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Results for "Brian Paul Bockelman"

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ROOT I/O compression algorithms and their performance impact within Run 3Jun 11 2019The LHCs Run3 will push the envelope on data-intensive workflows and, since at the lowest level this data is managed using the ROOT software framework, preparations for managing this data are starting already. At the beginning of LHC Run 1, all ROOT data ... More
Continuous Performance Benchmarking Framework for ROOTDec 07 2018Feb 21 2019Foundational software libraries such as ROOT are under intense pressure to avoid software regression, including performance regressions. Continuous performance benchmarking, as a part of continuous integration and other code quality testing, is an industry ... More
Evolution of ROOT package managementJun 11 2019ROOT is a large code base with a complex set of build-time dependencies; there is a significant difference in compilation time between the "core" of ROOT and the full-fledged deployment. We present results on a "delayed build" for internal ROOT packages ... More
Heterogeneous High Throughput Scientific Computing with APM X-Gene and Intel Xeon PhiOct 10 2014Electrical power requirements will be a constraint on the future growth of Distributed High Throughput Computing (DHTC) as used by High Energy Physics. Performance-per-watt is a critical metric for the evaluation of computer architectures for cost- efficient ... More
Designing Computing System Architecture and Models for the HL-LHC eraJul 20 2015This paper describes a programme to study the computing model in CMS after the next long shutdown near the end of the decade.
StashCache: A Distributed Caching Federation for the Open Science GridMay 16 2019Data distribution for opportunistic users is challenging as they neither own the computing resources they are using or any nearby storage. Users are motivated to use opportunistic computing to expand their data processing capacity, but they require storage ... More
Extending ROOT through ModulesDec 07 2018Dec 11 2018The ROOT software framework is foundational for the HEP ecosystem, providing capabilities such as IO, a C++ interpreter, GUI, and math libraries. It uses object-oriented concepts and build-time components to layer between them. We believe additional layering ... More
On the Geometric Interpretation of N = 2 Superconformal TheoriesSep 19 1994Dec 09 1994We clarify certain important issues relevant for the geometric interpretation of a large class of N = 2 superconformal theories. By fully exploiting the phase structure of these theories (discovered in earlier works) we are able to clearly identify their ... More
SciTokens: Demonstrating Capability-Based Access to Remote Scientific Data using HTCondorMay 22 2019The management of security credentials (e.g., passwords, secret keys) for computational science workflows is a burden for scientists and information security officers. Problems with credentials (e.g., expiration, privilege mismatch) cause workflows to ... More
HEPCloud, a New Paradigm for HEP Facilities: CMS Amazon Web Services InvestigationSep 29 2017Historically, high energy physics computing has been performed on large purpose-built computing systems. These began as single-site compute facilities, but have evolved into the distributed computing grids used today. Recently, there has been an exponential ... More
Error Floor Approximation for LDPC Codes in the AWGN ChannelFeb 13 2012Jun 09 2013This paper addresses the prediction of error floors of low-density parity-check (LDPC) codes with variable nodes of constant degree in the additive white Gaussian noise (AWGN) channel. Specifically, we focus on the performance of the sum-product algorithm ... More
Numerical Issues Affecting LDPC Error FloorsAug 07 2012Numerical issues related to the occurrence of error floors in floating-point simulations of belief propagation (BP) decoders are examined. Careful processing of messages corresponding to highly-certain bit values can sometimes reduce error floors by several ... More
reductus: a stateless Python data-reduction service with a browser frontendApr 23 2018The online data reduction service reductus transforms measurements in experimental science from laboratory coordinates into physically meaningful quantities with accurate estimation of uncertainties based on instrumental settings and properties. This ... More
LADAR-Based Mover Detection from Moving VehiclesSep 25 2017Detecting moving vehicles and people is crucial for safe operation of UGVs but is challenging in cluttered, real world environments. We propose a registration technique that enables objects to be robustly matched and tracked, and hence movers to be detected ... More
Binary Black Hole Accretion From a Circumbinary Disk: Gas Dynamics Inside the Central CavityOct 01 2013We present the results of 2D hydrodynamical simulations of circumbinary disk accretion using the finite-volume code DISCO. This code solves the 2D viscous Navier-Stokes equations on a high-resolution moving mesh which shears with the fluid flow, greatly ... More
Binary Black Hole Accretion During Inspiral and MergerSep 17 2014We present the results of 2D, moving mesh, viscous hydrodynamical simulations of accretion onto merging supermassive black hole (SMBH) binaries. We include viscous heating, shock heating, and radiative cooling, and simulate the transition from the "pre-decoupling" ... More
Ultra-deep mid-IR survey of a lensing clusterAug 13 1998We present the first results of mid-infrared (MIR) ultra-deep observations towards the lensing cluster Abell 2390 using the ISOCAM infrared camera on-board ESA's Infrared Space Observatory (ISO) satellite. They reveal a large number of luminous MIR sources. ... More
Disorder-Induced Electronic NematicityJun 11 2019We expose the theoretical mechanisms underlying disorder-induced nematicity in systems exhibiting strong fluctuations or ordering in the nematic channel. Our analysis consists of a symmetry-based Ginzburg-Landau approach and associated microscopic calculations. ... More
Situational Awareness based Risk-Adapatable Access Control in Enterprise NetworksOct 26 2017As the computing landscape evolves towards distributed architectures such as Internet of Things (IoT),enterprises are moving away from traditional perimeter based security models toward so called zero trust networking (ZTN) models that treat both the ... More
HEP Software Foundation Community White Paper Working Group - Data Analysis and InterpretationApr 09 2018At the heart of experimental high energy physics (HEP) is the development of facilities and instrumentation that provide sensitivity to new phenomena. Our understanding of nature at its most fundamental level is advanced through the analysis and interpretation ... More
An Elusive Z' Coupled to BeautyApr 08 1996Apr 24 1996By extending the standard gauge group to SU(3)_c \times SU(2)_L \times U(1)_Y \times U(1)_X with X charges carried only by the third family we accommodate the LEP measurement of R_b and predict a potentially measurable discrepancy in A_{FB}^{b} in e^+e^- ... More
Rucio - Scientific data managementFeb 26 2019Jun 06 2019Rucio is an open-source software framework that provides scientific collaborations with the functionality to organize, manage, and access their data at scale. The data can be distributed across heterogeneous data centers at widely distributed locations. ... More
Measuring Small Distances in N=2 Sigma ModelsNov 08 1993We analyze global aspects of the moduli space of K\"ahler forms for $N$=(2,2) conformal $\sigma$-models. Using algebraic methods and mirror symmetry we study extensions of the mathematical notion of length (as specified by a K\"ahler structure) to conformal ... More
Multiple Mirror Manifolds and Topology Change in String TheoryJan 12 1993Jan 15 1993We use mirror symmetry to establish the first concrete arena of spacetime topology change in string theory. In particular, we establish that the {\it quantum theories} based on certain nonlinear sigma models with topologically distinct target spaces can ... More
Approximating invariant densities of metastable systemsMay 02 2009We consider a piecewise smooth expanding map of the interval possessing two invariant subsets of positive Lebesgue measure and exactly two ergodic absolutely continuous invariant probability measures (ACIMs). When this system is perturbed slightly to ... More
Synchronization in networks of networks: the onset of coherent collective behavior in systems of interacting populations of heterogeneous oscillatorsJun 29 2007Jan 24 2008The onset of synchronization in networks of networks is investigated. Specifically, we consider networks of interacting phase oscillators in which the set of oscillators is composed of several distinct populations. The oscillators in a given population ... More
Simulation of Drosophila Circadian Oscillations, Mutations, and Light Responses by a Model with VRI, PDP-1, and CLKJan 23 2004A model of Drosophila circadian rhythm generation was developed to represent feedback loops based on transcriptional regulation of per, Clk (dclock), Pdp-1, and vri (vrille). The model postulates that histone acetylation kinetics make transcriptional ... More
Search for plant biomagnetism with a sensitive atomic magnetometerJun 17 2010Aug 16 2011We report what we believe is the first experimental limit placed on plant biomagnetism. Measurements with a sensitive atomic magnetometer were performed on the Titan arum (Amorphophallus titanum) inflorescence, known for its fast bio-chemical processes ... More
HEP Software Foundation Community White Paper Working Group -- Data Organization, Management and Access (DOMA)Nov 30 2018Without significant changes to data organization, management, and access (DOMA), HEP experiments will find scientific output limited by how fast data can be accessed and digested by computational resources. In this white paper we discuss challenges in ... More
Discovering Job Preemptions in the Open Science GridJul 17 2018The Open Science Grid(OSG) is a world-wide computing system which facilitates distributed computing for scientific research. It can distribute a computationally intensive job to geo-distributed clusters and process job's tasks in parallel. For compute ... More
A Mixture of Coalesced Generalized Hyperbolic DistributionsMar 10 2014Oct 27 2018A mixture of multiple scaled generalized hyperbolic distributions (MMSGHDs) is introduced. Then, a coalesced generalized hyperbolic distribution (CGHD) is developed by joining a generalized hyperbolic distribution with a multiple scaled generalized hyperbolic ... More
Unsupervised Learning via Mixtures of Skewed Distributions with Hypercube ContoursMar 10 2014Sep 17 2014Mixture models whose components have skewed hypercube contours are developed via a generalization of the multivariate shifted asymmetric Laplace density. Specifically, we develop mixtures of multiple scaled shifted asymmetric Laplace distributions. The ... More
Spatial and Spectral Modeling of the Gamma-ray Distribution in the Large Magellanic CloudFeb 15 2015Jul 17 2015We perform spatial and spectral analyses of the Large Magellanic Cloud (LMC) gamma-ray emission collected over 66 months by the Fermi Gamma-ray Space Telescope. In our spatial analysis, we model the LMC cosmic-ray distribution and gamma-ray production ... More
Interaction of Cygnus A with its environmentFeb 17 2015Cygnus A, the nearest truly powerful radio galaxy, resides at the centre of a massive galaxy cluster. Chandra X-ray observations reveal its cocoon shocks, radio lobe cavities and an X-ray jet, which are discussed here. It is argued that X-ray emission ... More
Pulsed single-photon spectrometer by frequency-to-time mapping using chirped fiber Bragg gratingsOct 10 2016Jul 29 2017A fiber-integrated spectrometer for single-photon pulses outside the telecommunications wavelength range based upon frequency-to-time mapping, implemented by chromatic group delay dispersion (GDD), and precise temporally-resolved single-photon counting, ... More
Multi-channel entanglement distribution using spatial multiplexing from four-wave mixing in atomic vaporJul 08 2015Four-wave mixing in atomic vapor allows for the generation of multi-spatial-mode states of light containing many pairs of two-mode entangled vacuum beams. This in principle can be used to send independent secure keys to multiple parties simultaneously ... More
Emergent defect states as a source of resistivity anisotropy in the nematic phase of iron pnictidesJul 01 2014We consider the role of potential scatterers in the nematic phase of Fe-based superconductors above the transition temperature to the (pi,0) magnetic state but below the orthorhombic structural transition. The anisotropic spin fluctuations in this region ... More
High-quality, large-grain MoS2 films grown on 100 mm sapphire substrates using a novel molybdenum precursorNov 12 2018Two-dimensional MoS2 is a crystalline semiconductor with high potential for numerous technologies. Research in recent years has sought to exploit the direct band gap and high carrier mobility properties of monolayer MoS2 for functional applications. To ... More
A reduced orbital period for the supermassive black hole binary candidate in the quasar PG 1302-102?Feb 10 2015Jul 31 2015Graham et al. (2015) have detected a 5.2 year periodic optical variability of the quasar PG 1302-102 at redshift $z=0.3$, which they interpret as the redshifted orbital period $(1+z)t_{\rm bin}$ of a putative supermassive black hole binary (SMBHB). Here ... More
The Migration of Gap-Opening Planets is not Locked to Viscous Disk EvolutionMay 14 2014Aug 01 2014Most standard descriptions of Type II migration state that massive, gap-opening planets must migrate at the viscous drift rate. This is based on the idea that the disk is separated into an inner and outer region and gas is considered unable to cross the ... More
A Chandra - VLA Investigation of the X-ray Cavity System and Radio Mini-Halo in the Galaxy Cluster RBS 797Apr 27 2012We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and VLA data. RBS 797 (z = 0.35), is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the ... More
Counterintuitive Reconstruction of the Polar O-Terminated ZnO Surface With Zinc Vacancies and HydrogenFeb 01 2017Understanding the structure of ZnO surface reconstructions and their resultant properties is crucial to the rational design of ZnO-containing devices ranging from optoelectronics to catalysts. Here, we are motivated by recent experimental work which showed ... More
Engineering Large Stark Shifts for Control of Individual Clock State QubitsApr 29 2016In quantum information science, the external control of qubits must be balanced with the extreme isolation of the qubits from the environment. Atomic qubit systems typically mitigate this balance through the use of gated laser fields that can create superpositions ... More
Reducing Cascading Failure Risk by Increasing Infrastructure Network InterdependencyOct 24 2014Jun 23 2015Increased coupling between critical infrastructure networks, such as power and communication systems, will have important implications for the reliability and security of these systems. To understand the effects of power-communication coupling, several ... More
The Rearrangement NumberDec 22 2016How many permutations of the natural numbers are needed so that every conditionally convergent series of real numbers can be rearranged to no longer converge to the same sum? We show that the minimum number of permutations needed for this purpose, which ... More
Optimized phase sensing in a truncated SU(1,1) interferometerFeb 12 2018Homodyne detection is often used for interferometers based on nonlinear optical gain media. For the configuration of a seeded, 'truncated SU(1,1)' interferometer Anderson et al. (Phys. Rev. A 95, 063843 (2017)) showed how to optimize the homodyne detection ... More
A Mixture of Coalesced Generalized Hyperbolic DistributionsMar 10 2014Jun 04 2015A mixture of coalesced generalized hyperbolic distributions (GHDs) is developed by joining a finite mixture of generalized hyperbolic distributions with a novel mixture of multiple scaled generalized hyperbolic distributions (MSGHDs). After detailing ... More
A Chandra study of the large-scale shock and cool filaments in Hydra A: Evidence for substantial gas dredge-up by the central outburstFeb 26 2011We present the results of a Chandra study of the Hydra A galaxy cluster, where a powerful AGN outburst created a large-scale cocoon shock. We investigated possible azimuthal variations in shock strength and shape, finding indications for a weak shock ... More
The Rearrangement NumberDec 22 2016May 13 2019How many permutations of the natural numbers are needed so that every conditionally convergent series of real numbers can be rearranged to no longer converge to the same sum? We define the \emph{rearrangement number}, a new cardinal characteristic of ... More
Graph Filters and the Z-LaplacianJul 18 2017In network science, the interplay between dynamical processes and the underlying topologies of complex systems has led to a diverse family of models with different interpretations. In graph signal processing, this is manifested in the form of different ... More
Atom interferometry in an optical cavitySep 25 2014We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beamsplitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such ... More
Aggressive Deep Driving: Model Predictive Control with a CNN Cost ModelJul 17 2017We present a framework for vision-based model predictive control (MPC) for the task of aggressive, high-speed autonomous driving. Our approach uses deep convolutional neural networks to predict cost functions from input video which are directly suitable ... More
Information Theoretic Model Predictive Control: Theory and Applications to Autonomous DrivingJul 07 2017We present an information theoretic approach to stochastic optimal control problems that can be used to derive general sampling based optimization schemes. This new mathematical method is used to develop a sampling based model predictive control algorithm. ... More
Autonomous Racing with AutoRally Vehicles and Differential GamesJul 14 2017Safe autonomous vehicles must be able to predict and react to the drivers around them. Previous control methods rely heavily on pre-computation and are unable to react to dynamic events as they unfold in real-time. In this paper, we extend Model Predictive ... More
Phase sensing beyond the standard quantum limit with a truncated SU(1,1) interferometerOct 21 2016An SU(1,1) interferometer replaces the beamsplitters in a Mach-Zehnder interferometer with nonlinear interactions and offers the potential of achieving high phase sensitivity in applications with low optical powers. We present a novel variation in which ... More
Mass scaling and non-adiabatic effects in photoassociation spectroscopy of ultracold strontium atomsJun 17 2014Jul 30 2014We report photoassociation spectroscopy of ultracold $^{86}$Sr atoms near the intercombination line and provide theoretical models to describe the obtained bound state energies. We show that using only the molecular states correlating with the $^1S_0$$+$$^3P_1$ ... More
Sky in Google Earth: The Next Frontier in Astronomical Data Discovery and VisualizationSep 05 2007Sep 10 2007Astronomy began as a visual science, first through careful observations of the sky using either an eyepiece or the naked eye, then on to the preservation of those images with photographic media and finally the digital encoding of that information via ... More
Epoxy-based broadband anti-reflection coating for millimeter-wave opticsJul 30 2013We have developed epoxy-based, broadband anti-reflection coatings for millimeter-wave astrophysics experiments with cryogenic optics. By using multiple-layer coatings where each layer steps in dielectric constant, we achieved low reflection over a wide ... More
Time-resolved Absorptance and Melt Pool Dynamics during Intense Laser Irradiation of MetalSep 11 2018High irradiance lasers incident on metal surfaces create a complex, dynamic process through which the metal can rapidly change from highly reflective to strongly absorbing. Absolute knowledge of this process underpins important industrial laser processes ... More
Understanding Human-Machine Networks: A Cross-Disciplinary SurveyNov 17 2015Jan 18 2017In the current hyper-connected era, modern Information and Communication Technology systems form sophisticated networks where not only do people interact with other people, but also machines take an increasingly visible and participatory role. Such human-machine ... More
Interstellar Polarization in M31Mar 10 2004The wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sightlines. Only one sightline had been measured previously.The globular clusters, S78, S150, S233 and Baade 327 were used as point sources to probe ... More
Characterization of the X-ray Coherence Properties of an Undulator Beamline at the Advanced Photon SourceFeb 15 2018In anticipation of the increased use of coherent x-ray methods and the need to upgrade beamlines to match improved source quality, we have characterized the coherence properties of the x-rays delivered by beamline 12ID-D at the Advanced Photon Source. ... More
The US Program in Ground-Based Gravitational Wave Science: Contribution from the LIGO LaboratoryMar 11 2019Recent gravitational-wave observations from the LIGO and Virgo observatories have brought a sense of great excitement to scientists and citizens the world over. Since September 2015,10 binary black hole coalescences and one binary neutron star coalescence ... More
Efficient real-time monitoring of an emerging influenza epidemic: how feasible?Aug 18 2016May 03 2019A prompt public health response to a new epidemic relies on the ability to monitor and predict its evolution in real time as data accumulate. The 2009 A/H1N1 outbreak in the UK revealed pandemic data as noisy, contaminated, potentially biased, and originating ... More
Holonomic Quantum Control by Coherent Optical Excitation in DiamondMay 01 2017Oct 02 2017Although geometric phases in quantum evolution were historically overlooked, their active control now stimulates strategies for constructing robust quantum technologies. Here, we demonstrate arbitrary single-qubit holonomic gates from a single cycle of ... More
Spatiotemporal Mapping of Photocurrent in a Monolayer Semiconductor Using a Diamond Quantum SensorMar 22 2019The detection of photocurrents is central to understanding and harnessing the interaction of light with matter. Although widely used, transport-based detection averages over spatial distributions and can suffer from low photocarrier collection efficiency. ... More
Results from GROCSE: A Real-time Search for Gamma Ray Burst Optical CounterpartsFeb 19 1997Apr 01 1997The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) has searched for contemporaneous optical counterparts to gamma ray bursts (GRBs) using an automated rapidly slewing wide field of view optical telescope at Lawrence Livermore National Laboratory. ... More
Increasing Parallelism in the ROOT I/O SubsystemApr 10 2018When processing large amounts of data, the rate at which reading and writing can take place is a critical factor. High energy physics data processing relying on ROOT is no exception. The recent parallelisation of LHC experiments' software frameworks and ... More
Data Access for LIGO on the OSGMay 17 2017During 2015 and 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) conducted a three-month observing campaign. These observations delivered the first direct detection of gravitational waves from binary black hole mergers. To search for ... More
SciTokens: Capability-Based Secure Access to Remote Scientific DataJul 12 2018The management of security credentials (e.g., passwords, secret keys) for computational science workflows is a burden for scientists and information security officers. Problems with credentials (e.g., expiration, privilege mismatch) cause workflows to ... More
An instrument for advanced in situ x-ray studies of metal-organic vapor phase epitaxy of III-nitridesFeb 09 2017May 14 2017We describe an instrument that exploits the ongoing revolution in synchrotron sources, optics, and detectors to enable in situ studies of metal-organic vapor phase epitaxy (MOVPE) growth of III-nitride materials using coherent x-ray methods. The system ... More
Freezing Subnetworks to Analyze Domain Adaptation in Neural Machine TranslationSep 14 2018Jan 15 2019To better understand the effectiveness of continued training, we analyze the major components of a neural machine translation system (the encoder, decoder, and each embedding space) and consider each component's contribution to, and capacity for, domain ... More
Entanglement sum rules in exactly solvable modelsSep 04 2012We compute the entanglement entropy of a wide class of exactly solvable models which may be characterized as describing matter coupled to gauge fields. Our principle result is an entanglement sum rule which states that entropy of the full system is the ... More
Mutual information and the structure of entanglement in quantum field theoryOct 19 2010I study the mutual information between spatial subsystems in a variety of scale invariant quantum field theories. While it is derived from the bare entanglement entropy, the mutual information offers a more refined probe of the entanglement structure ... More
A simple model of many-body localizationJul 01 2013We study a simple and tractable model of many-body localization. The main idea is to take a renormalization group perspective in which local entanglement is removed to reach a product state. The model is built from a random local unitary which implements ... More
Infinite dimensional symmetry of corner transfer matricesDec 16 1993Dec 17 1993We review some of the recent developments in two dimensional statistical mechanics in which corner transfer matrices provide the vital link between the physical system and the representation theory of quantum affine algebras. This opens many new possibilities, ... More
The movable cone via intersectionsNov 16 2011Dec 26 2012We characterize the movable cone of divisors using intersections against curves on birational models.
The Velocity Field of Quasar Broad Emission Line GasJan 25 2007In this Letter, the broad emission line (BEL) profiles of superluminal quasars with apparent jet velocities, $\beta_{a}>10$, (ultraluminal QSOs, or ULQSOs hereafter) are studied as a diagnostic of the velocity field of the BEL emitting gas in quasars. ... More
Fast Wave Polarization, Charge Horizons and the Time Evolution of Force-Free MagnetospheresJul 16 2004Numerical simulations of force-free, degenerate (ffde)pulsar and black hole magnetospheres are often based on 1-D characteristics. In particular, the plasma wave polarizations that can be propagated along the 1-D characteristics determine the time evolution ... More
The Extreme Ultraviolet Deficit and Magnetically Arrested Accretion in Radio Loud QuasarsDec 01 2014The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet (EUV) for the radio loud component of the quasar population (RLQs), compared to the radio quiet component ... More
Force Free Waves and Black Hole Magnetospheric CausalityOct 03 2002The force free approximation is often useful when describing tenuous plasmas in strong cosmic magnetic fields. Time evolution of any such system is governed by the information that can be transported along the characteristics of the plasma modes allowed ... More
Energy and Asymptotics of Ricci-Flat 4-Manifolds with a Killing FieldAug 22 2013Given a complete, Ricci-flat 4-manifold with a Killing field, we give an estimate on the manifold's energy in terms of a certain asymptotic quantity of the Killing field. If the Killing field has no zeros and satisfies a certain asymptotic condition, ... More
Two Universality Results for Polynomial Reproducing KernelsMay 30 2016We prove two new universality results for polynomial reproducing kernels of compactly supported measures. The first applies to measures on the unit circle with a jump and a singularity in the weight at $1$ and the second applies to area-type measures ... More
Intermediate polars in low statesOct 09 2003Although no intermediate polar (IP) has been observed in recent years to descend into a state of low rate of mass transfer, there are candidate stars that appear to be already in intermediate and low states. V709 Cas is probably an intermediate state ... More
Forced Edges and Graph StructureOct 04 2016For a degree sequence, we define the set of edges that appear in every labeled realization of that sequence as forced, while the edges that appear in none as forbidden. We examine structure of graphs whose degree sequences contain either forced or forbidden ... More
On Fitting ideals of logarithmic vector fields and Saito's criterionSep 15 2013Oct 17 2014The germ of an analytic set $(X,p)$ in $\mathbb{C}^n$ has an associated $\mathscr{O}_{\mathbb{C}^n,p}$-module $\mathrm{Der}(-\log X)$ of `logarithmic vector fields', the ambient germs of holomorphic vector fields tangent to the smooth locus of $X$. For ... More
The Weight Filtration on the Constant Sheaf on a Parameterized SpaceNov 11 2018May 16 2019On an $n$-dimensional locally reduced complex analytic space $X$ on which the shifted constant sheaf $\Q_X^\bullet[n]$ is perverse, it is well-known that, locally, $\Q_X^\bullet[n]$ underlies a mixed Hodge module of weight $\leq n$ on $X$, with weight ... More
Classification of subdivision rules for geometric groups of low dimensionSep 09 2014Subdivision rules create sequences of nested cell structures on CW-complexes, and they frequently arise from groups. In this paper, we develop several tools for classifying subdivision rules. We give a criterion for a subdivision rule to represent a Gromov ... More
Global aspects of the geometry of surfacesJul 23 2009Jul 30 2009These notes (prepared for the author's lectures at the Cracow Summer School on Linear Systems organized by S. Mueller-Stach and T. Szemberg, held March 23-27, 2009 at the Pedagogical University of Cracow under the sponsorship of the Deutsche Forschungsgemeinschaft) ... More
A Manifold Calculus Approach to Link Maps and the Linking NumberFeb 06 2007Jul 03 2007We study the space of "link maps": the space of maps of a disjoint union of compact, closed manifolds P_1, . . ., P_k into a manifold N whose images are pairwise disjoint. We apply the manifold calculus of functors developed by Goodwillie and Weiss to ... More
Controlling Area Blow-up in Minimal or Bounded Mean Curvature VarietiesJul 14 2012Jun 26 2015Consider a sequence of minimal varieties M_i in a Riemannian manifold N such that the boundary measures are uniformly bounded on compact sets. Let Z be the set of points at which the areas of the M_i blow up. We prove that Z behaves in some ways like ... More
Currents and Flat Chains Associated to Varifolds, with an Application to Mean Curvature FlowMay 14 2008Nov 09 2008We prove under suitable hypotheses that convergence of integral varifolds implies convergence of associated mod 2 flat chains and subsequential convergence of associated integer-multiplicity rectifiable currents. The convergence results imply restrictions ... More
Sub-Hermitian Geometry and the Quantitative Newlander-Nirenberg TheoremOct 26 2018Mar 15 2019Given a finite collection of $C^1$ complex vector fields on a $C^2$ manifold $M$ such that they and their complex conjugates span the complexified tangent space at every point, the classical Newlander-Nirenberg theorem gives conditions on the vector fields ... More
Pahs, Ionized Gas, and Molecular Hydrogen in Brightest Cluster Galaxies of Cool Core Clusters of GalaxiesMar 08 2011We present measurements of 5-25 {\mu}m emission features of brightest cluster galaxies (BCGs) with strong optical emission lines in a sample of 9 cool-core clusters of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. ... More
Discovery of Orbital-Selective Cooper Pairing in FeSeNov 07 2016FeSe is the focus of intense research interest because of its unusual non-magnetic nematic state and because it forms the basis for achieving the highest critical temperatures of any iron-based superconductor. However, its Cooper pairing mechanism has ... More
Visualizing Orbital-selective Quasiparticle Interference in the Hund's Metal State of FeSeFeb 06 2018High temperature superconductivity (HTS) in Cu-based materials is generated by strong electronic correlations due to proximity of the Mott insulator phase. By contrast, the undoped phase proximate to Fe-based HTS is never an insulator. But this striking ... More
Detection of PAH and Far-Infrared Emission from the Cosmic Eye: Probing the Dust and Star Formation of Lyman Break GalaxiesApr 10 2009We report the results of a Spitzer infrared study of the Cosmic Eye, a strongly lensed, L*_UV Lyman Break Galaxy (LBG) at z=3.074. We obtained Spitzer IRS spectroscopy as well as MIPS 24 and 70 micron photometry. The Eye is detected with high significance ... More
Resistance to TB drugs in KwaZulu-Natal: causes and prospects for controlJul 09 2011In 2005 there was an outbreak of XDR (extensively drug resistant) TB in Tugela Ferry, which is served by the Church of Scotland Hospital (COSH), in the uMzinyathi District, KwaZulu-Natal, South Africa. An investigation was carried out to determine if ... More
NuSTAR Detection of X-rays Concurrent with Gamma Rays in the Nova V5855 SgrDec 31 2018We report the first detection of hard (>10 keV) X-ray emission simultaneous with gamma rays in a nova eruption. Observations of the nova V5855 Sgr carried out with the NuSTAR satellite on Day 12 of the eruption revealed faint, highly absorbed thermal ... More
Persistence of Island Arrangements During Layer-by-Layer Growth Revealed Using Coherent X-raysApr 22 2018Understanding surface dynamics during epitaxial film growth is key to growing high quality materials with controllable properties. X-ray photon correlation spectroscopy (XPCS) using coherent x-rays opens new opportunities for in situ observation of atomic-scale ... More