Results for "Tilmann Hickel"

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Une note à propos du Jacobien de $n$ fonctions holomorphes à l'origine de $\mathbb{C}^n$Feb 04 2008Let $f_1,...,f_n$ be $n$ germs of holomorphic functions at the origin of $\mathbb{C}^n$ such that $f_i(0)=0$, $1\leq i\leq n$. We give a proof based on the J. Lipman's theory of residues via Hochschild Homology that the Jacobian of $f_1,...,f_n$ belongs ... More
Sur quelques aspects de la géométrie de l'espace des arcs tracés sur un espace analytiqueMay 24 2004Let $(X,x)$ be a germ of real or complex analytic space and $\mathcal{A}_{(X,x)}$ the space of germs of arcs on $(X,x)$. Let us consider $F_{x}: (X,x) \to (Y,y)$ a germ of a morphism and denote by $\mathcal{F}_{x}: \mathcal{A}_{(X,x)} \to \mathcal{A}_{(Y,y)}$ ... More
Fonction asymptotique de Samuel des sections hyperplanes et multiplicitéJan 12 2009Let $(A,\mathfrak{m}_A,k)$ be a local noetherian ring and $I$ an $\mathfrak{m}_A$-primary ideal. The asymptotic Samuel function (with respect to $I$) $\bar{v}_I$ $:$ $A\longrightarrow \mathbb{R}\cup {+\infty}$ is defined by $\bar{v}_I(x)=lim_{k \to \+infty}\frac{ord_I(x^k}{k}$, ... More
Electronic properties, low-energy Hamiltonian and superconducting instabilities in CaKFe$_4$As$_4$Jun 27 2017We analyze the electronic properties of the recently discovered stoichiometric superconductor CaKFe$_4$As$_4$ by combining an ab initio approach and a projection of the band structure to a lowenergy tight-binding Hamiltonian, based on the maximally localized ... More
On the Cover-Hart Inequality: What's a Sample of Size One Worth?Jun 15 2012Bob predicts a future observation based on a sample of size one. Alice can draw a sample of any size before issuing her prediction. How much better can she do than Bob? Perhaps surprisingly, under a large class of loss functions, which we refer to as ... More
Making and Evaluating Point ForecastsDec 04 2009Mar 07 2010Typically, point forecasting methods are compared and assessed by means of an error measure or scoring function, such as the absolute error or the squared error. The individual scores are then averaged over forecast cases, to result in a summary measure ... More
A rigorous analysis using optimal transport theory for a two-reflector design problem with a point sourceAug 17 2009We consider the following geometric optics problem: Construct a system of two reflectors which transforms a spherical wavefront generated by a point source into a beam of parallel rays. This beam has a prescribed intensity distribution. We give a rigorous ... More
Proper weak-coupling approach to the periodic s-d(f) exchange modelDec 22 2003The periodic s-d(f) exchange model is characterized by a wide variety of interesting applications, a simple mathematical structure and a limited number of reliable approximations which take care of the quantum nature of the participating spins. We suggest ... More
Multi-component vapor-liquid equilibrium model for LES and application to ECN Spray ASep 27 2016We present and evaluate a detailed multi-species two-phase thermodynamic equilibrium model for large-eddy simulations (LES) of liquid-fuel injection and mixing at high pressure. The model can represent the coexistence of supercritical states and multi-component ... More
Strictly and non-strictly positive definite functions on spheresNov 30 2011Oct 01 2013Isotropic positive definite functions on spheres play important roles in spatial statistics, where they occur as the correlation functions of homogeneous random fields and star-shaped random particles. In approximation theory, strictly positive definite ... More
Regime Transition in the Energy Cascade of Rotating TurbulenceNov 02 2018Transition from a split to a forward kinetic energy cascade system is explored in the context of rotating turbulence using direct numerical simulations with a three-dimensional isotropic random force uncorrelated with the velocity field. Our parametric ... More
On the algebraicity of Puiseux seriesMar 17 2015May 13 2015We deal with the algebraicity of a Puiseux series in terms of the properties of its coefficients. We show that the algebraicity of a Puiseux series for given bounded degree is determined by a finite number of explicit polynomial formulae. Conversely, ... More
A comparison of atomistic and continuum theoretical approaches to determine electronic properties of GaN/AlN quantum dotsNov 10 2008In this work we present a comparison of multiband k.p-models, the effective bond-orbital approach, and an empirical tight-binding model to calculate the electronic structure for the example of a truncated pyramidal GaN/AlN self-assembled quantum dot with ... More
Anomalous phonon lifetime shortening in paramagnetic CrN caused by magneto-lattice coupling: A combined spin and ab initio molecular dynamics studyFeb 08 2018We study the mutual coupling of spin fluctuations and lattice vibrations in paramagnetic CrN by combining atomistic spin dynamics and ab initio molecular dynamics. The two degrees of freedom are dynamically coupled leading to non-adiabatic effects. Those ... More
About algebraic Puiseux series in several variablesFeb 13 2017Feb 01 2019We deal with the algebraicity of an iterated Puiseux series in several variables in terms of the properties of its coefficients. Our aim is to generalize to several variables the results from [HM15]. We show that the algebraicity of such a series for ... More
Regime Transition in the Energy Cascade of Rotating TurbulenceNov 02 2018Apr 06 2019Transition from a split to a forward kinetic energy cascade system is explored in the context of rotating turbulence using direct numerical simulations with a three-dimensional isotropic random force uncorrelated with the velocity field. Our parametric ... More
Quantum-Confined Stark Effect in polar and nonpolar Wurtzite InN/GaN Heterostructures: Influence on Electronic Structure and Compensation by Coulomb AttractionJan 11 2013In this paper we systematically analyze the electronic structures of polar and nonpolar wurtzite-InN/GaN quantum dots and their modification due to the quantum-confined Stark effect caused by intrinsic fields. This is achieved by combining continuum elasticity ... More
Local proper scoring rules of order twoFeb 24 2011May 31 2012Scoring rules assess the quality of probabilistic forecasts, by assigning a numerical score based on the predictive distribution and on the event or value that materializes. A scoring rule is proper if it encourages truthful reporting. It is local of ... More
Lagrangian submanifolds of standard multisymplectic manifoldsSep 28 2018We give a detailed, self-contained proof of Geoffrey Martin's normal form theorem for Lagrangian submanifolds of standard multisymplectic manifolds (that generalises Alan Weinstein's famous normal form theorem in symplectic geometry), providing also complete ... More
Stochastic models which separate fractal dimension and Hurst effectSep 13 2001Fractal behavior and long-range dependence have been observed in an astonishing number of physical systems. Either phenomenon has been modeled by self-similar random functions, thereby implying a linear relationship between fractal dimension, a measure ... More
Existence and unicity of co-moments in multisymplectic geometryNov 09 2014Given a multisymplectic manifold $(M,\omega)$ and a Lie algebra $\frak{g}$ acting on it by infinitesimal symmetries, Fregier-Rogers-Zambon define a homotopy (co-)moment as an $L_{\infty}$-algebra-homomorphism from $\frak{g}$ to the observable algebra ... More
Combining Predictive DistributionsJun 08 2011Predictive distributions need to be aggregated when probabilistic forecasts are merged, or when expert opinions expressed in terms of probability distributions are fused. We take a prediction space approach that applies to discrete, mixed discrete-continuous ... More
Properization: Constructing Proper Scoring Rules via Bayes ActsJun 19 2018Aug 16 2018Scoring rules serve to quantify predictive performance. A scoring rule is proper if truth telling is an optimal strategy in expectation. Subject to customary regularity conditions, every scoring rule can be made proper, by applying a special case of the ... More
Infinite-dimensional manifolds as ringed spacesMar 23 2014Oct 10 2016We analyze the possibility of defining infinite-dimensional manifolds as ringed spaces. More precisely, we consider three definitions of manifolds modeled on locally convex spaces: in terms of charts and atlases, in terms of ringed spaces, and in terms ... More
An invitation to multisymplectic geometryApr 07 2018In this article we study multisymplectic geometry, i.e., the geometry of manifolds with a non-degenerate, closed differential form. First we describe the transition from Lagrangian to Hamiltonian classical field theories, and then we reformulate the latter ... More
The distribution function of the Galaxy's dark haloSep 23 2015Starting from the hypothesis that the Galaxy's dark halo responded adiabatically to the infall of baryons, we have constructed a self-consistent dynamical model of the Galaxy that satisfies a large number of observations, including measurements of gas ... More
Receiver Operating Characteristic (ROC) CurvesSep 13 2018Receiver operating characteristic (ROC) curves are used ubiquitously to evaluate covariates, markers, or features as potential predictors in binary problems. We distinguish raw ROC diagnostics and ROC curves, elucidate the special role of concavity in ... More
On the geometry and quantization of symplectic Howe pairsOct 05 2009We study the orbit structure and the geometric quantization of a pair of mutually commuting hamiltonian actions on a symplectic manifold. If the pair of actions fulfils a symplectic Howe condition, we show that there is a canonical correspondence between ... More
The geodesic flow on a Riemannian supermanifoldJul 09 2011We give a natural definition of geodesics on a Riemannian supermanifold and extend the usual geodesic flow defined on the cotangent bundle of the body of the supermanifold, associated to the induced Riemannian structure on the body, to a geodesic "superflow" ... More
Optical design of two-reflector systems, the Monge-Kantorovich mass transfer problem and Fermat's principleMar 31 2003May 22 2003It is shown that the problem of designing a two-reflector system transforming a plane wave front with given intensity into an output plane front with prescribed output intensity can be formulated and solved as the Monge-Kantorovich mass transfer problem. ... More
Integration of vector fields on smooth and holomorphic supermanifoldsOct 03 2012Dec 29 2012We give a new and self-contained proof of the existence and unicity of the flow for an arbitrary (not necessarily homogeneous) smooth vector field on a real supermanifold, and extend these results to the case of holomorphic vector fields on complex supermanifolds. ... More
Grain boundary diffusion in severely deformed Al-based alloyJan 24 2017Grain boundary diffusion in severely deformed Al-based AA5024 alloy is investigated. Different states are prepared by combination of equal channel angular processing and heat treatments, with the radioisotope $^{57}$Co being employed as a sensitive probe ... More
{110} planar faults in strained bcc metals: Origins and implications of a commonly observed artifact of classical potentialsOct 03 2018Large-scale atomistic simulations with classical potentials can provide valuable insights into microscopic deformation mechanisms and defect-defect interactions in materials. Unfortunately, these assets often come with the uncertainty of whether the observed ... More
Exact solution for the two-site Kondo-Lattice Model - a limiting case for an insulatorNov 28 2002The Kondo-lattice model is well established as a method to describe an exchange coupling between single conduction electrons and localized magnetic moments. As a nontrivial exact result the zero-bandwidth limit (atomic limit) can be used to test approximations ... More
Copula CalibrationJul 29 2013We propose notions of calibration for probabilistic forecasts of general multivariate quantities. Probabilistic copula calibration is a natural analogue of probabilistic calibration in the univariate setting. It can be assessed empirically by checking ... More
Implicit Large Eddy Simulation of Cavitation in Micro Channel FlowsJan 25 2014We present a numerical method for Large Eddy Simulations (LES) of compressible two-phase flows. The method is validated for the flow in a micro channel with a step-like restriction. This setup is representative for typical cavitating multi-phase flows ... More
Exact solution for the two-site correlated Kondo-Lattice Model - a limiting case for a metalNov 28 2002The correlated Kondo-lattice model is used to describe the interaction of electrons in a single conduction band with localized magnetic moments as well as their mutual repulsion. It is our intension to provide an analytical exact result for this model ... More
Predicting Inflation: Professional Experts Versus No-Change ForecastsOct 12 2010We compare forecasts of United States inflation from the Survey of Professional Forecasters (SPF) to predictions made by simple statistical techniques. In nowcasting, economic expertise is persuasive. When projecting beyond the current quarter, novel ... More
Low temperature features in the heat capacity of unary metals and intermetallics for the example of bulk aluminum and Al$_3$ScJan 24 2017We explore the competition and coupling of vibrational and electronic contributions to the heat capacity of Al and Al$_3$Sc at temperatures below 50 K combining experimental calorimetry with highly converged finite temperature density functional theory ... More
Carrier trapping in a quantum dash: optical signaturesJul 25 2012We theoretically study the optical properties and the electronic structure of highly elongated quantum dots (quantum dashes) and show how geometrical fluctuations affect the excitonic spec- trum of the system. The dependence of the absorption intensities ... More
Lindblad approach to spatio-temporal quantum dynamics of phonon-induced carrier capture processesMar 08 2017Mar 20 2017In view of the ultrashort spatial and temporal scales involved, carrier capture processes in nanostructures are genuine quantum phenomena. To describe such processes, methods with different levels of approximations have been developed. By properly tailoring ... More
Kinematics in galactic tidal tails - A source for Hypervelocity stars?Oct 04 2011[abridged] In this work we study in detail the kinematics of tidal debris stars to investigate the implications of the new scenario that the observed sample of Hypervelocity stars could partly originate from a dwarf-host galaxy collision. We use a suite ... More
Duality and reciprocity of fluctuation-dissipation relations in conductorsJun 06 2016By analogy with linear-response we formulate the duality and reciprocity properties of current and voltage fluctuations expressed by Nyquist relations including the intrinsic bandwidths of the respective fluctuations. For this purpose we individuate total-number ... More
Interpretation of point forecasts with unkown directiveJun 05 2015Feb 18 2019Point forecasts can be interpreted as functionals (i.e., point summaries) of predictive distributions. We consider the situation where forecasters' directives are hidden and develop methodology for the identification of the unknown functional based on ... More
Phonon-assisted dark exciton preparation in a quantum dotApr 12 2017In semiconductor quantum dots the coupling to the environment, i.e. to phonons, plays a crucial role for optical state preparation. We analyze the phonon impact on two methods for a direct optical preparation of the dark exciton, which is enabled by a ... More
Conserved quantities on multisymplectic manifoldsOct 18 2016Given a vector field on a manifold M, we define a globally conserved quantity to be a differential form whose Lie derivative is exact. Integrals of conserved quantities over suitable submanifolds are constant under time evolution, the Kelvin circulation ... More
Using proper divergence functions to evaluate climate modelsJan 24 2013Jul 16 2013It has been argued persuasively that, in order to evaluate climate models, the probability distributions of model output need to be compared to the corresponding empirical distributions of observed data. Distance measures between probability distributions, ... More
Ensemble model output statistics for wind vectorsJan 12 2012A bivariate ensemble model output statistics (EMOS) technique for the postprocessing of ensemble forecasts of two-dimensional wind vectors is proposed, where the postprocessed probabilistic forecast takes the form of a bivariate normal probability density ... More
Adaptive Reduced-Order Modeling for Non-Linear Fluid-Structure InteractionFeb 14 2017We present an adaptive reduced-order model for the efficient time-resolved simulation of fluid-structure interaction problems with complex and non-linear deformations. The model is based on repeated linearizations of the structural balance equations. ... More
Electron states in a double quantum dot with broken axial symmetryFeb 12 2014We study theoretically the electron states in a system of two vertically stacked quantum dots. We investigate the influence of the geometrical symmetry breaking (caused by the displacement as well as the ellipticity of the dots) on the electron states. ... More
Double quantum dot in a quantum dash: optical propertiesFeb 15 2013We study the optical properties of highly anisotropic quantum dot structures (quantum dashes) characterized by the presence of two trapping centers located along the structure. Such a system can exhibit some of the properties characteristic for double ... More
Influence of quantum dot geometry on p-shell transitions in differently charged quantum dotsAug 22 2017Absorption spectra of neutral, negatively and positively charged semiconductor quantum dots are studied theoretically. We provide an overview of the main energetic structure around the p-shell transitions, including the influence of nearby nominally dark ... More
Singular superspacesApr 28 2013Jun 20 2014We introduce a wide category of superspaces, called locally finitely generated, which properly includes supermanifolds but enjoys much stronger permanence properties, as are prompted by applications. Namely, it is closed under taking finite fibre products ... More
Uncertainty Quantification in Complex Simulation Models Using Ensemble Copula CouplingFeb 28 2013Dec 23 2013Critical decisions frequently rely on high-dimensional output from complex computer simulation models that show intricate cross-variable, spatial and temporal dependence structures, with weather and climate predictions being key examples. There is a strongly ... More
Expected Shortfall is jointly elicitable with Value at Risk - Implications for backtestingJul 01 2015Jul 12 2015In this note, we comment on the relevance of elicitability for backtesting risk measure estimates. In particular, we propose the use of Diebold-Mariano tests, and show how they can be implemented for Expected Shortfall (ES), based on the recent result ... More
A parametrized non-equilibrium wall-model for large-eddy simulationsNov 30 2015Wall-models are essential for enabling large-eddy simulations (LESs) of realistic problems at high Reynolds numbers. The present study is focused on approaches that directly model the wall shear stress, specifically on filling the gap between models based ... More
Effect of local anisotropy on fatigue crack initiation in a coarse grained nickel-base superalloyJun 06 2018In the present work, theoretical approaches, based on grain orientation dependent Young's modulus and Schmid factor are used to describe the influence of local grain orientation on crack initiation behaviour of the coarse grained nickel base superalloy ... More
Forecaster's Dilemma: Extreme Events and Forecast EvaluationDec 31 2015In public discussions of the quality of forecasts, attention typically focuses on the predictive performance in cases of extreme events. However, the restriction of conventional forecast evaluation methods to subsets of extreme observations has unexpected ... More
Influence of excited state decay and dephasing on phonon quantum state preparationJul 17 2019The coupling between single-photon emitters and phonons opens many possibilities to store and transmit quantum properties. In this paper we apply the independent boson model to describe the coupling between an optically driven two-level system and a discrete ... More
Probabilistic LCF Risk Evaluation of a Turbine Vane by Combined Size Effect and Notch Support ModelingFeb 19 2017A probabilistic risk assessment for low cycle fatigue (LCF) based on the so-called size effect has been applied on gas-turbine design in recent years. In contrast, notch support modeling for LCF which intends to consider the change in stress below the ... More
Probabilistic Forecasting and Comparative Model Assessment Based on Markov Chain Monte Carlo OutputAug 24 2016Nov 13 2017In Bayesian inference, predictive distributions are typically available only through a sample generated via Markov chain Monte Carlo (MCMC) or related algorithms. In this paper, we conduct a systematic analysis of how to make and evaluate probabilistic ... More
Coherent phonon lasing in a thermal quantum nanomachineJun 04 2018Aug 27 2018The notion of nanomachines has recently emerged to engage and use collective action of ensembles of nanoscale components or systems. Here we present a heat-gradient driven nanomachine concept which through appropriate coupling between quantum nanosystems ... More
Generating Custom Code for Efficient Query Execution on Heterogeneous ProcessorsSep 03 2017Processor manufacturers build increasingly specialized processors to mitigate the effects of the power wall to deliver improved performance. Currently, database engines are manually optimized for each processor: A costly and error prone process. In this ... More
Correlating the interstellar magnetic field with protostellar jets and its sourcesSep 09 2011This article combines new CCD polarimetric data with previous information about protostellar objects in a search for correlations involving the interstellar magnetic field. Specifically, we carried out an optical polarimetric study of a sample of 28 fields ... More
Probabilistic Forecasting and Comparative Model Assessment Based on Markov Chain Monte Carlo OutputAug 24 2016In Bayesian inference, predictive distributions are typically available only through a sample generated via Markov chain Monte Carlo (MCMC) or related algorithms. In this paper, we conduct a systematic analysis of how to make and evaluate probabilistic ... More
Probabilistic quantitative precipitation field forecasting using a two-stage spatial modelJan 22 2009Short-range forecasts of precipitation fields are needed in a wealth of agricultural, hydrological, ecological and other applications. Forecasts from numerical weather prediction models are often biased and do not provide uncertainty information. Here ... More
X-ray photoevaporation's limited success in the formation of planetesimals by the streaming instabilitySep 01 2017The streaming instability is often invoked as solution to the fragmentation and drift barriers in planetesimal formation, catalyzing the aggregation of dust on kyr timescales to grow km-sized cores. However there remains a lack of consensus on the physical ... More
Predictive Inference Based on Markov Chain Monte Carlo OutputAug 24 2016Mar 29 2019In Bayesian inference, predictive distributions are typically available only through a sample generated via Markov chain Monte Carlo or related algorithms. In this paper, we conduct a systematic analysis of how to make and evaluate probabilistic forecasts ... More
Spatially adaptive, Bayesian estimation for probabilistic temperature forecastsJul 17 2015Jun 15 2016Uncertainty in the prediction of future weather is commonly assessed through the use of forecast ensembles that employ a numerical weather prediction model in distinct variants. Statistical postprocessing can correct for biases in the numerical model ... More
Of Quantiles and Expectiles: Consistent Scoring Functions, Choquet Representations, and Forecast RankingsMar 27 2015Apr 17 2015In the practice of point prediction, it is desirable that forecasters receive a directive in the form of a statistical functional, such as the mean or a quantile of the predictive distribution. When evaluating and comparing competing forecasts, it is ... More
Multiscale dynamics of biological cells with chemotactic interactions: from a discrete stochastic model to a continuous descriptionJan 30 2006The Cellular Potts Model (CPM) has been used for simulating various biological phenomena such as differential adhesion, fruiting body formation of the slime mold Dictyostelium discoideum, angiogenesis, cancer invasion, chondrogenesis in embryonic vertebrate ... More
The cluster of galaxies Abell 376May 20 2003We present a dynamical analysis of the galaxy cluster Abell 376 based on a set of 73 velocities, most of them measured at Pic du Midi and Haute-Provence observatories and completed with data from the literature. Data on individual galaxies are presented ... More
When is the mode functional the Bayes classifier?Apr 28 2017In classification problems, the mode of the conditional probability distribution, i.e., the most probable category, is the Bayes classifier under zero-one or misclassification loss. Under any other cost structure, the mode fails to persist.
Section on the special year for mathematics of planet earth (MPE 2013)Jan 07 2013Dozens of research centers, foundations, international organizations and scientific societies, including the Institute of Mathematical Statistics, have joined forces to celebrate 2013 as a special year for the Mathematics of Planet Earth. In its five-year ... More
The affinely invariant distance correlationOct 09 2012Oct 16 2014Sz\'{e}kely, Rizzo and Bakirov (Ann. Statist. 35 (2007) 2769-2794) and Sz\'{e}kely and Rizzo (Ann. Appl. Statist. 3 (2009) 1236-1265), in two seminal papers, introduced the powerful concept of distance correlation as a measure of dependence between sets ... More
Non-Markovian spin transfer dynamics in magnetic semiconductors despite short memory timesMar 18 2013A quantum kinetic theory of the spin transfer between carriers and Mn atoms in a Mn doped diluted magnetic semiconductor is presented. It turns out that the typical memory time associated with these processes is orders of magnitude shorter than the time ... More
The OPD Photometric Survey of Open Clusters II. robust determination of the fundamental parameters of 24 open clustersAug 10 2016In the second paper of the series we continue the investigation of open cluster fundamental parameters using a robust global optimization method to fit model isochrones to photometric data. We present optical UBVRI CCD photometry (Johnsons-Cousins system) ... More
Optical polarization and near IR photometry of the proto-planetary nebula Hen 3-1475Dec 19 2002We present BVRI CCD aperture polarization and near-infrared photometry of the proto-planetary nebula Hen 3-1475. Its intrinsic polarization is high and shows a strong spectral dependence. The position angles in all bands are perpendicular to the axis ... More
Optical polarimetry of HH 135/HH 136Jan 31 2007We present optical linear polarimetry in the line of sight to HH135/HH136. The polarimetry of the field stars reveals two populations: one corresponds to a foreground interstellar component; the other originates in the interstellar medium in the vicinity ... More
Quantum dynamics of optical phonons generated by optical excitation of a quantum dotJun 15 2016Jul 15 2016The study of the fundamental properties of phonons is crucial to understand their role in applica- tions in quantum information science, where the active use of phonons is currently highly debated. A genuine quantum phenomenon associated with the fluctuation ... More
Coulomb effects on the photo-excited quantum dynamics of electrons in a plasmonic nanosphereOct 26 2017Oct 10 2018With recent experiments investigating the optical properties of progressively smaller plasmonic particles, quantum effects become increasingly more relevant, requiring a microscopic description. Using the density matrix formalism we analyze the photo-excited ... More
Phonon-induced enhancement of photon entanglement in quantum dot-cavity systemsFeb 13 2019We report on simulations of the degree of polarization entanglement of photon pairs simultaneously emitted from a quantum dot-cavity system that demand revisiting the role of phonons. Since coherence is a fundamental precondition for entanglement and ... More
On the Richtmyer-Meshkov instability evolving from a deterministic multimode planar interfaceFeb 06 2014Jun 13 2014We investigate the shock-induced turbulent mixing between a light and heavy gas, where a Richtmyer-Meshkov instability (RMI) is initiated by a $\Ma = 1.5$ shock wave. The prescribed initial conditions define a deterministic multimode interface perturbation ... More
Benchmarking Distributed Stream Processing EnginesFeb 23 2018Over the last years, stream data processing has been gaining attention both in industry and in academia due to its wide range of applications. To fulfill the need for scalable and efficient stream analytics, numerous open source stream data processing ... More
Comparison of different concurrences characterizing photon-pairs generated in the biexciton cascade in quantum dots coupled to microcavitiesDec 07 2017May 09 2018We compare three different notions of concurrence to measure the polarization entanglement of two-photon states generated by the biexciton cascade in a quantum dot embedded in a microcavity. We focus on the often-discussed situation of a dot with finite ... More
Ab initio explanation of disorder and off-stoichiometry in Fe-Mn-Al-C kappa carbidesJan 24 2017Carbides play a central role for the strength and ductility in many materials. Simulating the impact of these precipitates on the mechanical performance requires the knowledge about their atomic configuration. In particular, the C content is often observed ... More
A cut-cell finite volume - finite element coupling approach for fluid-structure interaction in compressible flowNov 20 2015Dec 21 2015We present a loosely coupled approach for the solution of fluid-structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet-Neumann partitioning. The interface motion in the Eulerian ... More
Labyrinth: Compiling Imperative Control Flow to Parallel DataflowsSep 18 2018Oct 15 2018Parallel dataflow systems have become a standard technology for large-scale data analytics. Complex data analysis programs in areas such as machine learning and graph analytics often involve control flow, i.e., iterations and branching. Therefore, systems ... More
In-depth Assessment of an Interactive Graph-based Approach for the Segmentation for Pancreatic Metastasis in Ultrasound Acquisitions of the Liver with two Specialists in Internal MedicineMar 12 2018The manual outlining of hepatic metastasis in (US) ultrasound acquisitions from patients suffering from pancreatic cancer is common practice. However, such pure manual measurements are often very time consuming, and the results repeatedly differ between ... More
Optical polarimetry and infrared photometry of two AM Her binaries: 1RXS J161008.0+035222 and 1RXS J231603.9-052713Apr 13 2006We present the first optical circular and linear polarization measurements of two polar candidates from ROSAT: 1RXS J161008.0+035222 and 1RXS J231603.9-052713. We also present H band near-infrared photometry of the last object. The presence of strong ... More
Optical polarimetric monitoring of the type II-plateau SN 2005afApr 25 2006Aims. Core-collapse supernovae may show significant polarization that implies non-spherically symmetric explosions. We observed the type II-plateau SN 2005af using optical polarimetry in order to verify whether any asphericity is present in the supernova ... More
Skill of global raw and postprocessed ensemble predictions of rainfall over northern tropical AfricaAug 15 2017Accumulated precipitation forecasts are of high socioeconomic importance for agriculturally dominated societies in northern tropical Africa. In this study, we analyze the performance of nine operational global ensemble prediction systems (EPSs) relative ... More
Stokes imaging of AM Her systems using 3D inhomogeneous models-II. Modelling X-ray and optical data of CP TucanaeApr 09 2013The viewing geometry of the polar CP Tuc that better explains its optical and X-ray light curves is controversial. Previous modelling of white-light polarimetric data considered the partial self-eclipse of an extended inhomogeneous emitting region. Alternatively, ... More
Iterative scheme for solving optimal transportation problems arising in reflector designOct 13 2011Nov 04 2011We consider the geometric optics problem of finding a system of two reflectors that transform a spherical wavefront into a beam of parallel rays with prescribed intensity distribution. Using techniques from optimal transportation theory, it has been shown ... More
Theory of the time-resolved Kerr rotation on trapped holesOct 22 2009Sep 13 2010We formulate a model of the time-resolved Kerr rotation experiment on a single hole in a semiconductor nanostructure (e.g., a quantum dot) or on an ensemble of trapped holes (e.g., in a quantum well) in a tilted magnetic field. We use a generic Markovian ... More
From strong to weak temperature dependence of the two-photon entanglement resulting from the biexciton cascade inside a cavityFeb 05 2019We investigate the degree of entanglement quantified by the concurrence of photon pairs that are simultaneously emitted in the biexciton-exciton cascade from a quantum dot in a cavity. Four dot-cavity configurations are compared that differ with respect ... More
Strain Analysis by a Total Generalized Variation Regularized Optical Flow ModelApr 20 2017Feb 28 2018In this paper we deal with the important problem of estimating the local strain tensor from a sequence of micro-structural images realized during deformation tests of engineering materials. Since the strain tensor is defined via the Jacobian of the displacement ... More
Rabi oscillations of a quantum dot exciton coupled to acoustic phonons: coherence and population readoutSep 27 2018While the advanced coherent control of qubits is now routinely carried out in low frequency (GHz) systems like single spins, it is far more challenging to achieve for two-level systems in the optical domain. This is because the latter evolve typically ... More
Gaussian Random Particles with Flexible Hausdorff DimensionFeb 05 2015Feb 12 2015Gaussian particles provide a flexible framework for modelling and simulating three-dimensional star-shaped random sets. In our framework, the radial function of the particle arises from a kernel smoothing, and is associated with an isotropic random field ... More
Benchmarking Distributed Stream Data Processing SystemsFeb 23 2018Jun 24 2019The need for scalable and efficient stream analysis has led to the development of many open-source streaming data processing systems (SDPSs) with highly diverging capabilities and performance characteristics. While first initiatives try to compare the ... More