Results for "Frederick R. Manby"

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The distinguishable cluster approximationMay 31 2013A new method that accurately describes strongly correlated states and captures dynamical correlation is presented. It is derived as a modification of coupled-cluster theory with single and double excitations (CCSD) through consideration of particle distinguishability ... More
Even-handed subsystem selection in projection-based embeddingSep 09 2018Projection-based embedding offers a simple framework for embedding correlated wavefunction methods in density functional theory. Partitioning between the correlated wavefunction and density functional subsystems is performed in the space of localized ... More
Commuting Elements and Spaces of HomomorphismsMar 08 2006May 19 2006This article records basic topological, as well as homological properties of the space of homomorphisms Hom(L,G) where L is a finitely generated discrete group, and G is a Lie group, possibly non-compact. If L is a free abelian group of rank equal to ... More
Analytical Gradients for Projection-Based Wavefunction-in-DFT EmbeddingMar 14 2019Projection-based embedding provides a simple, robust, and accurate approach for describing a small part of a chemical system at the level of a correlated wavefunction method while the remainder of the system is described at the level of density functional ... More
Density functional theory embedding for correlated wavefunctions: Improved methods for open-shell systems and transition metal complexesNov 26 2012Dec 17 2012Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability ... More
Tensor factorizations of local second-order Møller Plesset theoryAug 29 2010Efficient electronic structure methods can be built around efficient tensor representations of the wavefunction. Here we describe a general view of tensor factorization for the compact representation of electronic wavefunctions. We use these ideas to ... More
Machine learning for predictive condensed-phase simulationFeb 22 2013We show how machine learning techniques based on Bayesian inference can be used to reach new levels of realism in the computer simulation of molecular materials, focusing here on water. We train our machine-learning algorithm using accurate, correlated ... More
Electromagnetic Composites at the Compton ScaleSep 10 2011A new class of electromagnetic composite particles is proposed. The composites are very small (the Compton scale), potentially long-lived, would have unique interactions with atomic and nuclear systems, and, if they exist, could explain a number of otherwise ... More
Manifolds with non-stable fundamental groups at infinity, IIIMay 24 2005Mar 03 2009We continue our study of ends non-compact manifolds. The over-arching aim is to provide an appropriate generalization of Siebenmann's famous collaring theorem that applies to manifolds having non-stable fundamental group systems at infinity. In this paper ... More
Spherical alterations of handles: embedding the manifold plus constructionAug 25 2011Aug 27 2012A key tool in our earlier work on ends of manifolds high-dimensional manifolds was an ability to embed cobordisms provided by the Quillen Plus Construction into those ends. Here we develop a `spherical modification' trick which provides a constructive ... More
Orbit configuration spaces associated to discrete subgroups of PSL(2,R)Oct 24 2003The purpose of this article is to analyze several Lie algebras associated to "orbit configuration spaces" obtained from a group G acting freely, and properly discontinuously on the upper 1/2-plane H^2. The Lie algebra obtained from the descending central ... More
Commuting elements, simplicial spaces, and filtrations of classifying spacesDec 31 2008Sep 12 2011Using spaces of homomorphisms and the descending central series of the free groups, simplicial spaces are constructed for each integer q>1 and every topological group G, with realizations B(q,G) that filter the classifying space BG. In particular for ... More
Stochastic granular 5-dimensional space-time and quantum theoryJan 26 2016Dec 02 2018Much of quantum mechanics may be derived if one adopts a very strong form of Mach's Principle, requiring that in the absence of mass, space-time becomes not flat but stochastic. But points ('events'), having no extent, cannot tessellate the space-time ... More
A Chaotic, Deterministic Model for Quantum MechanicsJun 20 2014With the decline of the Copenhagen interpretation of quantum mechanics and the recent experiments indicating that quantum mechanics does actually embody 'objective reality', one might ask if a 'mechanical', conceptual model for quantum mechanics could ... More
Non-Commutative Formal Groups In Positive CharactersticFeb 07 2006We describe geometric non-commutative formal groups in terms of a geometric commutative formal group with a Poisson structure on its splay algebra. We describe certain natural properties of such Poisson structures and show that any such Poisson structure ... More
Reductions, Resolutions and the Copolarity of Isometric Group ActionsAug 03 2009We present some results on reductions and the copolarity of isometric group actions, which we obtained in our thesis. We also describe a resolution construction for isometric actions with respect to a reduction and give examples.
Geometry of Four-vector Fields on Quaternionic Flag ManifoldsApr 09 2001Mar 29 2002The purpose of this paper is to describe certain natural 4-vector fields on quaternionic flag manifolds, which geometrically determine the Bruhat cell decomposition. This structure naturally descends from the symplectic group, where it is related to the ... More
A highly scalable massively parallel fast marching method for the Eikonal equationFeb 25 2015In this study, we present a highly scalable massively parallel implementation of the fast marching method using a domain decomposition approach. Central to this algorithm is a novel restarted narrow band approach that coordinates the frequency of communications ... More
Admissibility Conditions for Degenerate Cyclotomic BMW AlgebrasMay 26 2009Jan 22 2010We study admissibility conditions for the parameters of degenerate cyclotomic BMW algebras. We show that the u-admissibility condition of Ariki, Mathas and Rui is equivalent to a simple module theoretic condition.
Cellularity of Cyclotomic Birman--Wenzl--Murakami algebrasJan 01 2008May 28 2008We show that the cyclotomic Birman-Wenzl-Murakami algebras are cellular by producing a cellular basis of affine tangle diagrams.
Remarks on Cyclotomic and Degenerate Cyclotomic BMW AlgebrasNov 15 2010May 08 2012We relate the structure of cyclotomic and degenerate cyclotomic BMW algebras, for arbitrary parameter values, to that for admissible parameter values. In particular, we show that these algebras are cellular. We characterize those parameter sets for affine ... More
Giving Text Analytics a BoostApr 25 2018The amount of textual data has reached a new scale and continues to grow at an unprecedented rate. IBM's SystemT software is a powerful text analytics system, which offers a query-based interface to reveal the valuable information that lies within these ... More
The Sub-Index of Critical Points of Distance FunctionsAug 30 2014Sep 23 2015We define a new notion---the sub-index of a critical point of a distance function. We show how sub-index affects the homotopy type of sublevel sets of distance functions.
Submetries, Souls, and Second Fundamental FormsJun 13 2016We give an optimal estimate for the norm of any submanifold's second fundamental form in terms of its focal radius and the lower sectional curvature bound of the ambient manifold. This is a special case of a similar theorem for intermediate Ricci curvature, ... More
Guiding Isotopies and Holomorphic MotionsApr 28 2013Jan 17 2014We develop an isotopy principle for holomorphic motions. Our main result concerns the extendability of a holomorphic motion of a finite subset $E$ of a Riemann surface $Y$ parameterized by a point $t$ in a pointed hyperbolic surface $(X, t_{0})$. If a ... More
On Cellular Algebras with Jucys Murphy ElementsJul 20 2009Nov 15 2010We study analogues of Jucys-Murphy elements in cellular algebras arising from repeated Jones basic constructions. Examples include Brauer and BMW algebras and their cyclotomic analogues.
Horizontally homothetic submersions and nonnegative curvatureFeb 01 2006Feb 07 2006We show that any horizontally homothetic submersion from a compact manifold of nonnegative sectional curvature is a Riemannian submersion.
New or Improved Orbital Periods of Cataclysmic BinariesNov 24 2017Nov 28 2017We present a table of 58 cataclysmic binary orbital periods determined using data from MDM Observatory. Most are heretofore unpublished; some are refinements of previously published periods.
Physical Structures of the Type Ia Supernova Remnant N103BJan 20 2017N103B is a Type Ia supernova remnant (SNR) projected in the outskirt of the superbubble around the rich cluster NGC 1850 in the Large Magellanic Cloud (LMC). We have obtained H$\alpha$ and continuum images of N103B with the $\textit{Hubble Space Telescope}$ ... More
Energy benchmarks for water clusters and ice structures from an embedded many-body expansionJul 14 2013We show how an embedded many-body expansion (EMBE) can be used to calculate accurate \emph{ab initio} energies of water clusters and ice structures using wavefunction-based methods. We use the EMBE described recently by Bygrave \emph{et al.} (J. Chem. ... More
Assessing the accuracy of quantum Monte Carlo and density functional theory for energetics of small water clustersApr 17 2012We present a detailed study of the energetics of water clusters (H$_2$O)$_n$ with $n \le 6$, comparing diffusion Monte Carlo (DMC) and approximate density functional theory (DFT) with well converged coupled-cluster benchmarks. We use the many-body decomposition ... More
The shape of the one-dimensional phylogenetic likelihood functionJul 13 2015Jul 21 2016By fixing all parameters in a phylogenetic likelihood model except for one branch length, one obtains a one-dimensional likelihood function. In this work, we introduce a mathematical framework to characterize the shapes of such one-dimensional phylogenetic ... More
Halász's theorem for Beurling generalized numbersFeb 11 2019We show that Hal\'{a}sz's theorem holds for Beurling numbers under the following two mild hypotheses on the generalized number system: existence of a positive density for the generalized integers and a Chebyshev upper bound for the generalized primes. ... More
Crystalline electric field effects in the electrical resistivity of PrOs$_4$Sb$_{12}$Mar 21 2003The temperature $T$ and magnetic field $H$ dependencies of the electrical resistivity $\rho$ of the recently discovered heavy fermion superconductor \PrOsSb{} have features that are associated with the splitting of the Pr$^{3+}$ Hund's rule multiplet ... More
Fractional nonlinear filtering problems and their associated fractional Zakai equationsMay 13 2013In this paper we discuss fractional generalizations of the filtering problem. The "fractional" nature comes from time-changed state or observation processes, basic ingredients of the filtering problem. The mathematical feature of the fractional filtering ... More
Cyclotomic Birman--Wenzl--Murakami algebras, I: Freeness and realization as tangle algebrasDec 02 2006May 28 2008The cyclotomic Birman-Wenzl-Murakami algebras are quotients of the affine BMW algebras in which the affine generator satisfies a polynomial relation. We show that the cyclotomic BMW algebras are free modules over any (admissible, integral) ground ring, ... More
DeepStreaks: identifying fast-moving objects in the Zwicky Transient Facility data with deep learningApr 11 2019We present DeepStreaks, a convolutional-neural-network, deep-learning system designed to efficiently identify streaking fast-moving near-Earth objects that are detected in the data of the Zwicky Transient Facility (ZTF), a wide-field, time-domain survey ... More
Quarter-fraction factorial designs constructed via quaternary codesAug 24 2009The research of developing a general methodology for the construction of good nonregular designs has been very active in the last decade. Recent research by Xu and Wong [Statist. Sinica 17 (2007) 1191--1213] suggested a new class of nonregular designs ... More
Non-crossing cumulants of type BJun 17 2002We establish connections between the lattices of non-crossing partitions of type B introduced by V. Reiner, and the framework of the free probability theory of D. Voiculescu. Lattices of non-crossing partitions (of type A, up to now) have played an important ... More
Finite Phase-separation FRET II: Determination of domain size from simulated dataMay 31 2011We have developed a new model to describe FRET efficiency (E FRET) between freely-diffusing membrane probes in phase-separated bilayers (Finite Phase-separation FRET, or FP-FRET), that in principle applies to any system where phase domain dimensions are ... More
Pan-chromatic observations of the remarkable nova LMC 2012Dec 19 2014We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2 days. In X-rays the super soft phase began 13$\pm$5 ... More
On spaces of commuting elements in Lie groupsFeb 25 2014Jun 02 2016The main purpose of this paper is to introduce a method to stabilize certain spaces of homomorphisms from finitely generated free abelian groups to a Lie group $G$, namely $Hom(\mathbb Z^n,G)$. We show that this stabilized space of homomorphisms decomposes ... More
Bulk and surface energetics of lithium hydride crystal: benchmarks from quantum Monte Carlo and quantum chemistryJul 21 2010Jul 22 2010We show how accurate benchmark values of the surface formation energy of crystalline lithium hydride can be computed by the complementary techniques of quantum Monte Carlo (QMC) and wavefunction-based molecular quantum chemistry. To demonstrate the high ... More
A survey on spaces of homomorphisms to Lie groupsDec 17 2014Jun 02 2016The purpose of this article is to give an exposition of topological properties of spaces of homomorphisms from certain finitely generated discrete groups to Lie groups $G$, and to describe their connections to classical representation theory, as well ... More
On the enumeration of tanglegrams and tangled chainsJul 17 2015Tanglegrams are a special class of graphs appearing in applications concerning cospeciation and coevolution in biology and computer science. They are formed by identifying the leaves of two rooted binary trees. We give an explicit formula to count the ... More
Interference in a Prototype of a two-dimensional Ion Trap Array Quantum SimulatorDec 20 2018Quantum mechanics dominates various effects in modern research from miniaturizing electronics, up to potentially ruling solid-state physics, quantum chemistry and biology. To study these effects experimental quantum systems may provide the only effective ... More
Computing minimal interpolants in $C^{1,1}(\mathbb{R}^d)$Nov 20 2014Oct 26 2016We consider the following interpolation problem. Suppose one is given a finite set $E \subset \mathbb{R}^d$, a function $f: E \rightarrow \mathbb{R}$, and possibly the gradients of $f$ at the points of $E$. We want to interpolate the given information ... More
Modelling 3D magnetic networks in a realistic solar atmosphereApr 25 2019May 02 2019The magnetic network extending from the photosphere (solar radius \simeq R_\odot) to lower corona (R_\odot + 10 Mm) plays an important role in the heating mechanisms of the solar atmosphere. Here we further develop the models with realistic open magnetic ... More
Knowledge-based system for collaborative process specificationSep 30 2015This paper presents an ontology-based approach for the design of a collaborative business process model (CBP). This CBP is considered as a specification of needs in order to build a collaboration information system (CIS) for a network of organisations. ... More
Constraining the equation of state of high-density cold matter using nuclear and astronomical measurementsApr 18 2019The increasing richness of data related to cold dense matter, from laboratory experiments to neutron star observations, requires a framework for constraining the properties of such matter that makes use of all relevant information. Here we present a rigorous ... More
Long-term variations of turbulent transport coefficients in a solar-like convective dynamo simulationSep 01 2017Oct 06 2017The Sun, aside from its eleven year sunspot cycle is additionally subject to long term variation in its activity. In this work we analyse a solar-like convective dynamo simulation, containing approximately 60 magnetic cycles, exhibiting equatorward propagation ... More
Time-dependent behaviour of quasar proximity zones at $z \sim 6$Mar 29 2019Since the discovery of $z\sim 6$ quasars two decades ago, studies of their Ly$\alpha$-transparent proximity zones have largely focused on their utility as a probe of cosmic reionization. But even when in a highly ionized intergalactic medium, these zones ... More
Planning as Optimization: Dynamically Discovering Optimal Configurations for Runtime SituationsMay 03 2019The large number of possible configurations of modern software-based systems, combined with the large number of possible environmental situations of such systems, prohibits enumerating all adaptation options at design time and necessitates planning at ... More
Rotational symmetry of self-expanders to the inverse mean curvature flow with cylindrical endsAug 06 2016We show that any complete, immersed self-expander to the inverse mean curvature flow, which has one end asymptotic to a cylinder, or has two ends asymptotic to two coaxial cylinders, must be rotationally symmetric.
Thermal Energy Generation in the EarthMay 29 2014We show that a recently introduced class of electromagnetic composite particles can explain some discrepancies in observations involving heat and helium released from the earth. Energy release during the formation of the composites and subsequent nuclear ... More
The Effect of Fluctuations on the Helium-Ionizing BackgroundSep 21 2012Oct 07 2013Interpretation of He II Ly{\alpha} absorption spectra after the epoch of He II reionization requires knowledge of the He II ionizing background. While past work has modelled the evolution of the average background, the standard cosmological radiative ... More
A combinatorial approach to the exponents of Moore spacesJun 02 2015In this article, we give a combinatorial approach to the exponents of the Moore spaces. Our result states that the projection of the $p^{r+1}$-th power map of the loop space of the $(2n+1)$-dimensional mod $p^r$ Moore space to its atomic piece containing ... More
A Radio Pulsar/X-ray Binary LinkMay 20 2009May 22 2009Radio pulsars with millisecond spin periods are thought to have been spun up by transfer of matter and angular momentum from a low-mass companion star during an X-ray-emitting phase. The spin periods of the neutron stars in several such low-mass X-ray ... More
Homotopy Brunnian links and the $κ$-invariantAug 22 2012Nov 14 2014We provide an alternative proof that Koschorke's $\kappa$-invariant is injective on the set of link homotopy classes of $n$-component homotopy Brunnian links $BLM(n)$. The existing proof (by Koschorke \cite{Koschorke97}) is based on the Pontryagin--Thom ... More
Large fluctuations in the hydrogen-ionizing background and mean free path following the epoch of reionizationSep 23 2015Extremely large opaque troughs in the Lyman-alpha forest have been interpreted as a sign of an extended reionization process below z~6. Such features are impossible to reproduce with simple models of the intergalactic ionizing background that assume a ... More
ZTF18aalrxas: A Type IIb Supernova from a very extended low-mass progenitorMar 21 2019We investigate ZTF18aalrxas, a double-peaked Type IIb core-collapse supernova (SN) discovered during science validation of the Zwicky Transient Facility (ZTF). ZTF18aalrxas was discovered while the optical emission was still rising towards the initial ... More
Shape oscillation of a levitated drop in an acoustic fieldOct 10 2013Oct 31 2013A `star drop' refers to the patterns created when a drop, flattened by some force, is excited into shape mode oscillations. These patterns are perhaps best understood as the two dimensional analog to the more common three dimensional shape mode oscillations. ... More
Noncompact manifolds that are inward tameSep 03 2015We continue our study of ends of non-compact manifolds, with a focus on the inward tameness condition. For manifolds with compact boundary, inward tameness, has significant implications. For example, such manifolds have stable homology at infinity in ... More
The Central Starburst and Ionization Mechanism in the LINER/H II Region Transition Nucleus in NGC 4569Apr 23 2002We present a comprehensive study to determine if the LINER/H II region transition spectrum in NGC 4569 can be generated solely by photoionization by the nuclear starburst. A review of the multiwavelength data from the literature reveals no additional ... More
Preliminary Trigonometric Parallaxes of 184 Late-T and Y Dwarfs and an Analysis of the Field Substellar Mass Function into the "Planetary" Mass RegimeDec 04 2018We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), USNO (18), NTT (14), and UKIRT (9). To complete the 20-pc census of $\ge$T6 dwarfs, we combine these measurements with previously published ... More
NuSTAR study of Hard X-Ray Morphology and Spectroscopy of PWN G21.5-0.9May 13 2014We present NuSTAR high energy X-ray observations of the pulsar wind nebula (PWN)/supernova remnant G21.5-0.9. We detect integrated emission from the nebula up to ~40 keV, and resolve individual spatial features over a broad X-ray band for the first time. ... More
A New Class of Changing-Look LINERsApr 24 2019We report the discovery of six active galactic nuclei (AGN) caught "turning on" during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as LINERs by weak narrow forbidden line emission in their archival ... More
Discovery of KiloHertz Quasi-Periodic Oscillations in the Z source GX 5-1Jun 03 1998We discovered two simultaneous kHz quasi-periodic oscillations (QPOs) in the bright low-mass X-ray binary and Z source GX 5-1 with the Rossi X-ray Timing Explorer. In the X-ray color-color and hardness-intensity diagram a clear Z track is traced out, ... More
19 dubious ways to compute the marginal likelihood of a phylogenetic tree topologyNov 28 2018The marginal likelihood of a model is a key quantity for assessing the evidence provided by the data in support of a model. The marginal likelihood is the normalizing constant for the posterior density, obtained by integrating the product of the likelihood ... More
The [Ne III] Jet of DG Tau and its Ionization ScenariosNov 07 2016Forbidden neon emission from jets of low-mass young stars can be used to probe the underlying high-energy processes in these systems. We analyze spectra of the jet of DG Tau obtained with the Very Large Telescope/X-Shooter spectrograph in 2010. [Ne III] ... More
Motional-Mode Analysis of Trapped IonsMay 04 2016We present two methods for characterization of motional-mode configurations that are generally applicable to the weak and strong-binding limit of single or multiple trapped atomic ions. Our methods are essential to realize control of the individual as ... More
Polars Changing State: Multiwavelength Long Term Photometry and Spectroscopy of QS Tel, V834 Cen, and BL HyiMar 03 2006Long term optical and near-infrared photometric and blue spectroscopic observations were obtained for QS Tel, V834 Cen, and BL Hyi. The optical light curves of all three polars displayed large magnitude changes during our observations. These same high/low ... More
Equipartitions and a Distribution for Numbers: A Statistical Model for Benford's LawMar 28 2015A statistical model for the fragmentation of a conserved quantity is analyzed, using the principle of maximum entropy and the theory of partitions. Upper and lower bounds for the restricted partitioning problem are derived and applied to the distribution ... More
Stable splittings, spaces of representations and almost commuting elements in Lie groupsOct 05 2010In this paper the space of almost commuting elements in a Lie group is studied through a homotopical point of view. In particular a stable splitting after one suspension is derived for these spaces and their quotients under conjugation. A complete description ... More
Quantum Walks on Trees with Disorder: Decay, Diffusion, and LocalizationJun 14 2012Quantum walks have been shown to have impressive transport properties compared to classical random walks. However, imperfections in the quantum walk algorithm can destroy any quantum mechanical speed-up due to Anderson localization. We numerically study ... More
Evidence for A Parsec-scale Jet from The Galactic Center Black Hole: Interaction with Local GasOct 01 2013Despite strong physical reasons that they should exist and decades of search, jets from the Galactic Center Black Hole, Sgr A*, have not yet been convincingly detected. Based on high-resolution Very Large Array images and ultra-deep imaging-spectroscopic ... More
The Lie module and its complexityMar 05 2015The complexity of a module is an important homological invariant that measures the polynomial rate of growth of its minimal projective resolution. For the symmetric group $\Sigma_n$, the Lie module $\mathsf{Lie}(n)$ has attracted a great deal of interest ... More
Ultra-Stable Environment Control for the NEID Spectrometer: Design and Performance DemonstrationFeb 20 2019Two key areas of emphasis in contemporary experimental exoplanet science are the detailed characterization of transiting terrestrial planets, and the search for Earth analog planets to be targeted by future imaging missions. Both of these pursuits are ... More
Permutation-based cluster size correction for voxel-based lesion-symptom mappingJun 01 2016Voxel-based lesion-symptom mapping (VLSM) is a major method for studying brain-behavior relationships that leverages modern neuroimaging analysis techniques to build on the classic approach of examining the relationship between location of brain damage ... More
Systematic Exploration of the High Likelihood Set of Phylogenetic Tree TopologiesNov 27 2018Bayesian Markov chain Monte Carlo explores tree space slowly, in part because it frequently returns to the same tree topology. An alternative strategy would be to explore tree space systematically, and never return to the same topology. In this paper, ... More
The Evolution of the HeII-Ionizing Background at Redshifts 2.3<z<3.8 Inferred from a Statistical Sample of 24 HST/COS HeII Ly$α$ Absorption SpectraAug 15 2018We present new measurements of the large-scale effective optical depth of HeII Ly$\alpha$ absorption, $\tau_{\rm eff}$, at $2.54<z<3.86$ toward 16 HeII-transparent quasars observed with the Cosmic Origins Spectrograph on the Hubble Space Telescope, to ... More
The Evolution of the HeII-Ionizing Background at Redshifts 2.3<z<3.8 Inferred from a Statistical Sample of 24 HST/COS HeII Ly$α$ Absorption SpectraAug 15 2018Apr 04 2019We present measurements of the large-scale (~40 comoving Mpc) effective optical depth of HeII Ly$\alpha$ absorption, $\tau_{\rm eff}$, at 2.54<z<3.86 toward 16 HeII-transparent quasars observed with the Cosmic Origins Spectrograph (COS) on the Hubble ... More
Feeding and Small-scale Feedback in Low-Luminosity AGNsDec 18 2012The unmatched X-ray resolution of Chandra allows probing the gas flow near quiescent supermassive black holes (BHs). The radius of BH gravitational influence on gas, called the Bondi radius, is resolved in Sgr A* and NGC 3115. Shallow accretion flow density ... More
On the convergence of the maximum likelihood estimator for the transition rate under a 2-state symmetric modelMar 10 2019Maximum likelihood estimators are used extensively to estimate unknown parameters of stochastic trait evolution models on phylogenetic trees. Although the MLE has been proven to converge to the true value in the independent-sample case, we cannot appeal ... More
The first tidal disruption flare in ZTF: from photometric selection to multi-wavelength characterizationSep 07 2018Feb 07 2019We present Zwicky Transient Facility (ZTF) observations of the tidal disruption flare AT2018zr/PS18kh reported by Holoien et al. and detected during ZTF commissioning. The ZTF light curve of the tidal disruption event (TDE) samples the rise-to-peak exceptionally ... More
A self-consistent 3D model of fluctuations in the helium-ionizing backgroundMar 29 2017Large variations in the effective optical depth of the He II Ly$\alpha$ forest have been observed at $z\gtrsim2.7$, but the physical nature of these variations is uncertain: either the Universe is still undergoing the process of He II reionization, or ... More
Quasar Ionization Front Lyα Emission in an Inhomogeneous Intergalactic MediumSep 02 2014The conditions within the ionization front of a quasar during reionization (T ~ 30,000 K, neutral hydrogen fraction ~ 0.5) are ideal for producing Lyman-alpha emission via collisional excitation of hydrogen atoms. Observations of this emission, which ... More
Estimation and Registration on GraphsOct 14 2010A statistical framework is introduced for a broad class of problems involving synchronization or registration of data across a sensor network in the presence of noise. This framework enables an estimation-theoretic approach to the design and characterization ... More
Commuting elements in central products of special unitary groupsMay 18 2009Oct 04 2010In this paper the space of commuting elements in the central product $G_{m,p}$ of $m$ copies of the special unitary group $SU(p)$ is studied, where $p$ is a prime number. In particular, a computation for the number of path connected components of these ... More
Determining the Nature of Late Gunn-Peterson Troughs with Galaxy SurveysAug 29 2017Recent observations have discovered long (up to ~110 Mpc/h), opaque Gunn-Peterson troughs in the z ~ 5.5 Lyman-alpha forest, which are challenging to explain with conventional models of the post-reionization intergalactic medium. Here we demonstrate that ... More
On the cohomology of Young modules for the symmetric groupMar 18 2008Dec 29 2009The main result of this paper is an application of the topology of the space $Q(X)$ to obtain results for the cohomology of the symmetric group on $d$ letters, $\Sigma_d$, with `twisted' coefficients in various choices of Young modules and to show that ... More
On representations and K-theory of the braid groupsOct 13 2001Jan 27 2002Let G be the fundamental group of the complement of a K(G,1) hyperplane arrangement (such as Artin's pure braid group) or more generally a homologically toroidal group (as defined in the paper). The subgroup of elements in the complex K-theory of BG which ... More
Multi-frequency control pulses for multi-level superconducting quantum circuitsSep 08 2009Superconducting quantum circuits, such as the superconducting phase qubit, have multiple quantum states that can interfere with ideal qubit operation. The use of multiple frequency control pulses, resonant with the energy differences of the multi-state ... More
Lie algebras associated to fiber-type arrangementsMay 10 2000Given a hyperplane arrangement in a complex vector space of dimension n, there is a natural associated arrangement of codimension k subspaces in a complex vector space of dimension k*n. Topological invariants of the complement of this subspace arrangement ... More
Airships: A New Horizon for ScienceFeb 26 2014The "Airships: A New Horizon for Science" study at the Keck Institute for Space Studies investigated the potential of a variety of airships currently operable or under development to serve as observatories and science instrumentation platforms for a range ... More
Muon Capture on the Proton and DeuteronAug 11 2008By measuring the lifetime of the negative muon in pure protium (hydrogen-1), the MuCap experiment determines the rate of muon capture on the proton, from which the proton's pseudoscalar coupling g_p may be inferred. A precision of 15% for g_p has been ... More
Almost Optimal Intervention Sets for Causal DiscoveryJun 13 2012We conjecture that the worst case number of experiments necessary and sufficient to discover a causal graph uniquely given its observational Markov equivalence class can be specified as a function of the largest clique in the Markov equivalence class. ... More
An $L^2-$stability estimate for periodic nonuniform sampling in higher dimensionsOct 31 2016We consider sampling strategies for a class of multivariate bandlimited functions $f$ that have a spectrum consisting of disjoint frequency bands. Taking advantage of the special spectral structure, we provide formulas relating $f$ to the samples $f(y), ... More
Interdefinability of defeasible logic and logic programming under the well-founded semanticsJun 10 2011We provide a method of translating theories of Nute's defeasible logic into logic programs, and a corresponding translation in the opposite direction. Under certain natural restrictions, the conclusions of defeasible theories under the ambiguity propagating ... More
Stochastic Hamiltonians for correlated electron modelsFeb 01 2019Feb 19 2019Microscopically conserving reduced models of many-body systems have a long, highly successful history. Established theories of this type are the random-phase approximation for Coulomb fluids and the particle-particle ladder model for nuclear matter. There ... More