Results for "Patrick Dufour"

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A New Generation of Cool White Dwarf Atmosphere Models. II. A DZ Star with Collision-Induced AbsorptionSep 28 2018In the first paper of this series (Blouin et al. 2018), we presented our upgraded cool white dwarf atmosphere code. In this second paper, we use our new models to analyze SDSS J080440.63+223948.6 (J0804+2239), the first DZ star to show collision-induced ... More
A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White DwarfsMay 06 2019As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their atmospheric compositions and the difficulties inherent ... More
Pressure Distortion of the H$_2$-He Collision-Induced Absorption at the Photosphere of Cool White Dwarf StarsSep 05 2017Collision-induced absorption (CIA) from molecular hydrogen is a dominant opacity source in the atmosphere of cool white dwarfs. It results in a significant flux depletion in the near-IR and IR parts of their spectra. Because of the extreme conditions ... More
Magnetic White Dwarfs with Heavy ElementsOct 05 2016Using our newly developed model atmosphere code appropriate for magnetic white dwarfs with metal lines in the Paschen-Back regime, we study various magnetic white dwarfs and explore the effects of various parameters such as the field geometry and the ... More
Infrared Opacities in Dense Atmospheres of Cool White Dwarf StarsOct 24 2016Dense, He-rich atmospheres of cool white dwarfs represent a challenge to the modeling. This is because these atmospheres are constituted of a dense fluid in which strong multi-atomic interactions determine their physics and chemistry. Therefore, the ideal-gas-based ... More
A New Generation of Cool White Dwarf Atmosphere Models Using Ab Initio CalculationsOct 04 2016Due to their high photospheric density, cool helium-rich white dwarfs (particularly DZ, DQpec and ultracool) are often poorly described by current atmosphere models. As part of our ongoing efforts to design atmosphere models suitable for all cool white ... More
A New Generation of Cool White Dwarf Atmosphere Models. I. Theoretical Framework and Applications to DZ StarsJul 17 2018The photospheres of the coolest helium-atmosphere white dwarfs are characterized by fluid-like densities. Under those conditions, standard approximations used in model atmosphere codes are no longer appropriate. Unfortunately, the majority of cool He-rich ... More
Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White DwarfsFeb 24 2012We present improved atmospheric parameters of nearby white dwarfs lying within 20 pc of the Sun. The aim of the current study is to obtain the best statistical model of the least-biased sample of the white dwarf population. A homogeneous analysis of the ... More
A Dark Spot on a Massive White DwarfNov 23 2015We present the serendipitous discovery of eclipse-like events around the massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We selected J1529+2928 for time-series photometry based on its spectroscopic temperature and surface gravity, ... More
New white dwarf stars in the Sloan Digital Sky Survey Data Release 10Nov 15 2014Nov 25 2014We report the discovery of 9 089 new spectroscopically confirmed white dwarfs and subdwarfs in the Sloan Digital Sky Survey Data Release 10. We obtain Teff, log g and mass for hydrogen atmosphere white dwarf stars (DAs) and helium atmosphere white dwarf ... More
Signs of a faint disc population at polluted white dwarfsAug 01 2014Oct 02 2014Observations of atmospheric metals and dust discs around white dwarfs provide important clues to the fate of terrestrial planetary systems around intermediate mass stars. We present Spitzer IRAC observations of 15 metal polluted white dwarfs to investigate ... More
The cool end of the DZ sequence in the SDSSOct 22 2010We report the discovery of cool DZ white dwarfs, which lie in the SDSS (u-g) vs. (g-r) two-color diagram across and below the main sequence. These stars represent the extension of the well-known DZ sequence towards cooler temperatures.
Infrared Variability of Two Dusty White DwarfsAug 28 2018The most heavily polluted white dwarfs often show excess infrared radiation from circumstellar dust disks, which are modeled as a result of tidal disruption of extrasolar minor planets. Interaction of dust, gas, and disintegrating objects can all contribute ... More
Numerical method for impulse control of Piecewise Deterministic Markov ProcessesNov 26 2010Aug 30 2011This paper presents a numerical method to calculate the value function for a general discounted impulse control problem for piecewise deterministic Markov processes. Our approach is based on a quantization technique for the underlying Markov chain defined ... More
Veronese curves and webs interpolationAug 18 2004Sep 01 2004Veronese webs appear as the natural way of passing to the quotient of curves in the projective space. In thi paper, we give the link between classical multidimensionnal webs and veronse webs by mean of interpolation.
The Policy Iteration Algorithm for Average Continuous Control of Piecewise Deterministic Markov ProcessesFeb 16 2009The main goal of this paper is to apply the so-called policy iteration algorithm (PIA) for the long run average continuous control problem of piecewise deterministic Markov processes (PDMP's) taking values in a general Borel space and with compact action ... More
The Starburst-Interstellar Medium Interaction of NGC 1569 I. Location and Nature of He II Sources Using Hubble Space Telescope WFPC2 ImagerySep 14 2000We present the detection of He II sources in the Im galaxy NGC 1569 from HST WFPC2 imagery. Out of the fifteen detections, seven were Wolf-Rayet stars, five were stellar clusters with associated He II emission, and three were sources of unknown origin. ... More
Shallow Ultraviolet Transits of WD 1145+017Apr 24 2019WD 1145+017 is a unique white dwarf system that has a heavily polluted atmosphere, an infrared excess from a dust disk, numerous broad absorption lines from circumstellar gas, and changing transit features, likely from fragments of an actively disintegrating ... More
Synthesis of Membrane-Electrode Assembly for Fuel Cells by Means of (Sub)-Atmospheric Plasma ProcessesFeb 06 2018An easy procedure to build up membrane-electrode assemblies for applications dedicated to miniaturized PEMFC using H2 or CH3OH by a two-steps atmospheric plasma process is reported. Firstly, catalyst nanoparticles are grafted on carbon substrates by spraying ... More
Astro 2020 Science White Paper: Evolved Planetary Systems around White DwarfsApr 09 2019Apr 12 2019Practically all known planet hosts will evolve into white dwarfs, and large parts of their planetary systems will survive this transition - the same is true for the solar system beyond the orbit of Mars. Spectroscopy of white dwarfs accreting planetary ... More
Identifying and Characterizing New Nearby White DwarfsOct 31 2006How confident are we that all of the nearest white dwarfs (WDs) have been identified? In an effort to answer this question, we have begun an initiative to identify and characterize new nearby WDs, particularly in the southern hemisphere. We estimate physical ... More
Optimal stopping for partially observed piecewise-deterministic Markov processesJul 12 2012Mar 11 2013This paper deals with the optimal stopping problem under partial observation for piecewise-deterministic Markov processes. We first obtain a recursive formulation of the optimal filter process and derive the dynamic programming equation of the partially ... More
Studying the influence of inclusion characteristics on the characteristic length involved in quasi-brittle materials using the lattice element methodNov 19 2016Unlike nonlocal models, there is no need to introduce an internal length in the constitutive law for lattice model at the mesoscopic scale. Actually, the internal length is not explicitly introduced but rather governed by the mesostructure characteristics ... More
SDSS J142625.71+575218.3, a Prototype for a New Class of Variable White DwarfMar 18 2008We present the results of a search for pulsations in six of the recently discovered carbon-atmosphere white dwarf ("hot DQ") stars. Based on our theoretical calculations, the star SDSS J142625.71+575218.3 is the only object expected to pulsate. We observe ... More
A Massive Magnetic Helium Atmosphere White Dwarf Binary in a Young Star ClusterJun 11 2019We have searched the Gaia DR2 catalogue for previously unknown hot white dwarfs in the direction of young open star clusters. The aim of this experiment was to try and extend the initial-final mass relation (IFMR) to somewhat higher masses, potentially ... More
A Comprehensive Spectroscopic Analysis of DB White DwarfsMay 27 2011We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White dwarfs also showing ... More
The bulk composition of exo-planetsMay 12 2015Priorities in exo-planet research are rapidly moving from finding planets to characterizing their physical properties. Of key importance is their chemical composition, which feeds back into our understanding of planet formation. For the foreseeable future, ... More
Automatic case acquisition from texts for process-oriented case-based reasoningApr 14 2013This paper introduces a method for the automatic acquisition of a rich case representation from free text for process-oriented case-based reasoning. Case engineering is among the most complicated and costly tasks in implementing a case-based reasoning ... More
Optical diagnostics and mass spectrometry on the afterglow of an atmospheric pressure Ar/O$_2$ radiofrequency plasma used for polymer surface treatmentMay 02 2016In the context of polymer surface treatment, the afterglow of an atmospheric pressure Ar/O$_2$ radiofrequency plasma is characterized by optical emission spectroscopy, laser induced fluorescence and mass spectrometry. The influence of the O$_2$ gas flow ... More
Stars with Unusual Compositions: Carbon and Oxygen in Cool White Dwarf StarsSep 30 2011I present a broad historical review on cool white dwarf stars with carbon and/or oxygen detected at the photosphere. This book chapter covers the observational signatures, physical properties, and evolution of DQ, DBQ and Hot DQ white dwarfs, and also ... More
Implication of a large θ_13 for the Tokai to Kamioka and Korea setupNov 16 2012In this paper, I present the implications of the large value of \theta_13 on the Tokai to Kamioka and Korea setup (T2KK). I study the sensitivity of T2KK when using a 750 kW beam (the design luminosity of T2K planned to be achieved by 2017) and a potential ... More
A technical note on divergence of the Wald statisticJun 13 2019The Wald test statistic has been shown to diverge (Dufour et al, 2013, 2017) under some conditions. This note links the divergence to eigenvalues of a polynomial matrix and establishes the divergence rate.
Towards Quality of Experience Determination for Video in Augmented Binocular Vision ScenariosJun 04 2014Mar 04 2015With the continuous growth in the consumer markets of mobile smartphones and increasingly in augmented reality wearable devices, several avenues of research investigate the relationships between the quality perceived by mobile users and the delivery mechanisms ... More
Multiwavelength Observations of Pulsar Wind NebulaeAug 27 2010The extended nebulae formed as pulsar winds expand into their surroundings provide information about the composition of the winds, the injection history from the host pulsar, and the material into which the nebulae are expanding. Observations from across ... More
High resolution X-ray observations of 3C 58Nov 10 2003As the presumed remnant of SN1181, 3C 58 houses one of the youngest known neutron stars in the Galaxy. The properties of this young pulsar and its associated wind nebula differ considerably from those of the Crab, and may well offer a more typical example ... More
Trajectories of Rubber Balloons used in Balloon Releases: Theory and ApplicationMar 10 2011Balloon releases are one of the main attractions of many fairs. Helium filled rubber balloons are released to carry postcards over preferably long distances. Although such balloons have been considered in atmospheric sciences and air safety analysis, ... More
On the origin of non self-gravitating filaments in the ISMJun 23 2013{Filaments are ubiquitous in the interstellar medium as recently emphasized by Herschel, yet their physical origin remains elusive} {It is therefore important to understand the physics of molecular clouds to investigate how filaments form and what is ... More
Formation of low-mass stars and brown dwarfsApr 23 2012These lectures attempt to expose the most important ideas, which have been proposed to explain the formation of stars with particular emphasis on the formation of brown dwarfs and low-mass stars. We first describe the important physical processes which ... More
Absence of spontaneous magnetic order at non-zero temperature in one- and two-dimensional Heisenberg and XY systems with long-range interactionsMay 06 2001May 27 2002The Mermin-Wagner theorem is strengthened so as to rule out magnetic long-range order at T>0 in one- or two-dimensional Heisenberg and XY systems with long-range interactions decreasing as R^{-alpha} with a sufficiently large exponent alpha. For oscillatory ... More
Non-quantized Dirac monopoles and strings in the Berry phase of anisotropic spin systemsApr 26 2004Aug 31 2004The Berry phase of an anisotropic spin system that is adiabatically rotated along a closed circuit C is investigated. It is shown that the Berry phase consists of two contributions: (i) a geometric contribution which can be interpreted as the flux through ... More
Interlayer exchange coupling: Preasymptotic correctionsAug 10 1998Sep 03 1999In the asymptotic limit, the interlayer exchange coupling decays as $D^{-2}$, where $D$ is the spacer thickness. A systematic procedure for calculating the preasymptotic corrections, i.e., the terms of order $D^{-n}$ with $n \ge 3$, is presented. The ... More
Testing CPT and Quantum Mechanics in the K_0-Kbar_0 SystemMay 12 1994I report a recent study done in collaboration with M.E. Peskin, on the time dependence of a kaon beam propagating according to a generalization of quantum mechanics due to Ellis, Hagelin, Nanopoulos and Srednicki, in which CP- and CPT-violating signatures ... More
The Formation of Globular Cluster SystemsOct 26 2002I briefly review models for the formation of globular cluster systems, and summarize the observational properties (i.e., formation efficiencies, metallicity distributions, kinematics and ages) of the globular cluster systems of M87 and M49: two thoroughly ... More
Tautochrone and Brachistochrone Shape Solutions for Rocking Rigid BodiesApr 11 2016Rocking rigid bodies appear in several shapes in everyday life: As furniture like rocking chairs and rocking cradles or as toys like rocking horses or tilting dolls. The familiar rocking motion of these objects, a non-linear combination of a rigid rotation ... More
(Yet) Another Theoretical Model of ThinkingNov 08 2015Feb 15 2016This paper presents a theoretical, idealized model of the thinking process with the following characteristics: 1) the model can produce complex thought sequences and can be generalized to new inputs, 2) it can receive and maintain input information indefinitely ... More
Double Witt groupsAug 03 2015The difference between slice and doubly-slice knots is reflected in algebra by the difference between metabolic and hyperbolic Blanchfield linking forms. We exploit this algebraic distinction to refine the classical Witt group of linking forms by defining ... More
p-adic uniformization and the action of Galois on certain affine correspondencesApr 18 2016Given two monic polynomials f and g with coefficients in a number field K, and some a in K, we examine the action of the absolute Galois group of K on the directed graph of iterated preimages of a under the correspondence g(y)=f(x), assuming that deg(f)>deg(g) ... More
Towards Better Response Times and Higher-Quality Queries in Interactive Knowledge Base DebuggingSep 08 2016Many AI applications rely on knowledge encoded in a locigal knowledge base (KB). The most essential benefit of such logical KBs is the opportunity to perform automatic reasoning which however requires a KB to meet some minimal quality criteria such as ... More
Fine structure of moments of the KMK transform of the Poissonized Plancharel measureJul 20 2016Aug 21 2016We consider asymptotics behavior of Poissonized Plancharel measures as the poissonization parameter $N$ goes to infinity. Recently Moll proved a convergent series expansion for statistics of a measure $\mu_\lambda$ which is the Kerov-Markov-Krein transform ... More
Investigation of the bi-drifting subpulses of radio pulsar B1839-04 utilising the open-source data-analysis project PSRSALSAMay 20 2016The usefulness and versatility of the PSRSALSA open-source pulsar data-analysis project is demonstrated through an analysis of the radio pulsar B1839-04. This study focuses on the phenomenon of bi-drifting, an effect where the drift direction of subpulses ... More
Algebraic approximation of Kähler threefolds of Kodaira dimension zeroJan 17 2016May 06 2016We prove that for a compact K\"ahler threefold with canonical singularities and vanishing first Chern class, the projective fibres are dense in the semiuniversal deformation space. This implies that every K\"ahler threefold of Kodaira dimension zero admits ... More
A Mehta-Ramanathan theorem for linear systems with basepointsJan 17 2015Oct 20 2015Let $(X, H)$ be a normal complex projective polarized variety and $\mathscr E$ an $H$-semistable sheaf on $X$. We prove that the restriction $\mathscr E\big|_C$ to a sufficiently positive general complete intersection curve $C \subset X$ passing through ... More
Truncated convolution of Möbius function and multiplicative energy of an integer $n$Mar 13 2019We establish an interesting upper bound for the moments of truncated Dirichlet convolutions of M\"obius functions, a function noted $M(n,z)$. Our result implies that $M(n,j)$ is usually quite small for $j \in \{1,\dots,n\}$. Also, we establish an estimate ... More
Addressing the Barriers to Interlingual Rule-based Machine Translation with a Concept Specification and Abstraction Semantic RepresentationJul 06 2018Sep 14 2018Interlingual machine translation offers the prospect of better preservation of meaning and requires fewer language/translation models than big data-based machine translation approaches. However, it lacks popularity primarily because of the extensive training ... More
SILEM : a new gaseous detector with integrated x-y readout planeJun 11 2007This works reports on gaseous detectors developments made in the frame of the EXO double-beta decay experiment. LEM (Large Electron Multiplication) are electron amplification grids based on GEM. They were developed in Neuchatel and showed remarquable ... More
Patching and Quillen K-TheoryJan 06 2014Mar 29 2014This paper provides an isomorphism $K_n (\mathscr{A}) \cong K_n (\mathscr{A}_1) \times_{K_n(\mathscr{A}_0)} K_n(\mathscr{A}_2)$ of $K$-groups, i.e., an exact sequence $0 \to K_n(\mathscr{A}) \to K_n(\mathscr{A}_1)\times K_n(\mathscr{A}_2) \to K_n(\mathscr{A}_0)$ ... More
Free augmented LD-systemsJul 10 2005Define an augmented LD-system, or ALD-system, to be a set equipped with two binary operations, one satisfying the left self-distributivity law $x * (y * z) = (x * y) * (x * z)$ and the other satisfying the mixed laws $(x o y) * z = x * (y * z)$ and $x ... More
Combinatorics of normal sequences of braidsNov 04 2005Many natural counting problems arise in connection with the normal form of braids--and seem to have never been considered so far. Here we solve some of them by analysing the normality condition in terms of the associated permutations, their descents and ... More
On a Singular Integrodifferential Equation arising from a Linearised Free Surface ProblemDec 14 2005A problem of linear surface waves discussed by Forbes(1984) initially gave rise to a singular integrodifferential equation over the real line. We have been able to transform this integrodifferential equation into a linear second order differential equation ... More
L^1 Ergodic Theorems for Random Group AveragesAug 04 2008Dec 17 2008This is an earlier, but more general, version of "An L^1 Ergodic Theorem for Sparse Random Subsequences". We prove an L^1 ergodic theorem for averages defined by independent random selector variables, in a setting of general measure-preserving group actions. ... More
Universally L^1-Bad Arithmetic SequencesMay 25 2009Oct 08 2009We present a modified version of Buczolich and Mauldin's proof that the sequence of square numbers is universally L^1-bad. We extend this result to a large class of sequences, including the dth powers and the set of primes; furthermore, we show that any ... More
Formule de Plancherel pour les fonctions de Whittaker sur un groupe réductif $p$-adiqueMay 12 2010We prove the Plancherel formula for Whittaker functions on a reductive p-adic group. This a sequel to our work on Paley-Wiener theorem. Our proof is close to the proof written by Waldspurger of the Harish-Chandra Plancherel formula for smooth functions ... More
New Proofs of Davies-Simon's Theorems about Ultracontractivity and Logarithmic Sobolev Inequalities related to Nash Type InequalitiesSep 05 2006We present new proofs of two theorems of E.B. Davies and B. Simon about ultracontractivity property for of semigroups of operators and logarithmic Sobolev inequalities with parameter (LSIWP for short) satisfied by the generator of the semigroup. In our ... More
Using an Encompassing Periodic Box to Perform Numerical Calculations on General DomainsJan 06 2016Apr 12 2016This paper shows how numerical methods on a regular grid in a box can be used to generate numerical schemes for problems in general smooth domains contained in the box with no need for a domain specific discretization. The focus is mainly be on spectral ... More
On motivic decompositions arising from the method of Bialynicki-BirulaJul 16 2004Aug 13 2004Recently, V. Chernousov, S. Gille and A. Merkurjev have obtained a decomposition of the motive of an isotropic smooth projective homogeneous variety analogous to the Bruhat decomposition. Using the method of Bialynicki-Birula, I generalize this decomposition ... More
A Partial Proof of a Conjecture of DrisFeb 04 2016Euler showed that if an odd perfect number $N$ exists, it must consist of two parts $N=q^k n^2$, with $q$ prime, $q \equiv k \equiv 1 \pmod{4}$, and gcd$(q,n)=1$. Dris conjectured that $q^k < n$. We first show that $q<n$ for all odd perfect numbers. Afterwards, ... More
A Class of Free Boundary Problems with Onset of a new PhaseOct 26 2006A class of diffusion driven Free Boundary Problems is considered which is characterized by the initial onset of a phase and by an explicit kinematic condition for the evolution of the free boundary. By a domain fixing change of variables it naturally ... More
Balanced truncation model order reduction in limited time intervals for large systemsJul 10 2017Jan 04 2018In this article we investigate model order reduction of large-scale systems using time-limited balanced truncation, which restricts the well known balanced truncation framework to prescribed finite time intervals. The main emphasis is on the efficient ... More
The Wreath Product of Semiprime Skew Braces is SemiprimeJul 25 2019In this note, we show that the semidirect and wreath product of two semiprime skew braces is also a semiprime skew brace.
More on the Nonexistence of Odd Perfect Numbers of a Certain FormDec 03 2015Euler showed that if an odd perfect number exists, it must be of the form $N = p^\alpha q_{1}^{2\beta_{1}}$ $\ldots$ $q_{k}^{2\beta_{k}}$, where $p, q_{1}, \ldots, q_k$ are distinct odd primes, $\alpha$, $\beta_{i} \geq 1$, for $1 \leq i \leq k$, with ... More
Trisection diagrams and twists of 4-manifoldsJun 04 2019A theorem of Katanaga, Saeki, Teragaito, and Yamada shows that the Price twist generalizes the Gluck twist of a 4-manifold. We are able to give a new proof of this theorem using certain trisection diagrams and recent techniques of Gay and Meier, and Kim ... More
Towards Optimizing Reiter's HS-Tree for Sequential DiagnosisJul 28 2019Reiter's HS-Tree is one of the most popular diagnostic search algorithms due to its desirable properties and general applicability. In sequential diagnosis, where the addressed diagnosis problem is subject to successive change through the acquisition ... More
Using Trajectories in Quantum CosmologyFeb 02 2019Quantum cosmology based on the Wheeler De Witt equation represents a simple way to implement plausible quantum effects in a gravitational setup. In its minisuperspace version wherein one restricts attention to FLRW metrics with a single scale factor and ... More
Dark Sectors from the Hidden Photon PerspectiveJul 24 2019The non-observation of dark matter (DM) by direct detection experiments suggests that any new interaction of DM with the Standard Model (SM) should be very weak. One of the simplest scenarios to achieve this is a dark sector that is charged under a new ... More
stdgpu: Efficient STL-like Data Structures on the GPUAug 16 2019Tremendous advances in parallel computing and graphics hardware opened up several novel real-time GPU applications in the fields of computer vision, computer graphics as well as augmented reality (AR) and virtual reality (VR). Although these applications ... More
Guidelines for Responsible and Human-Centered Use of Explainable Machine LearningJun 08 2019Explainable machine learning (ML) has been implemented in numerous open source and proprietary software packages and explainable ML is an important aspect of commercial predictive modeling. However, explainable ML can be misused, particularly as a faulty ... More
Discovering and Proving Invariants in Answer Set Programming and PlanningMay 08 2019Answer set programming (ASP) and planning are two widely used paradigms for solving logic programs with declarative programming. In both cases, the quality of the input programs has a major influence on the quality and performance of the solving or planning ... More
A comparison of first-order methods for the numerical solution of or-constrained optimization problemsMay 06 2019Mathematical programs with or-constraints form a new class of disjunctive optimization problems with inherent practical relevance. In this paper, we provide a comparison of three different first-order methods for the numerical treatment of this problem ... More
Garside and quadratic normalisation: a surveyApr 29 2015Starting from the seminal example of the greedy normal norm in braid monoids, we analyse the mechanism of the normal form in a Garside monoid and explain how it extends to the more general framework of Garside families. Extending the viewpoint even more, ... More
The group of fractions of a torsion free lcm monoid is torsion freeNov 19 2003Feb 04 2005We improve and shorten the argument given in(Journal of Algebra, vol.~210 (1998) pp~291--297). Inparticular, the fact that Artin braid groups are torsion free now follows from Garside\'s results almost immediately.
Geometric presentations for Thompson's groupsJul 07 2004Feb 04 2005We prove that Thompson's groups $F$ and $V$ are the geometry groups of associativity, and of associativity together with commutativity, respectively. We deduce new presentations of $F$ and $V$. These presentations lead to considering a certain subgroup ... More
Molecules in QSOs and QSO Absorption Line Systems at High RedshiftApr 24 1998Molecules dominate the cooling function of neutral metal-poor gas at high density. Observation of molecules at high redshift is thus an important tool toward understanding the physical conditions prevailing in collapsing gas. Up to now, detections are ... More
High Energy Studies of Pulsar Wind NebulaeNov 12 2008The extended nebulae formed as pulsar winds expand into their surroundings provide information about the composition of the winds, the injection history from the host pulsar, and the material into which the nebulae are expanding. Observations from across ... More
Thermal X-ray Spectra of Supernova RemnantsSep 23 2013The fast shocks that characterize supernova remnants heat circumstellar and ejecta material to extremely high temperatures, resulting in significant X-ray emission. The X-ray spectrum from an SNR carries a wealth of information about the temperature and ... More
Chandra Studies of Nonthermal Emission from Supernova Remnants and Pulsar Wind NebulaeDec 16 2002While supernova remnants (SNRs) have long been considered prime candidates as sources of cosmic rays, it is only recently that X-ray observations have identified several shell-type SNRs dominated by nonthermal emission, thus revealing shock-accelerated ... More
Isolated-Word Confusion Metrics and the PGPfone AlphabetAug 29 1996Although the confusion of individual phonemes and features have been studied and analyzed since (Miller and Nicely, 1955), there has been little work done on extending this to a predictive theory of word-level confusions. The PGPfone alphabet is a good ... More
Incorporating "Unconscious Reanalysis" into an Incremental, Monotonic ParserFeb 24 1995This paper describes an implementation based on a recent model in the psycholinguistic literature. We define a parsing operation which allows the reanalysis of dependencies within an incremental and monotonic processing architecture, and discuss search ... More
Effective field theories for QED bound states: extending Nonrelativistic QED to study retardation effectsAug 29 1996Nonrelativistic QED bound states are difficult to study because of the presence of at least three widely different scales: the masses, three-momenta ($p_i$) and kinetic energies ($K_i$) of the constituents. Nonrelativistic QED (NRQED), an effective field ... More
Using groups for investigating rewrite systemsSep 18 2006We describe several technical tools that prove to be efficient for investigating the rewrite systems associated with a family of algebraic laws, and might be useful for more general rewrite systems. These tools consist in introducing a monoid of partial ... More
The critical height is a moduli heightOct 25 2016The critical height of a rational function (with algebraic coefficients) is a natural measure of dynamical complexity, essentially an adelic analogue of the Lyapunov exponent. Coordinate-free, it is well-defined on moduli space, but bears no obvious relation ... More
Formation of proto-clusters and star formation within clusters: apparent universality of the initial mass function ?Jul 29 2012It is believed that the majority of stars form in clusters. Therefore it is likely that the gas physical conditions that prevail in forming clusters, largely determine the properties of stars that form and in particular the initial mass function. We develop ... More
Exact solutions of the aspherical axisymmetric gravo-magnetic condensationAug 29 2001We find exact and explicit solutions of the axisymmetric MHD equations of a self-gravitating polytropic gas. These solutions are able to describe a flat (uniform density) subsonic internal core, contracting homologously, of a collapsing cloud with aspherical ... More
Comment on "Space-Time Crystals of Trapped Ions": And Yet it Moves Not !Nov 20 2012A Comment on "Space-Time Crystals of Trapped ions", by Tongcang Li et al. (PRL 109, 163001 (2012); arXiv:1206.4772
Berry phase, topology, and diabolicity in quantum nano-magnetsNov 18 2005A topological theory of the diabolical points (degeneracies) of quantum magnets is presented. Diabolical points are characterized by their diabolicity index, for which topological sum rules are derived. The paradox of the the missing diabolical points ... More
Integer Subsets with High Volume and Low PerimeterFeb 07 2012We consider a certain variation of the 'isoperimetric problem' adopted for subsets of nonnegative integers. More specifically, we explore the sequence P(n) as described in OEIS A186053. We provide the first exact formulas for P(n) including multiple recursive ... More
Impact of a Warm Dark Matter late-time velocity dispersion on large-scale structuresJun 04 2012May 16 2013We investigate whether the late-time (at $z\leq 100$) velocity dispersion expected in Warm Dark Matter scenarios could have some effect on the cosmic web (i.e., outside of virialized halos). We consider effective hydrodynamical equations, with a pressurelike ... More
Ballistic aggregation for one-sided Brownian initial velocityDec 12 2008May 14 2009We study the one-dimensional ballistic aggregation process in the continuum limit for one-sided Brownian initial velocity (i.e. particles merge when they collide and move freely between collisions, and in the continuum limit the initial velocity on the ... More
Relaxation of a 1-D gravitational systemApr 12 2006Oct 03 2006We study the relaxation towards thermodynamical equilibrium of a 1-D gravitational system. This OSC model shows a series of critical energies $E_{cn}$ where new equilibria appear and we focus on the homogeneous ($n=0$), one-peak ($n=\pm 1$) and two-peak ... More
New Double-Mode and Other RR Lyrae Stars from WASP DataNov 05 201042 RRab, 46 RRc and 7 previously unidentified double-mode RR Lyrae stars were found in the publicly available data of the WASP archive. The Galactic double-mode RR Lyrae stars appear to show a bimodal period distribution.
Exact Algorithms for Maximum Clique: a computational studyJul 19 2012We investigate a number of recently reported exact algorithms for the maximum clique problem (MCQ, MCR, MCS, BBMC). The program code used is presented and critiqued showing how small changes in implementation can have a drastic effect on performance. ... More