Results for "J. C. Kasper"

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An association between anisotropic plasma heating and instabilities in the solar windNov 13 2009We present an analysis of the components of solar wind proton temperature perpendicular and parallel to the local magnetic field as a function of proximity to plasma instability thresholds. We find that $T_{\perp p}$ is enhanced near the mirror instability ... More
Global Poles of the Two-Loop Six-Point N=4 SYM integrandMay 02 2012Oct 22 2012Recently, a recursion relation has been developed, generating the four-dimensional integrand of the amplitudes of N=4 supersymmetric Yang-Mills theory for any number of loops and legs. In this paper, I provide a comparison of the prediction for the two-loop ... More
Constraints on the Global Structure of Magnetic Clouds: Transverse Size and CurvatureMay 31 2006Aug 21 2006We present direct evidence that magnetic clouds (MCs) have highly flattened and curved cross section resulting from their interaction with the ambient solar wind. Lower limits on the transverse size are obtained for three MCs observed by ACE and Ulysses ... More
Plasma Depletion and Mirror Waves Ahead of Interplanetary Coronal Mass EjectionsFeb 24 2006Jul 04 2006We find that the sheath regions between fast interplanetary coronal mass ejections (ICMEs) and their preceding shocks are often characterized by plasma depletion and mirror wave structures, analogous to planetary magnetosheaths. A case study of these ... More
Determining the Magnetic Field Orientation of Coronal Mass Ejections from Faraday RotationMay 18 2007We describe a method to measure the magnetic field orientation of coronal mass ejections (CMEs) using Faraday rotation (FR). Two basic FR profiles, Gaussian-shaped with a single polarity or "N"-like with polarity reversals, are produced by a radio source ... More
Temperature Anisotropy in a Shocked Plasma: Mirror-Mode Instabilities in the HeliosheathFeb 22 2007We show that temperature anisotropies induced at a shock can account for interplanetary and planetary bow shock observations. Shocked plasma with enhanced plasma beta is preferentially unstable to the mirror mode instability downstream of a quasi-perpendicular ... More
Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar windAug 10 2009The proton temperature anisotropy in the solar wind is known to be constrained by the theoretical thresholds for pressure anisotropy-driven instabilities. Here we use approximately 1 million independent measurements of gyroscale magnetic fluctuations ... More
Simultaneous Measurements of the Fried Parameter r_0 and the Isoplanatic Angle theta_0 using SCIDAR and Adaptive Optics - First ResultsJan 26 2001We present first results of a simultaneous atmospheric turbulence measurement campaign at the Calar Alto (Spain) 1.23m and 3.5m telescopes. A SCIDAR instrument and the Calar Alto Adaptive Optics system ALFA were used at the 1.23m and 3.5m telescopes respectively ... More
Integration-by-parts reductions from the viewpoint of computational algebraic geometryJun 30 2016Jul 07 2016Integration-by-parts reductions play a central role in perturbative QFT calculations. They allow the set of Feynman integrals contributing to a given observable to be reduced to a small set of basis integrals, and they moreover facilitate the computation ... More
Integration-by-parts reductions from unitarity cuts and algebraic geometryNov 03 2015Jul 07 2016We show that the integration-by-parts reductions of various two-loop integral topologies can be efficiently obtained by applying unitarity cuts to a specific set of subgraphs and solving associated polynomial (syzygy) equations.
Constructing D-Branes from K-TheoryJul 16 1999Aug 06 1999A detailed review of recent developments in the topological classification of D-branes in superstring theory is presented. Beginning with a thorough, self-contained introduction to the techniques and applications of topological K-theory, the relationships ... More
Brane Descent Relations in K-theoryApr 22 1999Jul 26 1999The various descent and duality relations among BPS and non-BPS D-branes are classified using topological K-theory. It is shown how the descent procedures for producing type-II D-branes from brane-antibrane bound states by tachyon condensation and $\klein$ ... More
The No-Triangle Hypothesis for N=8 SupergravityOct 03 2006We study the perturbative expansion of N=8 supergravity in four dimensions from the viewpoint of the ``no-triangle'' hypothesis, which states that one-loop graviton amplitudes in N=8 supergravity only contain scalar box integral functions. Our computations ... More
Stochastic Heating, Differential Flow, and the Alpha-to-Proton Temperature Ratio in the Solar WindJul 30 2013We extend previous theories of stochastic ion heating to account for the motion of ions along the magnetic field. We derive an analytic expression for the ion-to-proton perpendicular temperature ratio in the solar wind for any ion species, assuming that ... More
Solar Cycle Variations in the Elemental Abundance of Helium and Fractionation of Iron in the Fast Solar Wind - Indicators of an Evolving Energetic Release of Mass from the Lower Solar AtmosphereSep 07 2011We present and discuss the strong correspondence between evolution of the emission length scale in the lower transition region and in situ measurements of the fast solar wind composition during this most recent solar minimum. We combine recent analyses ... More
MHV-Vertices for Gravity AmplitudesSep 01 2005Dec 13 2005We obtain a CSW-style formalism for calculating graviton scattering amplitudes and prove its validity through the use of a special type of BCFW-like parameter shift. The procedure is illustrated with explicit examples.
Electron and proton heating by solar wind turbulenceJul 23 2009Previous formulations of heating and transport associated with strong magnetohydrodynamic (MHD) turbulence are generalized to incorporate separate internal energy equations for electrons and protons. Electron heat conduction is included. Energy is supplied ... More
Predictions for the First Parker Solar Probe EncounterFeb 08 2019We examine Alfv\'en Wave Solar atmosphere Model (AWSoM) predictions of the first Parker Solar Probe (PSP) encounter. We focus on the 12-day closest approach centered on the 1st perihelion. AWSoM (van der Holst et al., 2014) allows us to interpret the ... More
Laboratory comparison of coronagraphic concepts under dynamical seeing and high-order adaptive optics correctionFeb 15 2011The exoplanetary science through direct imaging and spectroscopy will largely expand with the forthcoming development of new instruments at the VLT (SPHERE), Gemini (GPI), Subaru (HiCIAO), and Palomar (Project 1640) observatories. All these ground-based ... More
Optimized U-MOT for experiments with ultracold atoms near surfacesNov 20 2003We present an integrated wire-based magnetooptical trap for the simplified trapping and cooling of large numbers of neutral atoms near material surfaces. With a modified U-shaped current-carrying Cu structure we collect $>3\times 10^8$ $^{87}$Rb atoms ... More
Compressive Coherent Structures at Ion Scales in the Slow Solar WindApr 26 2016We present a study of magnetic field fluctuations, in a slow solar wind stream, close to ion scales, where an increase of the level of magnetic compressibility is observed. Here, the nature of these compressive fluctuations is found to be characterized ... More
Band-Limited Coronagraphs using a halftone-dot process: II. Advances and laboratory results for arbitrary telescope aperturesNov 29 2011The band-limited coronagraph is a nearly ideal concept that theoretically enables perfect cancellation of all the light of an on-axis source. Over the past years, several prototypes have been developed and tested in the laboratory, and more emphasis is ... More
Maximal Unitarity at Two LoopsAug 04 2011Sep 03 2012We show how to compute the coefficients of the double box basis integrals in a massless four-point amplitude in terms of tree amplitudes. We show how to choose suitable multidimensional contours for performing the required cuts, and derive consistency ... More
Stringent Phenomenological Investigation into Heterotic String Optical UnificationOct 11 2005For the weakly coupled heterotic string (WCHS) there is a well-known factor of twenty conflict between the minimum string coupling unification scale, Lambda_H ~5x10^(17) GeV, and the projected MSSM unification scale, Lambda_U ~ 2.5x10^(16) GeV, assuming ... More
Band-Limited Coronagraphs using a Halftone-dot process: design guidelines, manufacturing, and laboratory resultsOct 07 2009The Exo-Planet Imaging Camera and Spectrograph (EPICS) for the future 42-meter European-Extremely Large Telescope, will enable direct images, and spectra for both young and old Jupiter-mass planets in the infrared. To achieve the required contrast, several ... More
MESS (Multi-purpose Exoplanet Simulation System): A Monte Carlo tool for the statistical analysis and prediction of exoplanets search resultsOct 21 2011The high number of planet discoveries made in the last years provides a good sample for statistical analysis, leading to some clues on the distributions of planet parameters, like masses and periods, at least in close proximity to the host star. We likely ... More
Phases of Thermal N=2 Quiver Gauge TheoriesAug 23 2007Jan 30 2008We consider large N U(N)^M thermal N=2 quiver gauge theories on S^1 x S^3. We obtain a phase diagram of the theory with R-symmetry chemical potentials, separating a low-temperature/high-chemical potential region from a high-temperature/low-chemical potential ... More
Position-space cuts for Wilson line correlatorsMay 11 2015Jun 16 2015We further develop the formalism for taking position-space cuts of eikonal diagrams introduced in [Phys.Rev.Lett. 114 (2015), no. 18 181602, arXiv:1410.5681]. These cuts are applied directly to the position-space representation of any such diagram and ... More
Imaginary parts and discontinuities of Wilson line correlatorsOct 21 2014May 11 2015We introduce a notion of position-space cuts of eikonal diagrams, the set of diagrams appearing in the perturbative expansion of the correlator of a set of straight semi-infinite Wilson lines. The cuts are applied directly to the position-space representation ... More
Uniqueness of two-loop master contoursMay 03 2012Oct 08 2012Generalized-unitarity calculations of two-loop amplitudes are performed by expanding the amplitude in a basis of master integrals and then determining the coefficients by taking a number of generalized cuts. In this paper, we present a complete classification ... More
Electromagnetic waves and electron anisotropies downstream of supercritical interplanetary shocksJul 26 2012We present waveform observations of electromagnetic lower hybrid and whistler waves with f_ci << f < f_ce downstream of four supercritical interplanetary (IP) shocks using the Wind search coil magnetometer. The whistler waves were observed to have a weak ... More
Shocklets, SLAMS, and field-aligned ion beams in the terrestrial foreshockJul 23 2012We present Wind spacecraft observations of ion distributions showing field-aligned beams (FABs) and large-amplitude magnetic fluctuations composed of a series of shocklets and short large-amplitude magnetic structures (SLAMS). We show that the SLAMS are ... More
Design, analysis, and testing of a microdot apodizer for the Apodized Pupil Lyot Coronagraph. II. The dot size impact. (Research Note)Apr 16 2009The Apodized Pupil Lyot Coronagraph (APLC) is a promising coronagraphic device for direct exoplanets detection on the European-Extremely Large Telescope. We present new near-IR laboratory results using binary apodizers -- the so-called microdots apodizer ... More
One-Loop NMHV Amplitudes involving Gluinos and Scalars in N=4 Gauge TheoryJul 18 2005Sep 15 2005We use Supersymmetric Ward Identities and quadruple cuts to generate n-pt NMHV amplitudes involving gluinos and adjoint scalars from purely gluonic amplitudes. We present a set of factors that can be used to generate one-loop NMHV amplitudes involving ... More
Schwinger pair production with ultracold atomsJun 03 2015Aug 08 2016We consider a system of ultracold atoms in an optical lattice as a quantum simulator for electron-positron pair production in quantum electrodynamics (QED). For a setup in one spatial dimension, we investigate the nonequilibrium phenomenon of pair production ... More
Smart TWAP trading in continuous-time equilibriaMar 22 2018Sep 14 2018This paper presents a continuous-time equilibrium model of TWAP trading and liquidity provision in a market with multiple strategic investors with heterogeneous intraday trading targets. We solve the model in closed-form and show there are infinitely ... More
The Luminosity Function at z~8 from 97 Y-band dropouts: Inferences About ReionizationFeb 17 2014Mar 25 2014[Abbreviated] We present the largest search to date for $z\sim8$ Lyman break galaxies (LBGs) based on 350 arcmin$^2$ of HST observations in the V-, Y-, J- and H-bands from the Brightest of Reionizing Galaxies (BoRG) survey. The BoRG dataset includes $\sim$50 ... More
Speckle Temporal Stability in eXtreme Adaptive Optics Coronagraphic ImagesMar 22 2012The major noise source limiting high-contrast imaging is due to the presence of quasi-static speckles. Speckle noise originates from wavefront errors caused by various independent sources, and it evolves on different timescales pending to their nature. ... More
Optimization of Apodized Pupil Lyot Coronagraph for ELTsJul 17 2007We study the optimization of the Apodized Pupil Lyot Coronagraph (APLC) in the context of exoplanet imaging with ground-based telescopes. The APLC combines an apodization in the pupil plane with a small Lyot mask in the focal plane of the instrument. ... More
A non-homogeneous ground state of the low-temperature Sakai-Sugimoto modelApr 12 2011May 31 2011We study the instability of the low-temperature QCD vacuum at large-N_c due to an axial chemical potential, using the holographic Sakai-Sugimoto model. We explicitly construct the ground state of the theory, which corresponds to a translationally non-invariant ... More
Self-Consistent Ion Cyclotron Anisotropy-Beta Relation for Solar Wind ProtonsJul 03 2013We derive a set of self-consistent marginally stable states for a system of ion-cyclotron waves propagating parallel to the large-scale magnetic field through a homogeneous proton-electron plasma. The proton distributions and the wave dispersions are ... More
Interplanetary Nanodust Detection by the Solar Terrestrial Relations Observatory/WAVES Low Frequency ReceiverMar 05 2013New measurements using radio and plasma-wave instruments in interplanetary space have shown that nanometer-scale dust, or nanodust, is a significant contributor to the total mass in interplanetary space. Better measurements of nanodust will allow us to ... More
Synthetic Radio Imaging for Quiescent and CME-flare ScenariosSep 25 2018Radio observations grant access to a wide range of physical processes through different emission mechanisms. These processes range from thermal and quiescent to eruptive phenomena, such as shock waves and particle beams. We present a new synthetic radio ... More
First principles structures and circular dichroism spectra for the close-packed and the 7/2 motif of collagenMay 01 2012May 03 2012The recently proposed close-packed motif for collagen is investigated using first principles semi-empirical wave function theory and Kohn-Sham density functional theory. Under these refinements the close-packed motif is shown to be stable. For the case ... More
Two-Loop Maximal Unitarity with External MassesAug 08 2012Jan 30 2013We extend the maximal unitarity method at two loops to double-box basis integrals with up to three external massive legs. We use consistency equations based on the requirement that integrals of total derivatives vanish. We obtain unique formulae for the ... More
Complete determination of the reflection coefficient in neutron specular reflection by absorptive non-magnetic mediaMay 15 2000Aug 07 2000An experimental method is proposed which allows the complete determination of the complex reflection coefficient for absorptive media for positive and negative values of the momenta. It makes use of magnetic reference layers and is a modification of a ... More
Information and Trading Targets in a Dynamic Market EquilibriumFeb 07 2015Sep 07 2015This paper investigates the equilibrium interactions between trading targets and private information in a multi-period Kyle (1985) market. There are two investors who each follow dynamic trading strategies: A strategic portfolio rebalancer who engages ... More
Maximal Unitarity for the Four-Mass Double BoxAug 21 2013Dec 17 2014We extend the maximal-unitarity formalism at two loops to double-box integrals with four massive external legs. These are relevant for higher-point processes, as well as for heavy vector rescattering, VV -> VV. In this formalism, the two-loop amplitude ... More
An Overview of Maximal Unitarity at Two LoopsDec 10 2012We discuss the extension of the maximal-unitarity method to two loops, focusing on the example of the planar double box. Maximal cuts are reinterpreted as contour integrals, with the choice of contour fixed by the requirement that integrals of total derivatives ... More
Cross-Order Integral Relations from Maximal CutsMar 23 2015May 01 2015We study the ABDK relation using maximal cuts of one- and two-loop integrals with up to five external legs. We show how to find a special combination of integrals that allows the relation to exist, and how to reconstruct the terms with one-loop integrals ... More
Largest eigenvalue distribution in the double scaling limit of matrix models: A Coulomb fluid approachFeb 20 1995Using thermodynamic arguments we find that the probability that there are no eigenvalues in the interval (-s,\infty) in the double scaling limit of Hermitean matrix models is O(exp(-s^{2m+1})) as s\to+\infty.Here m=1,2,3.. determine the m^{th} multi-critical ... More
MHV, CSW and BCFW: field theory structures in string theory amplitudesAug 19 2008Jan 15 2010Motivated by recent progress in calculating field theory amplitudes, we study applications of the basic ideas in these developments to the calculation of amplitudes in string theory. We consider in particular both non-Abelian and Abelian open superstring ... More
Introducing Cadabra: a symbolic computer algebra system for field theory problemsJan 25 2007Jun 14 2007Cadabra is a new computer algebra system designed specifically for the solution of problems encountered in field theory. It has extensive functionality for tensor polynomial simplification taking care of Bianchi and Schouten identities, for fermions and ... More
Comparison of coronagraphs for high contrast imaging in the context of Extremely Large TelescopesSep 17 2008We compare coronagraph concepts and investigate their behavior and suitability for planet finder projects with Extremely Large Telescopes (ELTs, 30-42 meters class telescopes). For this task, we analyze the impact of major error sources that occur in ... More
A field-theory motivated approach to symbolic computer algebraAug 01 2006Jun 12 2007Field theory is an area in physics with a deceptively compact notation. Although general purpose computer algebra systems, built around generic list-based data structures, can be used to represent and manipulate field-theory expressions, this often leads ... More
Simulation of planet detection with the SPHERE IFSMar 24 2011Aims. We present simulations of the perfomances of the future SPHERE IFS instrument designed for imaging extrasolar planets in the near infrared (Y, J, and H bands). Methods. We used the IDL package code for adaptive optics simulation (CAOS) to prepare ... More
Electron energy partition across interplanetary shocks: I. Methodology and Data ProductFeb 04 2019Mar 01 2019Analysis of 15314 electron velocity distribution functions (VDFs) within $\pm$2 hours of 52 interplanetary (IP) shocks observed by the \emph{Wind} spacecraft near 1 AU are introduced. The electron VDFs are fit to the sum of three model functions for the ... More
Dimensional reduction of dual topological theoriesMar 05 1996We describe the reduction from four to two dimensions of the SU(2) Donaldson-Witten theory and the dual twisted Seiberg-Witten theory, i.e. the Abelian topological field theory corresponding to the Seiberg--Witten monopole equations.
Aspects of dualityAug 30 1999This thesis discusses various aspects of duality in quantum field theory and string theory. In the first part we consider duality in topological quantum field theories, concentrating on the Donaldson and Seiberg-Witten theories as (dual) approaches to ... More
Dobrushin conditions for systematic scan with block dynamicsMar 15 2007Jun 12 2007We study the mixing time of systematic scan Markov chains on finite spin systems. It is known that, in a single site setting, the mixing time of systematic scan can be bounded in terms of the influences sites have on each other. We generalise this technique ... More
On systematic scan for sampling H-colourings of the pathJun 26 2007This paper is concerned with sampling from the uniform distribution on H-colourings of the n-vertex path using systematic scan Markov chains. An H-colouring of the n-vertex path is a homomorphism from the n-vertex path to some fixed graph H. We show that ... More
Electron energy partition across interplanetary shocks: I. Methodology and Data ProductFeb 04 2019Analysis of 15314 electron velocity distribution functions (VDFs) within $\pm$2 hours of 52 interplanetary (IP) shocks observed by the \emph{Wind} spacecraft near 1 AU are introduced. The electron VDFs are fit to the sum of three model functions for the ... More
Speckle temporal stability in XAO coronagraphic images II. Refine model for quasi-static speckle temporal evolution for VLT/SPHEREFeb 28 2013Observing sequences have shown that the major noise source limitation in high-contrast imaging is due to the presence of quasi-static speckles. The timescale on which quasi-static speckles evolve, is determined by various factors, among others mechanical ... More
Collisional Thermalization of Hydrogen and Helium in Solar Wind PlasmaNov 21 2013In situ observations of the solar wind frequently show the temperature of $\alpha$-particles (fully ionized helium), $T_\alpha$, to significantly differ from that of protons (ionized hydrogen), $T_p$. Many heating processes in the plasma act preferentially ... More
Empirical Constraints on Proton and Electron Heating in the Fast Solar WindJul 15 2009We analyze measured proton and electron temperatures in the high-speed solar wind in order to calculate the separate rates of heat deposition for protons and electrons. When comparing with other regions of the heliosphere, the fast solar wind has the ... More
Selecting Quasars by their Intrinsic VariabilityFeb 12 2010Sep 22 2010We present a new and simple technique for selecting extensive, complete and pure quasar samples, based on their intrinsic variability. We parametrize the single-band variability by a power-law model for the light-curve structure function, with amplitude ... More
Complete sets of logarithmic vector fields for integration-by-parts identities of Feynman integralsDec 26 2017Aug 01 2018Integration-by-parts identities between loop integrals arise from the vanishing integration of total derivatives in dimensional regularization. Generic choices of total derivatives in the Baikov or parametric representations lead to identities which involve ... More
Limits on Alpha Particle Temperature Anisotropy and Differential Flow from Kinetic Instabilities: Solar Wind ObservationsSep 16 2013Sep 19 2013Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure-anisotropy-driven instabilities such as the Alfv\'en/ion-cyclotron (A/IC) and ... More
Design, analysis and test of a microdots apodizer for the Apodized Pupil Lyot CoronagraphOct 31 2008Coronagraphic techniques are required to detect exoplanets with future Extremely Large Telescopes. One concept, the Apodized Pupil Lyot Coronagraph (APLC), is combining an apodizer in the entrance aperture and a Lyot opaque mask in the focal plane. This ... More
Persistent Supercurrent Atom ChipFeb 06 2007Rubidium 87 atoms are trapped in an Ioffe-Pritchard potential generated with a persistent supercurrent that flows in a loop circuit patterned on a sapphire surface. The superconducting circuit is a closed loop made of 100 micro meter wide MBE-grown MgB2 ... More
Performance of prototype BTeV silicon pixel detectors in a high energy pion beamAug 07 2001Aug 08 2001The silicon pixel vertex detector is a key element of the BTeV spectrometer. Sensors bump-bonded to prototype front-end devices were tested in a high energy pion beam at Fermilab. The spatial resolution and occupancies as a function of the pion incident ... More
Beam Test Results of the BTeV Silicon Pixel DetectorSep 07 2000The results of the BTeV silicon pixel detector beam test carried out at Fermilab in 1999-2000 are reported. The pixel detector spatial resolution has been studied as a function of track inclination, sensor bias, and readout threshold.
Beam Test of BTeV Pixel DetectorsNov 21 2000The silicon pixel vertex detector is one of the key elements of the BTeV spectrometer. Detector prototypes were tested in a beam at Fermilab. We report here on the measured spatial resolution as a function of the incident angles for different sensor-readout ... More
[Plasma 2020 Decadal] Multipoint Measurements of the Solar Wind: A Proposed Advance for Studying Magnetized TurbulenceMar 13 2019A multi-institutional, multi-national science team will soon submit a NASA proposal to build a constellation of spacecraft to fly into the near-Earth solar wind in a swarm spanning a multitude of scales in order to obtain critically needed measurements ... More
Implementing quantum electrodynamics with ultracold atomic systemsAug 11 2016We discuss the experimental engineering of model systems for the description of QED in one spatial dimension via a mixture of bosonic $^{23}$Na and fermionic $^6$Li atoms. The local gauge symmetry is realized in an optical superlattice, using heteronuclear ... More
Stability Properties of the Starobinsky Cosmological ModelOct 21 1994We discuss the instabilities appearing in the cosmological model with a quasi de Sitter phase following from a fourth-order gravity theory. Both the classical equation as well as the quantization in form of a Wheeler - De Witt equation are conformally ... More
L'-band AGPM vector vortex coronagraph's first light on VLT/NACO: Discovery of a late-type companion at two beamwidths from an F0V starApr 03 2013Context. High contrast imaging has thoroughly combed through the limited search space accessible with first-generation ground-based adaptive optics instruments and the Hubble Space Telescope. Only a few objects were discovered, and many non-detections ... More
Robust entanglement generation by reservoir engineeringMar 21 2012Following a recent proposal [C. Muschik et. al., Phys. Rev. A 83, 052312 (2011)], engineered dissipative processes have been used for the generation of stable entanglement between two macroscopic atomic ensembles at room temperature [H. Krauter et. al., ... More
Complete integration-by-parts reductions of the non-planar hexagon-box via module intersectionsMay 04 2018Jun 24 2018We present the powerful module-intersection integration-by-parts (IBP) method, suitable for multi-loop and multi-scale Feynman integral reduction. Utilizing modern computational algebraic geometry techniques, this new method successfully trims traditional ... More
Coronagraphic observations of Fomalhaut at solar system scalesDec 06 2012We report on a search for low mass companions within 10 AU of the star Fomalhaut, using narrow band observations at 4.05 microns obtained with the Apodizing Phase Plate (APP) coronagraph on the VLT/NaCo. Our observations place a model dependent upper ... More
A computational hierarchy in human cortexSep 07 2017Hierarchies feature prominently in anatomical accounts of cortical organisation. An open question is which computational (algorithmic) processes are implemented by these hierarchies. One renowned hypothesis is that cortical hierarchies implement a model ... More
The ERIS Adaptive Optics SystemJul 23 2016ERIS is the new AO instrument for VLT-UT4 led by a Consortium of Max-Planck Institut fuer Extraterrestrische Physik, UK-ATC, ETH-Zurich, ESO and INAF. The ERIS AO system provides NGS mode to deliver high contrast correction and LGS mode to extend high ... More
SINFONI - Integral Field Spectroscopy at 50 milli-arcsecond resolution with the ESO VLTJun 10 2003Jun 11 2003SINFONI is an adaptive optics assisted near-infrared integral field spectrometer for the ESO VLT. The Adaptive Optics Module (built by the ESO Adaptive Optics Group) is a 60-elements curvature-sensor based system, designed for operations with natural ... More
DecreaseKeys are Expensive for External Memory Priority QueuesNov 03 2016One of the biggest open problems in external memory data structures is the priority queue problem with DecreaseKey operations. If only Insert and ExtractMin operations need to be supported, one can design a comparison-based priority queue performing $O((N/B)\lg_{M/B} ... More
Loop and spin foam quantum gravity: a brief guide for beginnersJan 18 2006Feb 16 2006We review aspects of loop quantum gravity and spin foam models at an introductory level, with special attention to questions frequently asked by non-specialists.
The semantic mapping of words and co-words in contextsNov 23 2010Jan 29 2011Meaning can be generated when information is related at a systemic level. Such a system can be an observer, but also a discourse, for example, operationalized as a set of documents. The measurement of semantics as similarity in patterns (correlations) ... More
Motion on moduli spaces with potentialsJul 19 2001Jan 10 2002In the limit of small velocities, the dynamics of half-BPS Yang-Mills-Higgs solitons can be described by the geodesic approximation. Recently, it has been shown that quarter-BPS states require the addition of a potential term to this approximation. We ... More
Holographic dynamics of unstable branes in AdSDec 08 2004The gauge theory dual to the decay of an unstable D-particle in AdS is analysed in terms of coherent states. We discuss in detail how to count the number of particles in the decay product. We find, in agreement with the analysis in flat space, that the ... More
On utility maximization under convex portfolio constraintsFeb 02 2011Feb 22 2013We consider a utility-maximization problem in a general semimartingale financial model, subject to constraints on the number of shares held in each risky asset. These constraints are modeled by predictable convex-set-valued processes whose values do not ... More
Stability of utility-maximization in incomplete marketsJun 04 2007The effectiveness of utility-maximization techniques for portfolio management relies on our ability to estimate correctly the parameters of the dynamics of the underlying financial assets. In the setting of complete or incomplete financial markets, we ... More
Pair-correlation analysis of HD 10180 reveals a possible planetary orbit at about 0.92 AUSep 28 2010The pair-correlations between the positions of the six known planets in the exoplanetary system HD 10180 are studied. There are six non-trivial and almost equally spaced peaks. This demonstrates longer-ranged positional order between the orbits and suggests ... More
The ancient art of laying ropeApr 06 2010Aug 08 2010We describe a geometrical property of helical structures and show how it accounts for the early art of ropemaking. Helices have a maximum number of rotations that can be added to them -- and it is shown that this is a geometrical feature, not a material ... More
The geometrical origin of the strain-twist coupling in double helicesMar 28 2010May 07 2010The geometrical coupling between strain and twist in double helices is investigated. Overwinding, where strain leads to further winding, is shown to be a universal property for helices, which are stretched along their longitudinal axis when the initial ... More
Design of the LBNF Beamline Target StationDec 21 2016The Long Baseline Neutrino Facility (LBNF) project will build a beamline located at Fermilab to create and aim an intense neutrino beam of appropriate energy range toward the DUNE detectors at the SURF facility in Lead, South Dakota. Neutrino production ... More
The Color Variability of QuasarsSep 29 2011Nov 06 2011We quantify quasar color-variability using an unprecedented variability database - ugriz photometry of 9093 quasars from SDSS Stripe 82, observed over 8 years at ~60 epochs each. We confirm previous reports that quasars become bluer when brightening. ... More
Entanglement generated by dissipation and steady state entanglement of two macroscopic objectsJun 22 2010Sep 12 2011Entanglement is a striking feature of quantum mechanics and an essential ingredient in most applications in quantum information. Typically, coupling of a system to an environment inhibits entanglement, particularly in macroscopic systems. Here we report ... More
The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits: II- Survey description, results and performancesMay 07 2014In anticipation of the VLT/SPHERE planet imager guaranteed time programs, we have conducted a preparatory survey of 86 stars between 2009 and 2013 in order to identify new faint comoving companions to ultimately carry out a comprehensive analysis of the ... More
Probabilistic modelling of gait for remote passive monitoring applicationsDec 04 2018Jan 30 2019Passive and non-obtrusive health monitoring using wearables can potentially bring new insights into the user's health status throughout the day and may support clinical diagnosis and treatment. However, identifying segments of free-living data that sufficiently ... More
Adaptive Optics for AstronomyJan 27 2012Adaptive Optics is a prime example of how progress in observational astronomy can be driven by technological developments. At many observatories it is now considered to be part of a standard instrumentation suite, enabling ground-based telescopes to reach ... More
Horizon dependence of utility optimizers in incomplete modelsJun 25 2010Oct 01 2010This paper studies the utility maximization problem with changing time horizons in the incomplete Brownian setting. We first show that the primal value function and the optimal terminal wealth are continuous with respect to the time horizon $T$. Secondly, ... More