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
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
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
Gravitational Radiation from Preheating with Many FieldsJun 04 2010Jun 11 2010Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple ... More
Gauge Field Preheating at the End of InflationMay 30 2013Here we consider the possibility of preheating the Universe via the parametric amplification of a massless, U(1) abelian gauge field. We assume that the gauge field is coupled to the inflaton via a conformal factor with one free parameter. We present ... More
Simplicity of QC(S^n) and LIP(S^n)Jun 29 2005We prove that the groups of orientation preserving quasiconformal or bilipschitz homeomorphisms of S^n are simple in dimensions 2 and higher.
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
Probing the magnetic ground state of the molecular Dysprosium triangleNov 04 2010We present zero field muon spin lattice relaxation measurements of a Dysprosium triangle molecular magnet. The local magnetic fields sensed by the implanted muons indicate the coexistence of static and dynamic internal magnetic fields below $T^* ~35$ ... 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
Simple recurrence formulas to count maps on orientable surfacesFeb 25 2014Mar 19 2014We establish a simple recurrence formula for the number $Q_g^n$ of rooted orientable maps counted by edges and genus. We also give a weighted variant for the generating polynomial $Q_g^n(x)$ where $x$ is a parameter taking the number of faces of the map ... More
A finitely presented group with unbounded dead-end depthJun 22 2004Apr 10 2007The dead-end depth of an element g of a group G, with respect to a generating set A is the distance from g to the complement of the radius $d_A(1,g)$ closed ball, in the word metric $d_A$ defined with respect to A. We exhibit a finitely presented group ... More
Fluctuation spectroscopy as a probe of granular superconducting diamond filmsJun 19 2017We present resistance versus temperature data for a series of boron-doped nanocrystalline diamond films whose grain size is varied by changing the film thickness. Upon extracting the fluctuation conductivity near to the critical temperature we observe ... More
On the moduli space of A-infinity structuresOct 26 2014Nov 02 2014We study the moduli space of A-infinity structures on a topological space as well as the moduli space of A-infinity-ring structures on a fixed module spectrum. In each case we show that the moduli space sits in a homotopy fiber sequence in which the other ... 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
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
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
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
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
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
Tail asymptotics for busy periodsDec 08 2011Mar 10 2012The busy period for a queue is cast as the area swept under the random walk until it first returns to zero, $B$. Encompassing non-i.i.d. increments, the large-deviations asymptotics of $B$ is addressed, under the assumption that the increments satisfy ... More
Far from equilibrium monopole dynamics in spin iceJan 31 2014Condensed matter in the low temperature limit reveals much exotic physics associated with unusual orders and excitations, examples ranging from helium superfluidity to magnetic monopoles in spin ice. The far-from-equilibrium physics of such low temperature ... More
Exponential asymptotics for line solitons in two-dimensional periodic potentialsMay 02 2013As a first step toward a fully two-dimensional asymptotic theory for the bifurcation of solitons from infinitesimal continuous waves, an analytical theory is presented for line solitons, whose envelope varies only along one direction, in general two-dimensional ... 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
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
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
Effect of carrier concentration on magnetism and magnetic order in the pyrochlore iridatesJun 01 2014We present resistivity, magnetization, and zero field muon spin relaxation ($\mu$SR) data for the pyrochlore iridate materials Nd$_{2-x}$Ca$_{x}$Ir$_{2}$O$_{7}$ ($x = 0, 0.06$, and $0.10$) and Sm$_2$Ir$_2$O$_7$. While Nd$_{2}$Ir$_{2}$O$_{7}$ (Nd227) is ... More
μSR Study of Spin Dynamics in LiY$_{1-x}$Ho$_{x}$F$_{4}$Mar 02 2011We present zero-field {\mu}SR measurements for LiY$_{1-x}$Ho$_{x}$F$_{4}$ samples with x = 0.0017, 0.0085, 0.0406, and 0.0855. We characterize the dynamics associated with the formation of the (F-{\mu}-F)$^{-1}$ complex by comparing our data to Monte ... 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
An anisotropic local modification of crystal field levels in Pr-based pyrochlores: a muon-induced effect modelled using density functional theoryAug 21 2014Muon spin relaxation measurements on some quantum spin ice candidate materials, the insulating pyrochlores Pr2B2O7 (B = Sn, Zr, Hf), have been performed for temperatures in the range 0.05-280 K. The results are indicative of a static distribution of magnetic ... 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
Proximal magnetometry of monolayers of single molecule magnets on gold using polarized muonsSep 25 2009The magnetic properties of a monolayer of Fe4 single molecule magnets grafted onto a Au (111) thin film have been investigated using low energy muon spin rotation. The properties of the monolayer are compared to bulk Fe4. We find that the magnetic properties ... More
Measurement of Magnetic Exchange in Ferromagnet-Superconductor La2/3Ca1/3MnO3/YBa2Cu3O7 BilayersOct 18 2012The existence of coherent magnetic correlations in the normal phase of cuprate high-temperature superconductors has proven difficult to measure directly. Here we report on a study of ferromagnetic-superconductor bilayers of La2/3Ca1/3MnO3/YBa2Cu3O7 (LCMO/YBCO) ... More
Bulk Spin Polarization of Co$_{(1-x)}$Fe$_x$S$_2$Nov 27 2009We report on a new method to determine the degree of bulk spin polarization in single crystal Co$_{(1-x)}$Fe$_x$S$_2$ by modeling magnetic Compton scattering with {\it ab initio} calculations. Spin-dependent Compton profiles were measured for CoS$_2$ ... More
Determination of spin and orbital magnetization in the ferromagnetic superconductor UCoGeNov 25 2015The magnetism in the ferromagnetic superconductor UCoGe has been studied using a combination of magnetic Compton scattering, bulk magnetization, X-ray magnetic circular dichroism and electronic structure calculations, in order to determine the spin and ... 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
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
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
Magnetic order and the electronic ground state in the pyrochlore iridate Nd2Ir2O7Jan 22 2012Jan 29 2012We report a combined muon spin relaxation/rotation, bulk magnetization, neutron scattering, and transport study of the electronic properties of the pyrochlore iridate Nd2Ir2O7. We observe the onset of strongly hysteretic behavior in the temperature dependent ... More
Dynamic behavior of magnetic avalanches in the spin-ice compound Dy$_2$Ti$_2$O$_7$Jun 11 2014Avalanches of the magnetization, that is to say an abrupt reversal of the magnetization at a given field, have been previously reported in the spin-ice compound Dy$_{2}$Ti$_{2}$O$_{7}$. This out-of-equilibrium process, induced by magneto-thermal heating, ... More
Muon spin rotation studies of spin dynamics at avoided level crossings in LiY0.998Ho0.002F4Sep 05 2007We have studied the Ho3+ spin dynamics for LiY0.998Ho0.002F4 through the positive muon (mu+) transverse field depolarization rate lambda_TF as a function of temperature and magnetic field. We find sharp reductions in lambda_TF(H) at fields of 23, 46 and ... 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
Tracing the inner edge of the disk around HD 100546 with Ro-vibrational CO Emission LinesJul 01 2009In this paper we present high resolution 4.7micron spectra of the isolated Herbig Be star HD100546. HD100546 has been the subject of intense scrutiny because it is a young nearby star with a transitional disk. We observe the Delta v=1 ro-vibrational CO ... More
Boundary-reducing surgeries and bridge numberDec 31 2015Let $M$ be a $3$--dimensional handlebody of genus $g$. This paper gives examples of hyperbolic knots in $M$ with arbitrarily large genus $g$ bridge number which admit Dehn surgeries which are boundary-reducible manifolds.
Probing the Locally Generated Even and Odd Order Nonlinearity in Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O (2212) Microwave Resonators around TCDec 28 2012Spatial scanning of the synchronously generated 2nd and 3rd order intermodulation distortion in superconducting resonators uncovers local nonlinearity hot spots, and possible time reversal symmetry breaking, using a simple probe fashioned from coaxial ... 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
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
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
Near Infrared High Resolution Spectroscopy and Spectro-astrometry of Gas in Disks around Herbig Ae/Be StarsMar 10 2015In this review, we describe how high resolution near infrared spectroscopy and spectro-astrometry have been used to study the disks around Herbig~Ae/Be stars. We show how these tools can be used to identify signposts of planet formation and elucidate ... More
Dark Matter and Dark RadiationOct 28 2008Dec 16 2008We explore the feasibility and astrophysical consequences of a new long-range U(1) gauge field ("dark electromagnetism") that couples only to dark matter, not to the Standard Model. The dark matter consists of an equal number of positive and negative ... 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
Bulk electronic structure of optimally doped Ba(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$Sep 17 2009Feb 24 2010We report high-resolution, bulk Compton scattering measurements unveiling the Fermi surface of an optimally-doped iron-arsenide superconductor, Ba(Fe$_{0.93}$Co$_{0.07}$)$_2$As$_2$. Our measurements are in agreement with first-principles calculations ... More
Magnetic phase diagram of La$_{2-x}$Sr$_{x}$CoO$_{4}$ revised using muon-spin relaxationOct 21 2015We report the results of a muon-spin relaxation ($\mu$SR) investigation of La$_{2-x}$Sr$_{x}$CoO$_{4}$, an antiferromagnetic insulating series which has been shown to support charge ordered and magnetic stripe phases and an hourglass magnetic excitation ... More
Heat capacity measurements on FeAs-based compounds: a thermodynamic probe of electronic and magnetic statesNov 15 2008We report heat capacity measurements of the pnictide materials SmFeAsO$_{1-x}$F$_x$, NdFeAsO, LaFeAsO$_{1-x}$F$_x$ and LiFeAs. For SmFeAsO$_{1-x}$F$_x$, with x close to 0.1, we use 3 He measurements to demonstrate a transfer of entropy from the peak at ... More
Optimising a Muon Spectrometer for Measurements at the ISIS Pulsed Muon SourceApr 17 2014This work describes the development of a state-of-the-art muon spectrometer for the ISIS pulsed muon source. Conceived as a major upgrade of the highly successful EMU instrument, emphasis has been placed on making effective use of the enhanced flux now ... More
NIR Spectroscopy of the HAeBe Star HD 100546: III. Further Evidence of an Orbiting Companion?Sep 02 2014We report high resolution NIR spectroscopy of CO and OH emission from the Herbig Be star HD100546. We discuss how our results bear striking resemblance to several theoretically predicted signposts of giant planet formation. The properties of the CO and ... More
Detection of eccentric supermassive black hole binaries with pulsar timing arrays: Signal-to-noise ratio calculationsApr 03 2015Sep 10 2015We present a detailed analysis of the expected signal-to-noise ratios of supermassive black hole binaries on eccentric orbits observed by pulsar timing arrays. We derive several analytical relations that extend the results of Peters and Mathews [Phys. ... More
Gigahertz quantized charge pumping in graphene quantum dotsJul 27 2012Single electron pumps are set to revolutionize electrical metrology by enabling the ampere to be re-defined in terms of the elementary charge of an electron. Pumps based on lithographically-fixed tunnel barriers in mesoscopic metallic systems and normal/superconducting ... 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
Generators, Relations and Symmetries in Pairs of 3x3 Unimodular MatricesJan 06 2006Jan 23 2007Denote the free group on two letters by F2 and the SL(3,C)-representation variety of F2 by R = Hom(F2, SL(3,C)). There is a SL(3,C)-action on the coordinate ring of R, and the geometric points of the subring of invariants is an affine variety X. We determine ... More
Transcendence of the Hodge-Tate filtrationOct 17 2016For $C$ a complete algebraically closed extension of $\mathbb{Q}_p$, we show that a one-dimensional $p$-divisible group $G/ \mathcal{O}_C$ can be defined over a complete discretely valued subfield $L \subset C$ with Hodge-Tate period ratios contained ... 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
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
Transductive Adversarial Networks (TAN)Feb 08 2018Transductive Adversarial Networks (TAN) is a novel domain-adaptation machine learning framework that is designed for learning a conditional probability distribution on unlabelled input data in a target domain, while also only having access to: (1) easily ... 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
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
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
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
Basepoint freeness for big line bundles in positive characteristic, with applications to M_g and to 3-fold MMPMar 03 1997Mar 13 1998I give a necessary and sufficient condition for a nef and big line bundle in positive characteristic to be semi-ample, and then give two applications: I show that the relative dualizing sheaf of the universal curve is semi-ample, in positive characteristic, ... More
Percival's Conjecture for the Bunimovich Mushroom BilliardApr 28 2015Nov 28 2016The Laplace-Beltrami eigenfunctions on a compact Riemannian manifold $M$ whose geodesic billiard flow has mixed character have been conjectured by Percival to split into two complementary families, with all semiclassical mass supported in the completely ... More
Valence bond solid formalism for d-level one-way quantum computationDec 19 2005Mar 06 2006The d-level or qudit one-way quantum computer (d1WQC) is described using the valence bond solid formalism and the generalised Pauli group. This formalism provides a transparent means of deriving measurement patterns for the implementation of quantum gates ... More
Algebraic Independence in SL(3,C) Character Varieties of Free GroupsJul 04 2008Jul 27 2010Let X be the moduli space of SL(3,C) representations of a free group of rank r. In this paper we describe maximal algebraically independent subsets of certain minimal sets of coordinate functions on X. These subsets locally parametrize the moduli space. ... More
The $p$-adic Jacquet-Langlands correspondence and a question of SerreJun 18 2018We show that the completed Hecke algebra of $p$-adic modular forms is isomorphic to the completed Hecke algebra of continuous $p$-adic automorphic forms for the units of the quaternion algebra ramified at $p$ and $\infty$. This gives an affirmative answer ... 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
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
Classical Transitions for Flux VacuaJul 27 2012We present the simplest model for classical transitions in flux vacua. A complex field with a spontaneously broken U(1) symmetry is embedded in $M_2\times S_1$. We numerically construct different winding number vacua, the vortices interpolating between ... More
Consistency of post-Newtonian waveforms with numerical relativityDec 04 2006Oct 29 2007General relativity predicts the gravitational wave signatures of coalescing binary black holes. Explicit waveform predictions for such systems, required for optimal analysis of observational data, have so far been achieved using the post-Newtonian (PN) ... More
A Wide-field Survey of Two Z~0.5 Galaxy Clusters: Identifying the Physical Processes Responsible for the Observed Transformation of Spirals into S0sJul 27 2007We present new results from our comprehensive comparative survey of two massive, intermediate redshift galaxy clusters, Cl0024+17 (z=0.39) and MS0451-03 (z=0.54). We identify and study several key classes of `transition objects' whose stellar populations ... More
Chiral Dynamics in Photo-Pion Physics: Theory, Experiment, and Future Studies at the HI$γ$S FacilityFeb 20 2009A review of photo-pion experiments on the nucleon in the near threshold region is presented. Comparisons of the results are made with the predictions of the low energy theorems of QCD calculated using chiral perturbation theory (ChPT) which is based on ... More
The X-ray Transient 2XMMi J003833.3+402133: A Candidate Magnetar at High Galactic LatitudeAug 02 2011Aug 15 2012We present detailed analysis of the transient X-ray source 2XMMi J003833.3+402133 detected by XMM-Newton in January 2008 during a survey of M 31. The X-ray spectrum is well fitted by either a steep power law plus a blackbody model or a double blackbody ... More
An equivariant index formula for almost-CR manifoldsOct 02 2008Feb 01 2009We consider a consider the case of a compact manifold M, together with the following data: the action of a compact Lie group H and a smooth H-invariant distribution E, such that the H-orbits are transverse to E. These data determine a natural equivariant ... More
Power operations in the Kunneth spectral sequence and commutative HFp-algebrasFeb 22 2016In this paper, we prove the multiplicativity of the K\"unneth spectral sequence. This is established by an analogue of the Comparison Theorem from homological algebra, which we suspect may be useful for other spectral sequences. This multiplicativity ... More
Tree Oriented Data AnalysisSep 19 2014Sep 22 2014Complex data objects arise in many areas of modern science including evolutionary biology, nueroscience, dynamics of gene expression and medical imaging. Object oriented data analysis (OODA) is the statistical analysis of datasets of complex objects. ... More
Charmonium Suppression in Nuclear CollisionsSep 25 1996Measurements of $\psi$ and $\psi'$ production from experiment NA50 at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression by Vogt and myself. Data on centrality dependence and total cross sections are in good accord ... More
Extraordinary Baryon Fluctuations and the QCD Tricritical PointAug 24 1999The dynamic separation into phases of high and low baryon density in a heavy ion collision can enhance fluctuations of the net rapidity density of baryons compared to model expectations. We show how these fluctuations arise and how they can survive through ... More
Soft Collinear Effective Theory: An OverviewJul 22 2009In this talk I give an overview of soft collinear effective theory (SCET), including a discussion of some recent advances. First, I briefly cover the foundation upon which SCET is built, namely QCD factorization, and review the theoretical framework of ... More
Determining Color-Octet psi-Production Matrix Elements from gamma p and e p ProcessesOct 15 1996We calculated, within the NRQCD factorization formalism, the leading color-octet contributions to psi production in photon-nucleon and electron-nucleon collisions. The expressions obtained depend on the NRQCD matrix elements <O^{psi}_8(^1S_0)> and <O^{psi}_8(^3P_J)>. ... More
NRQCD Prediction for the Polarization of the J/psi Produced from b-decayAug 27 1996Presented at the Meeting of the Division of Particles and Fields, August 1996, in Minneapolis. The work presented here is based upon a recent paper (hep-ph/9608413) done in collaboration with Oscar F. Hernandez, Ivan Maksymyk, and Helene Nadeau. The NRQCD ... More
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
The AdS/CFT partition function, AdS as a lift of a CFT, and holographic RG flow from conformal deformationsOct 21 2015Jan 13 2016Conformal deformations manifest in the AdS/CFT correspondence as boundary conditions on the AdS field. Heretofore, double-trace deformations have been the primary focus in this context. To better understand multitrace deformations, we revisit the relationship ... 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
Optimal angle of the holomorphic functional calculus for the classical Ornstein-Uhlenbeck operator on $L^p$Dec 20 2018We 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
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
Assessing the performance of thermospheric modelling with data assimilation throughout solar cycles 23 and 24Mar 11 2015Data assimilation procedures have been developed for thermospheric models using satellite density measurements as part of the EU Framework Package 7 ATMOP Project. Two models were studied; one a general circulation model, TIEGCM, and the other a semi-empirical ... More
Empirical Constraints on Turbulence in Protoplanetary Accretion DisksNov 16 2010We present arcsecond-scale Submillimeter Array observations of the CO(3-2) line emission from the disks around the young stars HD 163296 and TW Hya at a spectral resolution of 44 m/s. These observations probe below the ~100 m/s turbulent linewidth inferred ... More
Gravitational Wave Production At The End Of InflationDec 11 2006Sep 20 2007We consider gravitational wave production due to parametric resonance at the end of inflation, or ``preheating''. This leads to large inhomogeneities which source a stochastic background of gravitational waves at scales inside the comoving Hubble horizon ... 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 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