Results for "Kelsey R. Allen"

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Few-Shot Bayesian Imitation Learning with Logic over ProgramsApr 12 2019We describe an expressive class of policies that can be efficiently learned from a few demonstrations. Policies are represented as logical combinations of programs drawn from a small domain-specific language (DSL). We define a prior over policies with ... More
Residual Policy LearningDec 15 2018Jan 03 2019We present Residual Policy Learning (RPL): a simple method for improving nondifferentiable policies using model-free deep reinforcement learning. RPL thrives in complex robotic manipulation tasks where good but imperfect controllers are available. In ... More
Mathematical Modelling of Auxin Transport in Plant Tissues: Flux meets Signalling and GrowthOct 22 2018Auxin has critical roles in plant growth, dependent upon its heterogeneous distribution in tissues. Exactly how auxin signalling and transport, and developmental processes such as growth coordinate to achieve the precise patterns of auxin observed experimentally ... More
A new physical phenomenon in ultra-high energy collisionsJul 09 2013We show that combining the published Pierre Auger Observatory measurements of the longitudinal_and_ lateral properties of UHE atmospheric showers, points to an unforeseen change in the nature of particle interactions at ultrahigh energy. A "toy model" ... More
Point island dynamics under fixed rate depositionFeb 15 2018Dec 12 2018In this paper we consider the dynamics of point islands during submonolayer deposition, in which the fragmentation of subcritical size islands is allowed. To understand asymptotics of solutions, we use methods of centre manifold theory, and for globalisation, ... More
On the Absorption of X-rays in the Interstellar MediumAug 28 2000We present an improved model for the absorption of X-rays in the ISM intended for use with data from future X-ray missions with larger effective areas and increased energy resolution such as Chandra and XMM, in the energy range above 100eV. Compared to ... More
Challenging a Newtonian prediction through Gaia wide binariesOct 19 2018Mar 07 2019Under Newtonian dynamics, the relative motion of the components of a binary star should follow a Keplerian scaling with separation. Once orientation effects and a distribution of ellipticities are accounted for, dynamical evolution can be modelled to ... More
Infinite Mixture Prototypes for Few-Shot LearningFeb 12 2019We propose infinite mixture prototypes to adaptively represent both simple and complex data distributions for few-shot learning. Our infinite mixture prototypes represent each class by a set of clusters, unlike existing prototypical methods that represent ... More
Segmentation of Facial Expressions Using Semi-Definite Programming and Generalized Principal Component AnalysisJun 09 2009Jun 10 2009In this paper, we use semi-definite programming and generalized principal component analysis (GPCA) to distinguish between two or more different facial expressions. In the first step, semi-definite programming is used to reduce the dimension of the image ... More
Probabilistic Kernel Support Vector MachinesApr 14 2019We propose a probabilistic enhancement of standard {\em kernel Support Vector Machines} for binary classification, in order to address the case when, along with given data sets, a description of uncertainty (e.g., error bounds) may be available on each ... More
Unsupervised Joint Alignment and Clustering using Bayesian NonparametricsOct 16 2012Joint alignment of a collection of functions is the process of independently transforming the functions so that they appear more similar to each other. Typically, such unsupervised alignment algorithms fail when presented with complex data sets arising ... More
Surface Phonons and Other Localized ExcitationsAug 13 1999The diatomic linear chain of masses coupled by harmonic springs is a textboook model for vibrational normal modes (phonons) in crystals. In addition to propagating acoustic and optic branches, this model is known to support a ``gap mode'' localized at ... More
On vertex, edge, and vertex-edge random graphsDec 08 2008Oct 13 2010We consider three classes of random graphs: edge random graphs, vertex random graphs, and vertex-edge random graphs. Edge random graphs are Erdos-Renyi random graphs, vertex random graphs are generalizations of geometric random graphs, and vertex-edge ... More
Quasar broad absorption line variability measurements using reconstructions of un-absorbed spectraOct 21 2013Jul 24 2014We present a two-epoch Sloan Digital Sky Survey and Gemini/GMOS+William Herschel Telescope/ISIS variability study of 50 broad absorption line quasars of redshift range 1.9 < z < 4.2, containing 38 Si IV and 59 C IV BALs and spanning rest-frame time intervals ... More
Build It, Break It, Fix It: Contesting Secure DevelopmentJul 02 2019Typical security contests focus on breaking or mitigating the impact of buggy systems. We present the Build-it, Break-it, Fix-it (BIBIFI) contest, which aims to assess the ability to securely build software, not just break it. In BIBIFI, teams build specified ... More
The semigroups of order 9 and their automorphism groupsJan 25 2013We report the number of semigroups with 9 elements up to isomorphism or anti-isomorphism to be 52,989,400,714,478 and up to isomorphism to be 105,978,177,936,292. We obtained these results by combining computer search with recently published formulae ... More
On the Kauffman-Jones polynomial for virtual singular linksOct 09 2016Jun 03 2019We extend the Kamada-Miyazawa polynomial to virtual singular links, which is valued in $\mathbb{Z}[A^2, A^{-2}, h]$. The decomposition of the resulting polynomial into two components, one in $\mathbb{Z}[A^2, A^{-2}]$ and the other in $\mathbb{Z}[A^2, ... More
DFT Calculations of Temperature-Dependent NQR Parameters in α-paradichlorobenzene and β-HMXMar 25 2019A method for first principles predictions of observed temperature-dependent NQR spectra is presented using density functional theory (DFT) and the isobaric T-dependent NQR frequencies of 35Cl and 14N nuclei are computed for the two molecular crystals ... More
The Opacity of Spiral Galaxies from Counts of Distant Background GalaxiesSep 05 2003We have applied the "Synthetic Field Method" on a sample of ~20 nearby galaxies in order to determine the opacity of their disks. We present preliminary results on the radial dependence of cold dust absorption for 3 examples. The spirals NGC4535 and NGC4725 ... More
Modeling Supervisor Safe Sets for Improving Collaboration in Human-Robot TeamsMay 09 2018When a human supervisor collaborates with a team of robots, their attention is divided and cognitive resources are at a premium. We aim to optimize the distribution of these resources and the flow of attention. To this end, we propose the model of an ... More
Large Angular Scale CMB Anisotropy Induced by Cosmic StringsSep 05 1996We simulate the anisotropy in the cosmic microwave background (CMB) induced by cosmic strings. By numerically evolving a network of cosmic strings we generate full-sky CMB temperature anisotropy maps. Based on $192$ maps, we compute the anisotropy power ... More
Automatically reduced degenerations of automatically normal varietiesSep 25 2007Let F be a flat family of projective schemes, whose geometric generic fiber is reduced and irreducible. We give conditions on a special fiber (a "limit" of the family) to guarantee that it too is reduced. These conditions often imply also that the generic ... More
Frobenius splitting, point-counting, and degenerationNov 25 2009Let f be a polynomial of degree n in ZZ[x_1,..,x_n], typically reducible but squarefree. From the hypersurface {f=0} one may construct a number of other subschemes {Y} by extracting prime components, taking intersections, taking unions, and iterating ... More
A compactly supported formula for equivariant localization, and, simplicial complexes of Bialynicki-Birula decompositionsJan 26 2008Let X be a projective scheme carrying a circle action S with isolated fixed points. We associate a simplicial complex Delta(X,S) of "closure chains" using a refinement of its Morse/Bialynicki-Birula decomposition. If this decomposition is a stratification ... More
Descent-cycling in Schubert calculusSep 11 2000We prove two lemmata about Schubert calculus on generalized flag manifolds G/B, and in the case of the ordinary flag manifold GL_n/B we interpret them combinatorially in terms of descents, and geometrically in terms of missing subspaces. One of them gives ... More
Holder Regularity for Nondivergence nonlocal parabolic equationsOct 31 2016May 14 2018This paper proves H\"older continuity of viscosity solutions to certain nonlocal parabolic equations that involve a generalized fractional time derivative of Marchaud or Caputo type. As a necessary and preliminary result, this paper first shows that viscosity ... More
The Category-Theoretic Arithmetic of InformationMar 25 2008Jul 21 2008We highlight the underlying category-theoretic structure of measures of information flow. We present an axiomatic framework in which communication systems are represented as morphisms, and information flow is characterized by its behavior when communication ... More
Compatibly Frobenius split subschemes are rigidJan 15 2009Schwede proved very recently in arXiv:0901.1154 that in a quasiprojective scheme X with a fixed Frobenius splitting, there are only finitely many subschemes {Y} that are compatibly split. (A simpler proof has already since been given in arXiv:0901.2098, ... More
Gauge Invariant Uniqueness Theorem for Corners of k-graphsJun 29 2005For a finitely aligned k-graph $\Lambda$ with X a set of vertices in $\Lambda$ we define a universal C*-algebra called $C^*(\Lambda,X)$ generated by partial isometries. We show that $C^*(\Lambda,X)$ is isomorphic to the corner $P_XC^*(\Lambda)P_X$, where ... More
Frobenius splitting and Möbius inversionFeb 11 2009We show that the fundamental class in K-homology of a Frobenius split scheme can be computed as a certain alternating sum over irreducible varieties, with the coefficients computed using M\"obius inversion on a certain poset. If G/P is a generalized flag ... More
Trivial Schur indices for noncommutative reality-based algebras with exactly two nonreal basis elementsMay 01 2019This article discusses the splitting fields of noncommutative reality-based algebras with positive degree map. We show that if the standard basis has only one nonreal pair, then the minimal field of definition for the RBA is always a splitting field. ... More
Randomly juggling backwardsJan 24 2016We recall the directed graph of _juggling states_, closed walks within which give juggling patterns, as studied by Ron Graham in [w/Chung, w/Butler]. Various random walks in this graph have been studied before by several authors, and their equilibrium ... More
The Forward GEM Tracker of STAR at RHICNov 14 2008The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is in the process of designing and constructing a forward tracking system based on triple GEM technology. This upgrade is necessary to give STAR ... More
Some schemes related to the commuting varietyJun 18 2003The_commuting variety_ is the pairs of NxN matrices (X,Y) such that XY = YX. We introduce the_diagonal commutator scheme_, {(X,Y) : XY-YX is diagonal}, which we prove to be a reduced complete intersection, one component of which is the commuting variety. ... More
Discovery of a low-eccentricity, high-inclination Kuiper belt object at 58 AUDec 16 2005We report the discovery of the first trans-neptunian object, designated 2004 XR190, with a nearly-cirular orbit beyond the 2:1 mean-motion resonance. Fitting an orbit to 23 astrometric observations spread out over 12 months yields an orbit of a=57.2\pm0.4, ... More
The relation between accretion rate and jet power in X-ray luminous elliptical galaxiesFeb 24 2006Jul 06 2006Using Chandra X-ray observations of 9 nearby, X-ray luminous ellipticals with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from the X-ray data and estimated black hole ... More
Coulomb-driven broken-symmetry states in doubly gated suspended bilayer grapheneOct 05 2010The non-interacting energy spectrum of graphene and its bilayer counterpart consists of multiple degeneracies owing to the inherent spin, valley and layer symmetries. Interactions among charge carriers are expected to spontaneously break these symmetries, ... More
Balanced normal cones and Fulton-MacPherson's intersection theoryDec 29 2005Let X be a subscheme of a reduced scheme Y. Then Y has a flat "degeneration to the normal cone" C_X Y of X, and this degeneration plays a key step in Fulton and MacPherson's "basic construction" in intersection theory. The intersection product has a canonical ... More
Schubert calculus and shifting of interval positroid varietiesAug 06 2014Consider k x n matrices with rank conditions placed on intervals of columns. The ranks that are actually achievable correspond naturally to upper triangular partial permutation matrices, and we call the corresponding subvarieties of Gr(k,n) the _interval ... More
A free boundary problem on three-dimensional conesApr 17 2017We consider a free boundary problem on cones depending on a parameter c and study when the free boundary is allowed to pass through the vertex of the cone. We show that when the cone is three-dimensional and c is large enough, the free boundary avoids ... More
CO emission from candidate photo-dissociation regions in M81Jun 22 2006Context At least a fraction of the atomic hydrogen in spiral galaxies is suspected to be the result of molecular hydrogen which has been dissociated by radiation from massive stars. Aims In this paper, we extend our earlier set of data from a small region ... More
Dynamical precursor of nematic order in a dense fluid of hard ellipsoids of revolutionSep 18 2001We investigate hard ellipsoids of revolution in a parameter regime where no long range nematic order is present but already finite size domains are formed which show orientational order. Domain formation leads to a substantial slowing down of a collective ... More
The Opacity of Spiral Galaxy Disks VI: Extinction, stellar light and colorSep 15 2005In this paper we explore the relation between dust extinction and stellar light distribution in disks of spiral galaxies. Extinction influences our dynamical and photometric perception of disks, since it can distort our measurement of the contribution ... More
AGN-Induced Cavities in NGC 1399 and NGC 4649Oct 30 2007We present an analysis of archival Chandra and VLA observations of the E0 galaxy NGC 1399 and the E2 galaxy NGC 4649 in which we investigate cavities in the surrounding X-ray emitting medium caused by the central AGN. We calculate the jet power required ... More
Separating Thermal and Nonthermal X-Rays in Supernova Remnants I: Total Fits to SN 1006 ADOct 20 2000The remnant of SN 1006 has an X-ray spectrum dominated by nonthermal emission, and pre-ASCA observations were well described by a synchrotron calculation with electron energies limited by escape. We describe the results of a much more stringent test: ... More
G 112-29 (=NLTT 18149), a Very Wide Companion to GJ 282 AB with a Common Proper Motion, Common Parallax, Common Radial Velocity and Common AgeOct 15 2009We have made a search for common proper motion (CPM) companions to the wide binaries in the solar vicinity. We found that the binary GJ 282AB has a very distant CPM companion (NLTT 18149) at a separation $s=1.09 \arcdeg$. Improved spectral types and radial ... More
Plasmas generated by ultra-violet light rather than electron impactDec 02 2013We analyze, in both plane and cylindrical geometries, a collisionless plasma consisting of an inner region where generation occurs by UV illumination, and an un-illuminated outer region with no generation. Ions generated in the inner region flow outwards ... More
Acceleration of dust particles by vortex ringNov 11 2009It is shown that nonlinear interaction between large amplitude circularly polarized EM wave and dusty plasma leads to a nonstationary ponderomotive force which in turn produces a vortex ring, and magnetic field. Then the ensuing vortex ring in the direction ... More
Estimation of black bear abundance by management zone in WisconsinMay 22 2019Estimates of population abundance are fundamental to wildlife management and conservation, but are difficult to obtain across large geographic scales and for cryptic species. We used a state-space model with age-at-harvest data in a Bayesian framework ... More
Finding Signatures of the Youngest StarburstsNov 22 2000Embedded massive starclusters have recently been identified in several nearby galaxies by means of the radio-wave thermal bremsstrahlung emission from their surrounding HII regions. Energy requirements imply that these optically-obscured starclusters ... More
Relational inductive biases, deep learning, and graph networksJun 04 2018Oct 17 2018Artificial intelligence (AI) has undergone a renaissance recently, making major progress in key domains such as vision, language, control, and decision-making. This has been due, in part, to cheap data and cheap compute resources, which have fit the natural ... More
Variable Hard X-ray Emission from the Candidate Accreting Black Hole in Dwarf Galaxy Henize 2-10Apr 13 2015We present an analysis of the X-ray spectrum and long-term variability of the nearby dwarf starburst galaxy Henize 2-10. Recent observations suggest that this galaxy hosts an actively accreting black hole with mass ~10^6 M_sun. The presence of an AGN ... More
The horofunction boundary of the lamplighter group $L_2$ with the Diestel-Leader metricOct 31 2014Jan 19 2016We fully describe the horofunction boundary $\partial_h L_2$ with the word metric associated with the generating set $\{t,at\}$ (i.e the metric arising in the Diestel-Leader graph $\text{DL}(2,2)$). The visual boundary $\partial_\infty L_2$ with this ... More
Visual boundaries of Diestel-Leader graphsJul 08 2013May 28 2015Diestel-Leader graphs are neither hyperbolic nor CAT(0), so their visual boundaries may be pathological. Indeed, we show that for $d>2$, $\partial\text{DL}_d(q)$ carries the indiscrete topology. On the other hand, $\partial\text{DL}_2(q)$, while not Hausdorff, ... More
Relational inductive bias for physical construction in humans and machinesJun 04 2018While current deep learning systems excel at tasks such as object classification, language processing, and gameplay, few can construct or modify a complex system such as a tower of blocks. We hypothesize that what these systems lack is a "relational inductive ... More
Structure and Evolution of the Opacity of Spiral DisksOct 19 2007Oct 23 2007The opacity of a spiral disk due to dust absorption influences every measurement we make of it in the UV and optical. Two separate techniques directly measure the total absorption by dust in the disk: calibrated distant galaxy counts and overlapping galaxy ... More
Structure and Evolution of the Opacity of Spiral DisksJan 18 2008The opacity of a spiral disk due to dust absorption influences every measurement we make of it in the UV and optical. Two separate techniques directly measure the total absorption by dust in the disk: calibrated distant galaxy counts and overlapping galaxy ... More
Realization of a Large-Acceptance Faraday Cup for 3 MeV ElectronsNov 27 2018The design, construction, installation, and testing of a Faraday Cup intended to measure the current of a 3 MeV, 1 microampere electron beam is described. Built as a current monitor for a M{\o}ller scattering measurement at the MIT High Voltage Research ... More
Weighing the Giants II: Improved Calibration of Photometry from Stellar Colors and Accurate Photometric RedshiftsAug 02 2012Apr 19 2014We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colors as well as to adjust the instrument flat field. By developing a spectroscopic model for the SDSS stellar locus in color-color space, synthesizing ... More
Weighing the Giants - I. Weak-lensing masses for 51 massive galaxy clusters: project overview, data analysis methods and cluster imagesAug 02 2012Apr 18 2014This is the first in a series of papers in which we measure accurate weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known at redshifts 0.15<z<0.7, in order to calibrate X-ray and other mass proxies for cosmological cluster experiments. ... More
Weighing the Giants - III. Methods and Measurements of Accurate Galaxy Cluster Weak-Lensing MassesAug 02 2012Apr 18 2014We report weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known. This cluster sample, introduced earlier in this series of papers, spans redshifts 0.15 < z_cl < 0.7, and is well suited to calibrate mass proxies for current cluster ... More
Robust Weak-lensing Mass Calibration of Planck Galaxy ClustersFeb 11 2014Oct 09 2014In light of the tension in cosmological constraints reported by the Planck team between their SZ-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing ... More
Luttinger liquid ARPES spectra from samples of Li$_{0.9}$Mo$_6$O$_{17}$ grown by the temperature gradient flux techniqueFeb 28 2004Aug 22 2004Angle resolved photoemission spectroscopy line shapes measured for quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$ samples grown by a temperature gradient flux technique are found to show Luttinger liquid behavior, consistent with all previous data by ... More
Hidden one-dimensional electronic structure and non-Fermi liquid angle resolved photoemission line shapes of $η$-Mo$_4$O$_{11}$Jul 15 2005Jul 25 2005We report angle resolved photoemission (ARPES) spectra of $\eta$-Mo$_4$O$_{11}$, a layered metal that undergoes two charge density wave (CDW) transitions at 109 K and 30 K. We have directly observed the ``hidden one-dimensional (hidden-1d)'' Fermi surface ... More
Among-site variability in the stochastic dynamics of East African coral reefsJun 27 2016Coral reefs are dynamic systems whose composition is highly influenced by unpredictable biotic and abiotic factors. Understanding the spatial scale at which long-term predictions of reef composition can be made will be crucial for guiding conservation ... More
Controlled and Uncontrolled Stochastic Norton-Simon-Massagué Tumor Growth ModelsMar 08 2019Tumorigenesis is a complex process that is heterogeneous and affected by numerous sources of variability. This study presents a stochastic extension of a biologically grounded tumor growth model, referred to as the Norton-Simon-Massagu\'e (NSM) tumor ... More
BEC-BCS crossover in a cold and magnetized two color NJL modelOct 08 2015Jan 23 2016The BEC-BCS crossover for a NJL model with diquark interactions is studied in the presence of an external magnetic field. Particular attention is paid to different regularization schemes used in the literature. A thorough comparison of results is performed ... More
Quantum oscillations from a two-dimensional electron gas at a Mott/band insulator interfaceSep 28 2012We report on the magnetotransport properties of a prototype Mott insulator/band insulator perovskite heterojunction in magnetic fields up to 31 T and at temperatures between 360 mK and 10 K. Shubnikov-de Haas oscillations in the magnetoresistance are ... More
Spin-orbit torque switching of synthetic antiferromagnetsJan 09 2017We report that synthetic antiferromagnets (SAFs) can be efficiently switched by spin-orbit torques (SOTs) and the switching scheme does not obey the usual SOT switching rule. We show that both the positive and negative spin Hall angle (SHA)-like switching ... More
Induced transparency by coupling of Tamm and defect states in tunable terahertz plasmonic crystalsMay 10 2016Photonic crystals and metamaterials have emerged as two classes of tailorable materials that enable precise control of light. Plasmonic crystals, which can be thought of as photonic crystals fabricated from plasmonic materials, Bragg scatter incident ... More
Inducing an Incipient Terahertz Finite Plasmonic Crystal in Coupled Two Dimensional Plasmonic CavitiesMay 10 2016We measured a change in the current transport of an antenna-coupled, multi-gate, GaAs/AlGaAs field-effect transistor when terahertz electromagnetic waves irradiated the transistor and attribute the change to bolometric heating of the electrons in the ... More
RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for SurveysFeb 18 2004We present a complete census of RR Lyrae stars in a halo field of the Andromeda galaxy. These deep observations, taken as part of a program to measure the star formation history in the halo, spanned a period of 41 days with sampling on a variety of time ... More
HST Snaphot Study of Variable Stars in Globular Clusters: Inner Region of NGC 6441May 19 2003[Abridged] We present the results of a Hubble Space Telescope snapshot program to survey the inner region of the globular cluster NGC 6441 for its variable stars. A total of 57 variable stars was found including 38 RR Lyrae stars, 6 Population II Cepheids, ... More
Spitzer observations of the Orion OB1 association: disk census in the low mass starsSep 06 2007We present new Spitzer Space Telescope observations of two fields in the Orion OB1 association. We report here IRAC/MIPS observations for 115 confirmed members and 41 photometric candidates of the ~10 Myr 25 Orionis aggregate in the OB1a subassociation, ... More
Inferring phenotypic trait evolution on large trees with many incomplete measurementsJun 07 2019Comparative biologists are often interested in inferring covariation between multiple biological traits sampled across numerous related taxa. To properly study these relationships, we must control for the shared evolutionary history of the taxa to avoid ... More
The Metallicity of the Intracluster Medium Over Cosmic Time: Further Evidence for Early EnrichmentJun 05 2017Sep 14 2017We use Chandra X-ray data to measure the metallicity of the intracluster medium (ICM) in 245 massive galaxy clusters selected from X-ray and Sunyaev-Zel'dovich (SZ) effect surveys, spanning redshifts $0<z<1.2$. Metallicities were measured in three different ... More
Nonequilibrium ac Josephson effect in mesoscopic Nb-InAs-Nb junctionsJan 03 1999Microwave irradiation of Nb-InAs-Nb junctions reveals frequency-doubled Josephson currents which persist to high temperatures, in the absence of a critical current. A nonequilibrium dynamical model, based on time-dependent Andreev bound states, successfully ... More
Smoothly compactifiable shear-free hyperboloidal data is dense in the physical topologyJun 18 2015We show that any polyhomogeneous asymptotically hyperbolic constant-mean-curvature solution to the vacuum Einstein constraint equations can be approximated, arbitrarily closely in H\"older norms determined by the physical metric, by shear-free smoothly ... More
The Sloan Nearby Cluster Weak Lensing SurveyAug 11 2009We describe and present initial results of a weak lensing survey of nearby ($\rm{z}\lesssim0.1$) galaxy clusters in the Sloan Digital Sky Survey (SDSS). In this first study, galaxy clusters are selected from the SDSS spectroscopic galaxy cluster catalogs ... More
Extreme AGN Feedback and Cool Core Destruction in the X-ray Luminous Galaxy Cluster MACS J1931.8-2634Oct 01 2010Oct 05 2010We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8-2634 using Chandra X-ray, Subaru optical, and VLA 1.4 GHz radio data. This cluster (z=0.352) harbors one of the most X-ray luminous cool cores yet discovered, with an equivalent ... More
Building Large Area CZT Imaging Detectors for a Wide-Field Hard X-ray Telescope - ProtoEXIST1Mar 31 2009Apr 03 2009We have constructed a moderately large area (32 cm2), fine pixel (2.5 mm pixel, 5 mm thick) CZT imaging detector which constitutes the first section of a detector module (256 cm2) developed for a balloon-borne wide-field hard X-ray telescope, ProtoEXIST1. ... More
Ubiquitous Water Masers in Nearby Star-Forming GalaxiesAug 19 2008We report the detection of water maser emission from four nearby galaxies hosting ultradense HII (UDHII) regions, He 2-10, the Antennae galaxies (NGC 4038/4039), NGC 4214, and NGC 5253, with the Green Bank Telescope. Our detection rate is 100%, and all ... More
Australia Telescope Compact Array Survey of Candidate Ultra-Compact and Buried HII Regions in the Magellanic CloudsJul 23 2004We present a systematic survey for ultracompact HII (UCHII) regions in the Magellanic Clouds. Understanding the physics of massive star formation (MSF) is a critical astrophysical problem. The study of MSF began in our galaxy with surveys of UCHII regions, ... More
Cryptocurrency Smart Contracts for Distributed Consensus of Public RandomnessJun 26 2019Most modern electronic devices can produce a random number. However, it is difficult to see how a group of mutually distrusting entities can have confidence in any such hardware-produced stream of random numbers, since the producer could control the output ... More
Initializing adaptive importance sampling with Markov chainsApr 29 2013Adaptive importance sampling is a powerful tool to sample from complicated target densities, but its success depends sensitively on the initial proposal density. An algorithm is presented to automatically perform the initialization using Markov chains ... More
Frictional cooling of positively charged particlesNov 11 2011Nov 14 2011One of the focuses of research and development towards the construction of a muon collider is muon beam preparation. Simulation of frictional cooling shows that it can achieve the desired emittance reduction to produce high-luminosity muon beams. We show ... More
Signal discovery in sparse spectra: a Bayesian analysisAug 25 2006A Bayesian analysis of the probability of a signal in the presence of background is developed, and criteria are proposed for claiming evidence for, or the discovery of a signal. The method is general and in particular applicable to sparsely populated ... More
HERA Collider PhysicsMar 17 1999HERA, the first electron-proton collider, has been delivering luminosity since 1992. It is the natural extension of an impressive series of fixed-target lepton-nucleon scattering experiments. The increase of a factor ten in center-of-mass energy over ... More
The Weil representation of a unitary group associated to a ramified quadratic extension of a finite local ringJun 17 2013We find all irreducible constituents of the Weil representation of a unitary group $U_m(A)$ of rank $m$ associated to a ramified quadratic extension $A$ of a finite, commutative, local and principal ring $R$ of odd characteristic. We show that this Weil ... More
On a gravitational self-interaction parameter for point-particlesAug 26 2017Relativistic, electrically neutral point-particles can be given mathematical foundation by doing a careful accounting of self-interaction energies. In this paper we examine a self-interaction parameter and present a continuous framework which interpolates ... More
The Mass Transference Principle: Ten Years OnApr 21 2017May 09 2017In this article we discuss the Mass Transference Principle due to Beresnevich and Velani and survey several generalisations and variants, both deterministic and random. Using a Hausdorff measure analogue of the inhomogeneous Khintchine-Groshev Theorem, ... More
Revolving FractalsMay 15 2019Davis and Knuth in 1970 introduced the notion of revolving sequences, as representations of a Gaussian integer. Later, Mizutani and Ito pointed out a close relationship between a set of points determined by all revolving sequences and a self-similar set, ... More
Finiteness of classifying spaces of relative diffeomorphism groups of 3-manifoldsDec 20 1997Dec 21 1997The main theorem shows that if M is an irreducible compact connected orientable 3-manifold with non-empty boundary, then the classifying space BDiff(M rel dM) of the space of diffeomorphisms of M which restrict to the identity map on boundary(M) has the ... More
Quasi-harmonic theory of thermal expansionJun 17 2019"Quasi-harmonic" (QH) theory (QHT) is sometimes incorrectly understood as a misguided way to do a low-order theory of anharmonic effects in crystals. The original and most widely accepted meaning of QHT is the use of T=0 volume (V)-dependent harmonic ... More
On hitting times and fastest strong stationary times for skip-free and more general chainsAug 31 2007May 06 2009An (upward) skip-free Markov chain with the set of nonnegative integers as state space is a chain for which upward jumps may be only of unit size; there is no restriction on downward jumps. In a 1987 paper, Brown and Shao determined, for an irreducible ... More
On the Cusp Forms of Congruence Subgroups of an almost Simple Lie groupJul 03 2012Aug 14 2013In this paper we address the issue of existence of cusp forms for almost simple Lie groups using the approach of the second author combined with local information on supercuspidal representations for $p$-adic groups known by the first author. We pay special ... More
The multidegree of the multi-image varietyJan 13 2017The multi-image variety is a subvariety of Gr(1,P^3)^n that models taking pictures with n rational cameras. We compute its cohomology class in the cohomology of Gr(1,P^3)^n, and from there its multidegree as a subvariety of (P^5)^n under the Pl\"ucker ... More
Testing models of new physics with UHE air shower observationsJul 26 2013Several air shower observatories have established that the number of muons produced in UHE air showers is significantly larger than that predicted by models. We argue that the only solution to this muon deficit, compatible with the observed Xmax distributions, ... More
Detecting and Correcting Speech RepairsJun 01 1994Jun 02 1994Interactive spoken dialog provides many new challenges for spoken language systems. One of the most critical is the prevalence of speech repairs. This paper presents an algorithm that detects and corrects speech repairs based on finding the repair pattern. ... More
A General Mass Transference PrincipleMar 07 2018Aug 17 2018In this paper we prove a general form of the Mass Transference Principle for $\limsup$ sets defined via neighbourhoods of sets satisfying a certain local scaling property. Such sets include self-similar sets satisfying the open set condition and smooth ... More