Results for "Daniel Dale"

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Early-time VLA observations and broad-band afterglow analysis of the Fermi-LAT detected GRB 130907ANov 26 2014Jul 21 2015We present multi-wavelength observations of the hyper-energetic gamma-ray burst (GRB) 130907A, a Swift-discovered burst with early radio observations starting at $\approx 4$ hr after the $\gamma$-ray trigger. GRB 130907A was also detected by the Fermi/LAT ... More
Low Dimensional Topology and Ordering GroupsMar 19 2014This expository paper explores the interaction of group ordering with topological questions, especially in dimensions 2 and 3. Among the topics considered are surfaces, braid groups, 3-manifolds and their structures such as foliations and mappings between ... More
The Convergence Depth of the Local Peculiar Velocity FieldAug 31 1999We have obtained Tully-Fisher (TF) measurements for some 3000 late-type galaxies in the field and in 76 clusters distributed throughout the sky between 10 and 200\h Mpc. The cluster data are applied to the construction of an I band TF template, resulting ... More
A controlled study of cold dust content in galaxies from $z=0-2$May 30 2017Jun 01 2017At $z=1-3$, the formation of new stars is dominated by dusty galaxies whose far-IR emission indicates they contain colder dust than local galaxies of a similar luminosity. We explore the reasons for the evolving IR emission of similar galaxies over cosmic ... More
The Infrared Spectral Energy Distribution of Normal Star-Forming Galaxies: Calibration at Far-Infrared and Submillimeter WavelengthsMay 06 2002May 06 2002New far-infrared and submillimeter data are used to solidify and to extend to long wavelengths the empirical calibration of the infrared spectral energy distribution (SED) of normal star-forming galaxies. As was found by Dale et al. (2001), a single parameter ... More
Luminous and obscured quasars and their host galaxiesDec 19 2017The most heavily-obscured, luminous quasars might represent a specific phase of the evolution of actively accreting supermassive black holes and their host galaxies, possibly related to mergers. We investigated a sample of the most luminous quasars at ... More
Effective local connectivity propertiesJun 16 2011Sep 16 2011We investigate, and prove equivalent, effective versions of local connectivity and uniformly local arcwise connectivity for connected and computably compact subspaces of Euclidean space. We also prove that Euclidean continua that are computably compact ... More
Dust-Corrected Star Formation Rates of Galaxies. II. Combinations of Ultraviolet and Infrared TracersAug 14 2011We present new calibrations of far-ultraviolet (FUV) attenuation as derived from the total infrared to FUV luminosity ratio (IRX) and the FUV-NUV color. We find that the IRX-corrected FUV luminosities are tightly and linearly correlated with the attenuation-corrected ... More
The mid-IR Luminosity Function at z<0.3 from 5MUSES: Understanding the Star-formation/AGN Balance from a Spectroscopic ViewApr 04 2011We present rest-frame 15 and 24 um luminosity functions and the corresponding star-forming luminosity functions at z<0.3 derived from the 5MUSES sample. Spectroscopic redshifts have been obtained for ~98% of the objects and the median redshift is ~0.12. ... More
Spitzer 70~$μ$m Emission as a SFR Indicator for Sub--Galactic RegionsOct 03 2010We use Spitzer 24 $\mu$m, 70 $\mu$m and ground based H$\alpha$ data for a sample of 40 SINGS galaxies to establish a star formation rate (SFR) indicator using 70 $\mu$m emission for sub--galactic ($\sim0.05-2\ \rm{kpc}$) line-emitting regions and to investigate ... More
Signatures of Galaxy-Cluster Interactions: Tully-Fisher Observations at z~0.1Apr 21 2003We have obtained new optical imaging and spectroscopic observations of 78 galaxies in the fields of the rich clusters Abell 1413 (z = 0.14), Abell 2218 (z = 0.18) and Abell 2670 (z = 0.08). We have detected line emission from 25 cluster galaxies plus ... More
Signatures of Interstellar-Intracluster Medium Interactions: Spiral Galaxy Rotation Curves in Abell 2029Apr 11 2000We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, ... More
Mid-Infrared Spectral Diagnostics of Nearby GalaxiesApr 01 2006The Spitzer Space Telescope is pushing into new frontiers in high redshift astronomy. Closer to home, Spitzer is making an equally large impact on our understanding of galaxy formation and evolution. In this contribution we present mid-infrared diagnostics ... More
Dust-Corrected Star Formation Rates of Galaxies. I. Combinations of H-alpha and Infrared TracersAug 03 2009We combine H-alpha emission-line and infrared continuum measurements of two samples of nearby galaxies to derive dust attenuation-corrected star formation rates (SFRs). We use a simple energy balance based method that has been applied previously to HII ... More
Structural Analysis of Superconducting Accelerator CavitiesAug 21 2000The static and dynamic structural behavior of superconducting cavities for various projects was determined by finite element structural analysis. The b = 0.61 cavity shape for the Neutron Science Project was studied in detail and found to meet all design ... More
Spectral Analysis of Iterated Rank-One PerturbationsFeb 07 2019The authors study the spectral theory of self-adjoint operators that are subject to certain types of perturbations. An iterative introduction of infinitely many randomly coupled rank-one perturbations is one of our settings. Spectral theoretic tools are ... More
Complemented Subspaces of L_p Determined by Partitions and WeightsOct 15 2002Many of the known complemented subspaces of L_p have realizations as sequence spaces. In this paper a systematic approach to defining these spaces which uses partitions and weights is introduced. This approach gives a unified description of many well-known ... More
Focusing and Polarization in Intuitionistic LogicAug 16 2007A focused proof system provides a normal form to cut-free proofs that structures the application of invertible and non-invertible inference rules. The focused proof system of Andreoli for linear logic has been applied to both the proof search and the ... More
Uniform exponential mixing and resonance free regions for convex cocompact congruence subgroups of $\operatorname{SL}_2(\mathbb{Z})$Oct 16 2014Sep 21 2015Let $\Gamma<\mathrm{SL}_2(\mathbb{Z})$ be a non-elementary finitely generated subgroup and let $\Gamma(q)$ be its congruence subgroup of level $q$ for each $q\in \mathbb{N}$. We obtain an asymptotic formula for the matrix coefficients of $L^2(\Gamma (q) ... More
Étoiles and ValuationsJun 19 2012Dec 02 2016We establish some properties of \'etoiles and associated valuations over complex analytic spaces, showing that Abhyankar's inequality holds. We give some examples of pathological behavior of these valuations. We prove a regularization theorem for complex ... More
Counterexamples to local monomialization in positive characteristicApr 29 2014Aug 08 2015In this paper we consider birational properties of ramification in excellent local rings. We give an example showing that local monomialization (and weak local monomialization) can fail for extensions of algebraic local rings in algebraic function fields ... More
The Role of the Gricean Maxims in the Generation of Referring ExpressionsApr 18 1996Grice's maxims of conversation [Grice 1975] are framed as directives to be followed by a speaker of the language. This paper argues that, when considered from the point of view of natural language generation, such a characterisation is rather misleading, ... More
Prime number theorems and holonomies for hyperbolic rational mapsMar 01 2016We discuss analogues of the prime number theorem for a hyperbolic rational map f of degree at least two on the Riemann sphere. More precisely, we provide counting estimates for the number of primitive periodic orbits of f ordered by their multiplier, ... More
Resolution of Singularities for 3-folds in positive characteristicJun 21 2006Nov 14 2007In this paper a concise, complete proof of resolution of singularities of 3-folds in positive characteristic (>5) is given. The first proof of this theorem was given by Abhyankar in 1966. The resolution morphism in our proof is an isomorphism over the ... More
Relational Sheaves for a Heyting AlgebraJan 04 2016We show that for a Heyting algebra ${\cal H}$, a relational-presheaf is an idempotent symmetric order-preserving lax-semifunctor. A relational-presheaf is a relational-sheaf, if it is an idempotent infima-preserving lax semifunctor. The associated relational-sheaf ... More
Tensor products and independent sums of $\Cal L_p$-spaces, $1<p<\infty$Apr 08 1996Two methods of constructing infinitely many isomorphically distinct $\Cal L_p$-spaces have been published. In this article we show that these constructions yield very different spaces and in the process develop methods for dealing with these spaces from ... More
Simultaneous Resolution of SingularitiesJan 24 1999We prove a local theorem on simultaneous resolution of singularities, which is valid in all dimensions. This theorem is proven in dimension 2 (and in all characteristics) by Abhyankar in his book "Ramification theoretic methods in algebraic geometry". ... More
Characterizations and Decompositions of Domains for Powers of Classical Sturm-Liouville OperatorsJan 17 2019We set out to build a framework for self-adjoint extension theory when the operators are powers of classical Sturm--Liouville operators. This is done by analyzing the structures of maximal and minimal domains, as well as the defect spaces. We focus to ... More
Finite Generation of Extensions of Associated Graded Rings Along a ValuationApr 19 2017May 03 2018In this paper we consider the question of when the associated graded ring along a valuation, ${\rm gr}_{\nu^*}(S)$, is a finite ${\rm gr}_{\nu^*}(R)$-module, where $S$ is a normal local ring which lies over a normal local ring $R$ and $\nu^*$ is a valuation ... More
A generalization of the Abhyankar Jung theorem to associated graded rings of valuationsNov 18 2014Suppose that R\rightarrow S is an extension of local domains and \nu^* is a valuation dominating S. We consider the natural extension of associated graded rings along the valuation gr_{\nu^*}(R)\rightarrow gr_{\nu^*}(S). We give examples showing that ... More
More about a successful vector-tensor theory of gravitationOct 27 2016The vector-tensor (VT) theory of gravitation revisited in this article was studied in previous papers, where it was proved that VT works and deserves attention. New observational data and numerical codes have motivated further development which is presented ... More
Braids, orderings and minimal volume cusped hyperbolic 3-manifoldsOct 11 2016It is well-known that there is a faithful representation of braid groups on automorphism groups of free groups, and it is also well-known that free groups are bi-orderable. We investigate which n-strand braids give rise to automorphisms which preserve ... More
Modeling the Effects of Star Formation Histories on Halpha and Ultra-Violet Fluxes in Nearby Dwarf GalaxiesSep 13 2011We consider the effects of non-constant star formation histories (SFHs) on Halpha and GALEX far ultra-violet (FUV) star formation rate (SFR) indicators. Under the assumption of a fully populated Chabrier IMF, we compare the distribution of Halpha-to-FUV ... More
Mid-Infrared Observations of Normal Star-Forming Galaxies: The Infrared Space Observatory Key Project SampleMay 04 2000We present mid-infrared maps and preliminary analysis for 61 galaxies observed with the ISOCAM instrument aboard the Infrared Space Observatory. Many of the general features of galaxies observed at optical wavelengths---spiral arms, disks, rings, and ... More
A Joint Model of the X-ray And Infrared Extragalactic Backgrounds: I. Model Construction And First ResultsDec 15 2012We present an extragalactic population model of the cosmic background light to interpret the rich high-quality survey data in the X-ray and IR bands. The model incorporates star-formation and supermassive black hole (SMBH) accretion in a co-evolution ... More
Quark Propagation in the Instantons of Lattice QCDJun 14 2013Jul 16 2013We quantitatively examine the extent to which instanton degress of freedom, contained within standard Monte-carlo generated gauge-field configurations, can maintain the characteristic features of the mass and renormalisation functions of the non-perturbative ... More
A Compendium of Far-Infrared Line and Continuum Emission for 227 Galaxies Observed by the Infrared Space ObservatoryMay 19 2008Far-infrared line and continuum fluxes are presented for a sample of 227 galaxies observed with the Long Wavelength Spectrometer on the Infrared Space Observatory. The galaxy sample includes normal star-forming systems, starbursts, and active galactic ... More
No Hubble Bubble in the Local UniverseJun 23 1999Zehavi et al. (1998) have suggested that the Hubble flow within 70/h Mpc may be accelerated by the existence of a void centered on the Local Group. Its underdensity would be ~20 %, which would result in a local Hubble distortion of about 6.5 %. We have ... More
Census of the Local Universe (CLU) I: Characterization of Galaxy Catalogs from Preliminary FieldsOct 13 2017We present a Census of the Local Universe (CLU) -- a combination of the largest area H$\alpha$ survey for nearby emission-line galaxies to date as well as a compilation of all publicly available galaxy catalogs out to a distance of 200 Mpc. With the Palomar ... More
The Nature of Low-Density Star FormationMar 13 2019How do stars manage to form within low-density, HI-dominated gas? Such environments provide a laboratory for studying star formation with physical conditions distinct from starbursts and the metal-rich disks of spiral galaxies where most effort has been ... More
Computing conformal maps onto circular domainsJul 24 2013We show that, given a non-degenerate, finitely connected domain $D$, its boundary, and the number of its boundary components, it is possible to compute a conformal mapping of $D$ onto a circular domain \emph{without} prior knowledge of the circular domain. ... More
Modeling Intercalated Group-4-Metal Nitride Halide Superconductivity with Interlayer Coulomb CouplingAug 11 2015Behavior consistent with Coulomb-mediated high-T$_C$ superconductivity is shown to be present in the intercalated group-4-metal nitride halides A$_x$(S)$_y$MNX, where the MNX host (M = Ti, Zr, Hf; X = Cl, Br) is partially intercalated with cations A$_x$ ... More
Dynamic Spectral Imaging of Decimetric Fiber Bursts in an Eruptive Solar FlareSep 24 2017Fiber bursts are a type of fine structure that is often superposed on type IV radio continuum emission during solar flares. Although studied for many decades, its physical exciter, emission mechanism, and association with the flare energy release remain ... More
Generalized Conditional Gradient for Sparse EstimationOct 17 2014Structured sparsity is an important modeling tool that expands the applicability of convex formulations for data analysis, however it also creates significant challenges for efficient algorithm design. In this paper we investigate the generalized conditional ... More
Scaling Relations of Local Spiral Galaxies.I. Observational FoundationsOct 15 2003(Abridged) This paper presents an exploration of two fundamental scaling relations of spiral galaxies, the luminosity-rotation speed (or Tully-Fisher; TF) relation, and the size-luminosity (SL) relation, and the dependences of their scatter, at red and ... More
Uniform congruence counting for Schottky semigroups in $\mathrm{SL}_2(\mathbf{Z})$Jan 14 2016Sep 07 2017Let $\Gamma$ be a Schottky semigroup in $\mathrm{SL}_2(\mathbf{Z})$, and for $q\in \mathbf N$, let $\Gamma(q):=\{\gamma\in \Gamma: \gamma= e \text{ (mod $q$)}\}$ be its congruence subsemigroup of level $q$. We prove the following uniform congruence counting ... More
Positivity and complexity of ideal sheavesJul 05 2000The problem of bounding the "complexity" of a polynomial ideal in terms of the degrees of its generators has attracted considerable interest, brought into focus by the influential survey of Bayer and Mumford. The present paper examines some of these results ... More
Boundary Conditions associated with the General Left-Definite Theory for Differential OperatorsJun 05 2017In the early 2000's, Littlejohn and Wellman developed a general left-definite theory for certain self-adjoint operators by fully determining their domains and spectral properties. The description of these domains do not feature explicit boundary conditions. ... More
Lattice homomorphisms in harmonic analysisDec 31 2018Feb 12 2019Let $S$ be a non-empty, closed subspace of a locally compact group $G$ that is a subsemigroup of $G$. Suppose that $X, Y$, and $Z$ are Banach lattices that are vector sublattices of the order dual $\mathrm{C}_{\mathrm{c}}(S,\mathbb R)^\sim$ of the real-valued, ... More
Ab initio calculations of the atomic and electronic structures of crystalline PEO3:LiCF3SO3 electrolytesOct 20 2015The PEO3:LiCF3SO3 polymer electrolyte has attracted significant research due to its enhanced stability at the lithium/polymer interface of high conductivity polymer batteries. Experimental studies have shown that, depending on the preparation conditions, ... More
A Two-Parameter Model for the Infrared/Submillimeter/Radio Spectral Energy Distributions of Galaxies and AGNFeb 06 2014A two-parameter semi-empirical model is presented for the spectral energy distributions of galaxies with contributions to their infrared-submillimeter-radio emission from both star formation and accretion disk-powered activity. This model builds upon ... More
The Connection Between Galaxy Environment and the Luminosity Function Slopes of Star-Forming RegionsJul 13 2016Jul 29 2016We present the first study of GALEX far ultra-violet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ~65,000 star-forming ... More
The Nature of the Second Parameter in the IRX-beta Relation for Local GalaxiesJul 05 2013We present an analysis of 98 galaxies of low-dust content, selected from the Spitzer Local Volume Legacy survey, aimed at examining the relation between the ultraviolet (UV) color, beta, and dust attenuation in normal star-forming galaxies. The IRX-beta ... More
Seeking the Local Convergence Depth. V. Tully-Fisher Peculiar Velocities for 52 Abell ClustersJul 05 1999Jul 08 1999We have obtained I band Tully-Fisher (TF) measurements for 522 late-type galaxies in the fields of 52 rich Abell clusters distributed throughout the sky between 50 and 200\h Mpc. Here we estimate corrections to the data for various forms of observational ... More
[O I] 63 micron Emission from High and Low Luminosity AGN GalaxiesDec 09 2003The Infrared Space Observatory was used to search for a tracer of the warm and dense neutral interstellar medium, the [O I] 63.18 micron line, in four ultraluminous IRAS sources lying at redshifts between 0.6 and 1.4. While these sources are quasars, ... More
Warm and Cold Molecular Gas in GalaxiesJan 20 2005New and archival interferometric 12CO(1->0) datasets from six nearby galaxies are combined with H_2 2.122um and H-alpha maps to explore in detail the interstellar medium in different star-forming galaxies. We investigate the relation between warm (H_2 ... More
Seeking the Local Convergence Depth. The Abell Cluster Dipole Flow to 200 Mpc/hOct 28 1998We have obtained new Tully-Fisher (TF) peculiar velocity measurements for 52 Abell galaxy clusters distributed throughout the sky between ~ 50 and 200 Mpc/h.The measurements are based on I band photometry and optical rotation curves for a sample of 522 ... More
Signatures of Galaxy-Cluster Interactions: Spiral Galaxy Rotation Curve Asymmetry, Shape, and ExtentDec 18 2000The environmental dependencies of the characteristics of spiral galaxy rotation curves are studied in this work. We use our large, homogeneously collected sample of 510 cluster spiral galaxy rotation curves to test the claim that the shape of a galaxy's ... More
Shrinking of Cluster Ellipticals: a Tidal Stripping explanation and Implications for the Intra-Cluster LightFeb 01 2006We look for evidence of tidal stripping in elliptical galaxies through the analysis of homogeneous CCD data corresponding to a sample of 228 elliptical galaxies belonging to 24 clusters of galaxies at $0.015<z<0.080$. We investigate departures from the ... More
The Infrared Spectral Energy Distribution of Normal Star-Forming GalaxiesNov 01 2000We present a new phenomenological model for the spectral energy distribution of normal star-forming galaxies between 3 and 1100 microns. A sequence of realistic galaxy spectra are constructed from a family of dust emission curves assuming a power law ... More
Evidence for the Heating of Atomic Interstellar Gas by PAHsOct 19 2000Nov 20 2000We report a strong correlation between the [CII] 158 micron cooling line and the mid-infrared flux in the 5-10 micron range in a wide variety of star-forming galaxies. The mid-infrared flux is dominated by Aromatic Feature Emission (AFE), which is thought ... More
The Stellar Halo and Tidal Streams of Messier 63Oct 19 2015We present new near-infrared (NIR) observations of M63 from the Extended Disk Galaxy Exploration Science (EDGES) Survey. The extremely deep 3.6 $\mu$m mosaic reaches 29 AB mag arcsec$^{-2}$ at the outer reaches of the azimuthally-averaged surface brightness ... More
Spitzer Observations Of The Supergiant Shell Region In IC 2574Aug 01 2005We present spatially resolved Spitzer imaging of the supergiant shell region of the M81 group dwarf galaxy IC 2574 obtained as part of the Spitzer Infrared Nearby Galaxies Survey. This region harbors one of the best nearby examples of a kinematically ... More
The Incidence of Highly-Obscured Star-Forming Regions in SINGS GalaxiesJun 24 2007Using the new capabilities of the Spitzer Space Telescope and extensive multiwavelength data from the Spitzer Infrared Nearby Galaxies Survey (SINGS), it is now possible to study the infrared properties of star formation in nearby galaxies down to scales ... More
Seeking the Local Convergence Depth. IV. Tully-Fisher Observations of 35 Abell ClustersJul 05 1999We present Tully-Fisher observations for 35 rich Abell clusters of galaxies. Results from I band photometry and optical rotation curve work comprise the bulk of this paper. This is the third such data installment of an all-sky survey of 52 clusters in ... More
Seeking the Local Convergence Depth. II. TF Observations of the Clusters A114, A119, A194, A2295, A2457, A2806, A3193, A3381, AND A3744Nov 06 1997We present Tully-Fisher (TF) observations for nine rich Abell clusters of galaxies. This is the second such data installment of an all-sky survey of 50 clusters in the redshift range 0.02 < z < 0.06. The data extends the TF study of nearby clusters of ... More
Seeking the Local Convergence Depth. I. TF Observations of the Clusters A168, A397, A569, A1139, A1228, and A1983May 11 1997We present first results of an all-sky observing program designed to improve the quality of the I band Tully-Fisher (TF) template and to obtain the reflex motion of the Local Group with respect to clusters to z = 0.06. We are obtaining between 5 and 15 ... More
Multiwavelength Observations of the Low Metallicity Blue Compact Dwarf Galaxy SBS 0335-052Jul 05 2001New infrared and millimeter observations from Keck, Palomar, ISO, and OVRO and archival data from the NRAO VLA and IRAS are presented for the low metallicity blue compact dwarf galaxy SBS 0335-052. Mid-infrared imaging shows this young star-forming system ... More
Towards an Understanding of the Mid-Infrared Surface Brightness of Normal GalaxiesAug 09 1999We report a mid-infrared color and surface brightness analysis of IC 10, NGC 1313, and NGC 6946, three of the nearby galaxies studied under the Infrared Space Observatory Key Project on Normal Galaxies. Images with < 9 arcsecond (170 pc) resolution of ... More
Polarization Sensitive Multi-Chroic MKIDsJul 13 2016We report on the development of scalable prototype microwave kinetic inductance detector (MKID) arrays tailored for future multi-kilo-pixel experiments that are designed to simultaneously characterize the polarization properties of both the cosmic microwave ... More
L-Edge Spectroscopy of Dilute, Radiation-Sensitive Systems Using a Transition-Edge-Sensor ArrayJun 29 2017Aug 18 2017We present X-ray absorption spectroscopy and resonant inelastic X-ray scattering (RIXS) measurements on the iron L-edge of 0.5 mM aqueous ferricyanide. These measurements demonstrate the ability of high-throughput transition-edge-sensor (TES) spectrometers ... More
Bordering for spectrally arbitrary sign patternsAug 30 2017We develop a matrix bordering technique that can be applied to an irreducible spectrally arbitrary sign pattern to construct a higher order spectrally arbitrary sign pattern. This technique generalizes a recently developed triangle extension method. We ... More
Direct Evidence of an Eruptive, Filament-Hosting Magnetic Flux Rope Leading to a Fast Solar Coronal Mass EjectionAug 27 2014Sep 12 2014Magnetic flux ropes (MFRs) are believed to be at the heart of solar coronal mass ejections (CMEs). A well-known example is the prominence cavity in the low corona that sometimes makes up a three-part white-light (WL) CME upon its eruption. Such a system, ... More
Parsing as Tree TraversalJul 29 1994This paper presents a unified approach to parsing, in which top-down, bottom-up and left-corner parsers are related to preorder, postorder and inorder tree traversals. It is shown that the simplest bottom-up and left-corner parsers are left recursive ... More
Exponential Mixing of Frame Flow for Convex Cocompact Hyperbolic ManifoldsDec 03 2016The aim of this paper is to establish exponential mixing of frame flow for the measure of maximal entropy on a convex cocompact hyperbolic manifold. Consequences include results on the decay of matrix coefficients and on effective equidistribution of ... More
The dual of the Bourgain-Delbaen spaceMay 18 1998Sep 26 2003It is shown that a script L_infty-space with separable dual constructed by Bourgain and Delbaen has small Szlenk index and thus does not have a quotient isomorphic to C(omega^omega). It follows that this is a script L_infty-space which is the same size ... More
A topological view of ordered groupsMar 19 2014We show how to use topological ideas, such as compactness, to establish orderability properties of infinite groups. A new application is to provide a left-ordering for the group of PL homeomorphisms of a connected surface with boundary which are fixed ... More
Large-scale effects of ionizing feedbackSep 27 2012I discuss recent work on gas expulsion and triggered star formation in, and unbinding of, embedded clusters, by ionizing radiation from O-type stars. Photoionization is not as effective a driver of any of these process as was perhaps once thought. Although ... More
Tutorial on the braid groupsOct 19 2010This is an introduction to the braid groups, as presented in the summer school and workshop on braid groups at the National University of Singapore in June 2007.
Ordered groups as a tensor categoryApr 09 2017It is a classical theorem that the free product of ordered groups is orderable. In this note we show that, using a method of G. Bergman, an ordering of the free product can be constructed in a functorial manner, in the category of ordered groups and order-preserving ... More
Invariant group orderings and Galois conjugatesMay 12 2006Mar 04 2008This paper investigates conditions under which a given automorphism of a residually torsion-free nilpotent group respects some ordering of the group. For free groups and surface groups, this has relevance to ordering the fundamental groups of three-dimensional ... More
Collection analysis for Horn clause programsAug 16 2007We consider approximating data structures with collections of the items that they contain. For examples, lists, binary trees, tuples, etc, can be approximated by sets or multisets of the items within them. Such approximations can be used to provide partial ... More
Understanding the impact of entropy on policy optimizationNov 27 2018Feb 05 2019Entropy regularization is commonly used to improve policy optimization in reinforcement learning. It is believed to help with \emph{exploration} by encouraging the selection of more stochastic policies. In this work, we analyze this claim using new visualizations ... More
Random Sentences from a Generalized Phrase-Structure Grammar InterpreterFeb 14 2007In numerous domains in cognitive science it is often useful to have a source for randomly generated corpora. These corpora may serve as a foundation for artificial stimuli in a learning experiment (e.g., Ellefson & Christiansen, 2000), or as input into ... More
Generating One-Anaphoric Expressions: Where Does the Decision Lie?May 09 1995Most natural language generation systems embody mechanisms for choosing whether to subsequently refer to an already-introduced entity by means of a pronoun or a definite noun phrase. Relatively few systems, however, consider referring to entites by means ... More
Mixing of frame flow for rank one locally symmetric spaces and measure classificationMar 10 2014Let $G$ be a connected simple linear Lie group of rank one, and let $\Gamma <G$ be a discrete Zariski dense subgroup admitting a finite Bowen-Margulis-Sullivan measure $m^{\operatorname{BMS}}$. We show that the right translation action of the one dimensional ... More
Term Encoding of Typed Feature StructuresDec 22 1995This paper presents an approach to Prolog-style term encoding of typed feature structures. The type feature structures to be encoded are constrained by appropriateness conditions as in Carpenter's ALE system. But unlike ALE, we impose a further independently ... More
Bose-Einstein Condensation of Atomic HydrogenSep 11 1998Oct 05 1998We report observation of Bose-Einstein condensation of a trapped, dilute gas of atomic hydrogen. The condensate and normal gas are studied by two-photon spectroscopy of the 1S-2S transition. Interactions among the atoms produce a shift of the resonance ... More
Bose-Einstein Condensation of Atomic HydrogenDec 20 1998We have observed Bose-Einstein condensation (BEC) of trapped atomic hydrogen, and studied it by two-photon spectroscopy of the 1S-2S transition. In these lecture notes we briefly review the history of spin-polarized atomic hydrogen and describe the final ... More
Optical Spectroscopy and Nebular Oxygen Abundances of the Spitzer/SINGS GalaxiesJul 26 2010Aug 15 2010We present intermediate-resolution optical spectrophotometry of 65 galaxies obtained in support of the Spitzer Infrared Nearby Galaxies Survey (SINGS). For each galaxy we obtain a nuclear, circumnuclear, and semi-integrated optical spectrum designed to ... More
The H-alpha Luminosity Function and Star Formation Rate Volume Density at z=0.8 from the NEWFIRM H-alpha SurveyNov 11 2010Jun 27 2011[Abridged] We present new measurements of the H-alpha luminosity function (LF) and SFR volume density for galaxies at z~0.8. Our analysis is based on 1.18$\mu$m narrowband data from the NEWFIRM H-alpha Survey, a comprehensive program designed to capture ... More
Nebular Attenuation in Hα-selected Star-forming Galaxies at z=0.8 from the NewHα SurveyJul 23 2012We present measurements of the dust attenuation of H\alpha-selected emission-line galaxies at z=0.8 from the NewH\alpha\ narrowband survey. The analysis is based on deep follow-up spectroscopy with Magellan/IMACS, which captures the strong rest-frame ... More
Untangling the Nature of Spatial Variations of Cold Dust Properties in Star Forming GalaxiesMay 19 2014We investigate the far-infrared (IR) dust emission for 20 local star forming galaxies from the Key Insights on Nearby Galaxies: A Far-IR Survey with Herschel (KINGFISH) sample. We model the far-IR/submillimeter spectral energy distribution (SED) using ... More
Cold Collision Frequency Shift of the 1S-2S Transition in HydrogenSep 11 1998Oct 05 1998We have observed the cold collision frequency shift of the 1S-2S transition in trapped spin-polarized atomic hydrogen. We find $\Delta \nu_{1S-2S} = -3.8(8)\times 10^{-10} n Hz cm^3$, where $n$ is the sample density. From this we derive the 1S-2S s-wave ... More
No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z~2 in CANDELS / 3D-HSTJul 28 2014We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3<z<2.4. We select galaxies undergoing gravitational ... More
Mid-infrared Spectral Properties of Post-Starburst QuasarsMay 27 2013We present Spitzer InfraRed Spectrograph (IRS) low-resolution spectra of 16 spectroscopically selected post-starburst quasars (PSQs) at z ~ 0.3. The optical spectra of these broad-lined active galactic nuclei (AGNs) simultaneously show spectral signatures ... More
The ACS Nearby Galaxy Survey Treasury. X. Quantifying the Star Cluster Formation Efficiency of Nearby Dwarf GalaxiesMar 21 2012Mar 27 2012We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses ... More
Signatures of Supersymmetry from the Early UniverseSep 01 2011Oct 11 2011Supersymmetry plays a fundamental role in the radiative stability of many inflationary models. Spontaneous breaking of the symmetry inevitably leads to fields with masses of order the Hubble scale during inflation. When these fields couple to the inflaton ... More
Desensitizing Inflation from the Planck ScaleApr 21 2010A new mechanism to control Planck-scale corrections to the inflationary eta parameter is proposed. A common approach to the eta problem is to impose a shift symmetry on the inflaton field. However, this symmetry has to remain unbroken by Planck-scale ... More
Casimir force in O(n) lattice models with a diffuse interfaceJun 23 2008On the example of the spherical model we study, as a function of the temperature $T$, the behavior of the Casimir force in O(n) systems with a diffuse interface and slab geometry $\infty^{d-1}\times L$, where $2<d<4$ is the dimensionality of the system. ... More