Results for "E. Willis"

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A graph-theoretic description of scale-multiplicative semigroups of automorphismsOct 01 2017It is shown that a flat subgroup, $H$, of the totally disconnected, locally compact group $G$ decomposes into a finite number of subsemigroups on which the scale function is multiplicative. The image, $P$, of a multiplicative semigroup in the quotient, ... More
A well posed acoustic analogy based on a moving acoustic mediumSep 20 2010For flows of a lossless gas, the stagnation enthalpy obeys a linear convected wave equation with coefficients which depend on the flow variables. This equation is self-adjoint and one has a reciprocity relation between source and observer. It fulfills ... More
Khovanov-Rozansky homology for infinite multi-colored braidsApr 19 2019We define a limiting $\mathfrak{sl}_N$ Khovanov-Rozansky homology for semi-infinite positive multi-colored braids, and we show that this limiting homology categorifies a highest-weight projector for a large class of such braids. This effectively completes ... More
Khovanov homology for links in $\#^r(S^2\times S^1)$Dec 17 2018We revisit Rozansky's construction of Khovanov homology for links $L$ in $S^2\times S^1$, extending it to define Khovanov homology $Kh(L)$ for links in $M^r=\#^r(S^2\times S^1)$ for any $r$. The graded Euler characteristic of $Kh(L)$ recovers the evaluation ... More
Tidy subgroups for commuting automorphisms of totally disconnected groups: an analogue of simultaneous triangularisation of matricesFeb 18 2003Let \alpha be an automorphism of the totally disconnected group G. The compact open subgroup, V, if G is tidy for \alpha if [\alpha(V') : \alpha(V')\cap V'] is minimised at V, where V' ranges over all compact open subgroups of G. Identifying a subgroup ... More
The scale function and latticesFeb 14 2016It is shown that, given a lattice H in a totally disconnected, locally compact group G, the contraction subgroups in G and the values of the scale function on G are determined by their restrictions to H. Group theoretic properties intrinsic to the lattice, ... More
State-of-the-art in selection of variables and functional forms in multivariable analysis -- outstanding issuesJul 01 2019How to select variables and identify functional forms for continuous variables is a key concern when creating a multivariable model. Ad hoc 'traditional' approaches to variable selection have been in use for at least 50 years. Similarly, methods for determining ... More
Contraction groups and scales of automorphisms of totally disconnected locally compact groupsFeb 10 2003Aug 15 2003We study contraction groups for automorphisms of totally disconnected locally compcat groups using the scale of the automorphism as a tool. The contraction group is shown to be unbounded when the inverse automorphism has non-trivial scale and this scale ... More
Decompositions of locally compact contraction groups, series and extensionsApr 04 2018A locally compact contraction group is a pair (G,f) where G is a locally compact group and f an automorphism of G which is contractive in the sense that the forward orbit under f of each g in G converges to the neutral element e, as n tends to infinity. ... More
Approximation of homogenized coefficients in deterministic homogenization and convergence rates in the asymptotic almost periodic settingJun 27 2019For a homogenization problem associated to a linear elliptic operator, we prove the existence of a distributional corrector and we find an approximation scheme for the homogenized coefficients. We also study the convergence rates in the asymptotic almost ... More
Anomalous discrete chiral symmetry in the Gross-Neveu model and loop gas simulationsMay 27 2009Jul 07 2009We investigate the discrete chiral transformation of a Majorana fermion on a torus. Depending on the boundary conditions the integration measure can change sign. Taking this anomalous behavior into account we define a chiral order parameter as a ratio ... More
Scale-multiplicative semigroups and geometry: automorphism groups of treesDec 04 2013A scale-multiplicative semigroup in a totally disconnected, locally compact group $G$ is one for which the restriction of the scale function on $G$ is multiplicative. The maximal scale-multiplicative semigroups in groups acting 2-transitively on the set ... More
Convexity of tableau sets for type A Demazure characters (key polynomials), parabolic Catalan numbersJun 09 2017Jul 18 2018This is the first of three papers that develop structures which are counted by a "parabolic" generalization of Catalan numbers. Fix a subset R of {1,..,n-1}. Consider the ordered partitions of {1,..,n} whose block sizes are determined by R. These are ... More
Amenability of Banach algebras of compact operatorsSep 08 1992In this paper we study conditions on a Banach space X that ensure that the Banach algebra K(X) of compact operators is amenable. We give a symmetrized approximation property of X which is proved to be such a condition. This property is satisfied by a ... More
The standing pool of genomic structural variation in a natural population of Mimulus guttatusAug 19 2013Major unresolved questions in evolutionary genetics include determining the contributions of different mutational sources to the total pool of genetic variation in a species, and understanding how these different forms of genetic variation interact with ... More
Stabilisation and drag reduction of pipe flows by flattening the base profileJun 14 2018Recent experimental observations (Kuehnen et al., 2018) have shown that flattening a turbulent streamwise velocity profile in pipe flow destabilises the turbulence so that the flow relaminarises. We show that a similar phenomenon exists for laminar pipe ... More
Species richness estimation with high diversity but spurious singletonsApr 09 2016The presence of uncommon taxa in high-throughput sequenced ecological samples pose challenges to the microbial ecologist, bioinformatician and statistician. It is rarely certain whether these taxa are truly present in the sample or the result of sequencing ... More
Stabilization of the Khovanov Homotopy Type of Torus LinksNov 09 2015The structure of the Khovanov homology of $(n,m)$ torus links has been extensively studied. In particular, Marko Stosic proved that the homology groups stabilize as $m\rightarrow\infty$. We show that the Khovanov homotopy types of $(n,m)$ torus links, ... More
Confidence sets for phylogenetic treesJul 28 2016Inferring evolutionary histories (phylogenetic trees) has important applications in biology, criminology and public health. However, phylogenetic trees are complex mathematical objects that reside in a non-Euclidean space, which complicates their analysis. ... More
The Nub of an Automorphism of a Totally Disconnected, Locally Compact GroupDec 19 2011To any automorphism, $\alpha$, of a totally disconnected, locally compact group, $G$, there is associated a compact, $\alpha$-stable subgroup of $G$, here called the \emph{nub} of $\alpha$, on which the action of $\alpha$ is topologically transitive. ... More
Why Money Trickles Up - Wealth & Income DistributionsMay 11 2011May 27 2011This paper combines ideas from classical economics and modern finance with the general Lotka-Volterra models of Levy & Solomon to provide straightforward explanations of wealth and income distributions. Using a simple and realistic economic formulation, ... More
Laser Welfare: First Steps in Econodynamic EngineeringAug 10 2004The paper starts with a brief review of present understanding of income distributions; especially with regard to recent work in the field of econophysics that draws parallels between income, wealth and energy distributions. Examples of alternative energy ... More
The Bowley RatioMay 11 2011The paper gives a simple algebraic description, and background justification, for the Bowley Ratio, the relative returns to labour and capital, in a simple economy.
Personalised Query Suggestion for Intranet Search with Temporal User ProfilingJan 09 2017Recent research has shown the usefulness of using collective user interaction data (e.g., query logs) to recommend query modification suggestions for Intranet search. However, most of the query suggestion approaches for Intranet search follow an "one ... More
Pricing, liquidity and the control of dynamic systems in finance and economicsMay 27 2011The paper discusses various practical consequences of treating economics and finance as an inherently dynamic and chaotic system. On the theoretical side this looks at the general applicability of the market-making pricing approach to economics in general. ... More
Modeling microbial abundances and dysbiosis with beta-binomial regressionFeb 07 2019Using a sample from a population to estimate the proportion of the population with a certain category label is a broadly important problem. In the context of microbiome studies, this problem arises when researchers wish to use a sample from a population ... More
A study of obliquely propagating longitudinal shear waves in a periodic laminateOct 24 2013The basic purpose of this work is to demonstrate, by quite simple and explicit calculation, the possibility that a simple laminate composed of ordinary materials can display the kind of response associated with a "metamaterial". Specifically, a wave of ... More
Some thoughts on dynamic effective properties -- a working documentNov 05 2013The main purpose of this work is to address the question of the utility of "effective constitutive relations" for problems in dynamics. This is done in the context of longitudinal shear waves in an elastic medium that is periodically laminated, with attention ... More
Green's function for longitudinal shear of a periodic laminateNov 05 2013The reasoning is a slight extension of that employed in my article [1] and its further development [2]. A formal solution to the title problem is presented for a general periodic laminate and its application for the construction of "effective constitutive ... More
A Colored Khovanov Homotopy Type And Its Tail For B-Adequate LinksFeb 11 2016Jun 06 2016We define a Khovanov homotopy type for $sl_2(\mathbb{C})$ colored links and quantum spin networks and derive some of its basic properties. In the case of $n$-colored B-adequate links, we show a stabilization of the homotopy types as the coloring $n\rightarrow\infty$, ... More
Confidence sets for phylogenetic treesJul 28 2016Oct 13 2017Inferring evolutionary histories (phylogenetic trees) has important applications in biology, criminology and public health. However, phylogenetic trees are complex mathematical objects that reside in a non-Euclidean space, which complicates their analysis. ... More
Locally normal subgroups of totally disconnected groups. Part II: Compactly generated simple groupsJan 14 2014Jan 04 2017We use the structure lattice, introduced in Part I, to undertake a systematic study of the class $\mathscr S$ consisting of compactly generated, topologically simple, totally disconnected locally compact groups that are non-discrete. Given $G \in \mathscr ... More
Simple groups of automorphisms of trees determined by their actions on finite subtreesDec 09 2013Oct 04 2014We introduce the notion of the $k$-closure of a group of automorphisms of a locally finite tree, and give several examples of the construction. We show that the $k$-closure satisfies a new property of automorphism groups of trees that generalises Tits' ... More
Locally normal subgroups of totally disconnected groups. Part I: General theoryApr 18 2013Jun 20 2016Let G be a totally disconnected, locally compact group. A closed subgroup of G is locally normal if its normaliser is open in G. We begin an investigation of the structure of the family of closed locally normal subgroups of G. Modulo commensurability, ... More
Locally normal subgroups of simple locally compact groupsMar 27 2013We announce various results concerning the structure of compactly generated simple locally compact groups. We introduce a local invariant, called the structure lattice, which consists of commensurability classes of compact subgroups with open normaliser, ... More
Correlated photon pairs generated from a warm atomic ensembleNov 11 2010We present measurements of the cross-correlation function of photon pairs at 780 nm and 1367 nm, generated in a hot rubidium vapor cell. The temporal character of the biphoton is determined by the dispersive properties of the medium where the pair generation ... More
Non-degenerate four-wave mixing in rubidium vapor: transient regimeOct 06 2010We investigate the transient response of the generated light from Four-Wave Mixing (FWM) in the diamond configuration using a step-down field excitation. The transients show fast decay times and oscillations that depend on the detunings and intensities ... More
Thermal and Non-thermal Plasmas in the Galaxy Cluster 3C 129Feb 03 2003Jul 23 2003We describe new Chandra spectroscopy data of the cluster which harbors the prototypical "head tail" radio galaxy 3C 129 and the weaker radio galaxy 3C 129.1. We combined the Chandra data with Very Large Array (VLA) radio data taken at 0.33, 5, and 8 GHz ... More
Chemo-kinematics of the Milky Way from the SDSS-III MARVELS SurveyMar 30 2018Combining stellar atmospheric parameters, such as effective temperature, surface gravity, and metallicity, with barycentric radial velocity data provides insight into the chemo-dynamics of the MilkyWay and our local Galactic environment. We analyze 3075 ... More
Absolute absorption and fluorescence measurements over a dynamic range of 10$^6$ with cavity-enhanced laser-induced fluorescenceAug 08 2013Oct 14 2013We describe a novel experimental setup that combines the advantages of both laser-induced fluorescence and cavity ring-down techniques. The simultaneous and correlated measurement of the ring-down and fluorescence signals yields absolute absorption coefficients ... More
Dynamics of self-generated, large amplitude magnetic fields following high-intensity laser matter interactionOct 16 2012The dynamics of magnetic fields with amplitude of several tens of Megagauss, generated at both sides of a solid target irradiated with a high intensity (? 1019W/cm2) picosecond laser pulse, has been spatially and temporally resolved using a proton imaging ... More
Engineering of Neutral Excitons and Exciton Complexes in Transition Metal Dichalcogenide Monolayers through External Dielectric ScreeningMay 30 2017In order to fully exploit the potential of transition metal dichalcogenide monolayers (TMD-MLs), the well-controlled creation of atomically sharp lateral heterojunctions within these materials is highly desirable. A promising approach to create such heterojunctions ... More
Two-Photon Dichroic Atomic Vapor Laser Lock Using Electromagnetically Induced Transparency and AbsorptionJan 19 2009May 14 2009We demonstrate a technique to lock the frequency of a laser to a transition between two excited states in Rb vapor in the presence of a weak magnetic field. We use a ladder configuration from specific hyperfine sublevels of the 5S 1/2, 5P 3/2, and 5D ... More
Modified Mott-Schottky Analysis of Nanocrystal Solar CellsDec 07 2011Mott-Schottky analysis is adapted to determine the built-in bias (Vbi) and doping density (N) of lead sulfide-zinc oxide colloidal quantum dot heterojunction solar cells. We show that charge injection barriers at the solar cell's electrodes create a constant ... More
A Mass Model for Estimating the Gamma Ray Background of the Burst and Transient Source ExperimentNov 19 2002Orbiting x-ray and gamma ray instruments are subject to large background count rates due to local particle fluxes in the space environment. The ability of an instrument to make calibrated measurements of the flux from a source of interest is highly dependent ... More
Young Stellar Objects in the Massive Star Forming Region W49Sep 18 2015Dec 16 2015We present the initial results of our investigation of the star-forming complex W49, one of the youngest and most luminous massive star forming regions in our Galaxy. We used Spitzer/Infrared Array Camera (IRAC) data to investigate massive star formation ... More
The complex chemistry of hot cores in Sagittarius B2(N): Influence of cosmic-ray ionization and thermal historyJun 11 2019As the number of complex organic molecules (COMs) detected in the interstellar medium increases, it becomes important to place meaningful constraints on the formation pathways of these species. The molecular cloud SgrB2(N) is host to several hot molecular ... More
In-situ, variable thickness, liquid crystal film target inserter for moderate repetition rate intense laser applicationsJul 29 2015Aug 18 2015Liquid crystal films have recently been demonstrated as variable thickness, planar targets for ultra-intense laser matter experiments and applications such as ion acceleration. By controlling the parameters of film formation, including liquid crystal ... More
Radio polarimetric imaging of the interstellar medium: magnetic field and diffuse ionized gas structure near the W3/W4/W5/HB3 complexDec 08 1998We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1' over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features ... More
Experimental evidence for narrow baryons in the mass range 1.0$\le$ M $\le$1.46 GeVJul 04 2002The reaction p p $\to$ p ${\pi^+}X$ was studied at different incident energies around T$_{p}$=2 GeV. Narrow baryonic structures were observed in the missing mass M$_{X}$ and in the invariant mass M$_{p\pi^{+}}$. The masses of these structures are: 1004, ... More
X-ray versus infrared selection of distant galaxy clusters: A case study using the XMM-LSS and SpARCS cluster samplesApr 17 2018We present a comparison of two samples of z>0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray selected XMM-LSS distant cluster survey ... More
Evidence for the Independence of Waged and Unwaged Income, Evidence for Boltzmann Distributions in Waged Income, and the Outlines of a Coherent Theory of Income DistributionJun 28 2004Two sets of high quality income data are analysed in detail, one set from the UK, one from the USA. It is firstly demonstrated that both a log-normal distribution and a Boltzmann distribution can give very accurate fits to both these data sets. The absence ... More
The Khovanov homology of infinite braidsOct 14 2016We show that the limiting Khovanov chain complex of any infinite positive braid categorifies the Jones-Wenzl projector. This result extends Lev Rozansky's categorification of the Jones-Wenzl projectors using the limiting complex of infinite torus braids. ... More
Fairly Random: The Impact of Winning the Toss on the Probability of WinningMay 27 2016In a competitive sport, every little thing matters. Yet, many sports leave some large levers out of the reach of the teams, and in the hands of fate. In cricket, world's second most popular sport by some measures, one such lever---the toss---has been ... More
Spatio-temporal Correlations in the Manna Model in one, three and five dimensionsAug 02 2016Jul 30 2017Although the paradigm of criticality is centred around spatial correlations and their anomalous scaling, not many studies of Self-Organised Criticality (SOC) focus on spatial correlations. Often, integrated observables, such as avalanche size and duration, ... More
Relating the type A alcove path model to the right key of a semistandard Young tableau, with Demazure character consequencesJun 15 2015There are several combinatorial methods that can be used to produce type A Demazure characters (key polynomials). The alcove path model of Lenart and Postnikov provides a procedure that inputs a semistandard tableau $T$ and outputs a saturated chain in ... More
Totally disconnected groups from Baumslag-Solitar groupsJan 21 2013May 26 2013For each Baumslag-Solitar group BS(m,n) (m,n nonzero integers), a totally disconnected, locally compact group, G_{m,n}, is constructed so that BS(m,n) is identified with a dense subgroup of G_{m,n}. The scale function on G_{m,n}, a structural invariant ... More
Spatio-temporal Correlations in the Manna Model in one, three and five dimensionsAug 02 2016Although the paradigm of criticality is centred around spatial correlations and their anomalous scaling, very few studies of Self-Organised Criticality (SOC) are concerned with spatial correlations. Instead, integrated observables, such as avalanche size ... More
On the spectrum of the reduced wave operator with cylindrical discontinuityFeb 14 1999Consider the differential operator H = -(1/m(x))L, where L is the N-dimensional Laplacian, in the weighted Hilbert space of square integrable functions on N-dimensional Euclidean space with weight m(x)dx. Here m(x) is a positive step function with a surface ... More
Local homeomorphisms that *-commute with the shiftOct 27 2010Exel and Renault proved that a sliding block code on a one-sided shift space coming from a progressive block map is a local homeomorphism. We provide a counterexample showing that the converse does not hold. We use this example to generalize the notion ... More
Colored Khovanov-Rozansky homology for infinite braidsSep 19 2017We show that the limiting unicolored $\mathfrak{sl}(N)$ Khovanov-Rozansky chain complex of any infinite positive braid categorifies a highest-weight projector. This result extends an earlier result of Cautis categorifying highest-weight projectors using ... More
The Compact Approximation Property does not imply the Approximation PropertyMay 04 1992It is shown how to construct, given a Banach space which does not have the approximation property, another Banach space which does not have the approximation property but which does have the compact approximation property.
Computing power series expansions of modular formsApr 30 2012Sep 30 2012We exhibit a method to numerically compute power series expansions of modular forms on a cocompact Fuchsian group, using the explicit computation a fundamental domain and linear algebra.
Feedback, Dynamics, and Optimal Control in Climate EconomicsDec 19 2018Mar 19 2019For his work in the economics of climate change, Professor William Nordhaus was a co-recipient of the 2018 Nobel Memorial Prize for Economic Sciences. A core component of the work undertaken by Nordhaus is the Dynamic Integrated model of Climate and Economy, ... More
New Descriptions of Demazure Tableaux and Right Keys, with Applications to ConvexityJul 29 2014The right key of a semistandard Young tableau is a tool used to find Demazure characters for $sl_n(\mathbb{C})$. This thesis gives methods to obtain the right and left keys by inspection of the semistandard Young tableau. Given a partition $\lambda$ and ... More
Equilibria, periodic orbits and computing themAug 09 2019Sep 10 2019In this short exposition, we describe equilibria and periodic orbits in terms of the flow map, {\Phi}, and discuss the essentials of the Jacobian-free Newton-Krylov (JFNK) method that can be used to find them. This method requires little more than calls ... More
The Scale and Tidy Subgroups for Endomorphisms of Totally Disconnected Locally Compact GroupsDec 05 2013The scale of an endomorphism, $\alpha$, of a totally disconnected, locally compact group $G$ is the minimum index $[\alpha(U) : \alpha(U)\cap U]$, for $U$ a compact, open subgroup of $G$. A structural characterization of subgroups at which the minimum ... More
The Openpipeflow Navier--Stokes SolverMay 10 2017Jun 05 2017Pipelines are used in a huge range of industrial processes involving fluids, and the ability to accurately predict properties of the flow through a pipe is of fundamental engineering importance. Armed with parallel MPI, Arnoldi and Newton--Krylov solvers, ... More
Optimization of the magnetic dynamoSep 07 2012Dec 19 2012In stars and planets, magnetic fields are believed to originate from the motion of electrically conducting fluids in their interior, through a process known as the dynamo mechanism. In this Letter, an optimization procedure is used to simultaneously address ... More
Estimating Diversity via Frequency RatiosAug 14 2014Dec 09 2014We wish to estimate the total number of classes in a population based on sample counts, especially in the presence of high latent diversity. Drawing on probability theory that characterizes distributions on the integers by ratios of consecutive probabilities, ... More
Towards Eco-friendly Database Management SystemsSep 09 2009Database management systems (DBMSs) have largely ignored the task of managing the energy consumed during query processing. Both economical and environmental factors now require that DBMSs pay close attention to energy consumption. In this paper we approach ... More
Equilibria, periodic orbits and computing themAug 09 2019In this short exposition, we describe equilibria and periodic orbits in terms of the flow map, {\Phi}, and discuss the essentials of the Jacobian-free Newton-Krylov (JFNK) method that can be used to find them. This method requires little more than calls ... More
Acceleration of generalized hypergeometric functions through precise remainder asymptoticsFeb 15 2011Aug 17 2011We express the asymptotics of the remainders of the partial sums {s_n} of the generalized hypergeometric function q+1_F_q through an inverse power series z^n n^l \sum_k c_k/n^k, where the exponent l and the asymptotic coefficients {c_k} may be recursively ... More
A Modified Mass Concept could explain both the Dark Matter and the Dark Energy PhenomenonDec 13 2010Some consequences of a Modified Mass Concept (MMC) are discussed. According to MMC the inertial mass is not only determined by its energy, but also by a scalar field f depending on other masses. The concept consistently describes the galactic rotation ... More
Luminosity Functions of XMM-LSS C1 Galaxy ClustersSep 21 2009Sep 22 2009CFHTLS optical photometry has been used to study the galaxy luminosity functions of 14 X-ray selected clusters from the XMM-LSS survey. These are mostly groups and poor clusters, with masses (M_{500}) in the range 0.6 to 19x10 ^{13} M_solar and redshifts ... More
The reduced wave equation in layered materialsFeb 14 1999Let H = -(1/m(x))L be the reduced wave operator defined on the N-dimensional Euclidean space, where \f L is the Laplacian. Here m(x) is a positive step function with possible countably infinte surfaces of discontinuity (separating surfaces) under the ... More
The uniqueness of the solution of the Schrodinger equation with discontinuous coefficientsNov 30 1998Consider the Schroeodinger equation: - Du(x) - l(x)u + s(x)u = 0, where D is the Laplacian, l(x) > 0 and s(x) is dominated by l(x). We shall extend the celebrated Kato's result on the asymptotic behavior of the solution to the case where l(x) has unbounded ... More
A Direct Way to Find the Right Key of a Semistandard Young TableauOct 27 2011The right and left key of a semistandard Young tableau were introduced by Lascoux and Schutzenberger in 1990. Most prominently, the right key is a tool used to find Demazure characters for sl(n,C). Previous methods used to compute these keys require introducing ... More
Homological Properties of the Algebra of Compact Operators on a Banach SpaceDec 04 2012The conditions on a Banach space, $E$, under which the algebra, $\mathcal{K}(E)$, of compact operators on $E$ is right flat or homologically unital are investigated. These homological properties are related to factorization in the algebra and it is shown ... More
Evidence of polarisation in the prompt gamma-ray emission from GRB 930131 and GRB 960924May 05 2005The true nature of the progenitor to GRBs remains elusive; one characteristic that would constrain our understanding of the GRB mechanism considerably is gamma-ray polarimetry measurements of the initial burst flux. We present a method that interprets ... More
Gamma-Ray All Sky Imaging with BATSEAug 23 2004The BATSE mission aboard CGRO observed the whole sky for 9 years in the 20 keV - 2 MeV energy band. Flat-fielding of the temporal variations in the background present in the data set has been accomplished through a GEANT3 Monte-Carlo simulation - the ... More
A large-scale CO survey of the Rosette Molecular Cloud: assessing the effects of O stars on surrounding molecular gasFeb 24 2009We present a new large-scale survey of J=3-2 12CO emission covering 4.8 square degrees around the Rosette Nebula. Approximately 2000 compact clumps are identified, with a spatially-invariant power law mass distribution index of -1.8. Most of the inner ... More
The BATSE 9 year histories of the brightest AGNAug 24 2004The Burst and Transient Source Experiment (BATSE) aboard CGRO monitored the whole sky through 8 NaI(Tl) crystal scintillators sensitive in the 20 keV - 2 MeV energy band continuously from April 1991 until June 2000. Results are presented on the long term ... More
A description of sources detected by INTEGRAL during the first 4 years of observationsMar 02 2007Mar 06 2007Parameters from the literature, such as positions, photoelectric absorption (nH), spin and orbital periods, and distances or redshifts, were collected for all ~500 sources detected by INTEGRAL-ISGRI so far. We investigate where new and previously-known ... More
Time-resolved characterization of the formation of a collisionless shockApr 24 2013We report on the temporally and spatially resolved detection of the precursory stages that lead to the formation of an unmagnetized, supercritical collision-less shock in a laser-driven laboratory experiment. The measured evolution of the electrostatic ... More
Liquid crystal films as on-demand, variable thickness (50-5000 nm) targets for intense lasersMay 22 2014We have developed a new type of target for intense laser-matter experiments that offers significant advantages over those currently in use. The targets consist of a liquid crystal film freely suspended within a metal frame. They can be formed rapidly ... More
Transient electric fields in laser plasmas observed by proton streak deflectometryJan 25 2008A novel proton imaging technique was applied which allows a continuous temporal record of electric fields within a time window of several nanoseconds. This "proton streak deflectometry" was used to investigate transient electric fields of intense (~ 10^17 ... More
Observation and characterization of laser-driven Phase Space Electron HolesAug 31 2009The direct observation and full characterization of a Phase Space Electron Hole (EH) generated by laser-matter interaction is presented. This structure has been detected via proton radiography during the interaction between an intense laser pulse (t=1ns ... More
Possible Indication of Narrow Baryonic Resonances Produced in the 1720-1790 MeV Mass RegionNov 05 2004Signals of two narrow structures at M=1747 MeV and 1772 MeV were observed in the invariant masses M_{pX} and M_{\pi^{+}X} of the pp->ppX and pp->p\pi^{+}X reactions respectively. Many tests were made to see if these structures could have been produced ... More
Generation and Observation of Coherent, Long--Lived Structures in a Laser--Plasma ChannelFeb 21 2007In recent experiments of laser pulse interaction at relativistic intensities with a low density plasma, the proton radiography technique showed evidence of long--lived field structures generated after the self-channeling of the laser pulse. We present ... More
Nm-sized cryogenic hydrogen clusters for a laser-driven proton sourceOct 31 2018A continuous cryogenic hydrogen cluster-jet target has been developed for laser-plasma interaction studies, in particular as a source for the acceleration of protons. Major advantages of the cluster-jet target are the compatibility with pulsed high repetition ... More
The XXL Survey: XVII. X-ray and Sunyaev-Zel'dovich Properties of the Redshift 2.0 Galaxy Cluster XLSSC 122Mar 23 2017We present results from a 100 ks XMM-Newton observation of galaxy cluster XLSSC 122, the first massive cluster discovered through its X-ray emission at $z\approx2$. The data provide the first precise constraints on the bulk thermodynamic properties of ... More
A deep, narrow J-band search for proto-galactic Lyman Alpha emission at redshifts z~9Dec 17 2004We present a deep, narrow J-band search for proto--galactic Lyman Alpha emission at redshifts z~9. We combine an exceptionally deep image of the Hubble Deep Field South, obtained using a narrow band filter centred on the wavelength 1.187 microns using ... More
Exceptional Points, Nonnormal Matrices, Hierarchy of Spin Matrices and an Eigenvalue ProblemJan 14 2013Jan 10 2014Exceptional points of a class of non-hermitian Hamilton operators $\hat H$ of the form $\hat H=\hat H_0+i\hat H_1$ are studied, where $\hat H_0$ and $\hat H_1$ are hermitian operators. Finite dimensional Hilbert spaces are considered. The linear operators ... More
Spin Operators, Pauli Group, Commutators, Anti-Commutators, Kronecker Product and ApplicationsMay 22 2014Jun 02 2014Pauli spin matrices, Pauli group, commutators, anti-commutators and the Kronecker product are studied. Applications to eigenvalue problems, exponential functions of such matrices, spin Hamilton operators, mutually unbiased bases, Fermi operators and Bose ... More
Directions of automorphisms of Lie groups over local fields compared to the directions of Lie algebra automorphismsOct 30 2006To each totally disconnected, locally compact topological group G and each group A of automorphisms of G, a pseudo-metric space of ``directions'' has been associated by U. Baumgartner and the second author. Given a Lie group G over a local field, it is ... More
Movability of Localized Excitations in Nonlinear Discrete Systems - a Separatrix ProblemMar 14 1994We analyze the effect of internal degrees of freedom on the movability properties of localized excitations on defect-free nonlinear Hamiltonian lattices by means of properties of a local phase space which is at least of dimension six. We formulate generic ... More
Uncertainty in phylogenetic tree estimatesNov 10 2016Estimating phylogenetic trees is an important problem in evolutionary biology, environmental policy and medicine. Although trees are estimated, their uncertainties are discarded by mathematicians working in tree space. Here we explicitly model the multivariate ... More
Exponential of a Matrix, a Nonlinear Problem and Quantum GatesNov 11 2013Oct 03 2014We describe solutions of the matrix equation $\exp(z(A-I_n))=A$, where $z \in {\mathbb C}$. Applications in quantum computing are given. Both normal and nonnormal matrices are studied. For normal matrices, the Lambert W-function plays a central role.
Kinematic dynamo action in a sphere: Effects of periodic time-dependent flows on solutions with axial dipole symmetrySep 28 2004Choosing a simple class of flows, with characteristics that may be present in the Earth's core, we study the ability to generate a magnetic field when the flow is permitted to oscillate periodically in time. The flow characteristics are parameterised ... More