Results for "David Thompson"

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Coding Sequence Density Estimation Via Topological PressureSep 27 2011Jan 08 2014We give a new approach to coding sequence (CDS) density estimation in genomic analysis based on the topological pressure, which we develop from a well known concept in ergodic theory. Topological pressure measures the "weighted information content" of ... More
The weak specification property for geodesic flows on CAT(-1) spacesJun 20 2016Jun 28 2018We prove that the geodesic flow on a compact locally CAT(-1) space has the weak specification property, and give various applications. We show that every H\"older potential on the space of geodesics has a unique equilibrium state. We establish the equidistribution ... More
Cosmic Ray Studies with the Fermi Gamma-ray Space Telescope Large Area TelescopeJan 04 2012The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope provides both direct and indirect measurements of Galactic cosmic rays (CR). The LAT high-statistics observations of the 7 GeV - 1 TeV electron plus positron spectrum and limits on ... More
Strong symbolic dynamics for geodesic flow on CAT(-1) spaces and other metric Anosov flowsAug 13 2018We prove that the geodesic flow on a compact, locally CAT(-1) metric space can be coded by a suspension flow over an irreducible shift of finite type with H\"older roof function. This is achieved by showing that the geodesic flow is a metric Anosov flow, ... More
An Origin for Multi-Phase Gas in Galactic Winds and HalosJul 15 2015Dec 08 2015The physical origin of high velocity cool gas seen in galactic winds remains unknown. Following Wang (1995), we argue that radiative cooling in initially hot thermally-driven outflows can produce fast neutral atomic and photoionized cool gas. The inevitability ... More
Keck Deep Fields. IV. Luminosity Dependent Clustering and Galaxy Downsizing in UV-Selected Galaxies at z=4, 3, and 2Jun 10 2011We investigate the luminosity dependent clustering of rest-frame UV selected galaxies at z~4, 3, 2.2, and 1.7 in the Keck Deep Fields (KDFs), which are complete to R = 27 and cover 169 arcmin^2. We find that at z~4 and 3, UV-bright galaxies cluster more ... More
Sub-L* Galaxies at Redshifts z~4, 3, and 2: Their UV Luminosity Function and Luminosity DensitySep 15 2005We use very deep (R_lim=27) UGRI imaging to study the evolution of the faint end of the UV-selected galaxy luminosity function from z~4 to z~2. We find that the luminosity function evolves with time and that this evolution is differential with luminosity: ... More
The Multiwavelength Approach to Unidentified Gamma-Ray SourcesJul 20 2004As the highest-energy photons, gamma rays have an inherent interest to astrophysicists and particle physicists studying high-energy, nonthermal processes. Gamma-ray telescopes complement those at other wavelengths, especially radio, optical, and X-ray, ... More
Trigonometric Parallaxes for 1,507 Nearby Mid-to-Late M-dwarfsDec 11 2013The MEarth survey is a search for small rocky planets around the smallest, nearest stars to the Sun as identified by high proper motion with red colors. We augmented our planetary search time series with lower cadence astrometric imaging and obtained ... More
Gamma Ray Pulsars: ObservationsJan 03 2001High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that: the light curves usually have double-peak structures (suggesting ... More
The Impact of Stellar Rotation on the Detectability of Habitable Planets Around M DwarfsApr 11 2016Stellar activity and rotation frustrate the detection of exoplanets through the radial velocity technique. This effect is particularly of concern for M dwarfs, which can remain magnetically active for billions of years. We compile rotation periods for ... More
Abelian surfaces over finite fields with prescribed groupsJul 02 2013Let A be an abelian surface over F_q, the field of q elements. The rational points on A/\F_q form an abelian group A(\F_q) \simeq \Z/n_1\Z \times \Z/n_1 n_2 \Z \times \Z/n_1 n_2 n_3\Z \times\Z/n_1 n_2 n_3 n_4\Z. We are interested in knowing which groups ... More
Unifying inference on brain network variations in neurological diseases: The Alzheimer's caseOct 19 2015There is growing interest in understanding how the structural interconnections among brain regions change with the occurrence of neurological diseases. Diffusion weighted MRI imaging has allowed researchers to non-invasively estimate a network of structural ... More
Space Detectors for Gamma Rays (100 MeV - 100 GeV): from EGRET to Fermi LATJun 25 2015The design of spaceborne high-energy (E>100 MeV) gamma-ray detectors depends on two principal factors: (1) the basic physics of detecting and measuring the properties of the gamma rays; and (2) the constraints of operating such a detector in space for ... More
A Quantum Bousso BoundMar 10 2003The Bousso bound requires that one quarter the area of a closed codimension two spacelike surface exceeds the entropy flux across a certain lightsheet terminating on the surface. The bound can be violated by quantum effects such as Hawking radiation. ... More
Keck Deep Fields. II. The UV Galaxy Luminosity Function at z~4, 3, and 2Jul 21 2005Jan 05 2006We use very deep UGRI multi-field imaging obtained at the Keck telescope to study the evolution of the rest-frame 1700A galaxy luminosity function as the Universe doubles its age from z~4 to z~2. The depth of our imaging allows us to constrain the faint ... More
Gamma Ray Pulsars: Multiwavelength ObservationsDec 10 2003High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The seven or more pulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show that: the light curves ... More
AdS Solutions of 2D Type 0ADec 15 2003May 04 2004We present a two-parameter family of AdS solutions to the two-dimensional type 0A effective action.
Descent Relations in Type 0A/0BMay 31 2001Mar 26 2002The type 0 theories have twice as many stable D-branes as the type II theories. In light of this added complication, we find the descent relations for D-branes in the type 0A and 0B theories. In addition, we work out how the two types of D-branes differ ... More
A Search for Additional Bodies in the GJ 1132 Planetary System from 21 Ground-based Transits and a 100 Hour Spitzer CampaignNov 29 2016We present the results of a search for additional bodies in the GJ 1132 system through two methods: photometric transits and transit timing variations of the known planet. We collected 21 transit observations of GJ 1132b with the MEarth-South array since ... More
Keck Deep Fields. III. Luminosity-dependent Evolution of the Ultraviolet Luminosity and Star Formation Rate Densities at z~4, 3, and 2May 17 2006We use the Keck Deep Fields UGRI catalog of z~4, 3, and 2 UV-selected galaxies to study the evolution of the rest-frame 1700A luminosity density at high redshift. The ability to reliably constrain the contribution of faint galaxies is critical and our ... More
Keck Deep Fields. I. Observations, Reductions, and the Selection of Faint Star-Forming Galaxies at Redshifts z~4, 3, and 2Jul 19 2005We introduce a very deep, R_lim~27, multicolor imaging survey of very faint star-forming galaxies at z~4, z~3, z~2.2, and z~1.7. This survey, carried out on the Keck I telescope, uses the very same UGRI filter system that is employed by the Steidel team ... More
Detecting Cross-Lingual Plagiarism Using Simulated Word EmbeddingsDec 29 2017Jan 03 2018Cross-lingual plagiarism (CLP) occurs when texts written in one language are translated into a different language and used without acknowledging the original sources. One of the most common methods for detecting CLP requires online machine translators ... More
Some Graftings of Complex Projective Structures with Schottky HolonomyDec 10 2010Jan 27 2013Let $\mathcal{G}^*(S,\rho)$ be the graph whose vertices are marked complex projective structures with holonomy $\rho$ and whose edges are graftings from one vertex to another. If $\rho$ is quasi-Fuchsian, a theorem of Goldman implies that $\mathcal{G}^*(S,\rho)$ ... More
Finding geodesics in a triangulated 2-sphereAug 25 2014Sep 09 2014Let S be a triangulated 2-sphere with fixed triangulation T. We apply the methods of thin position from knot theory to obtain a simple version of the three geodesics theorem for the 2-sphere [5]. In general these three geodesics may be unstable, corresponding, ... More
Functional inequalities for Feynman-Kac semigroupsNov 08 2018Using stochastic analysis, we prove various gradient estimates and Harnack inequalities for Feynman-Kac semigroups with possibly unbounded potentials. One of the main results is a derivative formula which can be used to characterize a lower bound on Ricci ... More
Normaloid Weighted Composition Operators on $H^2$Nov 26 2017Jul 26 2018When \ph\ is an analytic self-map of the unit disk with Denjoy-Wolff point $a \in \D$, and $\rho(\W) = \psi(a)$, we give an exact characterization for when \W\ is normaloid. We also determine the spectral radius, essential spectral radius, and essential ... More
When is a bit worth much more than kT ln2?May 26 2017Physical processes thatobtain, process, and erase information involve tradeoffs between information and energy. The fundamental energetic value of a bit of information exchanged with a reservoir at temperature T is kT ln2. This paper investigates the ... More
An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-type M DwarfsSep 04 2015Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H-alpha emission), rotation period, and stellar age. Previous ... More
Relationship of EUV Irradiance Coronal Dimming Slope and Depth to Coronal Mass Ejection Speed and MassJul 18 2016Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind ... More
Near-infrared Metallicities, Radial Velocities and Spectral Types for 447 Nearby M DwarfsOct 03 2013We present metallicities, radial velocities and near-infrared spectral types for 447 M dwarfs determined from moderate resolution (R~2000) near-infrared (NIR) spectra obtained with IRTF/SpeX. These M dwarfs are targets of the MEarth Survey, a transiting ... More
Minimal complexes of cotorsion flat modulesFeb 09 2017Nov 21 2018Let R be a commutative noetherian ring. We give criteria for a complex of cotorsion flat R-modules to be minimal, in the sense that every self homotopy equivalence is an isomorphism. To do this, we exploit Enochs' description of the structure of cotorsion ... More
Stable Local CohomologyMar 05 2015Let $R$ be a Gorenstein local ring, $\frak{a}$ an ideal in $R$, and $M$ an $R$-module. The local cohomology of $M$ supported at $\frak{a}$ can be computed by applying the $\frak{a}$-torsion functor to an injective resolution of $M$. Since $R$ is Gorenstein, ... More
Far-infrared/sub-millimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by the Herschel SPIRE instrument -- I. Central positionsFeb 22 2016Dust grains play a key role in the physics of star-forming regions, even though they constitute only $\sim$1 % of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature ($T_{dust}$), emissivity spectral index ... More
First observations of the magnetic field inside the Pillars of Creation: Results from the BISTRO surveyMay 29 2018We present the first high-resolution, submillimeter-wavelength polarimetric observations of -- and thus direct observations of the magnetic field morphology within -- the dense gas of the Pillars of Creation in M16. These 850$\,\mu$m observations, taken ... More
Tori and Heegaard splittingsMar 27 2016Haken showed that the Heegaard splittings of reducible 3-manifolds are reducible, that is, a reducing 2-sphere can be found which intersects the Heegaard surface in a single simple closed curve. When the genus of the "interesting" surface increases from ... More
Dehn surgery on complicated fibered knots in the 3-sphereApr 17 2016Let K be a fibered knot in the 3-sphere. We show that if the monodromy of K is sufficiently complicated, then Dehn surgery on K cannot yield a lens space. Work of Yi Ni shows that if K has a lens space surgery then it is fibered. Combining this with our ... More
Tracing Inflows and Outflows with Absorption Lines in Circumgalactic GasSep 23 2013Oct 11 2013We examine how HI and metal absorption lines within low-redshift galaxy halos trace the dynamical state of circumgalactic gas, using cosmological hydrodynamic simulations that include a well-vetted heuristic model for galactic outflows. We categorize ... More
The rotation and Galactic kinematics of mid M dwarfs in the Solar NeighborhoodNov 03 2015Feb 18 2016Rotation is a directly-observable stellar property, and drives magnetic field generation and activity through a magnetic dynamo. Main sequence stars with masses below approximately 0.35Msun (mid-to-late M dwarfs) are fully-convective, and are expected ... More
The rate of escape of random walks on polycyclic and metabelian groupsOct 05 2010Sep 13 2011We use subgroup distortion to determine the rate of escape of a simple random walk on a class of polycyclic groups, and we show that the rate of escape is invariant under changes of generating set for these groups. For metabelian groups, we define a stronger ... More
An Unstable Change of Rings for Morava E-TheorySep 12 2014Mar 16 2018The Bousfield-Kan (or unstable Adams) spectral sequence can be constructed for various homology theories such as Brown-Peterson homology theory BP, Johnson-Wilson theory $E(n)$, or Morava $E$-theory $E_n$. For nice spaces the $E_2$-term is given by Ext ... More
Methods for Detecting Paraphrase PlagiarismDec 29 2017Paraphrase plagiarism is one of the difficult challenges facing plagiarism detection systems. Paraphrasing occur when texts are lexically or syntactically altered to look different, but retain their original meaning. Most plagiarism detection systems ... More
A generalisation of Dickson's commutative division algebrasFeb 28 2019Dickson's commutative semifields are an important class of finite division algebras. We generalise Dickson's construction of commutative division algebras by doubling both finite field extensions and central simple algebras and not restricting us to the ... More
Discovery and Precise Characterization by the MEarth Project of LP 661-13, an Eclipsing Binary Consisting of Two Fully Convective Low-mass StarsSep 12 2016We report the detection of stellar eclipses in the LP 661-13 system. We present the discovery and characterization of this system, including high resolution spectroscopic radial velocities and a photometric solution spanning two observing seasons. LP ... More
Duality Symmetric Strings, Dilatons and O(d,d) Effective ActionsDec 07 2007Dec 10 2007We calculate the background field equations for the T-duality symmetric string building on previous work by including the effect of the Dilaton up to two-loops. Inclusion of the Dilaton allows us to obtain the full beta functionals of the duality symmetric ... More
Computational Analysis of Perfect-Information Position AuctionsAug 04 2014After experimentation with other designs, the major search engines converged on the weighted, generalized second-price auction (wGSP) for selling keyword advertisements. Notably, this convergence occurred before position auctions were well understood ... More
Duality Symmetric String and M-TheoryJun 11 2013Dec 09 2014We review recent developments in duality symmetric string theory. We begin with the world sheet doubled formalism which describes strings in an extended space time with extra coordinates conjugate to winding modes. This formalism is T-duality symmetric ... More
The `Real' Schwarz LemmaDec 02 2010The purpose of this note is to discuss the real analogue of the Schwarz lemma from complex analysis.
60dB high-extinction auto-configured Mach--Zehnder interferometerSep 01 2016Imperfections in integrated photonics manufacturing have a detrimental effect on the maximal achievable visibility in interferometric architectures. These limits have profound implications for further photonics technological developments and in particular ... More
Membranes with a boundaryApr 01 2009May 07 2009We investigate the recently developed theory of multiple membranes. In particular, we consider open membranes, i.e. the theory defined on a membrane world volume with a boundary. We first restrict our attention to the gauge sector of the theory. We obtain ... More
The weak specification property for geodesic flows on CAT(-1) spacesJun 20 2016We prove that the geodesic flow on a compact locally CAT(-1) space has the weak specification property, and give various applications of this property. We show that every H\"older continuous function on the space of geodesics has a unique equilibrium ... More
Limits on the event rates of fast radio transients from the V-FASTR experimentMay 26 2012We present the first results from the V-FASTR experiment, a commensal search for fast transient radio bursts using the Very Long Baseline Array (VLBA). V-FASTR is unique in that the widely spaced VLBA antennas provide a discriminant against non-astronomical ... More
A Machine Learning Classifier for Fast Radio Burst Detection at the VLBAJun 28 2016Time domain radio astronomy observing campaigns frequently generate large volumes of data. Our goal is to develop automated methods that can identify events of interest buried within the larger data stream. The V-FASTR fast transient system was designed ... More
Taxicab ButterfliesJan 26 2015The Butterfly Theorem is explored in Taxicab Geometry.
Taxicab Calculus: Trig DerivativesMay 16 2012The set of trigonometric functions in taxicab geometry is completed and derivatives of all of the taxicab trigonometric functions are explored.
The Nature of Length, Area, and Volume in Taxicab GeometryJan 14 2011While the concept of straight-line length is well understood in taxicab geometry, little research has been done into the length of curves or the nature of area and volume in this geometry. This paper sets forth a comprehensive view of the basic dimensional ... More
Taxicab Angles and TrigonometryJan 14 2011A natural analogue to angles and trigonometry is developed in taxicab geometry. This structure is then analyzed to see which, if any, congruent triangle relations hold. A nice application involving the use of parallax to determine the exact (taxicab) ... More
Homodyne detection and optical parametric amplification: a classical approach applied to proposed "loophole-free" Bell testsDec 17 2005Recent proposed ``loophole-free'' Bell tests are discussed in the light of classical models for the relevant features of optical parametric amplification and homodyne detection. The Bell tests themselves are uncontroversial: there are no obvious loopholes ... More
Timing, ``Accidentals'' and Other Artifacts in EPR ExperimentsNov 20 1997Nov 25 1997Subtraction of ``accidentals'' in Einstein-Podolsky-Rosen experiments frequently changes results compatible with local realism into ones that appear to demonstrate non-locality. The validity of the procedure depends on the unproven assumption of the independence ... More
Mather-Jacobian multiplier ideals on toric varietiesDec 29 2016This paper provides a formula for the Mather-Jacobian multiplier ideals of torus invariant ideals on (not necessarily normal) toric varieties that generalizes Howald's formula for the multiplier ideal of monomial ideals in a polynomial ring.
Learning Fast Sparsifying TransformsNov 24 2016May 28 2017Given a dataset, the task of learning a transform that allows sparse representations of the data bears the name of dictionary learning. In many applications, these learned dictionaries represent the data much better than the static well-known transforms ... More
QED Phenomena in an Ultrastrong Magnetic Field. I. Electron-Photon Scattering, Pair Creation, and AnnihilationApr 06 2019We evaluate several basic electrodynamic processes as modified by the presence of a very strong magnetic field, exceeding $B_{\rm Q} \equiv m^2/e = 4.4\times 10^{13}$ G. These results are needed to build models of dissipative phenomena outside magnetars ... More
Equations for superelliptic curves over their minimal field of definitionMay 18 2014Jul 23 2014Let $\mathcal X_g$ be a genus $g\geq 2$ superelliptic curve, $F$ its field of moduli, and $K$ the minimal field of definition. In this short note we construct an equation of the curve $\mathcal X_g$ over its minimal field of definition $K$ when $\mathcal ... More
Wave function representation of probability distributionsDec 21 2017Jan 05 2018Orthogonal decomposition of the square root of a probability density function in the Hermite basis is a useful low-dimensional parameterization of continuous probability distributions over the reals. This representation is formally similar to the representation ... More
CHIRRUP: a practical algorithm for unsourced multiple accessNov 02 2018Unsourced multiple access abstracts grantless simultaneous communication of a large number of devices (messages) each of which transmits (is transmitted) infrequently. It provides a model for machine-to-machine communication in the Internet of Things ... More
Fibered knots and Property 2RJan 15 2009It is shown, using sutured manifold theory, that if there are any 2-component counterexamples to the Generalized Property R Conjecture, then any knot of least genus among components of such counterexamples is not a fibered knot. The general question of ... More
Surgery on a knot in (Surface x I)Jul 02 2008Jul 03 2008Suppose F is a compact orientable surface, K is a knot in F x I, and N is the 3-manifold obtained by some non-trivial surgery on K. If F x {0} compresses in N, then there is an annulus in F x I with one end K and the other end an essential simple closed ... More
Pulling subdivisions of cones and blowups of monomial ideals on affine toric varietiesDec 29 2016This short note solves the following problem: Given a map of normal toric varieties corresponding to a coherent subdivision of a cone, find an ideal such that the given map is the blowup of that ideal.
3FGLzoo. Classifying 3FGL Unassociated Fermi-LAT Gamma-ray Sources by Artificial Neural NetworksMay 27 2017In its first four years of operation, the Fermi Large Area Telescope (LAT) detected 3033 $\gamma$-ray emitting sources. In the Fermi-LAT Third Source Catalogue (3FGL) about 50% of the sources have no clear association with a likely $\gamma$-ray emitter. ... More
Identifying Key Cyber-Physical Terrain (Extended Version)Jan 25 2017The high mobility of Army tactical networks, combined with their close proximity to hostile actors, elevates the risks associated with short-range network attacks. The connectivity model for such short range connections under active operations is extremely ... More
Heavy Quark Effective Theory, Interpolating Fields and Bethe-Salpeter AmplitudesJul 19 1994We use the LSZ reduction theorem and interpolating fields, alongwith the heavy quark effective theory, to investigate the structure of the Bethe-Salpeter amplitude for heavy hadrons. We show how a simple form of this amplitude, used extensively in heavy ... More
Multiplier ideals of monomial space curvesJun 09 2010Feb 22 2011The goal of this paper is to produce a formula for the multiplier ideals of monomial space curves in the spirit of Howald's formula for the multiplier ideals of monomial ideals. This is achieved by constructing a toric blowup of affine space in such a ... More
Four new eclipsing mid M-dwarf systems from the New Luyten Two Tenths catalogAug 09 2018Using data from the MEarth-North and MEarth-South transit surveys, we present the detection of eclipses in four mid M-dwarf systems: LP 107-25, LP 261-75, LP 796-24, and LP 991-15. Combining the MEarth photometry with spectroscopic follow-up observations, ... More
Analysis of a trunk reservation policy in the framework of fog computingApr 13 2016We analyze in this paper a system composed of two data centers with limited capacity in terms of servers. When one request for a single server is blocked at the first data center, this request is forwarded to the second one. To protect the single server ... More
Generalized beta-transformations and the entropy of unimodal mapsFeb 10 2016Jan 11 2017Generalized beta-transformations are the class of piecewise continuous interval maps given by taking the beta-transformation $x \mapsto \beta x ~\pmod 1$, where $\beta>1$, and replacing some of the branches with branches of constant negative slope. If ... More
Derivative and divergence formulae for diffusion semigroupsJan 13 2017Apr 23 2018For a semigroup $P_t$ generated by an elliptic operator on a smooth manifold $M$, we use straightforward martingale arguments to derive probabilistic formulae for $P_t(V(f))$, not involving derivatives of $f$, where $V$ is a vector field on $M$. For non-symmetric ... More
Pseudolattices, del Pezzo surfaces, and Lefschetz fibrationsAug 20 2018Motivated by the relationship between numerical Grothendieck groups induced by the embedding of a smooth anticanonical elliptic curve into a del Pezzo surface, we define the notion of a quasi del Pezzo homomorphism between pseudolattices and establish ... More
QED Phenomena in an Ultrastrong Magnetic Field. II. Electron-Positron Scattering, $e^\pm$-Ion Scattering, and Relativistic BremsstrahlungApr 06 2019This paper continues the approach of Kostenko \& Thompson to calculating quantum electrodynamic processes in the ultrastrong magnetic field near some neutron stars, such as magnetars or merging binary neutron stars. Here we consider electron-positron ... More
Generalised T-duality and Integrable DeformationsDec 15 2015We review some recent developments in the construction of integrable $\eta$- and $\lambda$-deformations of the $AdS_5 \times S^5$ superstring. We highlight their link with Poisson-Lie T-duality.
Future Facilities for Gamma-Ray Pulsar StudiesOct 17 2003Pulsars seen at gamma-ray energies offer insight into particle acceleration to very high energies, along with information about the geometry and interaction processes in the magnetospheres of these rotating neutron stars. During the next decade, a number ... More
Arbitrary Sectioning of Angles in Taxicab GeometryJan 14 2011A construction to arbitrarily section a taxicab angle into an equal number of angles in (pure) taxicab geometry is presented.
Formation and evolution of primordial black holes after hybrid inflationApr 27 2005We examine the formation and evolution of primordial black holes (PBH's) after hybrid inflation. Our goal is to assess the effects of various theoretical uncertainties on the extrapolation from a given inflation model to a spectrum of primordial black ... More
An Introduction to Generalised Dualities and their Applications to Holography and IntegrabilityApr 25 2019These pedagogical lectures given at the Corfu Summer Institute 2018 review two generalised notions of T-duality, non-Abelian T-duality and Poisson-Lie duality, and their applications. We explain how each of these has seen recent application in the context ... More
Bielliptic curves of genus 3 in the hyperelliptic moduliMay 20 2013In this paper we study bielliptic curves of genus 3 defined over an algebraically closed field $k$ and the intersection of the moduli space $\M_3^b$ of such curves with the hyperelliptic moduli $\H_3$. Such intersection $\S$ is an irreducible, 3-dimensional, ... More
ADE surfaces and their moduliDec 21 2017Jan 12 2018We define a class of surfaces and surface pairs corresponding to the ADE root lattices and construct compactifications of their moduli spaces, generalizing Losev-Manin spaces of curves.
Fast Winds Drive Slow Shells: A Model for the Circumgalactic Medium as Galactic Wind-Driven BubblesApr 02 2018Sep 03 2018Successful models of the low redshift circumgalactic medium (CGM) must account for (1) a large amount of gas, (2) relatively slow gas velocities, (3) a high degree of metal enrichment, (4) the similar absorption properties around both star-forming and ... More
Isoperimetric problems in sectors with densityDec 02 2010We consider the isoperimetric problem in planar sectors with density $r^{p}$, and with density $a>1$ inside the unit disk and $1$ outside. We characterize solutions as a function of sector angle. We also solve the isoperimetric problem in $\mathbb{R}^{n}$ ... More
Detailed Chemical Abundances in the r-Process-Rich Ultra-Faint Dwarf Galaxy Reticulum 2Jan 15 2016The ultra-faint dwarf galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey. We have observed the four brightest red giants in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber System. We present ... More
Limits on Fast Radio Bursts from Four Years of the V-FASTR ExperimentMay 23 2016The V-FASTR experiment on the Very Long Baseline Array was designed to detect dispersed pulses of milliseconds duration, such as fast radio bursts (FRBs). We use all V-FASTR data through February 2015 to report V-FASTR's upper limits on the rates of FRBs, ... More
Forming Super Star Clusters in the Central Starburst of NGC 253Apr 05 2018Oct 24 2018NGC 253 hosts the nearest nuclear starburst. Previous observations show a region rich in molecular gas, with dense clouds associated with recent star formation. We used ALMA to image the 350 GHz dust continuum and molecular line emission from this region ... More
A numerical study of the correspondence between paths in a causal set and geodesics in the continuumDec 13 2005This paper presents the results of a computational study related to the path-geodesic correspondence in causal sets. For intervals in flat spacetimes, and in selected curved spacetimes, we present evidence that the longest maximal chains (the longest ... More
The gauge structure of generalised diffeomorphismsAug 29 2012Oct 24 2012We investigate the generalised diffeomorphisms in M-theory, which are gauge transformations unifying diffeomorphisms and tensor gauge transformations. After giving an En(n)-covariant description of the gauge transformations and their commutators, we show ... More
Strong symbolic dynamics for geodesic flow on CAT(-1) spaces and other metric Anosov flowsAug 13 2018Apr 04 2019We prove that the geodesic flow on a compact, locally CAT(-1) metric space can be coded by a suspension flow over an irreducible shift of finite type with H\"older roof function. This is achieved by showing that the geodesic flow is a metric Anosov flow, ... More
Supersymmetric Branes in AdS_2 x S^2 x CY_3Jun 14 2004The problem of finding supersymmetric brane configurations in the near-horizon attractor geometry of a Calabi-Yau black hole with magnetic-electric charges (p^I,q_I) is considered. Half-BPS configurations, which are static for some choice of global AdS2 ... More
Aspects of Multiple MembranesMar 25 2008This paper examines various aspects of the recently proposed theory of coincident membranes by Bagger and Lambert. These include the properties of open membranes and the resulting boundary theory with an interpretation in terms of the fivebrane and marginal ... More
Background Field Equations for the Duality Symmetric StringAug 16 2007Sep 13 2007This paper describes the background field equations for strings in T-duality symmetric formalisms in which the dimension of target space is doubled and the sigma model supplemented with constraints. These are calculated by demanding the vanishing of the ... More
The TOP-SCOPE survey of Planck Galactic Cold Clumps: Survey overview and results of an exemplar source, PGCC G26.53+0.17Nov 13 2017Dec 19 2017The low dust temperatures (<14 K) of Planck Galactic Cold Clumps (PGCCs) make them ideal targets to probe the initial conditions and very early phase of star formation. TOP-SCOPE is a joint survey program targeting ~2000 PGCCs in J=1-0 transitions of ... More
Distribution of squarefree values of sequences associated with elliptic curvesOct 12 2012May 02 2013Let E be a non-CM elliptic curve defined over Q. For each prime p of good reduction, E reduces to a curve E_p over the finite field F_p. For a given squarefree polynomial f(x,y), we examine the sequences f_p(E) := f(a_p(E), p), whose values are associated ... More
Duality Invariant M-theory: Gauged supergravities and Scherk-Schwarz reductionsJul 31 2012Oct 20 2012We consider the reduction of the duality invariant approach to M-theory by a U-duality group valued Scherk-Schwarz twist. The result is to produce potentials for gauged supergravities that are normally associated with non-geometric compactifications. ... More
Optimization and NP_R-Completeness of Certain FewnomialsApr 26 2009Nov 06 2010We give a high precision polynomial-time approximation scheme for the supremum of any honest n-variate (n+2)-nomial with a constant term, allowing real exponents as well as real coefficients. Our complexity bounds count field operations and inequality ... More