Results for "Stefan Winkler"

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Systematic study of color spaces and components for the segmentation of sky/cloud imagesJan 17 2017Sky/cloud imaging using ground-based Whole Sky Imagers (WSI) is a cost-effective means to understanding cloud cover and weather patterns. The accurate segmentation of clouds in these images is a challenging task, as clouds do not possess any clear structure. ... More
High-Dynamic-Range Imaging for Cloud SegmentationMar 02 2018Sky/cloud images obtained from ground-based sky-cameras are usually captured using a fish-eye lens with a wide field of view. However, the sky exhibits a large dynamic range in terms of luminance, more than a conventional camera can capture. It is thus ... More
Predicting GPS-based PWV Measurements Using Exponential SmoothingMar 15 2019Global Positioning System (GPS) derived precipitable water vapor (PWV) is extensively being used in atmospheric remote sensing for applications like rainfall prediction. Many applications require PWV values with good resolution and without any missing ... More
Study of Clear Sky Models for SingaporeAug 24 2017The estimation of total solar irradiance falling on the earth's surface is important in the field of solar energy generation and forecasting. Several clear-sky solar radiation models have been developed over the last few decades. Most of these models ... More
Multi-label Cloud Segmentation Using a Deep NetworkMar 15 2019Different empirical models have been developed for cloud detection. There is a growing interest in using the ground-based sky/cloud images for this purpose. Several methods exist that perform binary segmentation of clouds. In this paper, we propose to ... More
CloudSegNet: A Deep Network for Nychthemeron Cloud Image SegmentationApr 16 2019We analyze clouds in the earth's atmosphere using ground-based sky cameras. An accurate segmentation of clouds in the captured sky/cloud image is difficult, owing to the fuzzy boundaries of clouds. Several techniques have been proposed that use color ... More
WAHRSIS: A Low-cost, High-resolution Whole Sky Imager With Near-Infrared CapabilitiesMay 21 2016Apr 19 2017Cloud imaging using ground-based whole sky imagers is essential for a fine-grained understanding of the effects of cloud formations, which can be useful in many applications. Some such imagers are available commercially, but their cost is relatively high, ... More
EEG-based Evaluation of Cognitive Workload Induced by Acoustic Parameters for Data SonificationAug 18 2018Data Visualization has been receiving growing attention recently, with ubiquitous smart devices designed to render information in a variety of ways. However, while evaluations of visual tools for their interpretability and intuitiveness have been commonplace, ... More
Systematic Study of Weather Variables for Rainfall DetectionMay 04 2018Numerous weather parameters affect the occurrence and amount of rainfall. Therefore, it is important to study these parameters and their interdependency. In this paper, different weather and time-related variables -- relative humidity, solar radiation, ... More
A Data-Driven Approach for Accurate Rainfall PredictionJul 10 2019In recent years, there has been growing interest in using Precipitable Water Vapor (PWV) derived from Global Positioning System (GPS) signal delays to predict rainfall. However, the occurrence of rainfall is dependent on a myriad of atmospheric parameters. ... More
Global weak solutions in a three-dimensional chemotaxis-Navier-Stokes systemOct 22 2014The chemotaxis-Navier-Stokes system linking the chemotaxis equations \[ n_t + u\cdot\nabla n = \Delta n - \nabla \cdot (n\chi(c)\nabla c) \] and \[ c_t + u\cdot\nabla c = \Delta c-nf(c) \] to the incompressible Navier-Stokes equations, \[ u_t + (u\cdot\nabla)u ... More
How far do chemotaxis-driven forces influence regularity in the Navier-Stokes system?Jun 18 2015A three-dimensional chemotaxis-Navier-Stokes system is considered. It is known that for all suitably regular initial data, a corresponding initial-boundary value problem admits at least one global weak solution which can be obtained as the pointwise limit ... More
Global existence and stabilization in a degenerate chemotaxis-Stokes system with mildly strong diffusion enhancementApr 19 2017A class of chemotaxis-Stokes systems generalizing the prototype \[\left\{ \begin{array}{rcl} n_t + u\cdot\nabla n &=& \nabla \cdot \big(n^{m-1}\nabla n\big) - \nabla \cdot \big(n\nabla c\big), c_t + u\cdot\nabla c &=& \Delta c-nc, u_t +\nabla P &=& \Delta ... More
Error estimates for variational normal derivatives and Dirichlet control problems with energy regularizationAug 03 2018This article deals with error estimates for the finite element approximation of variational normal derivatives and, as a consequence, error estimates for the finite element approximation of Dirichlet boundary control problems with energy regularization. ... More
Error estimates for the finite element approximation of bilinear boundary control problemsJan 11 2019In this article a special class of nonlinear optimal control problems involving a bilinear term in the boundary condition is studied. These kind of problems arise for instance in the identification of an unknown space-dependent Robin coefficient from ... More
Approximate Solutions of 4-regular Matchstick Graphs with 51 -- 62 VerticesJun 27 2019A 4-regular matchstick graph is a planar unit-distance graph whose vertices have all degree 4. Examples of 4-regular matchstick graphs are currently known for all number of vertices $\geq$ 52 except for 53, 55, 56, 58, 59, 61, and 62. In this article ... More
Singular structure formation in a degenerate haptotaxis model involving myopic diffusionJun 16 2017We consider the system \[ u_t=\big(d(x)u\big)_{xx} - \big(d(x)uw_x\big)_x, \quad w_t=-ug(w), \] which arises as a simple model for haptotactic migration in heterogeneous environments, such as typically occurring in the invasive dynamics of glioma. A particular ... More
Bit Commitment from Non-Signaling CorrelationsNov 21 2008Aug 31 2010Central cryptographic functionalities such as encryption, authentication, or secure two-party computation cannot be realized in an information-theoretically secure way from scratch. This serves as a motivation to study what (possibly weak) primitives ... More
On the existence of 4-regular matchstick graphsApr 30 2017Jun 30 2017A matchstick graph is a planar unit-distance graph. That is a graph drawn with straight edges in the plane such that the edges have unit length, and non-adjacent edges do not intersect. We call a matchstick graph 4-regular if every vertex has only degree ... More
Minimal completely asymmetric (4; n)-regular matchstick graphsSep 13 2016May 01 2018A matchstick graph is a graph drawn with straight edges in the plane such that the edges have unit length, and non-adjacent edges do not intersect. We call a matchstick graph $(m;n)$-regular if every vertex has only degree $m$ or $n$. In this article ... More
New minimal (4; n)-regular matchstick graphsApr 25 2016May 01 2018A matchstick graph is a graph drawn with straight edges in the plane such that the edges have unit length, and non-adjacent edges do not intersect. We call a matchstick graph ($m;n)$-regular if every vertex has only degree $m$ or $n$. In this article ... More
Distilling Non-LocalitySep 18 2008Mar 05 2009Two parts of an entangled quantum state can have a correlation in their joint behavior under measurements that is unexplainable by shared classical information. Such correlations are called non-local and have proven to be an interesting resource for information ... More
New minimal (4,n)-regular matchstick graphsApr 25 2016Sep 14 2016A matchstick graph is a graph drawn with straight edges in the plane such that the edges have unit length, and non-adjacent edges do not intersect. We call a matchstick graph ($m,n)$-regular if every vertex has only degree $m$ or $n$. In this article ... More
A 3-regular matchstick graph of girth 5 consisting of 54 verticesMar 08 2019In 2010 it was proved that a 3-regular matchstick graph of girth 5 must consist at least of 30 vertices. The smallest known example consisted of 180 vertices. In this article we construct an example consisting of 54 vertices and prove its geometrical ... More
Minimal completely asymmetric (4,n)-regular matchstick graphsSep 13 2016A matchstick graph is a graph drawn with straight edges in the plane such that the edges have unit length, and non-adjacent edges do not intersect. We call a matchstick graph $(m,n)$-regular if every vertex has only degree $m$ or $n$. In this article ... More
4-regular planar unit triangle graphs without additional trianglesFeb 03 2019In this article we proof the existence of 4-regular planar unit-distance graphs consisting only of unit triangles without additional triangles. It is shown that the smallest number of unit triangles is $\leq$6422.
PersEmoN: A Deep Network for Joint Analysis of Apparent Personality, Emotion and Their RelationshipNov 21 2018Personality and emotion are both central to affective computing. Existing works solve them individually. In this paper we investigate if such high-level affect traits and their relationship can be jointly learned from face images in the wild. To this ... More
Color-based Segmentation of Sky/Cloud Images From Ground-based CamerasJun 12 2016Sky/cloud images captured by ground-based cameras (a.k.a. whole sky imagers) are increasingly used nowadays because of their applications in a number of fields, including climate modeling, weather prediction, renewable energy generation, and satellite ... More
Slow growth of solutions of super-fast diffusion equations with unbounded initial dataMay 13 2016We study positive solutions of the super-fast diffusion equation in the whole space with initial data which are unbounded as $|x|\to\infty$. We find an explicit dependence of the slow temporal growth rate of solutions on the initial spatial growth rate. ... More
A Gagliardo-Nirenberg-type inequality and its applications to decay estimates for solutions of a degenerate parabolic equationOct 31 2017We establish a Gagliardo-Nirenberg-type inequality in $\mathbb{R}^n$ for functions which decay fast as $|x|\to\infty$. We use this inequality to derive upper bounds for the decay rates of solutions of a degenerate parabolic equation. Moreover, we show ... More
Mixing times and moving targetsOct 18 2012We consider irreducible Markov chains on a finite state space. We show that the mixing time of any such chain is equivalent to the maximum, over initial states $x$ and moving large sets $(A_s)_s$, of the hitting time of $(A_s)_s$ starting from $x$. We ... More
Can extra updates delay mixing?Dec 02 2011We consider Glauber dynamics (starting from an extremal configuration) in a monotone spin system, and show that interjecting extra updates cannot increase the expected Hamming distance or the total variation distance to the stationary distribution. We ... More
Compactifications, Hartman functions and (weak) almost periodicityOct 04 2005Oct 10 2008In this paper we investigate Hartman functions on a topological group $G$. Recall that $(\iota, C)$ is a group compactification of $G$ if $C$ is a compact group, $\iota: G\to C$ is a continuous group homomorphism and $\iota(G)$ is dense in $C$. A complex-valued ... More
Boundedness in a quasilinear parabolic-parabolic Keller-Segel system with subcritical sensitivityJun 27 2011We consider the quasilinear parabolic-parabolic Keller-Segel system $$ u_t=\nabla \cdot (D(u)\nabla u) - \nabla \cdot (S(u)\nabla v), \qquad x\in\Omega, \ t>0, v_t=\Delta v -v + u, x\in\Omega, \ t>0, $$ under homogeneous Neumann boundary conditions in ... More
Does indirectness of signal production reduce the explosion-supporting potential in chemotaxis-haptotaxis systems? Global classical solvability in a class of models for cancer invasion (and more)Apr 25 2019We propose and study a class of parabolic-ODE models involving chemotaxis and haptotaxis of a species following signals indirectly produced by another, non-motile one. The setting is motivated by cancer invasion mediated by interactions with the tumor ... More
Finite element error estimates for normal derivatives on boundary concentrated meshesApr 16 2018This paper is concerned with approximations and related discretization error estimates for the normal derivatives of solutions of linear elliptic partial differential equations. In order to illustrate the ideas, we consider the Poisson equation with homogeneous ... More
Global weak solutions to a strongly degenerate haptotaxis modelMar 14 2016We consider a one-dimensional version of a model obtained in [C. Engwer, A. Hunt, and C. Surulescu: Effective equations for anisotropic glioma spread with proliferation: a multiscale approach and comparisons with previous settings, IMA J. Math. Med. Biol. ... More
A degenerate fourth-order parabolic equation modeling Bose-Einstein condensation. Part II: Finite-time blow-upJan 05 2014A degenerate fourth-order parabolic equation modeling condensation phenomena related to Bose-Einstein particles is analyzed. The model is a Fokker-Planck-type approximation of the Boltzmann-Nordheim equation, only keeping the leading order term. It maintains ... More
A degenerate fourth-order parabolic equation modeling Bose-Einstein condensation. Part I: Local existence of solutionsJan 05 2014A degenerate fourth-order parabolic equation modeling condensation phenomena related to Bose-Einstein particles is analyzed. The model is a Fokker-Planck-type approximation of the Boltzmann-Nordheim equation, only keeping the leading order term. It maintains ... More
Blow-up profiles for the parabolic-elliptic Keller-Segel system in dimensions $n\ge 3$Feb 09 2018We study the blow-up asymptotics of radially decreasing solutions of the parabolic-elliptic Keller-Segel-Patlak system in space dimensions $n\ge 3$. In view of the biological background of this system and of its mass conservation property, blowup is usually ... More
Optimization of a partial differential equation on a complex networkJul 17 2019Differential equations on metric graphs can describe many phenomena in the physical world but also the spread of information on social media. To efficiently compute the solution is a hard task in numerical analysis. Solving a design problem, where the ... More
Design of low-cost, compact and weather-proof whole sky imagers for high-dynamic-range capturesApr 19 2017Ground-based whole sky imagers are popular for monitoring cloud formations, which is necessary for various applications. We present two new Wide Angle High-Resolution Sky Imaging System (WAHRSIS) models, which were designed especially to withstand the ... More
Detecting Rainfall Onset Using Sky ImagesOct 21 2016Ground-based sky cameras (popularly known as Whole Sky Imagers) are increasingly used now-a-days for continuous monitoring of the atmosphere. These imagers have higher temporal and spatial resolutions compared to conventional satellite images. In this ... More
Machine Learning Techniques and Applications For Ground-based Image AnalysisJun 09 2016Ground-based whole sky cameras have opened up new opportunities for monitoring the earth's atmosphere. These cameras are an important complement to satellite images by providing geoscientists with cheaper, faster, and more localized data. The images captured ... More
Estimation of solar irradiance using ground-based whole sky imagersJun 08 2016Apr 06 2017Ground-based whole sky imagers (WSIs) can provide localized images of the sky of high temporal and spatial resolution, which permits fine-grained cloud observation. In this paper, we show how images taken by WSIs can be used to estimate solar radiation. ... More
On the Success Rate of Crossover Operators for Genetic Programming with Offspring SelectionSep 23 2013Genetic programming is a powerful heuristic search technique that is used for a number of real world applications to solve among others regression, classification, and time-series forecasting problems. A lot of progress towards a theoretic description ... More
Estimation of solar irradiance using ground-based whole sky imagersJun 08 2016Ground-based whole sky imagers (WSIs) can provide localized images of the sky of high temporal and spatial resolution, which permits fine-grained cloud observation. In this paper, we show how images taken by WSIs can be used to estimate solar radiation. ... More
Impossibility of Growing Quantum Bit CommitmentsMay 05 2011Sep 27 2011Quantum key distribution (QKD) is often, more correctly, called key growing. Given a short key as a seed, QKD enables two parties, connected by an insecure quantum channel, to generate a secret key of arbitrary length. Conversely, no key agreement is ... More
A Deep Network for Arousal-Valence Emotion Prediction with Acoustic-Visual CuesMay 02 2018In this paper, we comprehensively describe the methodology of our submissions to the One-Minute Gradual-Emotion Behavior Challenge 2018.
WAHRSIS: A Low-cost, High-resolution Whole Sky Imager With Near-Infrared CapabilitiesMay 21 2016Cloud imaging using ground-based whole sky imagers is essential for a fine-grained understanding of the effects of cloud formations, which can be useful in many applications. Some such imagers are available commercially, but their cost is relatively high, ... More
Short-term prediction of localized cloud motion using ground-based sky imagersOct 21 2016Fine-scale short-term cloud motion prediction is needed for several applications, including solar energy generation and satellite communications. In tropical regions such as Singapore, clouds are mostly formed by convection; they are very localized, and ... More
Nighttime sky/cloud image segmentationMay 30 2017Imaging the atmosphere using ground-based sky cameras is a popular approach to study various atmospheric phenomena. However, it usually focuses on the daytime. Nighttime sky/cloud images are darker and noisier, and thus harder to analyze. An accurate ... More
Rough Set Based Color Channel SelectionNov 03 2016Color channel selection is essential for accurate segmentation of sky and clouds in images obtained from ground-based sky cameras. Most prior works in cloud segmentation use threshold based methods on color channels selected in an ad-hoc manner. In this ... More
Effective Dynamics of 2D Bloch Electrons in External Fields Derived From SymmetryJun 11 2019We develop a comprehensive theory for the effective dynamics of Bloch electrons based on symmetry. We begin with a scheme to systematically derive the irreducible representations (IRs) characterizing the Bloch functions. Starting from a tight-binding ... More
Effective Resistance-based Germination of Seed Sets for Community DetectionOct 31 2018Community detection is, at its core, an attempt to attach an interpretable function to an otherwise indecipherable form. The importance of labeling communities has obvious implications for identifying clusters in social networks, but it has a number of ... More
Hard constraints and the bethe lattice: adventures at the interface of combinatorics and statistical physicsApr 28 2003Statistical physics models with hard constraints, such as the discrete hard-core gas model (random independent sets in a graph), are inherently combinatorial and present the discrete mathematician with a relatively comfortable setting for the study of ... More
Long Distance Transport of Ultracold Atoms using a 1D optical latticeMay 30 2006Jun 20 2006We study the horizontal transport of ultracold atoms over macroscopic distances of up to 20 cm with a moving 1D optical lattice. By using an optical Bessel beam to form the optical lattice, we can achieve nearly homogeneous trapping conditions over the ... More
The Unusual Effectiveness of Averaging in GAN TrainingJun 12 2018Feb 26 2019We examine two different techniques for parameter averaging in GAN training. Moving Average (MA) computes the time-average of parameters, whereas Exponential Moving Average (EMA) computes an exponentially discounted sum. Whilst MA is known to lead to ... More
Investigating the generalizability of EEG-based Cognitive Load Estimation Across VisualizationsSep 12 2018We examine if EEG-based cognitive load (CL) estimation is generalizable across the character, spatial pattern, bar graph and pie chart-based visualizations for the nback~task. CL is estimated via two recent approaches: (a) Deep convolutional neural network, ... More
A Data-driven Approach to Detecting Precipitation from Meteorological Sensor DataMay 04 2018Precipitation is dependent on a myriad of atmospheric conditions. In this paper, we study how certain atmospheric parameters impact the occurrence of rainfall. We propose a data-driven, machine-learning based methodology to detect precipitation using ... More
Polarized indistinguishable single photons from a quantum dot in an elliptical micropillarSep 28 2018The key challenge to scalable optical quantum computing, boson sampling, and quantum metrology is sources of single photons with near-unity system efficiency and simultaneously near-perfect indistinguishability in all degrees of freedom (including spectral, ... More
Validity of time reversal for testing Granger causalitySep 25 2015Feb 11 2016Inferring causal interactions from observed data is a challenging problem, especially in the presence of measurement noise. To alleviate the problem of spurious causality, Haufe et al. (2013) proposed to contrast measures of information flow obtained ... More
Long-lived Feshbach molecules in a 3D optical latticeOct 27 2005We have created and trapped a pure sample of 87Rb2 Feshbach molecules in a three-dimensional optical lattice. Compared to previous experiments without a lattice we find dramatic improvements such as long lifetimes of up to 700 ms and a near unit efficiency ... More
PET: An Eye-tracking Dataset for Animal-centric PASCAL Object ClassesApr 06 2016We present the Pascal animal classes Eye Tracking database. Our database comprises eye movement recordings compiled from forty users for the bird, cat, cow, dog, horse and sheep {trainval} sets from the VOC 2012 image set. Different from recent eye-tracking ... More
The Unusual Effectiveness of Averaging in GAN TrainingJun 12 2018We show empirically that the optimal strategy of parameter averaging in a minmax convex-concave game setting is also strikingly effective in the non convex-concave GAN setting, specifically alleviating the convergence issues associated with cycling behavior ... More
Recognition of Advertisement Emotions with Application to Computational AdvertisingApr 03 2019Advertisements (ads) often contain strong affective content to capture viewer attention and convey an effective message to the audience. However, most computational affect recognition (AR) approaches examine ads via the text modality, and only limited ... More
The minimum Manhattan distance and minimum jump of permutationsJun 05 2017Aug 02 2018Let $\pi$ be a permutation of $\{1,2,\ldots,n\}$. If we identify a permutation with its graph, namely the set of $n$ dots at positions $(i,\pi(i))$, it is natural to consider the minimum $L^1$ (Manhattan) distance, $d(\pi)$, between any pair of dots. ... More
Topological Characterization of Consensus under General Message AdversariesMay 23 2019In this paper, we provide a rigorous characterization of consensus solvability in synchronous directed dynamic networks controlled by an arbitrary message adversary using point-set topology: We extend the approach introduced by Alpern and Schneider in ... More
The fast signal diffusion limit in Keller-Segel(-fluid) systemsMay 14 2018This paper deals with convergence of solutions to a class of parabolic Keller-Segel systems, possibly coupled to the (Navier-)Stokes equations in the framework of the full model \begin{eqnarray*} \left\{ \begin{array}{lcl} \, \, \partial_t n_{\epsilon} ... More
A Singular Differential Equation Stemming from an Optimal Control Problem in Financial EconomicsSep 22 2012Jul 24 2017We consider the ordinary differential equation $x^2 u'' = axu'+bu-c(u'-1)^2, x\in (0,x_0)$, with $a\in\mathbb{R}, b\in\mathbb{R}$, $c>0$ and the singular initial condition $u(0)=0$, which in financial economics describes optimal disposal of an asset in ... More
Venn GAN: Discovering Commonalities and Particularities of Multiple DistributionsFeb 09 2019We propose a GAN design which models multiple distributions effectively and discovers their commonalities and particularities. Each data distribution is modeled with a mixture of $K$ generator distributions. As the generators are partially shared between ... More
Cloud Radiative Effect Study Using Sky CameraMar 15 2017The analysis of clouds in the earth's atmosphere is important for a variety of applications, viz. weather reporting, climate forecasting, and solar energy generation. In this paper, we focus our attention on the impact of cloud on the total solar irradiance ... More
Status Quo in Requirements Engineering: A Theory and a Global Family of SurveysMay 21 2018Dec 17 2018Requirements Engineering (RE) has established itself as a software engineering discipline during the past decades. While researchers have been investigating the RE discipline with a plethora of empirical studies, attempts to systematically derive an empirically-based ... More
Load-Balancing for Parallel Delaunay TriangulationsFeb 20 2019Computing the Delaunay triangulation (DT) of a given point set in $\mathbb{R}^D$ is one of the fundamental operations in computational geometry. Recently, Funke and Sanders (2017) presented a divide-and-conquer DT algorithm that merges two partial triangulations ... More
Anisotropic mesh refinement in polyhedral domains: error estimates with data in L^2(Ω)Mar 12 2013The paper is concerned with the finite element solution of the Poisson equation with homogeneous Dirichlet boundary condition in a three-dimensional domain. Anisotropic, graded meshes from a former paper are reused for dealing with the singular behaviour ... More
Supersymmetric Moduli Stabilization and High-Scale InflationApr 08 2014We study the back-reaction of moduli fields on the inflaton potential in generic models of F-term inflation. We derive the moduli corrections as a power series in the ratio of Hubble scale and modulus mass. The general result is illustrated with two examples, ... More
A Continuum of Extinction Rates for the Fast Diffusion EquationMar 15 2010We find a continuum of extinction rates for solutions $u(y,\tau)\ge 0$ of the fast diffusion equation $u_\tau=\Delta u^m$ in a subrange of exponents $m\in (0,1)$. The equation is posed in $\ren$ for times up to the extinction time $T>0$. The rates take ... More
Itineraries of rigid rotations and diffeomorphisms of the circleJan 10 2008Sep 30 2009We examine the itinerary of $0\in S^{1}=\R/\Z$ under the rotation by $\alpha\in\R\bs\Q$. The motivating question is: if we are given only the itinerary of 0 relative to $I\subset S^{1}$, a finite union of closed intervals, can we recover $\alpha$ and ... More
On the effect of the drive on self-organized criticalityOct 21 2014Mar 19 2015The well known Sandpile model of self-organized criticality generates avalanches of all length and time scales, without tuning any parameters. In the original models the external drive is randomly selected. Here we investigate a drive which depends on ... More
Migration-driven benefit in a two-species nutrient taxis systemMay 30 2018A model describing the competition of two species for a common nutrient is studied. It is assumed that one of the competitors is motionless while the other has the ability to move upwards gradients of the nutrient density. It is proved that under suitable ... More
The midpoint between dipole and parton showersJun 16 2015Sep 19 2015We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A ... More
Interactive Natural Language Acquisition in a Multi-modal Recurrent Neural ArchitectureMar 24 2017Feb 07 2018For the complex human brain that enables us to communicate in natural language, we gathered good understandings of principles underlying language acquisition and processing, knowledge about socio-cultural conditions, and insights about activity patterns ... More
Stochastic mortality models: An infinite dimensional approachJul 11 2019Demographic projections of future mortality rates involve a high level of uncertainty and require stochastic mortality models. The current paper investigates forward mortality models driven by a (possibly infinite dimensional) Wiener process and a compensated ... More
The H-Covariant Strong Picard GroupoidSep 08 2004Apr 25 2005The notion of H-covariant strong Morita equivalence is introduced for *-algebras over C = R(i) with an ordered ring R which are equipped with a *-action of a Hopf *-algebra H. This defines a corresponding H-covariant strong Picard groupoid which encodes ... More
A shortcut to (sun)flowers: Kernels in logarithmic space or linear timeApr 30 2015We investigate whether kernelization results can be obtained if we restrict kernelization algorithms to run in logarithmic space. This restriction for kernelization is motivated by the question of what results are attainable for preprocessing via simple ... More
Weak Limit of the 3-State Quantum Walk on the LineApr 04 2014May 21 2014We revisit the one dimensional discrete time quantum walk with 3 states and the Grover coin. We derive analytic expressions for observed the localization, an long time approximation for the probability density function (PDF). We also connect the time ... More
Streaming KernelizationMay 06 2014Kernelization is a formalization of preprocessing for combinatorially hard problems. We modify the standard definition for kernelization, which allows any polynomial-time algorithm for the preprocessing, by requiring instead that the preprocessing runs ... More
On the commutability of homogenization and linearization in finite elasticityNov 16 2010May 16 2011We study non-convex elastic energy functionals associated to (spatially) periodic, frame indifferent energy densities with a single non-degenerate energy well at SO(n). Under the assumption that the energy density admits a quadratic Taylor expansion at ... More
On a degenerate non-local parabolic problem describing infinite dimensional replicator dynamicsAug 25 2015We establish the existence of locally positive weak solutions to the homogeneous Dirichlet problem for \[ u_t = u \Delta u + u \int_\Omega |\nabla u|^2 \] in bounded domains $\Omega\subset\mathbb{R}^n$ and prove that solutions converge to $0$ if the initial ... More
Superstability of the yeast cell cycle dynamics: Ensuring causality in the presence of biochemical stochasticityMay 05 2006Gene regulatory dynamics is governed by molecular processes and therefore exhibits an inherent stochasticity. However, for the survival of an organism it is a strict necessity that this intrinsic noise does not prevent robust functioning of the system. ... More
The generating of Fractal Images Using MathCAD ProgramMar 24 2009This paper presents the graphic representation in the z-plane of the first three iterations of the algorithm that generates the Sierpinski Gasket. It analyzes the influence of the f(z) map when we represent fractal images.
Twisted Reidemeister torsion, the Thurston norm and fibered manifoldsJan 29 2013We prove that the twisted Reidemeister torsion of a 3-manifold corresponding to a fibered class is monic and we show that it gives lower bounds on the Thurston norm. The former fixes a flawed proof in [FV10], the latter gives a quick alternative argument ... More
Reidemeister torsion, the Thurston norm and Harvey's invariantsAug 31 2005Feb 25 2006Recently twisted and higher order Alexander polynomials were used by Cochran, Harvey, Friedl--Kim and Turaev to give lower bounds on the Thurston norm. We first show how Reidemeister torsion relates to these Alexander polynomials. We then give lower bounds ... More
A Hidden Signal in the Ulam sequenceJul 01 2015Jul 06 2016The Ulam sequence is defined as $a_1 =1, a_2 = 2$ and $a_n$ being the smallest integer that can be written as the sum of two distinct earlier elements in a unique way. This gives $$1, 2, 3, 4, 6, 8, 11, 13, 16, 18, 26, 28, 36, 38, 47, \dots$$ Ulam remarked ... More
New Bounds for the Traveling Salesman ConstantNov 25 2013Mar 27 2014Let $X_1, X_2, \dots, X_n$ be independent and uniformly distributed random variables in the unit square $[0,1]^2$ and let $L(X_1, \dots, X_n)$ be the length of the shortest traveling salesman path through these points. In 1959, Beardwood, Halton $\&$ ... More
Nonextensive statistical mechanics and complex scale-free networksSep 07 2006One explanation for the impressive recent boom in network theory might be that it provides a promising tool for an understanding of complex systems. Network theory is mainly focusing on discrete large-scale topological structures rather than on microscopic ... More
Aging Exponents in Self-Organized CriticalityJun 11 1997Aug 07 1997In a recent Letter [Phys. Rev. Lett. 79, 889 (1997) and cond-mat/9702054] we have demonstrated that the avalanches in the Bak-Sneppen model display aging behavior similar to glassy systems. Numerical results for temporal correlations show a broad distribution ... More
Stiffness of the Edwards-Anderson Model in all DimensionsAug 01 2005Sep 23 2005A comprehensive description in all dimensions is provided for the scaling exponent $y$ of low-energy excitations in the Ising spin glass introduced by Edwards and Anderson. A combination of extensive numerical as well as theoretical results suggest that ... More
Status of the NLO Corrections to the Photon Impact FactorJun 20 2002We present the status of the programme of calculating the next-to-leading order corrections to the virtual photon impact factor. In particular, we discuss new results for the transversely polarized photon. We briefly outline the definition of infrared ... More
Herwig++ for e+e- collisionsAug 03 2004Some results obtained with the new Monte Carlo event generator Herwig++ are presented. In its first version (1.0), Herwig++ is capable of simulating e+e- Annihilation events. We discuss its relevance for future e+e- colliders and show results on the multiplicity ... More