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
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
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
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
On complex highly regular embeddings and the extended Vassiliev conjectureOct 22 2014Oct 27 2015A continuous map C^d -> C^N is a complex k-regular embedding if any k pairwise distinct points in C^d are mapped by f into k complex linearly independent vectors in C^N. Our central result on complex k-regular embeddings extends results of Cohen & Handel ... More
A Hidden Markov Movement Model for rapidly identifying behavioral states from animal tracksDec 20 20161. Electronic telemetry is frequently used to document animal movement through time. Methods that can identify underlying behaviors driving specific movement patterns can help us understand how and why animals use available space, thereby aiding conservation ... 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
The Time Dependence of Fundamental Constants and Planck Scale PhysicsNov 14 2003A real aether model of the vacuum proposed by Allen Rothwarf based upon a degenerate Fermion fluid of polarizable particle-antiparticle pairs, leads to a big bang model of the universe where the velocity of light varies inversely with the square root ... More
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
A highly scalable massively parallel fast marching method for the Eikonal equationFeb 25 2015Dec 21 2016The fast marching method is a widely used numerical method for solving the Eikonal equation arising from a variety of scientific and engineering fields. It is long deemed inherently sequential and an efficient parallel algorithm applicable to large-scale ... More
Cellularity and the Jones basic constructionJun 08 2009Apr 14 2010We establish a framework for cellularity of algebras related to the Jones basic construction. Our framework allows a uniform proof of cellularity of Brauer algebras, ordinary and cyclotomic BMW algebras, walled Brauer algebras, partition algebras, and ... More
Spin Rates and Magnetic Fields of Millisecond PulsarsAug 25 2004Observations made using the Rossi X-ray Timing Explorer have shown that accreting weak-field neutron stars in low-mass X-ray binary systems (LMXBs) produce three distinct types of millisecond X-ray oscillations that can be used to determine the spin rates ... More
Momentum-space indirect interlayer excitons in transition metal dichalcogenide van der Waals heterostructuresMar 13 2018Monolayers of transition metal dichalcogenides (TMDCs) feature exceptional optical properties that are dominated by excitons, tightly bound electron-hole pairs. Forming van der Waals heterostructures by deterministically stacking individual monolayers ... More
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
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
Multilevel effects in the Rabi oscillations of a Josephson phase qubitJun 28 2008Dec 06 2009We present Rabi oscillation measurements of a Nb/AlOx/Nb dc superconducting quantum interference device (SQUID) phase qubit with a 100 um^2 area junction acquired over a range of microwave drive power and frequency detuning. Given the slightly anharmonic ... 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
Infinity-harmonic maps and morphismsOct 06 2008Jan 15 2011We propose a new notion called \emph{infinity-harmonic maps}between Riemannain manifolds. These are natural generalizations of the well known notion of infinity harmonic functions and are also the limiting case of $p$% -harmonic maps as $p\to \infty $. ... More
Local curvature estimates of long-time solutions to the Kähler-Ricci flowMar 14 2019We study the local curvature estimates of long-time solutions to the normalized K\"ahler-Ricci flow on compact K\"ahler manifolds with semi-ample canonical line bundles. Using these estimates, we prove that on such a manifold, the set of singular fibers ... More
Benford's Law and Continuous Dependent Random VariablesSep 22 2013Mar 09 2018Many mathematical, man-made and natural systems exhibit a leading-digit bias, where a first digit (base 10) of 1 occurs not 11\% of the time, as one would expect if all digits were equally likely, but rather 30\%. This phenomenon is known as Benford's ... More
A cell filtration of the restriction of a cell moduleApr 08 2015We give a new proof that the restriction of a cell module of the Hecke algebra of the symmetric group on $n$ letters, to the Hecke algebra of the symmetric group on $n-1$ letters, has a filtration by cell modules.
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
Regularization via Cheeger DeformationsFeb 18 2015We show that Cheeger deformations regularize $G$--invariant metrics in a very strong sense.
Visual Causal Feature LearningDec 07 2014Jun 04 2015We provide a rigorous definition of the visual cause of a behavior that is broadly applicable to the visually driven behavior in humans, animals, neurons, robots and other perceiving systems. Our framework generalizes standard accounts of causal learning ... 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
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
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
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
Hot Gas Lines in T Tauri StarsApr 12 2013For Classical T Tauri Stars (CTTSs), the resonance lines of N V, Si IV, and C IV, as well as the He II 1640 A line, act as diagnostics of the accretion process. Here we assemble a large high-resolution dataset of these lines in CTTSs and Weak T Tauri ... More
Seafloor identification in sonar imagery via simulations of Helmholtz equations and discrete optimizationOct 31 2016Feb 19 2017We present a multiscale approach for identifying features in ocean beds by solving inverse problems in high frequency seafloor acoustics. The setting is based on Sound Navigation And Ranging (SONAR) imaging used in scientific, commercial, and military ... More
Unsupervised Discovery of El Nino Using Causal Feature Learning on Microlevel Climate DataMay 30 2016We show that the climate phenomena of El Nino and La Nina arise naturally as states of macro-variables when our recent causal feature learning framework (Chalupka 2015, Chalupka 2016) is applied to micro-level measures of zonal wind (ZW) and sea surface ... 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
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
Exploring Reionization-Era Quasars III: Discovery of 16 Quasars at $6.4\lesssim z \lesssim 6.9$ with DESI Legacy Imaging Surveys and UKIRT Hemisphere Survey and Quasar Luminosity Function at $z\sim6.7$Oct 29 2018This is the third paper in a series aims at finding reionzation-era quasars with the combination of DESI Legacy imaging Surveys (DELS) and near-infrared imaging surveys, such as the UKIRT Hemisphere Survey (UHS), as well as the Wide-field Infrared Survey ... More
Hybrid setup for stable magnetic fields enabling robust quantum controlOct 27 2017Mar 13 2018Well controlled and highly stable magnetic fields are desired for a wide range of applications in physical research, including quantum metrology, sensing, information processing, and simulation. Here we introduce a low-cost hybrid assembly of rare-earth ... More
Multi-level Residual Networks from Dynamical Systems ViewOct 27 2017Feb 01 2018Deep residual networks (ResNets) and their variants are widely used in many computer vision applications and natural language processing tasks. However, the theoretical principles for designing and training ResNets are still not fully understood. Recently, ... 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
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
Distant White Dwarfs in the US Naval Observatory Flagstaff Station Parallax SampleSep 28 2018This paper presents new trigonometric parallaxes and proper motions for 214 stars. The measurements were made at the US Naval Observatory Flagstaff Station (NOFS) between 1989 and 2017, and the average uncertainty in the parallax values is 0.6 mas. We ... More
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
The optical design of the six-meter CCAT-prime and Simons Observatory telescopesJul 17 2018A common optical design for a coma-corrected, 6-meter aperture, crossed-Dragone telescope has been adopted for the CCAT-prime telescope of CCAT Observatory, Inc., and for the Large Aperture Telescope of the Simons Observatory. Both are to be built in ... 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
The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and AbsorptionApr 04 2011We exploit the high sensitivity and moderate spectral resolution of the $HST$-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present ... 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
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
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
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
Discovery of Highly Blueshifted Broad Balmer and Metastable Helium Absorption Lines in a Tidal Disruption EventMar 13 2019We report the discovery of non-stellar hydrogen Balmer and metastable helium absorption lines accompanying a transient, high-velocity (0.05$c$) broad absorption line (BAL) system in the optical spectra of the tidal disruption event (TDE) AT2018zr ($z=0.071$). ... More
Benford's Law and Continuous Dependent Random VariablesNov 02 2011Sep 22 2013Many systems exhibit a digit bias. For example, the first digit base 10 of the Fibonacci numbers, or of $2^n$, equals 1 not 10% or 11% of the time, as one would expect if all digits were equally likely, but about 30% of the time. This phenomenon, known ... More
Modeling the HeII Transverse Proximity Effect: Constraints on Quasar Lifetime and ObscurationOct 12 2017Oct 27 2017The HeII transverse proximity effect - enhanced HeII Ly{\alpha} transmission in a background sightline caused by the ionizing radiation of a foreground quasar - offers a unique opportunity to probe the emission properties of quasars, in particular the ... 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
Self-Expanders to Inverse Curvature Flows by Homogeneous FunctionsJan 15 2017Jun 16 2018In this paper, we study self-expanding solutions to a large class of parabolic inverse curvature flows by homogeneous symmetric functions of principal curvatures in Euclidean spaces. These flows include the inverse mean curvature flow and many nonlinear ... More
Exploiting Points and Lines in Regression Forests for RGB-D Camera RelocalizationOct 28 2017Jul 28 2018Camera relocalization plays a vital role in many robotics and computer vision tasks, such as global localization, recovery from tracking failure and loop closure detection. Recent random forests based methods exploit randomly sampled pixel comparison ... More
Backtracking Regression Forests for Accurate Camera RelocalizationOct 22 2017Camera relocalization plays a vital role in many robotics and computer vision tasks, such as global localization, recovery from tracking failure, and loop closure detection. Recent random forests based methods directly predict 3D world locations for 2D ... 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
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
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
Differentially-Private "Draw and Discard" Machine LearningJul 11 2018Oct 10 2018In this work, we propose a novel framework for privacy-preserving client-distributed machine learning. It is motivated by the desire to achieve differential privacy guarantees in the local model of privacy in a way that satisfies all systems constraints ... More
Determining neutron star masses and radii using energy-resolved waveforms of X-ray burst oscillationsApr 08 2013Simultaneous, precise measurements of the mass $M$ and radius $R$ of neutron stars can yield uniquely valuable information about the still uncertain properties of cold matter at several times the density of nuclear matter. One method that could be used ... More
Testing the rotating hot spot model using X-ray burst oscillations from 4U 1636-536Mar 01 2013Precise and accurate measurements of neutron star masses and radii would provide valuable information about the still uncertain properties of cold matter at supranuclear densities. One promising approach to making such measurements involves analysis of ... 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
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
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
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
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
Comparing submillimeter polarized emission with near-infrared polarization of background stars for the Vela C molecular cloudMay 27 2016Feb 24 2017We present a large-scale combination of near-infrared (near-IR) interstellar polarization data from background starlight with polarized emission data at submillimeter (sub-mm) wavelengths for the Vela C molecular cloud. The near-IR data consist of more ... More
Thermal X-Ray Iron Line Emission from the Galactic Center Black Hole Sagittarius A*Nov 19 2005We model thermal X-ray emission from the accreting supermassive black hole Sagittarius A* at the Galactic Center. For the region inside $1.^{\prime\prime}5$ of the center, we use a {generalized} radiatively inefficient accretion flow (RIAF) model, and ... More
Where and When to Look? Spatio-temporal Attention for Action Recognition in VideosOct 01 2018Inspired by the observation that humans are able to process videos efficiently by only paying attention when and where it is needed, we propose a novel spatial-temporal attention mechanism for video-based action recognition. For spatial attention, we ... More
Peak Luminosities of the Hard States of GX 339-4: Implications for the Accretion Geometry, Disk Mass, and Black Hole MassMar 15 2007Jun 19 2007We have analyzed observations of the black hole transient {GX 339$-$4} made with the {\it Rossi} X-ray Timing Explorer (RXTE) and the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma-ray Observatory (CGRO). We have found a nearly ... 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
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
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
Second-order nonlinear mixing in planar photonic crystal microcavitiesDec 12 2006Second-harmonic and sum-frequency mixing phenomena associated with 3D-localized photonic modes are studied in InP-based planar photonic crystal microcavities excited by short-pulse radiation near 1550 nm. Three-missing-hole microcavities that support ... More
Particle pair creation by inflation of quantum vacuum fluctuations in an ion trapMar 13 2019The creation of matter and structure in our universe is currently described by an intricate interplay of quantum field theory and general relativity. Signatures of this process during an early inflationary period can be observed, while direct tests remain ... More
On Reay's relaxed Tverberg conjecture and generalizations of Conway's thrackle conjectureAug 15 2016Reay's relaxed Tverberg conjecture and Conway's thrackle conjecture are open problems about the geometry of pairwise intersections. Reay asked for the minimum number of points in Euclidean d-space that guarantees any such point set admits a partition ... More
Mass Determination and Detection of the Onset of Chromospheric Activity for the Sub-Stellar Object in EF EridaniJul 07 2006EF Eri is a magnetic cataclysmic variable that has been in a low accretion state for the past nine years. Low state optical spectra reveal the underlying Zeeman-split white dwarf absorption lines. These features are used to determine a value of 13-14 ... More
Fabrication and characterization of semiconducting half Heusler YPtSb thin filmsSep 27 2012Nov 30 2012The semiconducting half Heusler compound YPtSb was predicted theoretically to be capable of changing into topological insulator under proper strain. In this work, p type semiconducting half-Heusler YPtSb thin films were prepared by magnetron co-sputtering ... More
Origin of intermittent accretion-powered X-ray oscillations in neutron stars with millisecond spin periodsSep 24 2008Oct 05 2009We have shown previously that many of the properties of persistent accretion-powered millisecond pulsars can be understood if their X-ray emitting areas are near their spin axes and move as the accretion rate and structure of the inner disk vary. Here ... More
The Radius Rigidity Theorem for Manifolds of Positive CurvatureMay 26 1995Recall that the radius of a compact metric space $(X, dist)$ is given by $rad\ X = \min_{x\in X} \max_{y\in X} dist(x,y)$. In this paper we generalize Berger's $\frac{1}{4}$-pinched rigidity theorem and show that a closed, simply connected, Riemannian ... More
Indeterminate Space-time Quantum Mechanics: a Computer-augmented Framework using Wiener-like ProcessesJan 26 2016Wiener processes (the formalization of Brownian Motion random walk) provide a basis for a model of discrete, mobile elements (Dx, Dy, Dz, Dt) that 'tile' space-time. The possible migrations of these elements are shown graphically via computer simulation. ... More
An Integration Formula for Polar ActionsSep 07 2006We prove an analogue of Weyl's Integration Formula for compact Lie groups in the context of polar actions. We also show how certain classical examples from the literature can be viewed as special cases of our result.
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
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
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
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
A general Weyl-type Integration Formula for Isometric Group ActionsJan 16 2009We show that integration over a $G$-manifold $M$ can be reduced to integration over a minimal section $\Sigma$ with respect to an induced weighted measure and integration over a homogeneous space $G/N$. We relate our formula to integration formulae for ... More