Results for "Courtney Quinn"

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A More Accurate Fourier TransformJul 06 2015Fourier transform methods are used to analyze functions and data sets to provide frequencies, amplitudes, and phases of underlying oscillatory components. Fast Fourier transform (FFT) methods offer speed advantages over evaluation of explicit integrals ... More
Secrets of Successful Science ProjectsDec 28 2016Over the past several years, the authors have served as teachers, qualified scientists, mentors, and/or parents on dozens of science projects. These projects ranged from elementary school projects that can be completed in a weekend to high school and ... More
Powder Lot Variations: A Case Study with Varget - Hodgdon ExtremeJan 27 2015Small arms propellant distributor Hodgdon claims that rifle powders in its Extreme line have small velocity variations with both temperature changes and lot number. This paper reports on the variations in average velocity of four different lots of Hodgdon ... More
Impossible? Publication Quality Research with the Weakest 10% of Incoming FreshmenNov 30 2012Undergraduate research is widely regarded as a high impact practice. However, usually only the highest achieving students are rewarded with undergraduate research opportunities. This paper reports on the successful implementation of a student research ... More
High-speed measurement of rifle primer blast wavesFeb 08 2011This article describes a method and results for direct high-speed measurements of rifle primer blast waves employing a high-speed pressure transducer located at the muzzle to record the blast pressure wave produced by primer ignition. Our key findings ... More
Device for Underwater Laboratory Simulation of Unconfined Blast WavesJun 08 2015Shock tubes simulate blast waves to study their effects in air under laboratory conditions; however, few experimental models exist for simulating underwater blast waves that are needed for facilitating experiments in underwater blast transmission, determining ... More
Methods for Accurate Free Flight Measurement of Drag CoefficientsMar 18 2015This paper describes experimental methods for free flight measurement of drag coefficients to an accuracy of approximately 1%. There are two main methods of determining free flight drag coefficients, or equivalent ballistic coefficients: 1) measuring ... More
A $55 Shock Tube for Simulated Blast WavesFeb 21 2015Shock tubes are commonly employed to test candidate armor materials, validate numerical models, and conduct simulated blast experiments in animal models. As DoD interests desire to field wearable sensors as blast dosimeters, shock tubes may also serve ... More
Early Results from APOKASCSep 08 2014Asteroseismology and spectroscopy provide complementary constraints on the fundamental and chemical properties of stars. I describe the first results from APOKASC, a collaboration between the Kepler asteroseismic science consortium (KASC) and the SDSS-III ... More
An Acoustic Demonstration of Galileo's Law of Falling BodiesFeb 08 2011An acoustic method is presented for analyzing the time of falling motion. A ball is dropped from a measured height. The dropping device makes a distinct sound a well-determined time (roughly 14 milliseconds) after release. The ball subsequently makes ... More
Acoustic methods for measuring bullet velocityDec 27 2008This article describes two acoustic methods to measure bullet velocity with an accuracy of 1% or better. In one method, a microphone is placed within 0.1 m of the gun muzzle and a bullet is fired at a steel target 45 m away. The bullet's flight time is ... More
The Evening Tutoring Center at the United States Air Force AcademyFeb 09 2011The United States Air Force Academy (USAFA) has opened an Evening Tutoring Center to provide after-hours tutoring every evening before class days. The center focuses on first and second year courses in challenging quantitative disciplines: mathematics, ... More
Is it Possible to Accurately Identify a Shooter's Face as Illuminated by the Muzzle Flash of a 22 LR Pistol?Oct 22 2014The science of firearms muzzle flash has been dominated by three perspectives: 1) Does the muzzle flash reveal friendly positions to naked eye observers so as to draw fire from enemy combatants? 2) Can flash signatures be recognized by electronic surveillance ... More
Performance testing of lead free primers: blast waves, velocity variations, and environmental testingOct 23 2014Results are presented for lead free primers based on diazodinitrophenol (DDNP)compared with tests on lead styphnate based primers. First, barrel friction measurements in 5.56 mm NATO are presented. Second, shot to shot variations in blast waves are presented ... More
Terminal Performance of Lead-Free Pistol Bullets in Ballistic Gelatin Using Retarding Force Analysis from High Speed VideoApr 04 2016Due to concerns about environmental and industrial hazards of lead, a number of military, law enforcement, and wildlife management agencies are giving careful consideration to lead-free ammunition. The goal of lead-free bullets is to gain the advantages ... More
Gyroscopic Stability of Open Tipped Match Style Rifle BulletsJan 16 2014Oct 16 2014Earlier work has produced formulas for predicting stability of rifle bullets of near uniform density and also for plastic-tipped rifle bullets. These formulas have been shown to be accurate within 5%. However, the original Miller stability formula for ... More
Aerodynamic Drag and Gyroscopic StabilityAug 15 2013Oct 16 2014This paper describes the effects on aerodynamic drag of rifle bullets as the gyroscopic stability is lowered from 1.3 to 1.0. It is well known that a bullet can tumble for stability less than 1.0. The Sierra Loading Manuals (4th and 5th Editions) have ... More
Comparing Terminal Performance of .357 SIG and 9mm Bullets in Ballistic Gelatin Using Retarding Force Analysis from High Speed VideoAug 21 2015High-speed video has emerged as an valuable tool for quantifying bullet performance in ballistic gelatin. This paper presents the results of testing four .357 SIG bullets using high-speed video of bullet impacts in ballistic gelatin to determine retarding ... More
EI VideosApr 11 2012The Quantitative Reasoning Center (QRC) at USAFA has the institution's primary responsibility for offering after hours extra instruction (EI) in core technical disciplines (mathematics, chemistry, physics, and engineering mechanics). Demand has been tremendous, ... More
Illuminating Fourier Series with AudacityNov 20 2012This paper briefly describes some simple techniques for illuminating Fourier series and Fourier analysis with the Audacity sound recording program. These techniques are easily applied in the classroom and help students move beyond formula roulette in ... More
Studying the Internal Ballistics of a Combustion Driven Potato Cannon using High-speed VideoMay 04 2013A potato cannon was designed to accommodate several different experimental propellants and have a transparent barrel so the movement of the projectile could be recorded on high-speed video (at 2000 frames per second). Both combustion chamber and barrel ... More
Effects of periodic forcing on a Paleoclimate delay modelAug 07 2018Jan 11 2019We present a study of a delay differential equation (DDE) model for the Mid-Pleistocene Transition (MPT). We investigate the behavior of the model when subjected to periodic forcing. The unforced model has a bistable region consisting of a stable equilibrium ... More
Free products with amalgamation over central C*-subalgebrasSep 24 2018Dec 14 2018Let A and B be C*-algebras whose quotients are all RFD, and let C be a central C*-subalgebra in both A and B. We prove that the full amalgamated free product of A and B over C is then RFD. This generalizes Korchagin's result that amalgamated free products ... More
Why Cheating is WrongFeb 08 2011Mathieu Bouville's "Why is cheating wrong?" (Studies in Philosophy and Education, 29(1), 67-76, 2010) misses the mark by failing to consider the longer term consequences of cheating on student character development and longer term societal consequences ... More
A Tentative Role for FOXP2 in the Evolution of Dual Processing Modes and Generative AbilitiesAug 11 2014It has been suggested that the origins of cognitive modernity in the Middle/Upper Paleolithic following the appearance of anatomically modern humans was due to the onset of dual processing or contextual focus (CF), the ability to shift between different ... More
Measuring Bullet Velocity with a PC SoundcardJan 14 2006This article describes a simple method for using a PC soundcard to accurately measure bullet velocity. The method involves placing the microphone within a foot of the muzzle and firing at a steel target between 50 and 100 yards away. The time of flight ... More
Is Carbon Cycling Keeping Pace with Increases in Atmospheric Carbon Dioxide?Dec 20 2018Carbon dioxide (CO2) increase has been well documented, and global net primary production is of importance to a variety of ecological topics. Since CO2 increases primary production in laboratory experiments, the global effects of increasing CO2 on global ... More
Photometric Trends in the Visible Solar Continuum and Their Sensitivity to the Center-to-Limb ProfileFeb 23 2015Jun 25 2015Solar irradiance variations over solar rotational time-scales are largely determined by the passage of magnetic structures across the visible solar disk. Variations on solar cycle time scales are thought to be similarly due to changes in surface magnetism ... More
Echo-based measurement of the speed of soundFeb 14 2011The speed of sound in air can be measured by popping a balloon next to a microphone a measured distance away from a large flat wall, digitizing the sound waveform, and measuring the time between the sound of popping and return of the echo to the microphone. ... More
Potential-based analyses of first-order methods for constrained and composite optimizationMar 20 2019We propose potential-based analyses for first-order algorithms applied to constrained and composite minimization problems. We first propose ``idealized'' frameworks for algorithms in the strongly and non-strongly convex cases and argue based on a potential ... More
Small-Network Approximations for Geometrically Frustrated Ising SystemsJul 14 2011The study of frustrated spin systems often requires time-consuming numerical simulations. As the simplest approach, the classical Ising model is often used to investigate the thermodynamic behavior of such systems. Exploiting the small correlation lengths ... More
Plump Cutthroat Trout and Thin Rainbow Trout in a Lentic EcosystemOct 17 2012Background: Much has been written about introduced rainbow trout (Oncorhynchus mykiss) interbreeding and outcompeting cutthroat trout (Oncorhynchus clarkii). However, the specific mechanisms by which rainbow trout and their hybrids outcompete cutthroat ... More
The two-star model: exact solution in the sparse regime and condensation transitionApr 24 2015Apr 28 2015The $2$-star model is the simplest exponential random graph model that displays complex behavior, such as degeneracy and phase transition. Despite its importance, this model has been solved only in the regime of dense connectivity. In this work we solve ... More
Dual 2-complexes in 4-manifoldsSep 27 2000Concerns decompositions of smooth 4-manifolds as the union of two handlebodies, each with handles of index <=2 (``Heegard'' decompositions).Sample result: Two 2-complexes are (up to 2-deformation) dual spines of a Heegard decomposition of the 4-sphere ... More
Hyperelementary assembly for K-theory of virtually abelian groupsSep 13 2005Feb 16 2006Controlled $K$-theory is used to show that algebraic $K$-theory of virtually abelian groups is described by an assembly map defined using possibly-infinite hyperelementary subgroups. The Farrell-Jones summand (coming from infinite subgroups) is parameterized ... More
Homology manifolds and 4-dimensional surgeryApr 12 2005May 09 2005Withdrawn May 2005. There is an error in the even-dimensional case of the proof in the April 2005 version. The hoped-for 4-dimensional applications are unlikely to survive the repairs.
The CP Puzzle in the Strong InteractionsOct 03 2001This lecture, directed to an broad audience including non-specialists, presents a short review of the problem of strong CP symmetry maintenance. The problem is defined and the possible solutions briefly reviewed. I discuss the way in which Roberto Peccei ... More
Generalized network structures: The configuration model and the canonical ensemble of simplicial complexesFeb 12 2016Jun 06 2016Simplicial complexes are generalized network structures able to encode interactions occurring between more than two nodes. Simplicial complexes describe a large variety of complex interacting systems ranging from brain networks, to social and collaboration ... More
Dense Power-law Networks and Simplicial ComplexesFeb 05 2018There is increasing evidence that dense networks occur in on-line social networks, recommendation networks and in the brain. In addition to being dense, these networks are often also scale-free, i.e. their degree distributions follow $P(k)\propto k^{-\gamma}$ ... More
A controlled-topology proof of the product structure theoremOct 03 2006The controlled end and h-cobrodism theorems (Ends of maps I, 1979) are used to give quick proofs of the Top/PL and PL/DIFF product structure theorems.
Cores of s-cobordisms of 4-manifoldsMar 31 2004The main result is that an s-cobordism (topological or smooth) of 4-manifolds has a product structure outside a ``core'' sub s-cobordism. These cores are arranged to have quite a bit of structure, for example they are smooth and abstractly (forgetting ... More
B Physics and CP ViolationNov 14 2001These lectures provide a basic overview of topics related to the study of CP Violation in B decays. In the first lecture, I review the basics of discrete symmetries in field theories, the quantum mechanics of neutral but flavor-non-trivial mesons, and ... More
Group categories and their field theoriesNov 08 1998Nov 21 1999A group-category is an additively semisimple category with a monoidal product structure in which the simple objects are invertible. For example in the category of representations of a group, 1-dimensional representations are the invertible simple objects. ... More
CPT- and Lorentz-Violation Tests with Muon g-2Jun 29 2019The status of Lorentz- and CPT-violation searches using measurements of the anomalous magnetic moment of the muon is reviewed. Results from muon g-2 experiments have set the majority of the most stringent limits on Standard- Model Extension Lorentz and ... More
Capturing strong correlations in spin, electron and local moment systemsJun 19 2019We address the question of identifying degrees of freedom for quantum systems. Typically, quasi-particle descriptions of correlated matter are based upon the canonical algebras of bosons or fermions. Here we highlight that a special class of non-canonical ... More
Lectures on controlled topology: mapping cylinder neighborhoodsJan 22 2002The existence theorem for mapping cylinder neighborhoods is discussed as a prototypical example of controlled topology and its applications. The first of a projected series developed from lectures at the Summer School on High-Dimensional Topology, Trieste ... More
Controlled K-theory I: Basic theoryFeb 24 2004Sep 19 2005This paper provides a full controlled version of algebraic $K$-theory. This includes a rich array of assembly maps; the controlled assembly isomorphism theorem identifying the controlled group with homology; and the stability theorem describing the behavior ... More
Derivation of Delay Equation Climate Models Using the Mori-Zwanzig FormalismFeb 08 2019Models incorporating delay have been frequently used to understand climate variability phenomena, but often the delay is introduced through an ad-hoc physical reasoning, such as the propagation time of waves. In this paper, the Mori-Zwanzig formalism ... More
Derivation of Delay Equation Climate Models Using the Mori-Zwanzig FormalismFeb 08 2019May 17 2019Models incorporating delay have been frequently used to understand climate variability phenomena, but often the delay is introduced through an ad-hoc physical reasoning, such as the propagation time of waves. In this paper, the Mori-Zwanzig formalism ... More
A 2 Earth Radius Planet Orbiting the Bright Nearby K-Dwarf Wolf 503Jun 09 2018Since its launch in 2009, the Kepler telescope has found thousands of planets with radii between that of Earth and Neptune. Recent studies of the distribution of these planets have revealed a rift in the population near 1.5-2.0$R_{\bigoplus}$, informally ... More
The Mid-Pleistocene Transition induced by delayed feedback and bistabilityDec 20 2017The Mid-Pleistocene Transition, the shift from 41 kyr to 100 kyr glacial-interglacial cycles that occurred roughly 1 Myr ago, is often considered as a change in internal climate dynamics. Here we revisit the model of Quaternary climate dynamics that was ... More
Basin bifurcations, oscillatory instability and rate-induced thresholds for AMOC in a global oceanic box modelJan 29 2019The Atlantic Meridional Overturning Circulation (AMOC) transports substantial amounts of heat into the North Atlantic sector, and hence is of very high importance in regional climate projections. The AMOC has been observed to show multi-stability across ... More
Basin bifurcations, oscillatory instability and rate-induced thresholds for AMOC in a global oceanic box modelJan 29 2019Apr 11 2019The Atlantic Meridional Overturning Circulation (AMOC) transports substantial amounts of heat into the North Atlantic sector, and hence is of very high importance in regional climate projections. The AMOC has been observed to show multi-stability across ... More
The Mid-Pleistocene Transition induced by delayed feedback and bistabilityDec 20 2017Nov 09 2018The Mid-Pleistocene Transition, the shift from 41 kyr to 100 kyr glacial-interglacial cycles that occurred roughly 1 Myr ago, is often considered as a change in internal climate dynamics. Here we revisit the model of Quaternary climate dynamics that was ... More
Studies of single top quark production at the TevatronJan 19 2011In this paper we present several measurements of single top quark production from the CDF and D0 experiments at the Tevatron. The various analyses utilize integrated luminosity ranging from 2.1 to 4.8 fb -1. The results include the observation of single ... More
Dual decompositions of 4-manifolds II: linear invariantsSep 20 2001Mar 06 2004This paper continues the study of decompositions of a smooth 4-manifold into two handlebodies with handles of index $\leq2$. Part I gave existence results in terms of spines and chain complexes over the fundamental group of the ambient manifold. Here ... More
To Apply or Not to Apply: A Survey Analysis of Grant Writing Costs and BenefitsMar 13 2015We surveyed 113 astronomers and 82 psychologists active in applying for federally funded research on their grant-writing history between January, 2009 and November, 2012. We collected demographic data, effort levels, success rates, and perceived non-financial ... More
How Good a Clock is Rotation? The Stellar Rotation-Mass-Age Relationship for Old Field StarsMar 07 2012Dec 30 2013The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with a rotation ... More
Recursive strategy for decomposing Betti tables of complete intersectionsAug 17 2017We introduce a recursive decomposition algorithm for the Betti diagram of a complete intersection using the diagram of a complete intersection defined by a subset of the original generators. This alternative algorithm is the main tool that we use to investigate ... More
A Stability Formula for Plastic-Tipped Bullets Part 2: Experimental TestingOct 21 2014Part 1 of this paper describes a modification of the original Miller twist rule for computing gyroscopic bullet stability that is better suited to plastic-tipped bullets. The original Miller twist rule assumes a bullet of constant density, but it also ... More
Detection of the Stellar Intracluster Medium in Perseus (Abell 426)Mar 29 2017Hubble Space Telescope photometry from the ACS/WFC and WFPC2 cameras is used to detect and measure globular clusters (GCs) in the central region of the rich Perseus cluster of galaxies. A detectable population of Intragalactic GCs is found extending out ... More
There's No Comparison: Reference-less Evaluation Metrics in Grammatical Error CorrectionOct 07 2016Current methods for automatically evaluating grammatical error correction (GEC) systems rely on gold-standard references. However, these methods suffer from penalizing grammatical edits that are correct but not in the gold standard. We show that reference-less ... More
Fast Bayesian Inference for Exoplanet Discovery in Radial Velocity DataJan 27 2015Inferring the number of planets $N$ in an exoplanetary system from radial velocity (RV) data is a challenging task. Recently, it has become clear that RV data can contain periodic signals due to stellar activity, which can be difficult to distinguish ... More
Constraints on the Geometries of Black Holes in Classical and Semiclassical GravityNov 20 1997Constraints on the geometries of static spherically symmetric black holes are obtained by requiring that the spacetime curvature be analytic at the event horizon. Further constraints are obtained by requiring that the semiclassical trace equation be satisfied ... More
Constraints on Black Holes in Classical and Semiclassical Theories of GravityJul 11 1997Constraints on the geometry of a static spherically symmetric black hole are obtained by requiring the spacetime curvature to be analytic at the event horizon. For a zero temperature black hole further constraints are obtained by also requiring that the ... More
Imaging Cool Giant Planets in Reflected Light: Science Investigations and Synergy with Habitable PlanetsMar 22 2019Mar 26 2019Planned astronomical observatories of the 2020s will be capable of obtaining reflected light photometry and spectroscopy of cool extrasolar giant planets. Here we explain that such data are valuable both for understanding the origin and evolution of giant ... More
Evidence for Magnetoreception in Red Drum (Sciaenops ocellatus), Black Drum (Pogonias cromis), and Sea Catfish (Ariopsis felis)Nov 30 2015Over the past few decades, magnetoreception has been discovered in several species of teleost and elasmobranch fishes by employing varied experimental methods including conditioning experiments, observations of alignment with external fields, and experiments ... More
Measuring thrust and predicting trajectory in model rocketryMar 09 2009Methods are presented for measuring thrust using common force sensors and data acquisition to construct a dynamic force plate. A spreadsheet can be used to compute trajectory by integrating the equations of motion numerically. These techniques can be ... More
Homogeneous BandsNov 29 2016A countable band $B$ is called homogeneous if every isomorphism between finitely generated subbands extends to an automorphism of $B$. In this paper we give a complete classification of all the homogeneous bands. We prove that a homogeneous band belongs ... More
Cusp shapes of Hilbert-Blumenthal surfaces and floor simplicityNov 07 2017Apr 20 2018We introduce a new fundamental domain for the cusp stabilizer of a Hilbert modular group over a real quadratic field K=Q(sqrt n) of class number 1, computed using a Dirichlet domain for the maximal unipotent subgroup. This region is the product of R^+ ... More
``Theoretical mathematics'': Toward a cultural synthesis of mathematics and theoretical physicsJul 01 1993Is speculative mathematics dangerous? Recent interactions between physics and mathematics pose the question with some force: traditional mathematical norms discourage speculation, but it is the fabric of theoretical physics. In practice there can be benefits, ... More
Homogeneous BandsNov 29 2016Aug 10 2017A countable band $B$ is called homogeneous if every isomorphism between finitely generated subbands extends to an automorphism of $B$. In this paper we give a complete classification of all the homogeneous bands. We prove that a homogeneous band belongs ... More
Summary and Outlook for 9th International Symposium on Heavy Flavor PhysicsNov 14 2001This is the summary talk of a meeting held at the California Institute of Technology Sept 10-13, 2001. I do not attempt to summarize all the beautiful experimental results we have seen this week, nor to repeat the lively theoretical discussions that have ... More
Fermi surface enlargement on the Kondo latticeFeb 26 2019The Kondo lattice model is a paradigmatic model for the description of local moment systems, a class of materials exhibiting a range of strongly correlated phenomena including heavy fermion formation, magnetism, quantum criticality and unconventional ... More
Excited states in Bethe ansatz solvable models and the dressing of spin and chargeNov 23 2012Jun 21 2013A general formalism for the study of excitations above equilibrium in Bethe ansatz solvable models is presented. Nonzero temperature expressions for dressed energy, momentum, spin and charge are obtained, and it is found that the dressed spin and charge ... More
Fragmentation of protoplanetary disks around M-dwarfsJul 23 2016We investigate the conditions required for planet formation via gravitational instability (GI) and protoplanetary disk (PPD) fragmentation around M-dwarfs. Using a suite of 64 SPH simulations with $10^6$ particles, the parameter space of disk mass, temperature, ... More
Homogeneity of Inverse SemigroupsJun 03 2017Aug 11 2017An inverse semigroup $S$ is a semigroup in which every element has a unique inverse in the sense of semigroup theory, that is, if $a \in S$ then there exists a unique $b\in S$ such that $a = aba$ and $b = bab$. We say that an inverse semigroup $S$ is ... More
Spin Observables in Antilambda-Lambda Production from Antiproton-Proton Annihilation with a Transverse Inital State PolarizationAug 04 2000The formalism describing the scattering of two spin-1/2 objects is reviewed for the case of antilambda-lambda production from antiproton-proton annihilation. It is shown that an experiment utilizing a transverse target polarization can, in principle, ... More
Bayesian analysis of polarization measurementsFeb 01 2012A detailed and formal account of polarization measurements using Bayesian analysis is given based on the assumption of gaussian error for the Stokes parameters. This analysis is crucial for the measurement of the polarization degree and angle at very ... More
Prediction of Schottky barriers at electrified junctions for photocatalysis and microelectronicsAug 01 2018Nov 07 2018We consider the electronic barriers that develop in the depletion region of a semiconductor connected to an electrode or immersed in an electrolyte. These barriers govern the current-voltage characteristics of Schottky diodes and the light-harvesting ... More
The (In)Stability of Planetary SystemsJan 09 2004We present results of numerical simulations which examine the dynamical stability of known planetary systems, a star with two or more planets. First we vary the initial conditions of each system based on observational data. We then determine regions of ... More
Finite domination and Novikov rings. Laurent polynomial rings in several variablesOct 16 2014We present a homological characterisation of those chain complexes of modules over a Laurent polynomial ring in several indeterminates which are finitely dominated over the ground ring (that is, are a retract up to homotopy of a bounded complex of finitely ... More
Finite domination and Novikov rings. Laurent polynomial rings in two variablesNov 21 2012May 19 2013Let C be a bounded cochain complex of finitely generated free modules over the Laurent polynomial ring L = R[x,1/x,y,1/y]. The complex C is called R-finitely dominated if it is homotopy equivalent over R to a bounded complex of finitely generated projective ... More
A Variational Bayes Approach to Decoding in a Phase-Uncertain Digital ReceiverJul 04 2011This paper presents a Bayesian approach to symbol and phase inference in a phase-unsynchronized digital receiver. It primarily extends [Quinn 2011] to the multi-symbol case, using the variational Bayes (VB) approximation to deal with the combinatorial ... More
Quantum-continuum calculation of the surface states and electrical response of silicon in solutionJan 06 2017Jul 20 2017A wide range of electrochemical reactions of practical importance occur at the interface between a semiconductor and an electrolyte. We present an embedded density-functional theory method using the recently released self-consistent continuum solvation ... More
The equilibrium landscape of the Heisenberg spin chainApr 26 2019We characterise the equilibrium landscape, the entire manifold of local equilibrium states, of an interacting integrable quantum model. Focusing on the isotropic Heisenberg spin chain, we describe in full generality two complementary frameworks for addressing ... More
The equilibrium landscape of the Heisenberg spin chainApr 26 2019May 20 2019We characterise the equilibrium landscape, the entire manifold of local equilibrium states, of an interacting integrable quantum model. Focusing on the isotropic Heisenberg spin chain, we describe in full generality two complementary frameworks for addressing ... More
Modulated trapping of interacting bosons in one dimensionAug 18 2014We investigate the response of harmonically confined bosons with contact interactions (trapped Lieb-Liniger gas) to modulations of the trapping strength. We explain the structure of resonances at a series of driving frequencies, where size oscillations ... More
An $A_{\infty}$-coalgebra Structure on a Closed Compact SurfaceJan 24 2018Jul 30 2018Let $P$ be an $n$-gon with $n\geq3.$ There is a formal combinatorial $A_\infty$-coalgebra structure on cellular chains $C_*(P)$ with non-vanishing higher order structure when $n\geq5$. If $X_g$ is a closed compact surface of genus $g\geq2$ and $P_g$ is ... More
N-body simulations of terrestrial planet growth with resonant dynamical frictionOct 16 2018We investigate planetesimal accretion via a direct N-body simulation of an annulus at 1 AU orbiting a 1 $M_{\odot}$ star. The planetesimal ring, which initially contains N = $10^6$ bodies is evolved into the oligarchic growth phase. Unlike previous lower ... More
A Statistical Examination of the Short Term Stability of the Upsilon Andromedae SystemJun 09 2000Because of the high eccentricities (~0.3) of two of the possible planets about the star Upsilon Andromeda, the stability of the system requires careful study. We present results of 1000 numerical simulations which explore the orbital parameter space as ... More
Finite domination and Novikov rings. Iterative approachAug 15 2011Oct 12 2011Suppose C is a bounded chain complex of finitely generated free modules over the Laurent polynomial ring L = R[x,1/x]. Then C is R-finitely dominated, ie, homotopy equivalent over R to a bounded chain complex of finitely generated projective R-modules, ... More
Pieces of Eight: 8-bit Neural Machine TranslationApr 13 2018Neural machine translation has achieved levels of fluency and adequacy that would have been surprising a short time ago. Output quality is extremely relevant for industry purposes, however it is equally important to produce results in the shortest time ... More
Triple cascade behaviour in QG and drift turbulence and generation of zonal jetsMay 08 2009We study quasi-geostrophic turbulence and plasma drift turbulence within the Charney-Hasegawa-Mima (CHM) model. We focus, theoretically and using numerical simulations, on conservation of {\em zonostrophy} and on its role in the formation of the zonal ... More
Hubbard-Shastry lattice modelsNov 22 2011Feb 24 2012We consider two lattice models for strongly correlated electrons which are exactly-solvable in one dimension. Along with the Hubbard model and the su(2|2) spin chain, these are the only parity-invariant models that can be obtained from Shastry's R-matrix. ... More
Permutation Group Symmetry and CorrelationsJun 11 2013Correlation factors are constructed that are consistent with the permutation symmetry group of N Fermions at given value of the filling factor.
Into the third dimension: stochastic measurements of Stokes parameters within the Poincaré sphereOct 05 2014Inspired by recent use of polarimetry to study the Cosmic Microwave Background and extragalatic supernovae, a foray into the statistical properties of Stokes parameters expressed in spherical coordinates is began, allowing circular polarization and linear ... More
Axiomatic approach to radiation reaction of scalar point particles in curved spacetimeMay 10 2000Several different methods have recently been proposed for calculating the motion of a point particle coupled to a linearized gravitational field on a curved background. These proposals are motivated by the hope that the point particle system will accurately ... More
Cusp shapes of Hilbert-Blumenthal surfacesNov 07 2017Jun 27 2019We introduce a new fundamental domain for the cusp stabilizer of a Hilbert modular group over a real quadratic field K=Q(sqrt n). This is constructed as the union of Dirichlet domains for the maximal unipotent group, over the leaves in a foliation of ... More
Review of Magnetic Shark Deterrents: Hypothetical Mechanisms and Evidence for SelectivityNov 24 2014Several papers published since 2006 describe effects of magnetic fields on elasmobranchs and assess their utility in reducing negative interactions between sharks and humans, including bycatch reduction. Most of these repeat a single untested hypothesis ... More