Results for "Eric Nielsen"

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Characterization of lemniscate atmospheric aberrations in Gemini Planet Imager dataJul 18 2018A semi analytic framework for simulating the effects of atmospheric seeing in Adaptive Optics systems on an 8-m telescope is developed with the intention of understanding the origin of the wind-butterfly, a characteristic two-lobed halo in the PSF of ... More
Trigonometric quasi-greedy bases for $L^p(\bT;w)$Nov 28 2006We give a complete characterization of $2\pi$-periodic weights $w$ for which the usual trigonometric system forms a quasi-greedy basis for $L^p(\bT;w)$, i.e., bases for which simple thresholding approximants converge in norm. The characterization implies ... More
The Domain Walls of Gauged Maximal Supergravities and their M-theory OriginApr 14 2004May 28 2004We consider gauged maximal supergravities with CSO(p,q,r) gauge groups and their relation to the branes of string and M-theory. The gauge groups are characterised by n mass parameters, where n is the transverse dimension of the brane. We give the scalar ... More
A Uniform Analysis of 118 Stars with High-Contrast Imaging: Long Period Extrasolar Giant Planets are Rare around Sun-like StarsSep 24 2009We expand on the results of Nielsen et al. (2008), using the null result for giant extrasolar planets around the 118 target stars from the VLT NACO H and Ks band planet search (Masciadri et al. 2005), the VLT and MMT Simultaneous Differential Imaging ... More
Domain Walls and the Creation of StringsMar 28 2003May 27 2003The phenomenon of creation of strings, occurring when particles pass through a domain wall and related to the Hanany-Witten effect via dualities, is discussed in ten and nine dimensions. We consider both the particle actions in massive backgrounds as ... More
A Bayesian Framework for Exoplanet Direct Detection and Non-DetectionSep 21 2018Rigorously quantifying the information in high contrast imaging data is important for informing follow-up strategies to confirm the substellar nature of a point source, constraining theoretical models of planet-disk interactions, and deriving planet occurrence ... More
Instanton constraints in supersymmetric gauge theories II. N=2 Yang-Mills theoryMar 15 2005The analysis in previous publications of the instanton constraints required to produce a finite action of the theory is carried out also for N=2 supersymmetric Yang-Mills theory.
SSSC-AM: A Unified Framework for Video Co-Segmentation by Structured Sparse Subspace Clustering with Appearance and Motion FeaturesMar 14 2016Sep 28 2016Video co-segmentation refers to the task of jointly segmenting common objects appearing in a given group of videos. In practice, high-dimensional data such as videos can be conceptually thought as being drawn from a union of subspaces corresponding to ... More
Asymptotics for the ruin time of a piecewise exponential Markov process with jumpsAug 31 2016In this paper a class of Ornstein--Uhlenbeck processes driven by compound Poisson processes is considered. The jumps arrive with exponential waiting times and are allowed to be two-sided. The jumps are assumed to form an iid sequence with distribution ... More
Transient Quintessence from Group Manifold Reductions or how all roads lead to RomeDec 10 2003Jan 08 2004We investigate the accelerating phases of cosmologies supported by a metric, scalars and a single exponential scalar potential. The different solutions can be represented by trajectories on a sphere and we find that quintessence happens within the "arctic ... More
Watching coherent molecular structural dynamics during photoreaction: beyond kinetic descriptionNov 04 2015Nov 13 2015A deep understanding of molecular photo-transformations is challenging because of the complex interaction between the configurations of electrons and nuclei. An initial optical excitation dissipates energy into electronic and structural degrees of freedom, ... More
Entropy stable wall boundary conditions for the three-dimensional compressible Navier-Stokes equationsNov 18 2014Nov 27 2014Non-linear entropy stability and a summation-by-parts framework are used to derive entropy stable wall boundary conditions for the three-dimensional compressible Navier--Stokes equations. A semi-discrete entropy estimate for the entire domain is achieved ... More
On non-stationary solutions to MSDDEs: representations and the cointegration spaceMar 05 2019In this paper we study solutions to multivariate stochastic delay differential equations (MSDDEs) which have stationary increments, and we show that this modeling framework is in many ways similar to the discrete-time cointegrated VAR model. In particular, ... More
AI Meets Austen: Towards Human-Robot Discussions of Literary MetaphorApr 07 2019Artificial intelligence is revolutionizing formal education, fueled by innovations in learning assessment, content generation, and instructional delivery. Informal, lifelong learning settings have been the subject of less attention. We provide a proof-of-concept ... More
The maximum theoretical performance of unconcentrated solar photovoltaic and thermoelectric generator systemsSep 18 2017Nov 14 2017The maximum efficiency for photovoltaic (PV) and thermoelectric generator (TEG) systems without concentration is investigated. Both a combined system where the TEG is mounted directly on the back of the PV and a tandem system where the incoming sunlight ... More
Fully Simulatable Quantum-Secure Coin-Flipping and ApplicationsFeb 04 2011Jun 23 2011We propose a coin-flip protocol which yields a string of strong, random coins and is fully simulatable against poly-sized quantum adversaries on both sides. It can be implemented with quantum-computational security without any set-up assumptions, since ... More
A Characterization of Sparse Nonstationary Gabor ExpansionsJun 28 2016Apr 19 2017We investigate the problem of constructing sparse time-frequency representations with flexible frequency resolution, studying the theory of nonstationary Gabor frames in the framework of decomposition spaces. Given a painless nonstationary Gabor frame, ... More
Weighted Thresholding and Nonlinear ApproximationNov 06 2017We present a new method for performing nonlinear approximation with redundant dictionaries. The method constructs an $m-$term approximation of the signal by thresholding with respect to a weighted version of its canonical expansion coefficients, thereby ... More
Limit theorems for quadratic forms and related quantities of discretely sampled continuous-time moving averagesJul 04 2018Aug 17 2018The limiting behavior of Toeplitz type quadratic forms of stationary processes has received much attention through decades, particularly due to its importance in statistical estimation of the spectrum. In the present paper we study such quantities in ... More
The Origins Space Telescope: Towards An Understanding of Temperate Planetary AtmospheresMar 21 2018The Origins Space Telescope (OST) is one of four mission concepts currently being studied by NASA in preparation for the Astrophysics 2020 Decadal Survey. With active cooling (~4 K), OST will be sensitive in mid- to far-IR wavelengths, using imaging and ... More
Lessons for WFIRST CGI from ground-based high-contrast systemsJan 13 2019The Coronagraph Instrument (CGI) for NASA's Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to ... More
New Photometry and Spectra of AB Doradus C: An Accurate Mass Determination of a Young Low-Mass Object with Theoretical Evolutionary TracksMar 21 2007We present new photometric and spectroscopic measurements for the unique, young, low-mass evolutionary track calibrator AB Dor C. While the new Ks photometry is similar to that previously published in Close et al. (2005) the spectral type is found to ... More
A Reflective Gaussian Coronagraph for ExAO: Laboratory PerformanceOct 21 2006Oct 24 2006We report laboratory results of a coronagraphic test bench to assess the intensity reduction differences between a "Gaussian" tapered focal plane coronagraphic mask and a classical hard-edged "Top Hat" function mask at Extreme Adaptive Optics (ExAO) Strehl ... More
The Gemini NICI Planet-Finding Campaign : Discovery of a Substellar L Dwarf Companion to the Nearby Young M Dwarf CD-35 2722Jan 14 2011Jan 18 2011We present the discovery of a wide (67 AU) substellar companion to the nearby (21 pc) young solar-metallicity M1 dwarf CD-35 2722, a member of the ~100 Myr AB Doradus association. Two epochs of astrometry from the NICI Planet-Finding Campaign confirm ... More
Imaging Cool Giant Planets in Reflected Light: Science Investigations and Synergy with Habitable PlanetsMar 22 2019Mar 26 2019Planned astronomical observatories of the 2020s will be capable of obtaining reflected light photometry and spectroscopy of cool extrasolar giant planets. Here we explain that such data are valuable both for understanding the origin and evolution of giant ... More
Improved age constraints for the AB Dor quadruple system - The binary nature of AB Dor BNov 20 2006We present resolved NACO photometry of the close binary AB Dor B in H- and Ks-band. AB Dor B is itself known to be a wide binary companion to AB Dor A, which in turn has a very low-mass close companion named AB Dor C. These four known components make ... More
Very high contrast IFU spectroscopy of AB Doradus C: 9 mag contrast at 0.2" without a coronagraph using spectral deconvolutionMar 21 2007We present an extension of the spectral deconvolution method (Sparks & Ford 2002) to achieve very high contrast at small inner working radii. We apply the method to the specific case of ground based adaptive optics fed integral field spectroscopy (without ... More
TensorFlow.js: Machine Learning for the Web and BeyondJan 16 2019Feb 28 2019TensorFlow.js is a library for building and executing machine learning algorithms in JavaScript. TensorFlow.js models run in a web browser and in the Node.js environment. The library is part of the TensorFlow ecosystem, providing a set of APIs that are ... More
The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets Around Debris Disk StarsJul 02 2013We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.5" and 14.1 mag at 1" separation. Follow-up ... More
The Gemini NICI Planet-Finding CampaignAug 23 2010Our team is carrying out a multi-year observing program to directly image and characterize young extrasolar planets using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1-meter telescope. NICI is the first instrument on a large telescope ... More
The Bianchi Classification of Maximal D=8 Gauged SupergravitiesJun 19 2003Aug 26 2003We perform the generalised dimensional reduction of D=11 supergravity over three-dimensional group manifolds as classified by Bianchi. Thus, we construct eleven different maximal D=8 gauged supergravities, two of which have an additional parameter. One ... More
The Demographics and Atmospheres of Giant Planets with the ELTsMar 14 2019Gas giants are the most readily detectable exoplanets but fundamental questions about their system architectures, formation, migration, and atmospheres have been unanswerable with the current generation of ground- and space-based facilities. The dominant ... More
Constraints on Extrasolar Planet Populations from VLT NACO/SDI and MMT SDI and Direct Adaptive Optics Imaging Surveys: Giant Planets are Rare at Large SeparationsJun 28 2007Oct 10 2007We examine the implications for the distribution of extrasolar planets based on the null results from two of the largest direct imaging surveys published to date. Combining the measured contrast curves from 22 of the stars observed with the VLT NACO adaptive ... More
Information geometries and Microeconomic TheoriesJan 16 2009More than thirty years ago, Charnes, Cooper and Schinnar (1976) established an enlightening contact between economic production functions (EPFs) -- a cornerstone of neoclassical economics -- and information theory, showing how a generalization of the ... More
Magellan Adaptive Optics first-light observations of the exoplanet $β$ Pic b. I. Direct imaging in the far-red optical with MagAO+VisAO and in the near-IR with NICIMar 03 2014We present the first ground-based CCD ($\lambda < 1\mu$m) image of an extrasolar planet. Using MagAO's VisAO camera we detected the extrasolar giant planet (EGP) $\beta$ Pictoris b in $Y$-short ($Y_S$, 0.985 $\mu$m), at a separation of $0.470 \pm 0.010''$ ... More
The Spectrum of Darkonium in the SunJul 01 2016Dark matter that gets captured in the Sun may form positronium-like bound states if it self-interacts via light dark photons. In this case, dark matter can either annihilate to dark photons or recombine in bound states which subsequently also decay to ... More
Instanton constraints and renormalizationApr 21 2005The renormalization is investigated of one-loop quantum fluctuations around a constrained instanton in $\phi ^4$-theory with negative coupling. It is found that the constraint should be renormalized also. This indicates that in general only renormalizable ... More
Physical Interpretation of Cylindrically Symmetric Static Gravitational FieldsMay 15 1997The explicit relationship is determined between the interior properties of a static cylindrical matter distribution and the metric of the exterior space-time according to Einstein gravity for space-time dimensionality larger or equal to four. This is ... More
Lévy processes in storage and inventory problemsMar 24 2013Apr 14 2013In this paper we consider storage and inventory systems. Our aim is to apply and review main results of the fluctuation theory of stochastic processes in the context of storage and inventory modeling. We describe systems where the inflow is due to a L\'evy ... More
Nonnegative minors of minor matricesJan 07 2011Feb 08 2012Using the relationship between totally nonnegative matrices and directed acyclic weighted planar networks, we show that $2\times 2$ minors of minor matrices of totally nonnegative matrices are also nonnegative. We give a combinatorial interpretation for ... More
Video Extrapolation with an Invertible Linear EmbeddingMar 01 2019We predict future video frames from complex dynamic scenes, using an invertible neural network as the encoder of a nonlinear dynamic system with latent linear state evolution. Our invertible linear embedding (ILE) demonstrates successful learning, prediction ... More
Mathematical Properties of Dynamic Systems and the Foundations of Quantum TheoryJun 11 2011Sep 29 2016While it is almost universally accepted that quantum theory is strange, and that the world view it implies is elusive, there is considerably less consensus as to why this is the case. This article will explore the possibility that part of the reason the ... More
Anderson's considerations on the flow of superfluid helium: some offshootsJun 21 2014Apr 17 2015Nearly five decades have elapsed since the seminal 1966 paper of P.W. Anderson on the flow of superfluid helium, $^4$He at that time. Some of his "Considerations" -- the role of the quantum phase as a dynamical variable, the interplay between the motion ... More
Eulerian series as modular forms revisitedApr 15 2013Jun 04 2014Recently, Bringmann, Ono, and Rhoades employed harmonic weak Maass forms to prove results on Eulerian series as modular forms. By changing the setting to Appell--Lerch sums, we shorten the proof of one of their main theorems. In addition we discuss connections ... More
Threefield identities and simultaneous representations of primes by binary quadratic formsAug 07 2012Kaplansky [2003] proved a theorem on the simultaneous representation of a prime $p$ by two different principal binary quadratic forms. Later, Brink found five more like theorems and claimed that there were no others. By putting Kaplansky-like theorems ... More
The Role of Electrical and Thermal Contact Resistance for Joule Breakdown of Single-Wall Carbon NanotubesMay 13 2008Several data sets of electrical breakdown in air of single-wall carbon nanotubes (SWNTs) on insulating substrates are collected and analyzed. A universal scaling of the Joule breakdown power with nanotube length is found, which appears independent of ... More
Locomotion in complex fluids: Integral theoremsOct 15 2014The biological fluids encountered by self-propelled cells display complex microstructures and rheology. We consider here the general problem of low-Reynolds number locomotion in a complex fluid. {Building on classical work on the transport of particles ... More
Apparent slip due to the motion of suspended particles in flows of electrolyte solutionsMar 02 2004We consider pressure-driven flows of electrolyte solutions in small channels or capillaries in which tracer particles are used to probe velocity profiles. Under the assumption that the double layer is thin compared to the channel dimensions, we show that ... More
Continuous breakdown of Purcell's scallop theorem with inertiaJun 25 2007Purcell's scallop theorem defines the type of motions of a solid body - reciprocal motions - which cannot propel the body in a viscous fluid with zero Reynolds number. For example, the flapping of a wing is reciprocal and, as was recently shown, can lead ... More
Floppy swimming: Viscous locomotion of actuated elasticaOct 05 2006May 07 2007Actuating periodically an elastic filament in a viscous liquid generally breaks the constraints of Purcell's scallop theorem, resulting in the generation of a net propulsive force. This observation suggests a method to design simple swimming devices - ... More
Quantum Correlations in Large-Dimensional States of High SymmetryOct 13 2011May 23 2012In this article, we investigate how quantum correlations behave for the so-called Werner and pseudo-pure families of states. The latter refers to states formed by mixing any pure state with the totally mixed state. We derive closed expressions for the ... More
Power-law tail distributions and nonergodicityMay 27 2004May 28 2004We establish an explicit correspondence between ergodicity breaking in a system described by power-law tail distributions and the divergence of the moments of these distributions.
Non-Markovian Beables vs. Massive ParallelismMar 16 2010A simple dynamical model over a discrete classical state space is presented. In a certain limit, it reduces to one in a class of models subsuming Bell's field-theoretic version of Bohmian mechanics. But it exhibits the massive parallelism native to quantum ... More
Aging in the trap model as a relaxation further away from equilibriumOct 17 2012The aging regime of the trap model, observed for a temperature T below the glass transition temperature T_g, is a prototypical example of non-stationary out-of-equilibrium state. We characterize this state by evaluating its "distance to equilibrium", ... More
Global fluctuations and Gumbel statisticsJun 07 2005Oct 18 2005We explain how the statistics of global observables in correlated systems can be related to extreme value problems and to Gumbel statistics. This relationship then naturally leads to the emergence of the generalized Gumbel distribution G_a(x), with a ... More
Density waves in the inner parts of disk galaxiesJan 11 2002Density waves in the central kpc of galaxies, taking the form of spirals, bars and/or lopsided density distributions, are potential actors of the redistribution of angular momentum. They may thus play an important role in the overall evolution of the ... More
Recent developments in heterotic compactificationsJan 26 2008In this short review, we outline three sets of developments in understanding heterotic string compactifications. First, we outline recent progress in heterotic analogues of quantum cohomology computations. Second, we discuss a potential swampland issue ... More
Intégralité des coefficients de Taylor de racines d'applications miroirDec 10 2010We prove the integrality of the Taylor coefficients of roots of mirror maps at the origin. By mirror maps, we mean formal power series z.exp(G(z)/F(z)), where F(z) and G(z)+log(z)F(z) are particular solutions of certain generalized hypergeometric differential ... More
Dynkin Diagrams of ${CP}^1$ OrbifoldsApr 27 1993We investigate $N=2$ supersymmetric sigma model orbifolds of the sphere in the large radius limit. These correspond to $N=2$ superconformal field theories. Using the equations of topological-anti-topological fusion for the topological orbifold, we compute ... More
i-MARK: A New Subtraction Division GameSep 14 2015Nov 09 2015Given two finite sets of integers $S\subseteq\NNN\setminus\{0\}$ and $D\subseteq\NNN\setminus\{0,1\}$,the impartial combinatorial game $\IMARK(S,D)$ is played on a heap of tokens. From a heap of $n$ tokens, each player can moveeither to a heap of $n-s$ ... More
Tropical Realization Spaces for Polyhedral ComplexesAug 11 2010Jun 15 2012Tropicalization is a procedure that assigns polyhedral complexes to algebraic subvarieties of a torus. If one fixes a weighted polyhedral complex, one may study the set of all subvarieties of a toric variety that have that complex as their tropicalization. ... More
On estimates for the $\displaystyle \bar \partial $ equation in Stein manifoldsFeb 03 2016Feb 17 2016We generalize to intersection of strictly $c$ -convex domains in Stein manifold, $ L^{r}-L^{s}$ and Lipschitz estimates for the solutions of the $ \bar \partial $ equation done by Ma and Vassiliadou for domains in $ {\mathbb{C}}^{n}.$ For this we use ... More
A subordination Principle. ApplicationsMay 10 2011Jan 14 2014The subordination principle states roughly : if a property is true for Hardy spaces in some kind of domains in $C^n$ then it is also true for the Bergman spaces of the same kind of domains in $C^{n-1}$. We give applications of this principle to Bergman-Carleson ... More
On separated Carleson sequences in the unit disc of ${\mathbb{C}}.$Sep 19 2011Sep 18 2012The interpolating sequences for $H^{\infty}({\mathbb{D}}),$ the bounded holomorphic function in the unit disc ${\mathbb{D}}$ of the complex plane ${\mathbb{C}},$ {\small where characterised by L. Carleson by metric conditions on the points. They are also ... More
Broken causal lens rigidity and sky shadow rigidity of Lorentzian manifoldsDec 16 2015Aug 25 2016We prove that the topology, smooth structure, and metric of a compact Lorentzian manifold with boundary is uniquely determined by data at the boundary. The data consists of the lengths and directions of future-directed once-broken geodesics connecting ... More
What is the theoretical time precision achievable using a dCFD algorithm ?Jun 16 2016The time precision achievable using standard analog methods is well known. Several expressions for timing methods using digitized signals have been recently proposed in workshops, conferences or training courses. Most of them are only partially exact. ... More
Analysis and Calibration of Natural Guide Star Adaptive Optics DataJan 30 1996From natural guide star adaptive optics data taken with the Come-On Plus and with the Starfire Optical Range Generation II instruments in the JHK bands and in the I band respectively, we describe and analyse the point spread function. The ultimate exploitation ... More
Pseudo Harmonic MorphismsAug 09 1996We study a geometrical condition (PHWC) which is weaker than horizontal weak conformality. In particular, we show that harmonic maps satisfying this condition, which will be called {\em pseudoharmonic morphisms}, include harmonic morphisms and can be ... More
Counting d-polytopes with d+3 verticesNov 18 2005We completely solve the problem of enumerating combinatorially inequivalent $d$-dimensional polytopes with $d+3$ vertices. A first solution of this problem, by Lloyd, was published in 1970. But the obtained counting formula was not correct, as pointed ... More
Gram Charlier and Edgeworth expansion for sample varianceSep 18 2018In this paper, we derive a valid Edgeworth expansions for the Bessel corrected empirical variance when data are generated by a strongly mixing process whose distribution can be arbitrarily. The constraint of strongly mixing process makes the problem not ... More
On regions of convergence of quaternionic hyperholomorphic functionsSep 17 2018Nov 25 2018We extend the theorem of Cauchy-Hadamard and the theorem of Abel on convergence of series to quaternionic analysis with the Fueter Operator and the Moisil Theodoresco operator. We find a region of convergence that is more than two times bigger than the ... More
T-statistic for Autoregressive processSep 11 2018In this paper, we discuss the distribution of the t-statistic under the assumption of normal autoregressive distribution for the underlying discrete time process. This result generalizes the classical result of the traditional t-distribution where the ... More
Sobolev embeddings with weights in complete riemannian manifoldsFeb 21 2019We prove Sobolev embedding Theorems with weights for vector bundles in a complete riemannian manifold. As a consequence, under geometric hypotheses, we improve some "classical" Sobolev embedding Theorems for vector bundles in a complete riemannian manifold. ... More
Cyclic Sieving, Necklaces, and BraceletsDec 11 2018Mar 17 2019We split the q-Schr\"oder numbers into an "even" and "odd" part. The Schr\"oder numbers are known to enumerate certain necklaces, and the even part turns out to be a $q$-analogue for the set of bracelets. The even and odd parts are symmetric and unimodal, ... More
Kalman filter demystified: from intuition to probabilistic graphical model to real case in financial marketsNov 28 2018Dec 13 2018In this paper, we revisit the Kalman filter theory. After giving the intuition on a simplified financial markets example, we revisit the maths underlying it. We then show that Kalman filter can be presented in a very different fashion using graphical ... More
Pairwise Quasar Correlations and Bell's InequalityNov 01 2018Dec 07 2018Viewing two sources at sufficient distance and angular separation can assure, by light-travel-time arguments, the acausality of their emitted photons. Using these photons to set apparatus parameters in a laboratory-based quantum-mechanical experiment ... More
The Big Bang is a Coordinate Singularity for $k = -1$ Inflationary FLRW SpacetimesOct 16 2018Jan 30 2019We show the big bang is a coordinate singularity for a large class of $k = -1$ inflationary FLRW spacetimes which we have dubbed 'Milne-like.' By introducing a new set of coordinates, the big bang appears as a past boundary of the universe where the metric ... More
The Integral Chow Ring of $\bar{M}_2$Apr 17 2019In this paper we compute the Chow ring of the moduli stack $\bar{M}_2$ of stable curves of genus 2 with integral coefficients.
Scanning for time: Science and art on a photocopierDec 22 2018Combine the scanning properties of a common office photocopier with an object in motion to create stunning imagery. Produce a scan or hard copy that records the artifact of two motions, the moving object and the moving photocopier scan bar. Images illustrate ... More
Quenched asymptotics for interacting diffusions on inhomogeneous random graphsNov 22 2018Mar 29 2019The aim of the paper is to address the behavior in large population of diffusions interacting on a random, possibly diluted and inhomogeneous graph. This is the natural continuation of a previous work, where the homogeneous Erd\H os-R\'enyi case was considered. ... More
Intermittent turbulent dynamo at very low and high magnetic Prandtl numbersSep 20 2011Nov 09 2011Context: Direct numerical simulations have shown that the dynamo is efficient even at low Prandtl numbers, i.e., the critical magnetic Reynolds number Rm_c necessary for the dynamo to be efficient becomes smaller than the hydrodynamic Reynolds number ... More
Density-matrix renormalization group methods for momentum- and frequency-resolved dynamical correlation functionsAug 19 2008Several density-matrix renormalization group methods have been proposed to compute the momentum- and frequency-resolved dynamical correlation functions of low-dimensional strongly correlated systems. The most relevant approaches are discussed in this ... More
Identification of significant features in DNA microarray dataApr 13 2013DNA microarrays are a relatively new technology that can simultaneously measure the expression level of thousands of genes. They have become an important tool for a wide variety of biological experiments. One of the most common goals of DNA microarray ... More
Construction of initial data for 3+1 numerical relativityApr 02 2007Nov 07 2007This lecture is devoted to the problem of computing initial data for the Cauchy problem of 3+1 general relativity. The main task is to solve the constraint equations. The conformal technique, introduced by Lichnerowicz and enhanced by York, is presented. ... More
Bar-driven fueling of galactic nuclei: a 2D viewSep 27 2004I discuss evidences for bar-driven gas fueling in the central regions of galaxies, focusing on scales down to about 10 pc. I thus mention the building of inner disks, and the link with resonances, as well as the corresponding kinematic signatures such ... More
Integral Field Spectrographs: a user's viewSep 25 2007We easily tend to think of Integral-Field Spectrographs (IFS) along two opposing trends: as either the beautiful combination between photometry and spectroscopy, or as our worst nightmare including the dark side of both worlds. I favour a view where each ... More
Secular evolution in the central regions of galaxiesSep 10 2001In this paper, I mention a few processes which may play a role in the evolution of the central regions of galaxies. In this context, I briefly discuss some issues regarding the formation of bulges in spirals, the role of supermassive black holes, and ... More
Discrete Torsion, Quotient Stacks, and String OrbifoldsOct 15 2001This is the writeup of a lecture given at the May Wisconsin workshop on mathematical aspects of orbifold string theory. In the first part of this lecture, we review recent work on discrete torsion, and outline how it is currently understood in terms of ... More
What Transcription Factors Can't Do: On the Combinatorial Limits of Gene Regulatory NetworksDec 19 2013Jan 27 2014A proof is presented that gene regulatory networks (GRNs) based solely on transcription factors cannot control the development of complex multicellular life. GRNs alone cannot explain the evolution of multicellular life in the Cambrian Explosion. Networks ... More
On the complexity of learning a language: An improvement of Block's algorithmDec 11 2012Language learning is thought to be a highly complex process. One of the hurdles in learning a language is to learn the rules of syntax of the language. Rules of syntax are often ordered in that before one rule can applied one must apply another. It has ... More
Deeply Virtual Compton Scattering at JLab Hall ASep 27 2007The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e,e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, ... More
Meunier ConjectureSep 01 2012Fr\'ed\'eric Meunier's question about a multicolored Sperner lemma is addressed, leaving the question of connectivity for the color hypergraphs of such a multicolored simplex. Sperner's lemma asserts the existence of a simplex using all the colors for ... More
Color superconductivity in the Nambu Jona-Lasinio model complemented by a Polyakov loopJun 08 2016The color superconductivity was studied with an adaptation of the Nambu and Jona-Lasinio model (NJL). This one was coupled to a Polyakov loop, to form the PNJL model. A $\mu$-dependent Polyakov loop potential was considered. An objective of the presented ... More
Quantum Collapse of a Charged $n$-dimensional BTZ-like Domain WallMay 20 2016We investigate both the classical and quantum gravitational collapse of a charged, non-rotating $n$-dimensional BTZ black hole in AdS space. This is done by first deriving the conserved mass of a "spherically" symmetric domain wall, which is then taken ... More
Bounding the Space of Holographic CFTs with ChaosFeb 26 2016Oct 14 2016Thermal states of quantum systems with many degrees of freedom are subject to a bound on the rate of onset of chaos, including a bound on the Lyapunov exponent, $\lambda_L\leq 2\pi /\beta$. We harness this bound to constrain the space of putative holographic ... More
Closed subgroups of the polynomial automorphism group containing the affine subgroupSep 09 2016We prove that, in characteristic zero, closed subgroups of the polynomial automorphisms group containing the affine group contain the whole tame group.
The rigid Horowitz-Myers conjectureFeb 19 2016The "new positive energy conjecture" Horowitz and Myers (1999) probes a possible nonsupersymmetric AdS/CFT correspondence. We consider a version formulated for complete, asymptotically Poincar\'e-Einstein Riemannian metrics $(M,g)$ with bounded scalar ... More
Theoretical approaches to the statistical physics of interacting non-conservative unitsAug 30 2016The aim of this review is to provide a concise overview of some of the generic approaches that have been developed to deal with the statistical description of large systems of interacting non-conservative 'units'. The latter notion includes, e.g., inelastic ... More
On the Oscillations of Second Order Linear Differential EquationsNov 09 2016This paper extends the discriminant associated to second order linear constant coefficient differential equations to general second order linear differential equations. The main result of this paper is that the discriminant of a second order linear differential ... More
Maximal Green Sequences for Cluster Algebras Associated to the n-TorusDec 11 2014Given a marked surface (S,M) we can add arcs to the surface to create a triangulation, T, of that surface. For each triangulation, T, we can associate a cluster algebra. In this paper we will consider the torus of genus n with two interior marked points ... More