Results for "Sarah T. Stewart"

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The structure of terrestrial bodies: Impact heating, corotation limits and synestiasMay 22 2017During accretion, terrestrial bodies attain a wide range of thermal and rotational states, which are accompanied by significant changes in physical structure (size, shape, pressure and temperature profile, etc.). However, variations in structure have ... More
Collisional Stripping and Disruption of Super-EarthsJul 02 2009The final stage of planet formation is dominated by collisions between planetary embryos. The dynamics of this stage determine the orbital configuration and the mass and composition of planets in the system. In the solar system, late giant impacts have ... More
The Formation of the Collisional Family around the Dwarf Planet HaumeaMar 30 2010Haumea, a rapidly rotating elongated dwarf planet (~ 1500 km in diameter), has two satellites and is associated with a "family" of several smaller Kuiper Belt objects (KBOs) in similar orbits. All members of the Haumea system share a water ice spectral ... More
Minimum Radii of Super-Earths: Constraints from Giant ImpactsMar 01 2010The detailed interior structure models of super-Earth planets show that there is degeneracy in the possible bulk compositions of a super-Earth at a given mass and radius, determined via radial velocity and transit measurements, respectively. In addition, ... More
Water/Icy Super-Earths: Giant Impacts and Maximum Water ContentJul 19 2010Water-rich super-Earth exoplanets are expected to be common. We explore the effect of late giant impacts on the final bulk abundance of water in such planets. We present the results from smoothed particle hydrodynamics simulations of impacts between differentiated ... More
Tidal evolution of the Moon from a high-obliquity, high-angular-momentum EarthFeb 09 2018In the giant impact hypothesis for lunar origin, the Moon accreted from an equatorial circum-terrestrial disk; however the current lunar orbital inclination of 5 degrees requires a subsequent dynamical process that is still debated. In addition, the giant ... More
Collisional stripping of planetary crustsDec 07 2017Geochemical studies of planetary accretion and evolution have invoked various degrees of collisional erosion to explain differences in bulk composition between planets and chondrites. Here we undertake a full, dynamical evaluation of 'crustal stripping' ... More
Compositional evolution during rocky protoplanet accretionSep 24 2015The Earth appears non-chondritic in its abundances of refractory lithophile elements, posing a significant problem for our understanding of its formation and evolution. It has been suggested that this non-chondritic composition may be explained by collisional ... More
Full Numerical Simulations of Catastrophic Small Body CollisionsNov 02 2008The outcome of collisions between small icy bodies, such as Kuiper belt objects, is poorly understood and yet a critical component of the evolution of the trans-Neptunian region. The expected physical properties of outer solar system materials (high porosity, ... More
Collisions Between Gravity-Dominated Bodies: 1. Outcome Regimes and Scaling LawsJun 29 2011Jan 05 2012Collisions are the core agent of planet formation. In this work, we derive an analytic description of the dynamical outcome for any collision between gravity-dominated bodies. We conduct high-resolution simulations of collisions between planetesimals; ... More
Self-Assembly in the Growth of Precious OpalJan 04 2010It is proposed that primary nucleation of amorphous microspherulites of hydrated silica in natural proto-precious-opal can be followed by a long range superlattice ordering process by means of electrostatic self-assembly. Necessary conditions in the thermodynamics ... More
On the complexity of deciding whether the distinguishing chromatic number of a graph is at most twoJul 03 2009In an article [3] published recently in this journal, it was shown that when k >= 3, the problem of deciding whether the distinguishing chromatic number of a graph is at most k is NP-hard. We consider the problem when k = 2. In regards to the issue of ... More
Using photoemission spectroscopy to probe a strongly interacting Fermi gasApr 30 2008Ultracold atom gases provide model systems in which many-body quantum physics phenomena can be studied. Recent experiments on Fermi gases have realized a phase transition to a Fermi superfluid state with strong interparticle interactions. This system ... More
Prospecting for exo-Earths in multiple planet systems with a gas giantSep 11 2018In this work, we hunt for the best places to find exo-Earths in the currently known exoplanet population. While it is still unclear whether Jupiter had a beneficial or detrimental effect on the creation of the right environment for a habitable Earth to ... More
Properties of the single Jovian planet population and the pursuit of Solar system analoguesApr 18 2018While the number of exoplanets discovered continues to increase at a rapid rate, we are still to discover any system that truly resembles the Solar system. Existing and near future surveys will likely continue this trend of rapid discovery. To see if ... More
Planet gaps in the dust layer of 3D protoplanetary disks: I. Hydrodynamical simulations of T Tauri disksMay 25 2010Context: While sub-micron- and micron-sized dust grains are generally well mixed with the gas phase in protoplanetary disks, larger grains will be partially decoupled and as a consequence have a different distribution from that of the gas. This has ramifications ... More
SPH simulations of grain growth in protoplanetary disksJun 09 2008Aims: In order to understand the first stages of planet formation, when tiny grains aggregate to form planetesimals, one needs to simultaneously model grain growth, vertical settling and radial migration of dust in protoplanetary disks. In this study, ... More
Direct observation of the Fermi surface in an ultracold atomic gasMar 30 2012The ideal (i.e. noninteracting), homogeneous Fermi gas, with its characteristic sharp Fermi surface in the momentum distribution, is a fundamental concept relevant to the behavior of many systems. With trapped Fermi gases of ultracold atoms, one can realize ... More
Verification of universal relations in a strongly interacting Fermi gasFeb 09 2010Many-body fermion systems are important in many branches of physics, including condensed matter, nuclear, and now cold atom physics. In many cases, the interactions between fermions can be approximated by a contact interaction. A recent theoretical advance ... More
Dust evolution in protoplanetary disksDec 05 2007Jan 10 2008We investigate the behaviour of dust in protoplanetary disks under the action of gas drag using our 3D, two-fluid (gas+dust) SPH code. We present the evolution of the dust spatial distribution in global simulations of planetless disks as well as of disks ... More
3D SPH simulations of grain growth in protoplanetary disksSep 19 2007We present the first results of the treatment of grain growth in our 3D, two-fluid (gas+dust) SPH code describing protoplanetary disks. We implement a scheme able to reproduce the variation of grain sizes caused by a variety of physical processes and ... More
SPH Simulations of Accretion Disks and Narrow RingsJul 12 1995We model a massless viscous disk using Smoothed Particle Hydrodynamics (SPH) and note that it evolves according to the Lynden-Bell \& Pringle theory (1974) until a non-axisymmetric instability develops at the inner edge of the disk. This instability may ... More
3D SPH simulations of grain growth in protoplanetary disksDec 05 2007Jan 10 2008We present the first results of the treatment of grain growth in our 3D, two-fluid (gas+dust) SPH code describing protoplanetary disks. We implement a scheme able to reproduce the variation of grain sizes caused by a variety of physical processes and ... More
Erosive Hit-and-Run Impact Events: Debris UnboundNov 16 2015Erosive collisions among planetary embryos in the inner solar system can lead to multiple remnant bodies, varied in mass, composition and residual velocity. Some of the smaller, unbound debris may become available to seed the main asteroid belt. The makeup ... More
Revisiting the "radial-drift barrier" of planet formation and its relevance in observed protoplanetary discsNov 14 2011Context. To form metre-sized pre-planetesimals in protoplanetary discs, growing grains have to decouple from the gas before they are accreted onto the central star during their phase of fast radial migration and thus overcome the so-called "radial-drift ... More
Insights into Quasar UV Spectra Using Unsupervised Clustering AnalysisMar 10 2016Machine learning can provide powerful tools to detect patterns in multi-dimensional parameter space. We use K-means -a simple yet powerful unsupervised clustering algorithm which picks out structure in unlabeled data- to study a sample of quasar UV spectra ... More
Improved Coincident and Coherent Detection Statistics for Searches for Gravitational Wave Ringdown SignalsOct 09 2013Oct 15 2013We study an improved method for detecting gravitational wave (GW) signals from perturbed black holes by earth-based detectors in the quest for searching for intermediate-mass black holes (IMBHs). Such signals, called ringdowns, are damped sinusoids whose ... More
On the maximum grain size entrained by photoevaporative windsAug 29 2016We model the behaviour of dust grains entrained by photoevaporation-driven winds from protoplanetary discs assuming a non-rotating, plane-parallel disc. We obtain an analytic expression for the maximum entrainable grain size in extreme-UV radiation-driven ... More
2D condensation model for the inner Solar Nebula: an enstatite-rich environmentJan 07 2016Infrared observations provide the dust composition in the protoplanetary discs surface layers, but can not probe the dust chemistry in the midplane, where planet formation occurs. Meteorites show that dynamics was important in determining the dust distribution ... More
Growing dust grains in protoplanetary discs - III. Vertical settlingOct 09 2013Nov 06 2013We aim to derive a simple analytic model to understand the essential properties of vertically settling growing dust grains in laminar protoplanetary discs. Separating the vertical dynamics from the motion in the disc midplane, we integrate the equations ... More
Erosive Hit-and-Run Impact Events: Debris UnboundNov 16 2015Oct 31 2016Erosive collisions among planetary embryos in the inner solar system can lead to multiple remnant bodies, varied in mass, composition and residual velocity. Some of the smaller, unbound debris may become available to seed the main asteroid belt. The makeup ... More
Constraints on the Source of Lunar Cataclysm ImpactorsDec 10 2009Multiple impact basins formed on the Moon about 3.8 Gyr ago in what is known as the lunar cataclysm or late heavy bombardment. Many workers currently interpret the lunar cataclysm as an impact spike primarily caused by main-belt asteroids destabilized ... More
Physical effects of collisions in the Kuiper beltMay 27 2007Collisions are a major modification process over the history of the Kuiper Belt. Recent work illuminates the complex array of possible outcomes of individual collisions onto porous, volatile bodies. The cumulative effects of such collisions on the surface ... More
Algorithmic Diversity for Software SecurityDec 13 2013Software diversity protects against a modern-day exploits such as code-reuse attacks. When an attacker designs a code-reuse attack on an example executable, it relies on replicating the target environment. With software diversity, the attacker cannot ... More
An iterated search for influence from the future on the Large Hadron ColliderDec 05 2007Dec 15 2007We analyse an iterated version of Nielsen and Ninomiya (N&N)'s proposed card game experiment to search for a specific type of backward causation on the running of the Large Hadron Collider (LHC) at CERN. We distinguish "endogenous" and "exogenous" potential ... More
Lectures on the stable homotopy of BGOct 31 2007Mar 30 2009This paper is a survey of the stable homotopy theory of BG for G a finite group. It is based on a series of lectures given at the Summer School associated with the Topology Conference at the Vietnam National University, Hanoi, August 2004.
The Threshold t-tbar Cross Section at NNLL OrderJul 13 2001The total cross section for top quark pair production close to threshold in e+e- annihilation is investigated. Details are given about the calculation at next-to-next-to-leading logarithmic order. The summation of logarithms leads to a convergent expansion ... More
Gamma-rays Associated with Nearby Thunderstorms at Ground LevelAug 07 2014The TGF and Energetic Thunderstorm Rooftop Array (TETRA) is an array of NaI scintillators located at rooftop level on the campus of Louisiana State University in Baton Rouge, Louisiana. From July 2010 through March 2014, TETRA has detected 28 millisecond-duration ... More
ASCA observations of deep ROSAT fields V. The X-ray spectrum of hard X-ray selected QSOsMay 08 2001We present an analysis of the \rosat and \asca spectra of 21 broad line AGN (QSOs) with $z\sim 1$ detected in the 2-10 keV band with the \asca \gis. The summed spectrum in the \asca band is well described by a power-law with $\Gamma=1.56\pm0.18$, flatter ... More
The discovery of a high redshift type 2 QSOSep 04 1995We report the discovery of a high redshift, narrow emission-line galaxy identified in the optical follow-up of deep ROSAT fields. The object has a redshift of z=2.35 and its narrow emission lines together with its high optical and X-ray luminosity imply ... More
p-wave Feshbach moleculesMar 03 2007May 01 2008We have produced and detected molecules using a p-wave Feshbach resonance between 40K atoms. We have measured the binding energy and lifetime for these molecules and we find that the binding energy scales approximately linearly with magnetic field near ... More
Thermal Inflation and the Gravitational Wave BackgroundJan 28 2008Apr 29 2008We consider the impact of thermal inflation -- a short, secondary period of inflation that can arise in supersymmetric scenarios -- on the stochastic gravitational wave background. We show that while the primordial inflationary gravitational wave background ... More
Jet Mass Spectra in Higgs + One Jet at NNLLFeb 04 2013Jul 29 2013The invariant mass of a jet is a benchmark variable describing the structure of jets at the LHC. We calculate the jet mass spectrum for Higgs plus one jet at the LHC at next-to-next-to-leading logarithmic (NNLL) order using a factorization formula. At ... More
Jet Regions from Event Shapes and the N-Jet Soft Function at Hadron CollidersSep 14 2011The N-jettiness event shape divides phase space into N+2 regions, each containing one jet or beam. These jet regions are insensitive to the distribution of soft radiation and, with a geometric measure for N-jettiness, have circular boundaries. We give ... More
Superconductivity in Undoped Single Crystals of BaFe2As2: Field and Current DependenceJul 25 2009In previous work in undoped MFe2As2, partial drops in the resistivity indicative of traces of superconductivity have been observed in some samples of M=Ba (Tc ~ 20 K, up to 25% drop in resistivity) and M=Ca (Tc ~ 10 K, up to 45 % drop in resistivity.) ... More
MOSAIK: A hash-based algorithm for accurate next-generation sequencing read mappingSep 04 2013This paper presents an accurate short-read mapper for next-generation sequencing data which is widely used in the 1000 Genomes Project, and human clinical and other species genome studies.
Predicting multiple planet stability and habitable zone companions in the TESS eraJan 31 2019We present an approach that is able to both rapidly assess the dynamical stability of multiple planet systems, and determine whether an exoplanet system would be capable of hosting a dynamically stable Earth-mass companion in its habitable zone. We conduct ... More
The Major and Minor Galaxy Merger Rates at z < 1.5Aug 11 2011Calculating the galaxy merger rate requires both a census of galaxies identified as merger candidates, and a cosmologically-averaged `observability' timescale T_obs(z) for identifying galaxy mergers. While many have counted galaxy mergers using a variety ... More
ASCA observations of deep ROSAT fields I. the nature of the X-ray source populationsApr 15 1997We present ASCA GIS observations (total exposure 100-200 ksec) of three fields which form part of our deep ROSAT survey. We detect 26 sources down to a limiting flux (2-10 keV) of 5x10^{-14} erg cm-2 s-1. Sources down to this flux level contribute 30 ... More
ASCA observations of deep ROSAT fields IV.IR and hard X-ray observations of an obscured high-redshift QSOOct 26 1998We use UKIRT and ASCA observations to determine the nature of a high redshift (z=2.35) narrow-line AGN, previously discovered by Almaini et al. (1995). The UKIRT observations show a broad Halpha line while no Hbeta line is detected. This together with ... More
TETRA Observation of Gamma Rays at Ground Level Associated with Nearby ThunderstormsDec 19 2013Terrestrial Gamma ray Flashes (TGFs) -- very short, intense bursts of electrons, positrons, and energetic photons originating from terrestrial thunderstorms -- have been detected with satellite instruments. TETRA, an array of NaI(Tl) scintillators at ... More
Predicting Dust Distribution in Protoplanetary DiscsOct 31 2003We present the results of three-dimensional numerical simulations that include the effects of hydrodynamical forces and gas drag upon an evolving dusty gas disk. We briefly describe a new parallel, two phase numerical code based upon the smoothed particle ... More
Computational Topology for Regular Closed SetsFeb 26 2004The Boolean algebra of regular closed sets is prominent in topology, particularly as a dual for the Stone-Cech compactification. This algebra is also central for the theory of geometric computation, as a representation for combinatorial operations on ... More
Delayed Impact of Fair Machine LearningMar 12 2018Apr 07 2018Fairness in machine learning has predominantly been studied in static classification settings without concern for how decisions change the underlying population over time. Conventional wisdom suggests that fairness criteria promote the long-term well-being ... More
On the problem of non-zero word error rates for fixed rate error correction codes in continuous variable quantum key distributionMay 16 2016Oct 05 2016The maximum operation range of continuous variable quantum key distribution systems has shown to be improved by employing high efficiency forward error correction codes such as multi-edge low-density parity-check codes. In this paper, we show that the ... More
Forecasting [C II] line-intensity mapping measurements between the end of reionization and the epoch of galaxy assemblyDec 19 2018We combine recent simulation work on the SFR--[C II] correlation at high redshift with empirical modeling of the galaxy--halo connection (via UniverseMachine) to forecast [C II] auto power spectra from $z\sim4$ to $z\sim8$. We compare these to sensitivities ... More
A Collisional Origin to Earth's Non-chondritic Composition?Oct 13 2014Several lines of evidence indicate a non-chondritic composition for Bulk Earth. If Earth formed from the accretion of chondritic material, its non-chondritic composition, in particular the super-chondritic 142Nd/144Nd and low Mg/Fe ratios, might be explained ... More
Photon production from gluon mediated quark-anti-quark annihilation at confinementApr 07 2015Jun 20 2015Heavy ion collisions at RHIC produce direct photons at low transverse momentum, $p_{T}$ from 1-3 GeV/c, in excess of the $p$$+$$p$ spectra scaled by the nuclear overlap factor, $T_{AA}$. These low $p_{T}$ photons have a large azimuthal anisotropy, $v_{2}$. ... More
Exactness of free and amenable groups by the construction of Ozawa kernelsSep 15 2004Jun 01 2005Using properties of their Cayley graphs, specific examples of Ozawa kernels are constructed for both free and amenable groups, thus showing that these groups satisfy Property O. It is deduced both that these groups are exact and satisfy Yu's Property ... More
Landau Levels, Anisotropy and HolographyJun 13 2013We analyze properties of field theories dual to extremal black branes in (4+1) dimensions with anisotropic near-horizon geometries. Such gravity solutions were recently shown to fall into nine classes which align with the Bianchi classification of real ... More
On the polynomial Szemerédi's theorem in finite fieldsFeb 06 2018Let $P_1,\dots,P_m\in\mathbb{Z}[y]$ be any linearly independent polynomials with zero constant term. We show that there exists a $\gamma>0$ such that any subset of $\mathbb{F}_q$ of size at least $q^{1-\gamma}$ contains a nontrivial polynomial progression ... More
Factorization, Effective Field Theory, and B-> D^(*) X DecaysSep 14 2002Nov 21 2002In this proceedings I review the soft-collinear effective theory (SCET), an effective theory for energetic particles. I also discuss factorization in exclusive and inclusive B-> D^(*)X decays, and tests which can help distinguish whether factorization ... More
Bound States in NRQCD/NRQED and the Renormalization GroupSep 15 2000The application of renormalization group techniques to bound states in non-relativistic QED and QCD is discussed. For QED bound states like Hydrogen and positronium, the renormalization group allows large logarithms of the velocity, ln v (or equivalently ... More
Applications of Chiral Perturbation Theory in Reactions with Heavy ParticlesJul 21 1999Effective field theory techniques are used to describe the interaction of heavy hadrons in a model independent way. Predictability is obtained by exploiting the symmetries of QCD. Heavy hadron chiral perturbation theory is reviewed and used to describe ... More
Maximum-likelihood detection of sources among Poissonian noiseJan 21 2009A maximum likelihood (ML) technique for detecting compact sources in images of the x-ray sky is examined. Such images, in the relatively low exposure regime accessible to present x-ray observatories, exhibit Poissonian noise at background flux levels. ... More
The Soft-Collinear Effective TheoryJul 20 2002In this talk I review an effective field theory that has been developed for processes with energetic hadrons, referred to as the Soft-Collinear Effective Theory. After outlining properties of the effective theory I briefly discuss its application to the ... More
Observational Constraints on Theories with a Blue Spectrum of Tensor ModesNov 28 2007Jul 13 2008Motivated by the string gas cosmological model, which predicts a blue tilt of the primordial gravitational wave spectrum, we examine the constraints imposed by current and planned observations on a blue tilted tensor spectrum. Starting from an expression ... More
UBe13 and U1-xThxBe13: Unconventional SuperconductorsDec 23 2018Jan 14 2019UBe13 was the second discovered heavy fermion superconductor, and numerous pieces of evidence exist that imply that it is an unconventional (non-BCS, non-s wave pairing symmetry) superconductor. Exhibiting even more signs of unconventional superconductivity, ... More
An Explicit Construction of Type A Demazure AtomsJul 28 2007Apr 02 2009Demazure characters of type A, which are equivalent to key polynomials, have been decomposed by Lascoux and Sch\"{u}tzenberger into standard bases. We prove that the resulting polynomials, which we call Demazure atoms, can be obtained from a certain specialization ... More
Asymptotic Growth of Associated Primes of Certain Graph IdealsApr 15 2012Dec 05 2012We specify a class of graphs, $H_t$, and characterize the irreducible decomposition of all powers of the cover ideals. This gives insight into the structure and stabilization of the corresponding associated primes; specifically, providing an answer to ... More
Random walks on the BMW monoid: an algebraic approachMay 17 2016May 31 2016We consider Metropolis-based systematic scan algorithms for generating Birman-Murakami-Wenzl (BMW) monoid basis elements of the BMW algebra. As the BMW monoid consists of tangle diagrams, these scanning strategies can be rephrased as random walks on links ... More
Racah Polynomials and Recoupling Schemes of $\mathfrak{su}(1,1)$Apr 14 2015Jul 23 2015The connection between the recoupling scheme of four copies of $\mathfrak{su}(1,1)$, the generic superintegrable system on the 3 sphere, and bivariate Racah polynomials is identified. The Racah polynomials are presented as connection coefficients between ... More
ALMA images of discs: are all gaps carved by planets?Sep 02 2015Protoplanetary discs are now routinely observed and exoplanets, after the numerous indirect discoveries, are starting to be directly imaged. To better understand the planet formation process, the next step is the detection of forming planets or of signposts ... More
Atom--Molecule Coherence in a Bose-Einstein CondensateApr 20 2002Apr 30 2002Coherent coupling between atoms and molecules in a Bose-Einstein condensate (BEC) has been observed. Oscillations between atomic and molecular states were excited by sudden changes in the magnetic field near a Feshbach resonance and persisted for many ... More
Patterning Superconductivity in a Topological InsulatorOct 27 2016While topological superconductors are predicted to provide building blocks for fault-tolerant quantum computing, one of the remaining challenges is to find a convenient experimental platform that would allow patterning of circuits. We find that superconductivity ... More
The pinnacle set of a permutationApr 18 2017Peak sets of a permutation record the indices of its peaks. These sets have been studied in a variety of contexts, including recent work by Billey, Burdzy, and Sagan, which enumerated permutations with prescribed peak sets. In this article, we look at ... More
Dust distribution in protoplanetary disks - Vertical settling and radial migrationAug 22 2005We present the results of a three dimensional, locally isothermal, non-self-gravitating SPH code which models protoplanetary disks with two fluids: gas and dust. We ran simulations of a 1 Msun star surrounded by a 0.01 Msun disk comprising 99% gas and ... More
Characterization of Low Mass K2 Planet Hosts Using Near-Infrared SpectroscopyAug 10 2018We present moderate resolution near-infrared spectra in $H, J$ and $K$ band of M dwarf hosts to candidate transiting exoplanets discovered by NASA's K2 mission. We employ known empirical relationships between spectral features and physical stellar properties ... More
Data-model comparison using FORWARD and CoMPNov 13 2015The FORWARD SolarSoft IDL package is a community resource for model-data comparison, with a particular emphasis on analyzing coronal magnetic fields. FORWARD allows the synthesis of coronal polarimetric signals at visible, infrared, and radio frequencies, ... More
On exponential sums over orbits in $\mathbb{F}_p^d$Jun 10 2016Aug 23 2016This paper proves a bound for exponential sums over orbits of vectors in $\mathbb{F}_p^d$ under subgroups of $\rm{GL}_d(\mathbb{F}_p)$. The main tool is a classification theorem for approximate groups due to Gill, Helfgott, Pyber, and Szab\'o.
Hidden Photons in beam dump experiments and in connection with Dark MatterDec 18 2012Hidden sectors with light extra U(1) gauge bosons, so-called hidden photons, recently received much interest as natural feature of beyond standard model scenarios like string theory and SUSY and because of their possible connection to dark matter. This ... More
The Asymptotics of Symbolic Generic Initial Systems of Six Points in P2Oct 31 2012Apr 30 2013Consider the ideal I in K[x,y,z] corresponding to six points of P2. We study the limiting behaviour of the symbolic generic initial system, of I obtained by taking the reverse lexicographic generic initial ideals of the symbolic powers of I. The main ... More
A 3-Local Characterization of the Harada--Norton Sporadic Simple GroupSep 25 2012We provide 3-local characterizations of the Harada--Norton sporadic simple group and its automorphism group. Both groups are examples of groups of parabolic characteristic three and we identify them from the structure of the normalizer of the centre of ... More
The Generic Initial Ideals of Powers of a 2-Complete IntersectionJun 25 2012Sep 30 2012We compute the reverse lexicographic generic initial ideals of the powers of a 2-complete intersection ideal I. In particular, we give six algorithms to compute these generic initial ideals, the choice of which depends on the power and on the relative ... More
A Decomposition of Schur functions and an analogue of the Robinson-Schensted-Knuth AlgorithmApr 19 2006Apr 02 2009We exhibit a weight-preserving bijection between semi-standard Young tableaux and semi-skyline augmented fillings to provide a combinatorial proof that the Schur functions decompose into nonsymmetric functions indexed by compositions. The insertion procedure ... More
Hairdressing in groups: a survey of combings and formal languagesOct 29 1998A group is combable if it can be represented by a language of words satisfying a fellow traveller property; an automatic group has a synchronous combing which is a regular language. This article surveys results for combable groups, in particular in the ... More
Multizeta values: Lie algebras and periods on $\mathfrak{M}_{0,n}$Nov 13 2009This thesis is a study of algebraic and geometric relations between multizeta values. In chapter 2, we prove a result which gives the dimension of the associated depth-graded pieces of the double shuffle Lie algebra in depths 1 and 2. In chapters 3 and ... More
Oracle inequalities for the Lasso in the high-dimensional Aalen multiplicative intensity modelJun 25 2012Oct 14 2013In a general counting process setting, we consider the problem of obtaining a prognostic on the survival time adjusted on covariates in high-dimension. Towards this end, we construct an estimator of the whole conditional intensity. We estimate it by the ... More
Infinite-dimensional cohomology of SL_2(Z[t, 1/t])Jun 05 2015For J an integral domain and F its field of fractions, we construct a map from the 3-skeleton of the classifying space for {\Gamma} = SL_2(J[t,1/t]) to a Euclidean building on which {\Gamma} acts. We then find an infinite family of independent cocycles ... More
sPHENIX: The next generation heavy ion detector at RHICNov 09 2016sPHENIX is a new collaboration and future detector project at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC). It seeks to answer fundamental questions on the nature of the quark gluon plasma (QGP), including its temperature dependence ... More
Varieties for modules of finite dimensional Hopf algebrasDec 02 2016We survey variety theory for modules of finite dimensional Hopf algebras, recalling some definitions and basic properties of support and rank varieties where they are known. We focus specifically on properties known for classes of examples such as finite ... More
Periods on the moduli space of genus 0 curvesNov 13 2009This report outlines a combinatorial recipe for computing the bases, whose elements are oriented polygons, of two cohomology spaces associated to multizeta values: the top dimensional de Rham cohomology of moduli spaces of genus 0 complex pointed curves ... More
Label-Free Supervision of Neural Networks with Physics and Domain KnowledgeSep 18 2016In many machine learning applications, labeled data is scarce and obtaining more labels is expensive. We introduce a new approach to supervising neural networks by specifying constraints that should hold over the output space, rather than direct examples ... More
Stasis Points and Approximating Two-CyclesApr 18 2005Generically, every fixed point for the differential inclusion x' in ConvexHull{f_1,f_2} can be approximated by an arbitrarily small two-cycle for the inclusion x' in {f_1,f_2}, where f_1, f_2 are a C^1 flows on R^n.
Program schemes with binary write-once arrays and the complexity classes they captureDec 03 2001We study a class of program schemes, NPSB, in which, aside from basic assignments, non-deterministic guessing and while loops, we have access to arrays; but where these arrays are binary write-once in that they are initialized to `zero' and can only ever ... More
On the Mathematics of Data Centre Network TopologiesMay 03 2016The theory of combinatorial designs has recently been used in order to build switch-centric data centre networks incorporating a large number of servers, in comparison with the popular Fat-Tree data centre network. The construction employed, called the ... More
The second cohomology of simple SL_2-modulesApr 03 2009Jul 27 2009Let $G$ be the simple algebraic group $SL_2$ defined over an algebraically closed field $K$ of characteristic $p>0$. In this paper, we find the second cohomology of all irreducible representations of $G$
The second cohomology of simple SL_3-modulesJul 27 2009Apr 10 2012Let G be the simple, simply connected algebraic group SL_3 defined over an algebraically closed field K of characteristic p>0. In this paper, we find H^2(G,V) for any irreducible G-module V. When p>7 we also find H^2(G(q),V) for any irreducible G(q)-module ... More
Extraction of the D^*Dπcoupling from D^* decaysMar 03 1998Jun 09 1998The decays D^* -> D\pi and D^* -> D\gamma are well described by heavy meson chiral perturbation theory. With the recent measurement of Br(D^{*+} -> D^+ \gamma), the D^{*0}, D^{*+}, and D_s^* branching fractions can be used to extract the D^*D\pi and D^*D\gamma ... More
On the freeness of the cyclotomic BMW algebras: admissibility and an isomorphism with the cyclotomic Kauffman tangle algebrasNov 27 2009The cyclotomic Birman-Murakami-Wenzl (BMW) algebras B_n^k, introduced by R. H\"aring-Oldenburg, are a generalisation of the BMW algebras associated with the cyclotomic Hecke algebras of type G(k,1,n) (aka Ariki-Koike algebras) and type B knot theory. ... More