inverse power-law decrease of late-time ... More
Comoving stars in Gaia DR1: An abundance of very wide separation co-moving pairsDec 07 2016Jun 01 2017The primary sample of the {\it Gaia} Data Release 1 is the Tycho-Gaia Astrometric Solution (TGAS): $\approx$ 2 million Tycho-2 sources with improved parallaxes and proper motions relative to the initial catalog. This increased astrometric precision presents ... More
The Nature of Ionized Gas in the Milky Way Galactic FountainApr 24 2019We address the spatial scale, ionization structure and metal content of gas at the Milky Way disk-halo interface detected as absorption in the foreground of seven halo blue horizontal branch stars (BHBs). The closely-spaced, high-latitude BHB sightlines ... More
The Global Surface Roughness of 25143 ItokawaMay 13 2019Surface roughness is an important metric in understanding how the geologic history of an asteroid affects its small-scale topography and it provides an additional means to quantitatively compare one asteroid with another. In this study, we report the ... More
YSix closely related YbT$_2$Zn$_{20}$ (T = Fe, Co, Ru, Rh, Os, Ir) heavy fermion compounds with large local moment degeneracyAug 18 2006Feb 20 2007Heavy fermion compounds represent one of the most strongly correlated forms of electronic matter and give rise to low temperature states that range from small moment ordering to exotic superconductivity, both of which are often in close proximity to quantum ... More
Monitoring spatial sustainable development: Semi-automated analysis of satellite and aerial images for energy transition and sustainability indicatorsOct 11 2018Solar panels are installed by a large and growing number of households due to the convenience of having cheap and renewable energy to power house appliances. In contrast to other energy sources solar installations are distributed very decentralized and ... More
Kronos & Krios: Evidence for accretion of a massive, rocky planetary system in a comoving pair of solar-type starsSep 15 2017We report and discuss the discovery of a comoving pair of bright solar-type stars, HD 240430 and HD 240429, with a significant difference in their chemical abundances. The two stars have an estimated 3D separation of $\approx 0.6$ pc ($\approx 0.01$ pc ... More
The spectral difference between solar flare HXR coronal and footpoint sources due to wave-particle interactionsMar 11 2011Investigate the spatial and spectral evolution of hard X-ray (HXR) emission from flare accelerated electron beams subject to collisional transport and wave-particle interactions in the solar atmosphere. We numerically follow the propagation of a power-law ... More
Chamber Structure of Double Hurwitz numbersMar 09 2010Double Hurwitz numbers count covers of the projective line by genus g curves with assigned ramification profiles over 0 and infinity, and simple ramification over a fixed branch divisor. Goulden, Jackson and Vakil have shown double Hurwitz numbers are ... More
Study of Xi Photoproduction from Threshold to W = 3.3 GeVAug 31 2018Nov 26 2018The doubly-strange Xi baryons provide an effective way to study a puzzle called the missing-baryons problem, where both quark models and lattice gauge theory predict more baryon excited states than are seen experimentally. However, few of these excited ... More
Neutrino pair annihilation above merger remnants: implications of a long-lived massive neutron starJan 08 2017Binary neutron star mergers are plausible progenitor candidates for short gamma-ray bursts (GRBs); however, a detailed explanation of their central engine is still lacking. The annihilation of neutrino pairs has been proposed as one of the possible powering ... More
Decentralized Certificate AuthoritiesJun 11 2017Oct 10 2017The security of TLS depends on trust in certificate authorities, and that trust stems from their ability to protect and control the use of a private signing key. The signing key is the key asset of a certificate authority (CA), and its value is based ... More
Tropical surface singularitiesJun 14 2011Sep 14 2012In this paper, we study tropicalisations of singular surfaces in toric threefolds. We completely classify singular tropical surfaces of maximal-dimensional type, show that they can generically have only finitely many singular points, and describe all ... More
Broccoli curves and the tropical invariance of Welschinger numbersApr 15 2011Sep 11 2013In this paper we introduce broccoli curves, certain plane tropical curves of genus zero related to real algebraic curves. The numbers of these broccoli curves through given points are independent of the chosen points - for arbitrary choices of the directions ... More
Tropical moduli spaces of stable maps to a curveMay 23 2017We construct moduli spaces of rational covers of an arbitrary smooth tropical curve in R^r as tropical varieties. They are contained in the balanced fan parametrizing tropical stable maps of the appropriate degree to R^r. The weights of the top-dimensional ... More
Tropical mirror symmetry in dimension oneSep 27 2018We prove a tropical mirror symmetry theorem for descendant Gromov-Witten invariants of the elliptic curve, generalizing a tropical mirror symmetry theorem for Hurwitz numbers of the elliptic curve. For the case of the elliptic curve, the tropical version ... More
The Fraction of Broken Waves in Natural Surf ZonesApr 15 2019This paper presents a novel quantification of the fraction of broken waves (Qb) in natural surf zones using data from seven wave-dominated Australian beaches. Qb is a critical, but rarely quantified, parameter for parametric surf zone energy dissipation ... More
Evidence for a circumplanetary disc around protoplanet PDS 70 bMay 15 2019We present the first observational evidence for a circumplanetary disc around the protoplanet PDS~70~b, based on a new spectrum in the $K$ band acquired with VLT/SINFONI. We tested three hypotheses to explain the spectrum: Atmospheric emission from the ... More
Attenuation of acoustic waves in glacial ice and salt domesJun 27 2005Two classes of natural solid media (glacial ice and salt domes) are under consideration as media in which to deploy instruments for detection of neutrinos with energy >1e18 eV. Though insensitive to 1e11 to 1e16 eV neutrinos for which observatories (e.g., ... More
Life in solid iceJul 02 2005Some microbes appear to be able to metabolize in glacial ice or permafrost. The rate depends on temperature, nutrient level, and bioelement availability, among other factors. I have developed a plausible argument that they do this while confined in veins ... More
Cocycle conjugacy classes of binary shiftsFeb 18 2016We show that every binary shift on the hyperfinite $II_1$ factor $R$ is cocycle conjugate to at least countably many non-conjugate binary shifts. This holds in particular for binary shifts of infinite commutant index.
Renormalization and blow-up for the 3D Euler equationsMay 22 2018Jul 27 2018In recent work we have developed a renormalization framework for stabilizing reduced order models for time-dependent partial differential equations. We have applied this framework to the open problem of finite-time singularity formation (blow-up) for ... More
Smoothed Particle Hydrodynamics and MagnetohydrodynamicsDec 08 2010This paper presents an overview and introduction to Smoothed Particle Hydrodynamics and Magnetohydrodynamics in theory and in practice. Firstly, we give a basic grounding in the fundamentals of SPH, showing how the equations of motion and energy can be ... More
Production of charm and charmonium with the ATLAS detector at 7 TeVOct 25 2010Oct 27 2010We report on the observation of the charm mesons D^\ast \pm, D^\pm and D_s ^\pm with 1.4 nb^-1 of data, and of the J/psi-->mu+mu- resonance with 78 nb-1 of data from the ATLAS detector in 7 TeV proton-proton collisions at the LHC. The resultant signals ... More
Modelling discontinuities and Kelvin-Helmholtz instabilities in SPHSep 18 2007Jun 02 2008In this paper we discuss the treatment of discontinuities in Smoothed Particle Hydrodynamics (SPH) simulations. In particular we discuss the difference between integral and differential representations of the fluid equations in an SPH context and how ... More
The marriage of gas and dustNov 04 2014Jan 08 2015Dust-gas mixtures are the simplest example of a two fluid mixture. We show that when simulating such mixtures with particles or with particles coupled to grids a problem arises due to the need to resolve a very small length scale when the coupling is ... More
Smoothed Particle Magnetohydrodynamics IV - Using the Vector PotentialSep 14 2009In this paper we investigate the use of the vector potential as a means of maintaining the divergence constraint in the numerical solution of the equations of Magnetohydrodynamics (MHD) using the Smoothed Particle Hydrodynamics (SPH) method. We derive ... More
Homological properties of color Lie superalgebrasJun 14 2005Jun 14 2005Let $\mathcal{L}=\mathcal{L}_{+}\oplus \mathcal{L}_{-}$ be a finite dimensional color Lie superalgebra over a field of characteristic 0 with universal enveloping algebra $U(\mathcal{L})$. We show that $\limfunc{gldim}(U(\mathcal{L}_{+}))= \limfunc{lFPD}(U(\mathcal{L}))= ... More
Ethylene oxide and Acetaldehyde in hot coresMar 10 2014[Abridged] Ethylene oxide and its isomer acetaldehyde are important complex organic molecules because of their potential role in the formation of amino acids. Despite the fact that acetaldehyde is ubiquitous in the interstellar medium, ethylene oxide ... More
Magnetic field-induced squeezing effect at RHIC and at the LHCFeb 19 2016In off-central heavy-ion collisions, the quark-gluon plasma (QGP) is exposed to the strongest magnetic fields ever created in the universe. Due to the paramagnetic nature of the QGP at high temperatures, the spatially inhomogeneous magnetic field configuration ... More
Tropical curves with a singularity in a fixed pointSep 10 2009Mar 26 2012In this paper, we study tropicalisations of families of curves with a singularity in a fixed point. The tropicalisation of such a family is a linear tropical variety. We describe its maximal dimensional cones using results about linear tropical varieties ... More
The tropical $j$-invariantMar 27 2008Mar 31 2008If (Q,A) is a marked polygon with one interior point, then a general polynomial f in K[x,y] with support A defines an elliptic curve C on the toric surface X_A. If K has a non-archimedean valuation into the real numbers we can tropicalize C to get a tropical ... More
Proceedings of the WSDM Cup 2017: Vandalism Detection and Triple ScoringDec 27 2017The WSDM Cup 2017 was a data mining challenge held in conjunction with the 10th International Conference on Web Search and Data Mining (WSDM). It addressed key challenges of knowledge bases today: quality assurance and entity search. For quality assurance, ... More
Chaotic Dispersal of Tidal DebrisJul 30 2015Apr 06 2016Several long, dynamically cold stellar streams have been observed around the Milky Way Galaxy, presumably formed from the tidal disruption of globular clusters. In integrable potentials---where all orbits are regular---tidal debris phase-mixes close to ... More
Multi-thermal dynamics and energetics of a coronal mass ejection in the low solar atmosphereDec 21 2012The aim of this work is to determine the multi-thermal characteristics and plasma energetics of an eruptive plasmoid and occulted flare observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). We study an event from 03-Nov-2010 (peaking ... More
Bayesian nonparametric multivariate convex regressionSep 01 2011In many applications, such as economics, operations research and reinforcement learning, one often needs to estimate a multivariate regression function f subject to a convexity constraint. For example, in sequential decision processes the value of a state ... More
Multivariate convex regression with adaptive partitioningMay 10 2011Nov 13 2011We propose a new, nonparametric method for multivariate regression subject to convexity or concavity constraints on the response function. Convexity constraints are common in economics, statistics, operations research, financial engineering and optimization, ... More
An algorithm for lifting points in a tropical varietyMay 16 2007Jul 28 2009The aim of this paper is to give a constructive proof of one of the basic theorems of tropical geometry: given a point on a tropical variety (defined using initial ideals), there exists a Puiseux-valued ``lift'' of this point in the algebraic variety. ... More
Cluster algebraic interpretation of infinite friezesNov 09 2016May 30 2017Originally studied by Conway and Coxeter, friezes appeared in various recreational mathematics publications in the 1970s. More recently, in 2015, Baur, Parsons, and Tschabold constructed periodic infinite friezes and related them to matching numbers in ... More