Results for "Sean R Giblin"

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Zig-zag ladders with staggered magnetic chirality in S = 3/2 compound beta-CaCr2O4Jun 18 2009The crystal and magnetic structures of the S = 3/2 chain antiferromagnet beta-CaCr2O4 have been investigated by means of specific heat, magnetization, muon relaxation and neutron powder diffraction between 300K and 1.5K. Owing to the original topology ... More
Observation of low frequency spin dynamics in INVAR Fe$_{65}$Ni$_{35}$Mar 10 2016Jun 02 2016We present ferromagnetic neutron spin echo measurements and muon spin relaxation ($\mu$SR) measurements of the spin dynamics in the ordered phase of the metallic alloy INVAR Fe$_{65}$Ni$_{35}$. Both techniques display evidence of slow spin dynamics in ... More
Mapping the first order magnetic transition in Yb$_2$Ti$_2$O$_7$May 12 2014The very nature of the ground state of the pyrochlore compound Yb$_2$Ti$_2$O$_7$ is much debated, as experimental results demonstrate evidence for both a disordered or a long-range ordered ground state. Indeed, the delicate balance of exchange interactions ... More
Dipolar spin ice states with fast monopole hopping rate in CdEr$_2$X$_4$ (X = Se, S)May 30 2017Mar 20 2018Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr$_2$Se$_4$ is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are ... More
Two-photon Lithography for 3D Magnetic Nanostructure FabricationJul 11 2017Ferromagnetic materials have been utilised as recording media within data storage devices for many decades. Confinement of the material to a two dimensional plane is a significant bottleneck in achieving ultra-high recording densities and this has led ... More
Experimental signature of the attractive Coulomb force between positive and negative magnetic monopoles in spin iceMar 31 2016Apr 26 2017A non-Ohmic current that grows exponentially with the square root of applied electric field is well known from thermionic field emission (the Schottky effect), electrolytes (the second Wien effect) and semiconductors (the Poole-Frenkel effect). It is ... More
Bridge numbers of knots in the page of an open bookFeb 14 2015Given any closed, connected, orientable $3$--manifold and integers $g\geq g(M), D > 0$, we show the existence of knots in $M$ whose genus $g$ bridge number is greater than $D$. These knots lie in a page of an open book decomposition of $M$, and the proof ... More
Observation of a superconducting glass state in granular superconducting diamondMar 05 2018The magnetic field dependence of the superconductivity in nanocrystalline boron doped diamond thin films is reported. Evidence of a glass state in the phase diagram is presented, as demonstrated by electrical resistance and magnetic relaxation measurements. ... More
Classification of continuously transitive circle groupsMar 01 2009Let G be a closed transitive subgroup of Homeo(S^1) which contains a non-constant continuous path f: [0,1] --> G. We show that up to conjugation G is one of the following groups: SO(2,R), PSL(2,R), PSL_k(2,R), Homeo_k(S^1), Homeo(S^1). This verifies the ... More
Thermal-error regime in high-accuracy gigahertz single-electron pumpingMar 14 2017Nov 13 2017Single-electron pumps based on semiconductor quantum dots are promising candidates for the emerging quantum standard of electrical current. They can transfer discrete charges with part-per-million (ppm) precision in nanosecond time scales. Here, we employ ... More
Geometry of isophote curvesDec 01 2009In this paper, we consider the intensity surface of a 2D image, we study the evolution of the symmetry sets (and medial axes) of 1-parameter families of iso-intensity curves. This extends the investigation done on 1-parameter families of smooth plane ... More
Magnetic Order in the Pyrochlore Iridates A2Ir2O7 (A = Y, Yb)Mar 29 2012We present results from muon spin relaxation/rotation, magnetization, neutron scattering and transport measurements on polycrystalline samples of the pyrochlore iridates Y2Ir2O7 (Y-227) and Yb2Ir2O7 (Yb-227). Well-defined spontaneous oscillations of the ... More
Magnetization and Hall effect studies on the pyrochlore iridate Nd2Ir2O7Dec 21 2012We present magnetization and Hall effect measurements on the pyrochlore iridate Nd2Ir2O7. Previous muon spin rotation measurements have shown that the system undergoes an unusual transition at T$_M$ = 110 K into a magnetic phase lacking long-range order, ... More
Pre-Symmetry Sets of 3D shapesMay 05 2005The investigation of 3D euclidean symmetry sets (SS) and medial axis is an important area, due in particular to their various important applications. The pre-symmetry set of a surface M in 3-space (resp. smooth closed curve in 2D) is the set of pairs ... More
Global Structure of a Black-Hole Cosmos and its ExtremesApr 06 1993We analyze the global structure of a family of Einstein-Maxwell solutions parametrized by mass, charge and cosmological constant. In a qualitative classification there are: (i) generic black-hole solutions, describing a Wheeler wormhole in a closed cosmos ... More
Most likely paths to error when estimating the mean of a reflected random walkJun 24 2009Jun 25 2010It is known that simulation of the mean position of a Reflected Random Walk (RRW) $\{W_n\}$ exhibits non-standard behavior, even for light-tailed increment distributions with negative drift. The Large Deviation Principle (LDP) holds for deviations below ... More
Bridge spectra of twisted torus knotsMar 25 2014We compute the genus zero bridge numbers and give lower bounds on the genus one bridge numbers for a large class of sufficiently generic hyperbolic twisted torus knots. As a result, the bridge spectra of these knots have two gaps which can be chosen to ... More
Estimating Loynes' exponentOct 28 2009Loynes' distribution, which characterizes the one dimensional marginal of the stationary solution to Lindley's recursion, possesses an ultimately exponential tail for a large class of increment processes. If one can observe increments but does not know ... More
Vertices and inflexions of plane sections of surfaces in R^3Feb 25 2005Oct 07 2005We investigate the behaviour of vertices and inflexions on 1-parameter families of curves on smooth surfaces in the 3-space, which include a singular member. In particular, we discuss the context where the curves evolve as sections of a smooth surface ... More
Evolution of spin relaxation processes in LiY$_{1-x}$Ho$_x$F$_4$ with increasing x studied via AC-susceptibility and muon spin relaxationJul 12 2012We present measurements of magnetic field and frequency dependences of the low temperature (T = 1.8 K) AC-susceptibility, and temperature and field dependences of the longitudinal field positive muon spin relaxation ({\mu}SR) for LiY$_{1-x}$Ho$_x$F$_4$ ... More
Calculating electron momentum densities and Compton profiles using the linear tetrahedron methodNov 13 2014A method for computing electron momentum densities and Compton profiles from ab initio calculations is presented. Reciprocal space is divided into optimally-shaped tetrahedra for interpolation, and the linear tetrahedron method is used to obtain the momentum ... More
Competing Interactions and Magnetic Frustration in Yb4LiGe4Oct 01 2011Nov 01 2011We have studied polycrystalline Yb4LiGe4, a ternary variant of the R5T4 family of layered compounds characterized by a very strong coupling between the magnetic and crystallographic degrees of freedom. The system is mixed valent, with non-magnetic Yb2+ ... More
Design and development of a low temperature, inductance based high frequency ac susceptometerOct 02 2018We report on the development of an induction based low temperature high frequency ac susceptometer capable of measuring at frequencies up to 3.5 MHz and at temperatures between 2 K and 300 K. Careful balancing of the detection coils and calibration have ... More
Thin Tree PositionAug 15 2014We introduce a method for creating a special type of tree, called a tree position, from a weighted graph. Leaves of the tree correspond to vertices of the original graph, and the tree edges contain information which can be used to partition these vertices. ... More
An application of topological graph clustering to protein function predictionAug 24 2014We use a semisupervised learning algorithm based on a topological data analysis approach to assign functional categories to yeast proteins using similarity graphs. This new approach to analyzing biological networks yields results that are as good as or ... More
Spectroastrometric Study of Ro-vibrational CO Emission from the Herbig Ae star HD~179218 with iSHELL on the NASA Infrared Telescope FacilityMay 07 2018We present analysis of commissioning $M-$band data acquired with the infrared echelle spectrograph (iSHELL) on {\it NASA's Infrared Telescope Facility}. In this paper we describe the delivered performance of the instrument for these $M-$band observations ... More
Creation of long-term coherent optical memory via controlled nonlinear interactions in Bose-Einstein condensatesSep 17 2009Dec 07 2009A Bose-Einstein condensate confined in an optical dipole trap is used to generate long-term coherent memory for light, and storage times of more than one second are observed. Phase coherence of the condensate as well as controlled manipulations of elastic ... More
How to Draw Graphs: Seeing and Redrafting Large Networks in Security and BiologyMar 03 2014A graph is a mathematical object consisting of a set of vertices and a set of edges connecting vertices. Graphs can be drawn on paper in various ways, but until recently all published methods of drawing graphs have had undesirable properties: (i) for ... More
Preheating in Full General RelativityJul 24 2019Aug 05 2019We investigate the importance of local gravity during preheating, the non-linear dynamics that may be responsible for starting the process of reheating the universe after inflation. We introduce three numerical methods that study a simple preheating scenario ... More
A Novel Single-Source Surface Integral Method to Compute Scattering from Dielectric ObjectsNov 18 2016Using the traditional surface integral methods, the computation of scattering from a dielectric object requires two equivalent current densities on the boundary of the dielectric. In this paper, we present an approach that requires only a single current ... More
Are we there yet? Understanding the challenges faced in complying with the General Data Protection Regulation (GDPR)Aug 22 2018The EU General Data Protection Regulation (GDPR), enforced from 25th May 2018, aims to reform how organisations view and control the personal data of private EU citizens. The scope of GDPR is somewhat unprecedented: it regulates every aspect of personal ... More
Demographics of Transition Discs in Ophiuchus and TaurusApr 20 2015Transition disc systems are young stars that appear to be on the verge of dispersing their protoplanetary discs. We explore the nature of these systems by comparing the stellar accretion rates and disc masses of transition discs and normal T Tauri stars ... More
High-Resolution Near Infrared Spectroscopy of HD~100546: IV. Orbiting Companion Disappears on ScheduleJul 31 2019HD~100546 is a Herbig Ae/Be star surrounded by a disk with a large central region that is cleared of gas and dust (i.e., an inner hole). High-resolution near-infrared spectroscopy reveals a rich emission spectrum of fundamental ro-vibrational CO emission ... More
A Hierarchy of Scheduler Classes for Stochastic AutomataOct 16 2017Stochastic automata are a formal compositional model for concurrent stochastic timed systems, with general distributions and non-deterministic choices. Measures of interest are defined over schedulers that resolve the nondeterminism. In this paper we ... More
Asynchronous and Dynamic Coverage Control Scheme for Persistent Surveillance MissionsSep 17 2016Feb 15 2017A decomposition-based coverage control scheme is proposed for multi-agent, persistent surveillance missions operating in a communication-constrained, dynamic environment. The proposed approach decouples high-level task assignment from low-level motion ... More
GAMA+KiDS: Alignment of galaxies in galaxy groups and its dependence on galaxy scaleMay 01 2019Jul 05 2019Intrinsic galaxy alignments are a source of bias for weak lensing measurements as well as a tool for understanding galaxy formation and evolution. In this work, we measure the alignment of shapes of satellite galaxies, in galaxy groups, with respect to ... More
Quantitative analysis of the interaction between a dc SQUID and an integrated micromechanical doubly clamped cantileverFeb 08 2019Based on the superconducting quantum interference device (SQUID) equations described by the resistively- and capacitively-shunted junction model coupled to the equation of motion of a damped harmonic oscillator, we provide simulations to quantitatively ... More
Ro-vibrational CO Detected in the $β$~Pictoris Circumstellar DiskJun 13 2011We present high resolution near-infrared spectra of $\beta$ Pictoris - a nearby young star with a debris disk. Fundamental low-J CO absorption lines are detected and strict upper limits are placed on the flux of v=2-1 low-J CO emission lines. The limit ... More
Gravitational Waves From the End of Inflation: Computational StrategiesDec 18 2007Parametric resonance or preheating is a plausible mechanism for bringing about the transition between the inflationary phase and a hot, radiation dominated universe. This epoch results in the rapid production of heavy particles far from thermal equilibrium ... More
On the road to per cent level accuracy II: calibration of the non-linear matter power spectrum for arbitrary cosmologiesJun 06 2019We introduce an emulator approach to predict the non-linear matter power spectrum for broad classes of beyond-$\Lambda$CDM cosmologies, using only a suite of $\Lambda$CDM $N$-body simulations. By including a range of suitably modified initial conditions ... More
Deep learning to generate in silico chemical property libraries and candidate molecules for small molecule identification in complex samplesMay 21 2019Comprehensive and unambiguous identification of small molecules in complex samples will revolutionize our understanding of the role of metabolites in biological systems. Existing and emerging technologies have enabled measurement of chemical properties ... More
Level sets of functions and symmetry sets of smooth surface sectionsApr 19 2005We prove that the level sets of a real C^s function of two variables near a non-degenerate critical point are of class C^[s/2] and apply this to the study of planar sections of surfaces close to the singular section by the tangent plane at hyperbolic ... More
On transversally elliptic operators and the quantization of manifolds with $f$-structureJan 30 2011Mar 23 2011An $f$-structure on a manifold $M$ is an endomorphism field $\phi\in\Gamma(M,\End(TM))$ such that $\phi^3+\phi=0$. Any $f$-structure $\phi$ determines an almost CR structure $E_{1,0}\subset T_\C M$ given by the $+i$-eigenbundle of $\phi$. Using a compatible ... More
BiLipschitz decomposition of Lipschitz maps between Carnot groupsJan 19 2015Aug 29 2015Let $f : G \to H$ be a Lipschitz map between two Carnot groups. We show that if $B$ is ball of $G$, then there exists a subset $Z \subset B$, whose image in $H$ under $f$ has small Hausdorff content, such that $B \backslash Z$ can be decomposed into a ... More
Coarse differentiation and quantitative nonembeddability for Carnot groupsApr 24 2013Jun 18 2013We give lower bound estimates for the macroscopic scale of coarse differentiability of Lipschitz maps from a Carnot group with the Carnot-Carath\'{e}odory metric $(G,\dcc)$ to a few different classes of metric spaces. Using this result, we derive lower ... More
Summary of Heavy Ion TheorySep 15 1994Sep 20 1994Can we study hot QCD using nuclear collisions? Can we learn about metallic hydrogen from the impact of comet Shoemaker-Levy 9 on Jupiter? The answer to both questions may surprise you! I summarize progress in relativistic heavy ion theory reported at ... More
Strange Disoriented Chiral CondensateApr 25 2002Disoriented chiral condensate can produce novel fluctuations of kaons as well as pions. Robust statistical observables can be used to extract the novel fluctuations from background contributions in K-short and K-charged correlation measurements in nuclear ... More
Dynamics of Chiral Symmetry Breaking in Nuclear CollisionsJul 25 1994Measurements of disoriented chiral condensates in heavy ion collisions at RHIC and the LHC can yield fundamental information on the nature of the QCD phase transition. I review theoretical efforts to understand the evolution of the condensate and present ... More
The Large Energy Expansion for B Decays: Soft Collinear Effective TheorySep 11 2003I this talk I give an introduction to the soft collinear effective theory by considering in detail the decay rate for $B \to X_s \gamma$ near the endpoint.
The Resummed Photon Spectrum in Radiative Upsilon Decays (And More)Sep 01 2003In this talk I present the results of two calculations that make use of Non-Relativistic QCD and the newly developed Soft-Collinear Effective Theory. The first process considered is inclusive radiative $\Upsilon$ decay. The second process considered is ... More
On the universality of the nonstationary idealApr 19 2017Sep 19 2017Burke \cite{MR1472122} proved that the generalized nonstationary ideal, denoted NS, is universal in the following sense: every normal ideal, and every tower of normal ideals of inaccessible height, is a canonical Rudin-Keisler projection of the restriction ... More
Deep Neural Network EnsemblesApr 11 2019Current deep neural networks suffer from two problems; first, they are hard to interpret, and second, they suffer from overfitting. There have been many attempts to define interpretability in neural networks, but they typically lack causality or generality. ... More
On the geometry of almost $\mathcal{S}$-manifoldsMar 23 2011Oct 20 2011An $f$-structure on a manifold $M$ is an endomorphism field $\phi$ satisfying $\phi^3+\phi=0$. We call an $f$-structure {\em regular} if the distribution $T=\ker\phi$ is involutive and regular, in the sense of Palais. We show that when a regular $f$-structure ... More
Commuting probabilities of finite groupsNov 04 2014Jun 24 2015The commuting probability of a finite group is defined to be the probability that two randomly chosen group elements commute. Let P \subset (0,1] be the set of commuting probabilities of all finite groups. We prove that every point of P is nearly an Egyptian ... More
The Bernstein presentation for general connected reductive groupsDec 28 2013Nov 10 2014Let F be a non-Archimedean local field and let G be a connected reductive affine algebraic F-group. Let I be an Iwahori subgroup of G(F) and denote by H(G; I) the Iwahori-Hecke algebra, i.e. the convolution algebra of complex-valued functions on G(F) ... More
Definability Aspects of the Denjoy IntegralSep 11 2016The Denjoy integral is an integral that extends the Lebesgue integral and can integrate any derivative. In this paper, it is shown that the graph of the indefinite Denjoy integral $f\mapsto \int_a^x f$ is a coanalytic non-Borel relation on the product ... More
Optimal angle of the holomorphic functional calculus for the classical Ornstein-Uhlenbeck operator on $L^p$Dec 20 2018Jun 05 2019We give a simple proof of the fact that the classical Ornstein-Uhlenbeck operator $L$ is R-sectorial of angle $arcsin|1-2/p|$ on $L^{p}(\mathbb{R}^{n},\exp(-|x|^2/2)dx)$ (for $1<p<\infty$). Applying the abstract holomorphic functional calculus theory ... More
Adjoining only the things you want: a survey of Strong Chang's Conjecture and related topicsAug 14 2019We survey some old and new results on strong variants of Chang's Conjecture and related topics.
Unique Continuation on Convex DomainsJul 03 2019In this paper, we adapt powerful tools from geometric analysis to get quantitative estimates on the quantitative strata of the generalized critical set of harmonic functions which vanish continuously on an open subset of the boundary of a convex domain. ... More
Betti Numbers of Graph IdealsOct 05 2004In this thesis we investigate certain types of monomial ideals of polynomial rings over fields. We are interested in minimal free resolutions of these ideals (or equivalently the quotients of the polynomial ring by the ideals) considered as modules over ... More
Random generation under the Ewens distributionAug 27 2018Jan 20 2019The Ewens sampling formula with parameter $\alpha$ is the distribution on $S_n$ which gives each $\pi\in S_n$ weight proportional to $\alpha^{C(\pi)}$, where $C(\pi)$ is the number of cycles of $\pi$. We show that, for any fixed $\alpha$, two Ewens-random ... More
Optimal preconditioners for systems defined by functions of Toeplitz matricesFeb 10 2018We propose several circulant preconditioners for systems defined by some functions $g$ of Toeplitz matrices $A_n$. In this paper we are interested in solving $g(A_n)\mathbf{x}=\mathbf{b}$ by the preconditioned conjugate method or the preconditioned minimal ... More
The Log-Convex Density Conjecture and vertical surface area in warped productsJul 22 2011Dec 22 2014We examine the vertical component of surface area in the warped product of a Euclidean interval and a fiber manifold with product density. We determine general conditions under which vertical fibers minimize vertical surface area among regions bounding ... More
Kottwitz's nearby cycles conjecture for a class of unitary Shimura varietiesDec 01 2011Oct 22 2016This paper proves that the nearby cycles complexes on a certain family of PEL local models are central with respect to the convolution product of sheaves on the corresponding affine flag varieties. As a corollary, the semisimple trace functions defined ... More
On the geometric quantization of contact manifoldsSep 10 2009Mar 24 2011Suppose that $(M,E)$ is a compact contact manifold, and that a compact Lie group $G$ acts on $M$ transverse to the contact distribution $E$. In an earlier paper, we defined a $G$-transversally elliptic Dirac operator $\dirac$, constructed using a Hermitian ... More
Minimal Affine Coordinates for SL(3,C) Character Varieties of Free GroupsSep 27 2007Jul 03 2008Let X be the moduli of SL(3,C) representations of a rank r free group. In this paper we determine minimal generators of the coordinate ring of X. This at once gives explicit global coordinates for the moduli and determines the dimension of the moduli's ... More
Conjugacy classes of non-translations in affine Weyl groups and applications to Hecke algebrasJun 21 2013Nov 11 2014Let W be an Iwahori-Weyl group of a connected reductive group G over a non-archimedean local field. I prove that if w is an element of W that does not act on the corresponding apartment of G by a translation then one can apply to w a sequence of conjugations ... More
Poisson Geometry of SL(3,C)-Character Varieties Relative to a Surface with BoundaryMar 09 2007Mar 03 2008The SL(3,C)-representation variety R of a free group F arises naturally by considering surface group representations for a surface with boundary. There is a SL(3,C)-action on the coordinate ring of R by conjugation. The geometric points of the subring ... More
Obtaining the One-Holed Torus from Pants: Duality in an SL(3,C)-Character VarietyMar 25 2008The SL(3,C)-representation variety R of a free group F arises naturally by considering surface group representations for a surface with boundary. There is a SL(3,C)-action on the coordinate ring of R. The geometric points of the subring of invariants ... More
Canonical bases for the quantum enveloping algebra of gl(m|1) and its modulesMay 13 2016We construct a crystal basis for the negative half of the quantum group U associated to the standard super Cartan datum of gl(m|1), which is compatible with known crystals on Kac modules and simple modules. We show that these crystals admit globalization ... More
Quantum osp(1|2n) knot invariants are the same as quantum so(2n+1) knot invariantsSep 11 2015We show that the quantum covering group associated to osp(1|2n) has an associated colored quantum knot invariant \`a la Reshetikhin-Turaev, which specializes to a quantum knot invariant for osp(1|2n), and to the usual quantum knot invariant for so(1+2n). ... More
Quantum supergroups IV. The modified formDec 17 2013Apr 23 2014We construct a canonical basis for a class of tensor product modules of a quantum covering group associated to a Kac-Moody Lie superalgebra of anisotropic type, and use these bases to construct a canonical basis for the modified form of a quantum covering ... More
Stratified $β$-numbers and traveling salesman in Carnot groupsFeb 08 2019We introduce a modified version of P. Jones's $\beta$-numbers for Carnot groups which we call stratified $\beta$-numbers. We show that an analogue of Jones's traveling salesman theorem on 1-rectifiability of sets holds for any Carnot group if we replace ... More
Dynamics of a Ferromagnetic Particle Levitated Over a SuperconductorOct 20 2018Apr 07 2019Under conditions where the angular momentum of a ferromagnetic particle is dominated by intrinsic spin, applied torque is predicted to cause gyroscopic precession of the particle. If the particle is sufficiently isolated from the environment, a measurement ... More
Local temperature for dynamical black holesDec 13 2008A local Hawking temperature was recently derived for any future outer trapping horizon in spherical symmetry, using a Hamilton-Jacobi tunneling method, and is given by a dynamical surface gravity as defined geometrically. Descriptions are given of the ... More
Instabilities in the AetherDec 05 2008Mar 23 2009We investigate the stability of theories in which Lorentz invariance is spontaneously broken by fixed-norm vector "aether" fields. Models with generic kinetic terms are plagued either by ghosts or by tachyons, and are therefore physically unacceptable. ... More
A feasible roadmap to identifying significant intercellular genomic heterogeneity in deep sequencing dataOct 28 2013Sep 27 2014Intercellular heterogeneity serves as both a confounding factor in studying individual clones and an information source in characterizing any heterogeneous tissues, such as blood, tumor systems. Due to inevitable sequencing errors and other sample preparation ... More
Vacancies, disorder-induced smearing of the electronic structure, and its implications for the superconductivity of anti-perovskite MgC$_{0.93}$Ni$_{2.85}$Aug 31 2017The anti-perovskite superconductor MgC$_{0.93}$Ni$_{2.85}$ was studied using high-resolution x-ray Compton scattering combined with electronic structure calculations. Compton scattering measurements were used to determine experimentally a Fermi surface ... More
SOFIA FIFI-LS Observations of Sgr B1: Ionization Structure and Sources of ExcitationOct 18 2018Oct 25 2018The current paradigm of Galactic Center (GC) gas motions and star formation envisions sequential star formation in streams of gas as they pass near the supermassive black hole, Sgr A*. This is based on the relative positions of dense molecular clouds, ... More
Adjoining only the things you want: a survey of Strong Chang's Conjecture and related topicsAug 14 2019Aug 16 2019We survey some old and new results on strong variants of Chang's Conjecture and related topics.
On the Canonical Representatives of a Finite Weyl GroupMay 27 2015Apr 18 2016Let K be a field and G a split connected reductive affine algebraic K-group. Let T be a split maximal torus of G, W its finite Weyl group, and R its root system. After fixing a realization of R in G and choosing a simple system for R, one gets a system ... More
Conjugation of Transitive Permutation Pairs and Dessins d'EnfantsJan 31 2017Apr 06 2017Let E be a finite set. Given permutations x and y of E that together generate a transitive subgroup, for which s is it true that x and the conjugate of y by s also generate a transitive subgroup? Such transitive permutation pairs encode dessins d'enfants, ... More
Least Effort Strategies for CybersecurityMay 30 2003Jul 24 2003Cybersecurity is an issue of increasing concern since the events of September 11th. Many questions have been raised concerning the security of the Internet and the rest of the US's information infrastructure. This paper begins to examine the issue by ... More
On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II RegionsApr 20 2004Although variations in elemental abundance ratios in the Milky Way Galaxy certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit ... More
X-rays from Superbubbles in the Large Magellanic Cloud IV: The Blowout Structure of N44Jun 13 1996We have used optical echelle spectra along with ROSAT and ASCA X-ray spectra to test the hypothesis that the southern portion of the N44 X-ray bright region is the result of a blowout structure. Three pieces of evidence now support this conclusion. First, ... More
A Predator Prey Approach to Diversity Based Defenses in Heterogeneous NetworksJan 03 2004In light of the rise of malicious attacks on the Internet, and the various networks and applications attached to it, new approaches towards modeling predatory activity in networks could be useful. Past research has simulated networks assuming that all ... More
Temporal evolution of chromospheric evaporation: case studies of the M1.1 flare on 2014 September 6 and X1.6 flare on 2014 September 10May 11 2015Jul 24 2015With observations from the Interface Region Imaging Spectrograph (IRIS), we track the complete evolution of $\sim$11 MK evaporation flows in an M1.1 flare on 2014 September 6 and an X1.6 flare on 2014 September 10. These hot flows, as indicated by the ... More
Phase resetting reveals network dynamics underlying a bacterial cell cycleOct 03 2012Genomic and proteomic methods yield networks of biological regulatory interactions but do not provide direct insight into how those interactions are organized into functional modules, or how information flows from one module to another. In this work we ... More
A microfabricated optically-pumped magnetic gradiometerJan 12 2017We report on the development of a microfabricated atomic magnetic gradiometer based on optical spectroscopy of alkali atoms in the vapor phase. The gradiometer, which operates in the spin-exchange relaxation free regime, has a length of 60 mm and cross ... More
Comment on 'Spin Ice: Magnetic Excitations without Monopole Signature Using $μ$SR' (arXiv:1110.0877)Nov 17 2011Dunsiger and co-workers have criticised our paper on magnetic monopole dynamics spin ice [S. T. Bramwell et al., Nature, 461 956 (2009)]. We consider their criticisms and results but show that these do not warrant any revision of our earlier conclusions. ... More
Rotation-induced macromolecular spooling of DNAJun 06 2017Genetic information is stored in a linear sequence of base-pairs; however, thermal fluctuations and complex DNA conformations such as folds and loops make it challenging to order genomic material for in vitro analysis. In this work, we discover that rotation-induced ... More
Absorption Efficiencies of Forsterite. I: DDA Explorations in Grain Shape and SizeFeb 04 2013We compute the absorption efficiency (Qabs) of forsterite using the discrete dipole approximation (DDA) in order to identify and describe what characteristics of crystal grain shape and size are important to the shape, peak location, and relative strength ... More
HST NICMOS Observations of the Polarization of NGC 1068Apr 18 2002We have observed the polarized light at 2 micron in the center of NGC 1068 with HST NICMOS Camera 2. The nucleus is dominated by a bright, unresolved source, polarized at a level of 6.0 pm 1.2% with a position angle of 122degr pm 1.5degr. There are two ... More
Steepening of the 820 micron continuum surface-brightness profile signals dust evolution in TW Hya's diskDec 17 2015Grain growth in planet-forming disks is the first step toward the formation of planets. The growth of grains and their inward drift leaves a distinct imprint on the dust surface-density distribution and the resulting surface-brightness profile of the ... More
Scalar Gravitational Radiation from Binaries: Vainshtein Mechanism in Time-dependent SystemsAug 07 2018Oct 04 2018We develop a full four-dimensional numerical code to study scalar gravitational radiation emitted from binary systems and probe the Vainshtein mechanism in situations that break the static and spherical symmetry, relevant for binary pulsars as well as ... More
High resolution radio emission from RCW 49/Westerlund 2Jul 24 2013Aug 19 2013RCW49 and its ionizing cluster form an extensive, complex region, widely studied at IR and optical wavelengths. Molonglo 843 MHz and ATCA data at 1.4 and 2.4 GHz showed two shells. Recent high-resolution IR imaging revealed a complex dust structure and ... More
Toward faithful templates for non-spinning binary black holes using the effective-one-body approachJun 25 2007Jan 04 2008We present an accurate approximation of the full gravitational radiation waveforms generated in the merger of non-eccentric systems of two non-spinning black holes. Utilizing information from recent numerical relativity simulations and the natural flexibility ... More
A low maintenance Sr optical lattice clockFeb 18 2016We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation ... More
Binary black hole late inspiral: Simulations for gravitational wave observationsDec 19 2006Sep 08 2007Coalescing binary black hole mergers are expected to be the strongest gravitational wave sources for ground-based interferometers, such as the LIGO, VIRGO, and GEO600, as well as the space-based interferometer LISA. Until recently it has been impossible ... More
X-Rays from Superbubbles in the Large Magellanic Cloud. V. The H II Complex N11Apr 01 1997The large H II complex N11 in the Large Magellanic Cloud contains OB associations at several different stages in their life histories. We have obtained ROSAT PSPC and HRI X-ray observations, Curtis Schmidt CCD images, echelle spectra in H-alpha and [N ... More