Results for "Joost Van de Weijer"

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Ensembles of Generative Adversarial NetworksDec 03 2016Ensembles are a popular way to improve results of discriminative CNNs. The combination of several networks trained starting from different initializations improves results significantly. In this paper we investigate the usage of ensembles of GANs. The ... More
On-the-fly Network Pruning for Object DetectionMay 11 2016Object detection with deep neural networks is often performed by passing a few thousand candidate bounding boxes through a deep neural network for each image. These bounding boxes are highly correlated since they originate from the same image. In this ... More
Review on Computer Vision Techniques in Emergency SituationAug 24 2017In emergency situations, actions that save lives and limit the impact of hazards are crucial. In order to act, situational awareness is needed to decide what to do. Geolocalized photos and video of the situations as they evolve can be crucial in better ... More
Rotate your Networks: Better Weight Consolidation and Less Catastrophic ForgettingFeb 08 2018In this paper we propose an approach to avoiding catastrophic forgetting in sequential task learning scenarios. Our technique is based on a network reparameterization that approximately diagonalizes the Fisher Information Matrix of the network parameters. ... More
Invertible Conditional GANs for image editingNov 19 2016Generative Adversarial Networks (GANs) have recently demonstrated to successfully approximate complex data distributions. A relevant extension of this model is conditional GANs (cGANs), where the introduction of external information allows to determine ... More
Does Multimodality Help Human and Machine for Translation and Image Captioning?May 30 2016Aug 16 2016This paper presents the systems developed by LIUM and CVC for the WMT16 Multimodal Machine Translation challenge. We explored various comparative methods, namely phrase-based systems and attentional recurrent neural networks models trained using monomodal ... More
Curvature dependence of the electrolytic liquid-liquid interfacial tensionSep 29 2008The interfacial tension of a liquid droplet surrounded by another liquid in the presence of microscopic ions is studied as a function of the droplet radius. An analytical expression for the interfacial tension is obtained within a linear Poisson-Boltzmann ... More
Stability of additive-free water-in-oil emulsionsOct 09 2008We calculate ion distributions near a planar oil-water interface within non-linear Poisson-Boltzmann theory, taking into account the Born self-energy of the ions in the two media. For unequal self-energies of cations and anions, a spontaneous charge separation ... More
Electrostatic Interactions between Janus ParticlesSep 17 2012In this paper we study the electrostatic properties of `Janus' spheres with unequal charge densities on both hemispheres. We introduce a method to compare primitive-model Monte Carlo simulations of the ionic double layer with predictions of (mean-field) ... More
A Triangular Tessellation Scheme for the Adsorption Free Energy at the Liquid-Liquid Interface: Towards Non-Convex Patterned ColloidsAug 24 2009We introduce a new numerical technique, namely triangular tessellation, to calculate the free energy associated with the adsorption of a colloidal particle at a flat interface. The theory and numerical scheme presented here are sufficiently general to ... More
Dense Regular Packings of Irregular Non-Convex ParticlesJul 04 2011Jul 05 2011We present a new numerical scheme to study systems of non-convex, irregular, and punctured particles in an efficient manner. We employ this method to analyze regular packings of odd-shaped bodies, not only from a nanoparticle but also both from a computational ... More
Geometric cohomology frames on Hausmann-Holm-Puppe conjugation spacesSep 21 2005For certain manifolds with an involution the mod 2 cohomology ring of the set of fixed points is isomorphic to the cohomology ring of the manifold, up to dividing the degrees by two. Examples include complex projective spaces and Grassmannians with the ... More
Effect of temperature and velocity on superlubricityOct 03 2012We study the effects of temperature and sliding velocity on superlubricity in numerical simulations of the Frenkel-Kontorova model. We show that resonant excitations of the phonons in an incommensurate sliding body lead to an effective friction and to ... More
Extended Picard complexes and linear algebraic groupsDec 06 2006For a smooth geometrically integral variety $X$ over a field $k$ of characteristic 0, we introduce and investigate the extended Picard complex $UPic(X)$. It is a certain complex of Galois modules of length 2, whose zeroth cohomology is $\bar{k}[X]^*/ ... More
Spontaneous Charging and Crystallization of Water Droplets in OilJul 29 2008Jul 31 2008We study the spontaneous charging and the crystallization of spherical micron-sized water-droplets dispersed in oil by numerically solving, within a Poisson-Boltzmann theory in the geometry of a spherical cell, for the density profiles of the cations ... More
Algebraic cycles and topology of real Enriques surfacesJun 07 1996For a real Enriques surface Y we prove that every homology class in H_1(Y(R), Z/2) can be represented by a real algebraic curve if and only if all connected components of Y(R) are orientable. Furthermore, we give a characterization of real Enriques surfaces ... More
Extended equivariant Picard complexes and homogeneous spacesOct 17 2010Sep 30 2011Let k be a field of characteristic 0 and let X be a smooth geometrically integral k-variety. In our previous paper we defined the extended Picard complex UPic(X) as a certain complex of Galois modules in degrees 0 and 1. We computed the isomorphism class ... More
Lattice-Boltzmann Simulations of Microswimmer-Tracer InteractionsJul 29 2016Hydrodynamic interactions in systems comprised of self-propelled particles, such as swimming microorganisms, and passive tracers have a significant impact on the tracer dynamics compared to the equivalent "dry" sample. However, such interactions are often ... More
Stirring by Periodic Arrays of MicroswimmersJun 01 2016The interaction between swimming microorganisms or artificial self-propelled colloids and passive (tracer) particles in a fluid leads to enhanced diffusion of the tracers. This enhancement has attracted strong interest, as it could lead to new strategies ... More
Information Storage and Retrieval for Probe Storage using Optical Diffraction PatternsApr 05 2011Jan 09 2012A novel method for fast information retrieval from a probe storage device is considered. It is shown that information can be stored and retrieved using the optical diffraction patterns obtained by the illumination of a large array of cantilevers by a ... More
Phase Behavior of a Family of Truncated Hard CubesDec 08 2014In continuation of our work in [A.P. Gantapara et al., Phys. Rev. Lett. 111, 015501 (2013)], we investigate here the thermodynamic phase behavior of a family of truncated hard cubes, for which the shape evolves smoothly from a cube via a cuboctahedron ... More
Phase diagram of colloidal hard superballs: from cubes via spheres to octahedraNov 18 2011Jan 13 2012The phase diagram of colloidal hard superballs, of which the shape interpolates between cubes and octahedra via spheres, is determined by free-energy calculations in Monte Carlo simulations. We discover not only a stable face-centered cubic (fcc) plastic ... More
Calibration of Phone Likelihoods in Automatic Speech RecognitionJun 14 2016In this paper we study the probabilistic properties of the posteriors in a speech recognition system that uses a deep neural network (DNN) for acoustic modeling. We do this by reducing Kaldi's DNN shared pdf-id posteriors to phone likelihoods, and using ... More
Variational Recurrent Auto-EncodersDec 20 2014Jun 15 2015In this paper we propose a model that combines the strengths of RNNs and SGVB: the Variational Recurrent Auto-Encoder (VRAE). Such a model can be used for efficient, large scale unsupervised learning on time series data, mapping the time series data to ... More
Diffusiophoretic Self-Propulsion for Partially Catalytic Spherical ColloidsDec 17 2014Feb 11 2015Colloidal spheres with a partial platinum surface coating perform auto-phoretic motion when suspended in hydrogen peroxide solution. We present a theoretical analysis of the self-propulsion velocity of these particles using a continuum multi-component, ... More
The Efficiency of Self-Phoretic Propulsion Mechanisms with Surface Reaction HeterogeneityFeb 25 2016We consider the efficiency of self-phoretic colloidal particles (swimmers) as a function of the heterogeneity in the surface reaction rate. The set of fluid, species, and electrostatic continuity equations is solved analytically using a linearization ... More
Mining Patterns with a Balanced IntervalMay 08 2007In many applications it will be useful to know those patterns that occur with a balanced interval, e.g., a certain combination of phone numbers are called almost every Friday or a group of products are sold a lot on Tuesday and Thursday. In previous work ... More
Deep Multi-scale Location-aware 3D Convolutional Neural Networks for Automated Detection of Lacunes of Presumed Vascular OriginOct 24 2016Lacunes of presumed vascular origin (lacunes) are associated with an increased risk of stroke, gait impairment, and dementia and are a primary imaging feature of the small vessel disease. Quantification of lacunes may be of great importance to elucidate ... More
Deep Multi-scale Location-aware 3D Convolutional Neural Networks for Automated Detection of Lacunes of Presumed Vascular OriginOct 24 2016Oct 29 2016Lacunes of presumed vascular origin (lacunes) are associated with an increased risk of stroke, gait impairment, and dementia and are a primary imaging feature of the small vessel disease. Quantification of lacunes may be of great importance to elucidate ... More
Mantle Convection, Plate Tectonics, and Volcanism on Hot Exo-EarthsJun 21 2011Recently discovered exoplanets on close-in orbits should have surface temperatures of 100's to 1000's of K. They are likely tidally locked and synchronously rotating around their parent stars and, if an atmosphere is absent, have surface temperature contrasts ... More
Inference in the FO(C) Modelling LanguageApr 25 2014Recently, FO(C), the integration of C-Log with classical logic, was introduced as a knowledge representation language. Up to this point, no systems exist that perform inference on FO(C), and very little is known about properties of inference in FO(C). ... More
FO(C): A Knowledge Representation Language of CausalityMay 08 2014May 09 2014Cause-effect relations are an important part of human knowledge. In real life, humans often reason about complex causes linked to complex effects. By comparison, existing formalisms for representing knowledge about causal relations are quite limited in ... More
Stable Tameness of Two-Dimensional Polynomial Automorphisms Over a Regular RingJul 23 2007Apr 19 2012In this paper it is established that all two-dimensional polynomial automorphisms over a regular ring R are stably tame. In the case R is a Dedekind Q-algebra, some stronger results are obtained. A key element in the proof is a theorem which yields the ... More
Automatic alignment for three-dimensional tomographic reconstructionMay 24 2017Jan 17 2018In tomographic reconstruction, the goal is to reconstruct an unknown object from a collection of line integrals. Given a complete sampling of such line integrals for various angles and directions, explicit inverse formulas exist to reconstruct the object. ... More
Selfduality of non-linear electrodynamics with derivative correctionsOct 05 2006In this paper we investigate how electromagnetic duality survives derivative corrections to classical non-linear electrodynamics. In particular, we establish that electromagnetic selfduality is satisfied to all orders in $\alpha'$ for the four-point function ... More
Clustering Co-occurrence of Maximal Frequent Patterns in StreamsMay 04 2007One way of getting a better view of data is using frequent patterns. In this paper frequent patterns are subsets that occur a minimal number of times in a stream of itemsets. However, the discovery of frequent patterns in streams has always been problematic. ... More
Is every toric variety an M-variety?Oct 11 2005A complex algebraic variety X defined over the real numbers is called an M-variety if the sum of its Betti numbers (for homology with closed supports and coefficients in Z/2) coincides with the corresponding sum for the real part of X. It has been known ... More
Clustering with Lattices in the Analysis of Graph PatternsMay 04 2007Mining frequent subgraphs is an area of research where we have a given set of graphs (each graph can be seen as a transaction), and we search for (connected) subgraphs contained in many of these graphs. In this work we will discuss techniques used in ... More
Stoichiometric YFe2O4-δ single crystals grown by the optical floating zone methodJul 20 2015We report the growth of YFe2O4-\delta\ single crystals by the optical floating zone method, showing for the first time the same magnetization as highly stoichiometric (\delta = 0.00) powder samples and sharp superstructure reflections in single crystal ... More
Limiting Spurious Flow in Simulations of Electrokinetic PhenomenaApr 07 2016Electrokinetic transport phenomena can strongly influence the behaviour of macromolecules and colloidal particles in solution, with applications in, e.g., DNA translocation through nanopores, electro-osmotic flow in nanocapillaries, and electrophoresis ... More
FO(C) and Related Modelling ParadigmsApr 25 2014Recently, C-Log was introduced as a language for modelling causal processes. Its formal semantics has been defined together with introductory examples, but the study of this language is far from finished. In this paper, we compare C-Log to other declarative ... More
Magnetodynamo Lifetimes for Rocky, Earth-Mass Exoplanets with Contrasting Mantle Convection RegimesApr 09 2013We used a thermal model of an iron core to calculate magnetodynamo evolution in Earth-mass rocky planets to determine the sensitivity of dynamo lifetime and intensity to planets with different mantle tectonic regimes, surface temperatures, and core properties. ... More
The Raspberry Model for Hydrodynamic Interactions Revisited. II. The Effect of ConfinementMar 09 2015Jul 05 2016The so-called 'raspberry' model refers to the hybrid lattice-Boltzmann (LB) and Langevin molecular dynamics scheme for simulating the dynamics of suspensions of colloidal particles, originally developed by [V. Lobaskin and B. D\"unweg, New J. Phys. 6, ... More
Clustering of Self-Propelled Triangles with Surface RoughnessJun 01 2016Sep 07 2016Self-propelled particles can spontaneously form dense phases from a dilute suspension in a process referred to as motility-induced phase separation. The properties of the out-of-equilibrium structures that are formed are governed by the specifics of the ... More
The Raspberry Model for Hydrodynamic Interactions Revisited. I. Periodic Arrays of Spheres and DumbbellsMar 09 2015Oct 08 2015The so-called 'raspberry' model refers to the hybrid lattice-Boltzmann and Langevin molecular dynamics scheme for simulating the dynamics of suspensions of colloidal particles, originally developed by [V. Lobaskin and B. D\"unweg, New J. Phys. 6, 54 (2004)], ... More
Nanoparticle Translocation through Conical Nanopores: A Finite Element Study of Electrokinetic TransportJun 21 2016Recent years have seen a surge of interest in nanopores because such structures show a strong potential for characterizing nanoparticles, proteins, DNA, and even single molecules. These systems have been extensively studied in experiment as well as by ... More
A secure additive protocol for card playersNov 01 2011Consider three players Alice, Bob and Cath who hold a, b and c cards, respectively, from a deck of d=a+b+c cards. The cards are all different and players only know their own cards. Suppose Alice and Bob wish to communicate their cards to each other without ... More
Deceleration and trapping of heavy diatomic molecules using a ring-deceleratorApr 21 2011Sep 10 2012We present an analysis of the deceleration and trapping of heavy diatomic molecules in low-field seeking states by a moving electric potential. This moving potential is created by a 'ring-decelerator', which consists of a series of ring-shaped electrodes ... More
Personalized Screening Intervals for Biomarkers using Joint Models for Longitudinal and Survival DataMar 22 2015Screening and surveillance are routinely used in medicine for early detection of disease and close monitoring of progression. Biomarkers are one of the primarily tools used for these tasks, but their successful translation to clinical practice is closely ... More
Actual Causation in CP-logicJul 25 2011Given a causal model of some domain and a particular story that has taken place in this domain, the problem of actual causation is deciding which of the possible causes for some effect actually caused it. One of the most influential approaches to this ... More
Equivalences between categories of modules and categories of comodulesApr 19 2006Aug 02 2006We show the close connection between appearingly different Galois theories for comodules introduced recently in [J. G\'omez-Torrecillas and J. Vercruysse, Comatrix corings and Galois Comodules over firm rings, arXiv:math.RA/0509106.] and [R. Wisbauer, ... More
Linearized polynomial maps over finite fieldsJan 05 2012Oct 08 2012We consider polynomial maps described by so-called "(multivariate) linearized polynomials". These polynomials are defined using a fixed prime power, say q. Linearized polynomials have no mixed terms. Considering invertible polynomial maps without mixed ... More
Quasi-co-Frobenius corings as Galois comodulesJun 09 2008Jun 09 2008We compare several quasi-Frobenius-type properties for corings that appeared recently in literature and provide several new characterizations for each of these properties. By applying the theory of Galois comodules with a firm coinvariant ring, we can ... More
The tame automorphism group in two variables over basic Artinian ringsOct 19 2009In a recent paper it has been established that over an Artinian ring R all two-dimensional polynomial automorphisms having Jacobian determinant one are tame if R is a Q-algebra. This is a generalization of the famous Jung-Van der Kulk Theorem, which deals ... More
Local units versus local projectivity. Dualisations: Corings with local structure mapsSep 10 2004Apr 19 2006We unify and generalize different notions of local units and local projectivity. We investigate the connection between these properties by constructing elementary algebras from locally projective modules. Dual versions of these constructions are discussed, ... More
Moving Charged Particles in Lattice Boltzmann-Based ElectrokineticsJul 15 2016The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled ... More
Dielectric properties of charge ordered LuFe2O4 revisited: The apparent influence of contactsMar 06 2012We show results of broadband dielectric measurements on the charge ordered, proposed to be mul- tiferroic material LuFe2O4. The temperature and frequency dependence of the complex permittivity as investigated for temperatures above and below the charge-oder ... More
Ionic Screening and Dissociation are Crucial for Understanding Chemical Self-Propulsion in WaterDec 06 2015Aug 16 2016Water is a polar solvent and hence supports the bulk dissociation of itself and its solutes into ions, and the re-association of these ions into neutral molecules in a dynamic equilibrium, e.g., ${\rm H_2O_2}\leftrightharpoons {\rm H^+~+~HO_2^-}$. Using ... More
Moving Charged Particles in Lattice Boltzmann-Based ElectrokineticsJul 15 2016Oct 25 2016The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled ... More
Intermolecular contrast in atomic force microscopy images without intermolecular bondsOct 07 2014Nov 03 2014Intermolecular features in atomic force microscopy (AFM) images of organic molecules have been ascribed to intermolecular bonds. A recent theoretical study [P. Hapala et al., Phys. Rev. B 90, 085421 (2014)] showed that these features can also be explained ... More
Hopf algebras---Variant notions and reconstruction theoremsFeb 16 2012Hopf algebras are closely related to monoidal categories. More precise, $k$-Hopf algebras can be characterized as those algebras whose category of finite dimensional representations is an autonomous monoidal category such that the forgetful functor to ... More
Tree Automata and Tree GrammarsOct 07 2015Lecture notes on tree language theory, in particular recognizable tree languages and finite state tree transformations.
Lowering the learning curve for declarative programming: a Python API for the IDP systemNov 03 2015Programmers may be hesitant to use declarative systems, because of the associated learning curve. In this paper, we present an API that integrates the IDP Knowledge Base system into the Python programming language. IDP is a state-of-the-art logical system, ... More
Context-Free Grammars with StorageAug 04 2014Context-free S grammars are introduced, for arbitrary (storage) type S, as a uniform framework for recursion-based grammars, automata, and transducers, viewed as programs. To each occurrence of a nonterminal of a context-free S grammar an object of type ... More
Simulating dynamic systems using Linear Time Calculus theoriesMay 07 2014To appear in Theory and Practice of Logic Programming (TPLP). Dynamic systems play a central role in fields such as planning, verification, and databases. Fragmented throughout these fields, we find a multitude of languages to formally specify dynamic ... More
Moving Charged Particles in Lattice Boltzmann-Based ElectrokineticsJul 15 2016Nov 22 2016The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled ... More
Deceleration and trapping of ammonia molecules in a traveling wave deceleratorJun 03 2013Aug 30 2013We have recently demonstrated static trapping of ammonia isotopologues in a decelerator that consists of a series of ring-shaped electrodes to which oscillating high voltages are applied [Quintero-P\'{e}rez et al., Phys. Rev. Lett. 110, 133003 (2013)]. ... More
Marker-based estimation of heritability in immortal populationsDec 21 2014Feb 16 2015Heritability is a central parameter in quantitative genetics, both from an evolutionary and a breeding perspective. For plant traits heritability is traditionally estimated by comparing within and between genotype variability. This approach estimates ... More
An integrated Micromegas UV-photon detectorMar 09 2010Preliminary results of a photon detector combining a Micromegas like multiplier coated with a UV-sensitive CsI photocathode are described. The multiplier is made in a CMOS compatible InGrid technology, which allows to post-process it directly on the surface ... More
Anisotropic Pauli spin blockade in hole quantum dotsJul 30 2016We present measurements on gate-defined double quantum dots in Ge-Si core-shell nanowires, which we tune to a regime with visible shell filling in both dots. We observe a Pauli spin blockade and can assign the measured leakage current at low magnetic ... More
Lattice-Boltzmann Hydrodynamics of Anisotropic Active MatterFeb 24 2016A plethora of active matter models exist that describe the behavior of self-propelled particles (or swimmers), both with and without hydrodynamics. However, there are few studies that consider shape-anisotropic swimmers and include hydrodynamic interactions. ... More
A Mems Tribometer for on-Chip Measurements of Dynamic Friction LoopsMay 02 2008A MEMS based tribometer has been developed that can be read out with nanometer and nano-Newton resolution, approaching the resolution and sensitivity of a friction force microscope (FFM). It can be used to study friction of MEMS device sidewall surfaces. ... More
Static trapping of polar molecules in a traveling wave deceleratorJan 10 2013Mar 13 2013We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator a moving potential is created by a series of ring-shaped electrodes to ... More
Highly tuneable hole quantum dots in Ge-Si core-shell nanowiresOct 11 2016We define single quantum dots of lengths varying from 60 nm up to nearly half a micron in Ge-Si core-shell nanowires. The charging energies scale inversely with the quantum dot length between 18 and 4 meV. Subsequently, we split up a long dot into a double ... More
Selective Trapping of DNA using Glass MicrocapillariesMay 31 2016We show experimentally that a cheap glass microcapillary can accumulate {\lambda}-phage DNA at its tip and deliver the DNA into the capillary using a combination of electro-osmotic flow, pressure-driven flow, and electrophoresis. We develop an efficient ... More
Understanding the Onset of Oscillatory Swimming in MicrochannelsMay 03 2016Self-propelled colloids (swimmers) in confining geometries follow trajectories determined by hydrodynamic interactions with the bounding surfaces. However, typically these interactions are ignored or truncated to lowest order. We demonstrate that higher-order ... More
Microfluidic Pumping by Micromolar Salt ConcentrationsOct 02 2016Oct 07 2016A colloidal ion-exchange-resin-based microfluidic pump is introduced and experimentally characterized. It operates in almost deionized water for periods exceeding 24h and effects fluid flows of um/s over hundreds of um. This fluid flow displays a far-field, ... More
The Equivalence Problem for Deterministic MSO Tree Transducers is DecidableJun 06 2005It is decidable for deterministic MSO definable graph-to-string or graph-to-tree transducers whether they are equivalent on a context-free set of graphs.
On the necessity of complexityNov 06 2012Wolfram's Principle of Computational Equivalence (PCE) implies that universal complexity abounds in nature. This paper comprises three sections. In the first section we consider the question why there are so many universal phenomena around. So, in a sense, ... More
Strategic polymorphism requires just two combinators!Dec 19 2002In previous work, we introduced the notion of functional strategies: first-class generic functions that can traverse terms of any type while mixing uniform and type-specific behaviour. Functional strategies transpose the notion of term rewriting strategies ... More
Three representations of the Ising modelJun 13 2016Oct 06 2016Statistical models that analyse (pairwise) relations between variables encompass assumptions about the underlying mechanism that generated the associations in the observed data. In the present paper we demonstrate that three Ising model representations ... More
Lie monads and dualitiesFeb 27 2013Dec 12 2013We study dualities between Lie algebras and Lie coalgebras, and their respective (co)representations. To allow a study of dualities in an infinite-dimensional setting, we introduce the notions of Lie monads and Lie comonads, as special cases of YB-Lie ... More
Design Patterns for Functional Strategic ProgrammingApr 09 2002In previous work, we introduced the fundamentals and a supporting combinator library for \emph{strategic programming}. This an idiom for generic programming based on the notion of a \emph{functional strategy}: a first-class generic function that cannot ... More
Turing-Taylor expansions for arithmetic theoriesApr 17 2014Aug 03 2015Turing progressions have been often used to measure the proof-theoretic strength of mathematical theories. Turing progressions based on $n$-provability give rise to a $\Pi_{n+1}$ proof-theoretic ordinal. As such, to each theory $U$ we can assign the sequence ... More
Decoupling of unphysical states in the minimal pure spinor formalism IJun 18 2009Jun 19 2009This is the first of a series of two papers where decoupling of unphysical states in the minimal pure spinor formalism is investigated. The multi-loop amplitude prescription for the minimal pure spinor superstring formulated in hep-th/0406055 involves ... More
On the duality of generalized Lie and Hopf algebrasMay 31 2013Mar 19 2014We show how, under certain conditions, an adjoint pair of braided monoidal functors can be lifted to an adjoint pair between categories of Hopf algebras. This leads us to an abstract version of Michaelis' theorem, stating that given a Hopf algebra $H$, ... More
A Note on the categorification of Lie algebrasFeb 16 2012In this short note we study Lie algebras in the framework of symmetric monoidal categories. After a brief review of the existing work in this field and a presentation of earlier studied and new examples, we examine which functors preserve the structure ... More
Dual Constructions for Partial Actions of Hopf AlgebrasMar 06 2014Apr 13 2015The duality between partial actions (partial $H$-module algebras) and co-actions (partial $H$-comodule algebras) of a Hopf algebra $H$ is fully explored in this work. A connection between partial (co)actions and Hopf algebroids is established under certain ... More
Collisions in piecewise flat gravity in 3+1 dimensionsFeb 19 2010We consider the (3+1)-dimensional locally finite gravity model proposed by 't Hooft. In particular we revisit the problem of resolving collisions of string defects. We provide a new geometric description of the configurations of strings using piecewise ... More
Cosmic Strings and Structure FormationOct 26 1998We discuss structure formation in cosmic string theories. Emphasis is laid on the properties of the peculiar velocity field, non-gaussian features and clusters of galaxies. It is found that the predicted peculiar velocity field is quiet ($v<150$ km/s ... More
Twisted Toroidal Lie AlgebrasJun 14 2001Using $n$ finite order automorphisms on a simple complex Lie algebra we construct twisted $n$-toroidal Lie algebras. Thus obtaining Lie algebras wich have a rootspace decomposition. For the case $n=2$ we list certain simple Lie algebras and their automorphisms, ... More
The vector k-constrained KP hierarchy and Sato's GrassmannianAug 30 1996We use the representation theory of the infinite matrix group to show that (in the polynomial case) the $n$--vector $k$--constrained KP hierarchy has a natural geometrical interpretation on Sato's infinite Grassmannian. This description generalizes the ... More
Worst possible sub-directions in high-dimensional modelsMar 27 2014We examine the rate of convergence of the Lasso estimator of lower dimensional components of the high-dimensional parameter. Under bounds on the $\ell_1$-norm on the worst possible sub-direction these rates are of order $\sqrt {|J| \log p / n }$ where ... More
Extending FO(ID) with Knowledge Producing Definitions: Preliminary ResultsJan 08 2013Previous research into the relation between ASP and classical logic has identified at least two different ways in which the former extends the latter. First, ASP program typically contain sets of rules that can be naturally interpreted as inductive definitions, ... More
Turing jumps through provabilityJan 21 2015Fixing some computably enumerable theory $T$, the Friedman-Goldfarb-Harrington (FGH) theorem says that over elementary arithmetic, each $\Sigma_1$ formula is equivalent to some formula of the form $\Box_T \varphi$ provided that $T$ is consistent. In this ... More
Minimal fibrations of dendroidal setsSep 03 2015We prove the existence of minimal models for fibrations between dendroidal sets in the model structure for infinity-operads, as well as in the covariant model structure for algebras and in the stable one for connective spectra. In an appendix, we explain ... More
Morita theory for coring extensions and cleft bicomodulesJan 19 2006Nov 01 2008A Morita context is constructed for any comodule of a coring and, more generally, for an $L$-$\cC$ bicomodule $\Sigma$ for a pure coring extension $(\cD:L)$ of $(\cC:A)$. It is related to a 2-object subcategory of the category of $k$-linear functors $\Mm^\Cc\to\Mm^\Dd$. ... More
Twisted GL_n Loop Group Orbit and Solutions of the WDVV EquationsApr 12 2000Apr 13 2000We show that all (n-component) KP tau-functions, which are related to the twisted loop group of $GL_n$, give solutions of the Darboux-Egoroff system of PDE's. Using the Geometry of the Grassmannian we construct from the corresponding wave function the ... More
The Adler-Shiota-van Moerbeke formula for the BKP hierarchyNov 22 1994We study the BKP hierarchy and prove the existence of an Adler--Shiota--van Moerbeke formula. This formula relates the action of the $BW_{1+\infty}$--algebra on tau--functions to the action of the ``additional symmetries'' on wave functions.
The $n$--TH Reduced BKP Hierarchy, the String Equation and $BW_{1+\infty}$--ConstraintsNov 10 1994We study the BKP hierarchy and its $n$--reduction, for the case that $n$ is odd. This is related to the principal realization of the basic module of the twisted affine Lie algebra $\hat{sl}_n^{(2)}$. We show that the following two statements for a BKP ... More