Results for "Steffen Kionke"

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On equivariant Euler-Poincaré characteristic in sheaf cohomologyJul 04 2013Let X be a topological Hausdorff space together with a continuous action of a finite group G. Let R be the ring of integers of a number field F. Let E be a G-sheaf of flat R-modules over X and let $\Phi$ be a G-stable paracompactifying family of supports ... More
A geometric approach to divergent points of higher dimensional Collatz mappingsNov 18 2015We define generalized Collatz mappings on free abelian groups of finite rank and study their iteration trajectories. Using geometric arguments we describe cones of points having a divergent trajectory and we deduce lower bounds for the density of the ... More
Lefschetz numbers of symplectic involutions on arithmetic groupsFeb 05 2013The reduced norm-one group G of a central simple algebra is an inner form of the special linear group, and an involution on the algebra induces an automorphism of G. We study the action of such automorphisms in the cohomology of arithmetic subgroups of ... More
On lower bounds for cohomology growth in p-adic analytic towersMay 22 2013Jan 09 2014Let p and l be two distinct prime numbers and let G be a group. We study the asymptotic behaviour of the mod-l Betti numbers in p-adic analytic towers of finite index subgroups. If X is a finite l-group of automorphisms of G, our main theorem allows to ... More
On $p$-adic limits of topological invariantsNov 01 2018The purpose of this article is to define and study new invariants of topological spaces: the $p$-adic Betti numbers and the $p$-adic torsion. These invariants take values in the $p$-adic numbers and are constructed from a virtual pro-$p$ completion of ... More
The growth of Betti numbers and approximation theoremsSep 03 2017These short lecture notes provide a brief introduction to the field of homology growth. They are composed out of two lectures, which I have given at the Borel seminar 2017 in Les Diablerets. We give a proof of L\"uck's approximation theorem, discuss generalizations ... More
Characters, $L^2$-Betti numbers and an equivariant approximation theoremFeb 08 2017Mar 01 2017Let $G$ be a group with a finite subgroup $H$. We define the $L^2$-multiplicity of an irreducible representation of $H$ in the $L^2$-homology of a proper $G$-CW-complex. These invariants generalize the $L^2$-Betti numbers. Our main results are approximation ... More
Groups acting on rooted trees and their representations on the boundaryJan 08 2018Apr 03 2018We consider groups that act on spherically symmetric rooted trees and study the associated representation of the group on the space of locally constant functions on the boundary of the tree. We introduce and discuss the new notion of locally 2-transitive ... More
Profinite invariants of arithmetic groupsJan 04 2019Jan 21 2019We prove that the sign of the Euler characteristic of arithmetic groups with CSP is determined by the profinite completion. In contrast, we construct examples showing that this is not true for the Euler characteristic itself and that the sign of the Euler ... More
On the growth of the first Betti number of arithmetic hyperbolic 3-manifoldsApr 17 2012We calculate the Lefschetz number of a Galois automorphism in the cohomology of certain arithmetic congruence groups arising from orders in quaternion algebras over number fields. As an application we give a lower bound for the first Betti number of a ... More
Zeta functions associated to admissible representations of compact p-adic Lie groupsJul 26 2017Feb 27 2019Let $G$ be a profinite group. A strongly admissible smooth representation $\rho$ of $G$ over $\mathbb{C}$ decomposes as a direct sum $\rho \cong \bigoplus_{\pi \in \mathrm{Irr}(G)} m_\pi(\rho) \, \pi$ of irreducible representations with finite multiplicities ... More
Zeta functions associated to admissible representations of compact p-adic Lie groupsJul 26 2017Aug 05 2018Let $G$ be a profinite group. A strongly admissible smooth representation $\rho$ of $G$ over $\mathbb{C}$ decomposes as a direct sum $\rho \cong \bigoplus_{\pi \in \mathrm{Irr}(G)} m_\pi(\rho) \, \pi$ of irreducible representations with finite multiplicities ... More
Positively finitely related profinite groupsNov 22 2016We define and study the class of positively finitely related (PFR) profinite groups. Positive finite relatedness is a probabilistic property of profinite groups which provides a first step to defining higher finiteness properties of profinite groups which ... More
Equivariant Benjamini-Schramm Convergence of Simplicial Complexes and $\ell^2$-MultiplicitiesMay 14 2019We define a variant of Benjamini-Schramm convergence for finite simplicial complexes with the action of a fixed finite group G which leads to the notion of random rooted simplicial G-complexes. For every random rooted simplicial G-complex we define a ... More
On geometric aspects of diffuse groupsNov 24 2014Dec 02 2014Bowditch introduced the notion of diffuse groups as a geometric variation of the unique product property. We elaborate on various examples and non-examples, keeping the geometric point of view from Bowditch's paper. In particular, we discuss fundamental ... More
CP Violation Makes Left-Right Symmetric Extensions With Non-Hermitian Mass Matrices Appear UnnaturalFeb 01 2010Mar 31 2010Following a similar recent analysis for CP violation in the electroweak sector of the standard model, we estimate the naturalness of a magnitude of CP violation (measured by the Jarlskog invariant J) close to the observed value in extensions of the standard ... More
A Modification of the Social Force Model by ForesightDec 03 2009The motion of pedestrian crowds (e.g. for simulation of an evacuation situation) can be modeled as a multi-body system of self driven particles with repulsive interaction. We use a few simple situations to determine the simplest allowed functional form ... More
Geometric Aspects of Gauge and Spacetime SymmetriesMar 03 2011We investigate several problems in relativity and particle physics where symmetries play a central role; in all cases geometric properties of Lie groups and their quotients are related to physical effects. The first part is concerned with symmetries in ... More
Multilevel Monte Carlo algorithms for Lévy-driven SDEs with Gaussian correctionJan 07 2011We introduce and analyze multilevel Monte Carlo algorithms for the computation of $\mathbb {E}f(Y)$, where $Y=(Y_t)_{t\in[0,1]}$ is the solution of a multidimensional L\'{e}vy-driven stochastic differential equation and $f$ is a real-valued function on ... More
Oded Schramm: From Circle Packing to SLEJul 12 2010In this note, I will describe some highlights of Oded Schramm's work in circle packings and the Koebe conjecture, as well as on SLE.
Spatial discretization of restricted group algebrasFeb 22 2010We consider spatial discretizations by the finite section method of the restricted group algebra of a finitely generated discrete group, which is represented as a concrete operator algebra via its left-regular representation. Special emphasis is paid ... More
GLR-Parsing of Word Lattices Using a Beam Search MethodJun 22 1995This paper presents an approach that allows the efficient integration of speech recognition and language understanding using Tomita's generalized LR-parsing algorithm. For this purpose the GLRP-algorithm is revised so that an agenda mechanism can be used ... More
Homotopy of Rational Maps and the Quantization of SkyrmionsOct 31 2002The Skyrme model is a classical field theory which models the strong interaction between atomic nuclei. It has to be quantized in order to compare it to nuclear physics. When the Skyrme model is semi-classically quantized it is important to take the Finkelstein-Rubinstein ... More
Finkelstein-Rubinstein constraints for the Skyrme model with pion massesSep 13 2005The Skyrme model is a classical field theory modelling the strong interaction between atomic nuclei. It has to be quantized in order to compare it to nuclear physics. When the Skyrme model is semi-classically quantized it is important to take the Finkelstein-Rubinstein ... More
On the Number of Many-to-Many Alignments of Multiple SequencesNov 02 2015Jul 24 2016We count the number of alignments of $N \ge 1$ sequences when match-up types are from a specified set $S\subseteq \mathbb{N}^N$. Equivalently, we count the number of nonnegative integer matrices whose rows sum to a given fixed vector and each of whose ... More
Group field theory and its cosmology in a matter reference frameAug 30 2018Sep 25 2018While the equations of general relativity take the same form in any coordinate system, choosing a suitable set of coordinates is essential in any practical application. This poses a challenge in background-independent quantum gravity, where coordinates ... More
Automated QCD and Electroweak Corrections with SherpaNov 21 2017Precise theoretical predictions are vital for the interpretation of Standard Model measurements and facilitate conclusive searches for New Physics phenomena at the LHC. In this contribution I highlight some of the ongoing efforts in the framework of the ... More
An Optimal Realization Algorithm for Bipartite Graphs with Degrees in Prescribed IntervalsAug 18 2017We consider the problem of constructing a bipartite graph whose degrees lie in prescribed intervals. Necessary and sufficient conditions for the existence of such graphs are well-known. However, existing realization algorithms suffer from large running ... More
Reasoning about proof and knowledgeSep 19 2017Dec 28 2018In previous work [Lewitzka, Log. J. IGPL 2017], we presented a hierarchy of classical modal systems, along with algebraic semantics, for the reasoning about intuitionistic truth, belief and knowledge. Deviating from G\"odel's interpretation of IPC in ... More
Corrections to the results derived in "A Unified Approach to Algorithms Generating Unrestricted and Restricted Integer Compositions and Integer Partitions"'; and a comparison of four restricted integer composition generation algorithmsMar 05 2014In this note, I discuss results on integer compositions/partitions given in the paper "A Unified Approach to Algorithms Generating Unrestricted and Restricted Integer Compositions and Integer Partitions". I also experiment with four different generation ... More
Jarnik-type InequalitiesJun 06 2013Sep 05 2014It is well known due to Jarnik that the set Bad of badly approximable numbers is of Hausdorff-dimension one. If Bad(c) denotes the subset of x in Bad for which the approximation constant c > c(x), then Jarnik was in fact more precise and gave nontrivial ... More
A modal logic amalgam of classical and intuitionistic propositional logicJun 09 2013Jun 03 2015A famous result, conjectured by G\"odel in 1932 and proved by McKinsey and Tarski in 1948, says that $\varphi$ is a theorem of intuitionistic propositional logic IPC iff its G\"odel-translation $\varphi'$ is a theorem of modal logic S4. In this paper, ... More
Comment on "Causality-violating Higgs singlets at the LHC"Feb 07 2013Aug 31 2013The spacetime of Ho and Weiler [Phys. Rev. D {\bf 87}, 045004 (2013)] supposedly admitting closed timelike curves (CTCs) is flat Minkowski spacetime with a compactified coordinate and can only contain CTCs if the compact direction is chosen to be timelike. ... More
Dual scattering channel schemes and transmission line methodsJun 25 2004Jun 30 2004Dual scattering channel (DSC) schemes naturally extend the transmission line matrix (TLM) numerical method beyond the lines set up by P.B.JOHNS and coworkers. Conceptually, DSC schemes retain from TLM the typical formal splitting of the computed fields ... More
DSC numerical solution of the Oberbeck-Boussinesq equationsMay 04 2005Jul 06 2005Dual Scattering Channel schemes generalise Johns' TLM algorithm and replace the latter in situations where the transmission line picture of wave propagation fails. This is notoriously the case in applications to fluid dynamics, for instance. In this paper, ... More
Growth and Scaling during Development and RegenerationAug 19 2016Life presents fascinating examples of self-organization and emergent phenomena. In multi-cellular organisms, a multitude of cells interact to form and maintain highly complex body plans of well-defined size. In this thesis, we investigate theoretical ... More
Data Compaction - Compression without DecompressionFeb 11 2014Data compaction is a new approach for lossless and lossy compression of read-only array data. The biggest advantage over existing approaches is the possibility to access compressed data without any decompression. This makes data compaction most suitable ... More
Lower S-Dimension of Fractal SetsMar 19 2010Oct 11 2010The interrelations between (upper and lower) Minkowski contents and (upper and lower) surface area based contents (S-contents) as well as between their associated dimensions have recently been investigated for general sets in R^d (cf. [3]). While the ... More
Opinion dynamics and wisdom under out-group discriminationJun 13 2013Oct 31 2016We study a DeGroot-like opinion dynamics model in which agents may oppose other agents. As an underlying motivation, in our setup, agents want to adjust their opinions to match those of the agents of their 'in-group' and, in addition, they want to adjust ... More
Remarks on Nitsche's functional: The rotationally symmetric caseSep 23 2004We investigate existence and stability of rotationally symmetric critical immersions of variational problems of higher order which were considered by Nitsche.
Quivers for silting mutationApr 10 2015We give a combinatorial mutation rule for Aihara's and Iyama's silting mutation. As an application, we reprove Keller-Yang's mutation rule for Ginzburg algebras, and obtain an analog of that rule for arbitrary dimension.
Remarks on Seshadri constantsJul 09 1995Given a smooth complex projective variety $X$ and an ample line bundle $L$ on $X$. Fix a point $x\in X$. We consider the question, are there conditions which guarantee the maxima of the Seshadri constant of $L$ at $x$, i.e $\eps(L,x)=\root n \of {L^n}$? ... More
Does black-hole evaporation imply that physics is non-unitary, and if so, what must the laws of physics look like? An EssayMay 10 2009Stephen Hawking's discovery of black hole evaporation had the remarkable consequence that information is destroyed by a black hole, which can only be accommodated by modifying the laws of quantum mechanics. Different attempts to evade the information ... More
Fractal algebras of discretization sequencesOct 06 2011These are the lecture notes for a course at the Summer School on "Applied Analysis" at the Technical University Chemnitz in September 2011. We start with the definition of a fractal algebra and show that the fractal property is enormously useful for several ... More
On Sharpness of Error Bounds for Single Hidden Layer Feedforward Neural NetworksNov 13 2018A new quantitative extension of the uniform boundedness principle is used to show sharpness of error bounds for sigmoid and ReLU function approximation. Neural networks perform such operations. Best possible approximation errors of neural networks with ... More
The slippage paradoxMar 11 2011Buying or selling assets leads to transaction costs for the investor. On one hand, it is well know to all market practionaires that the transaction costs are positive on average and present therefore systematic loss. On the other hand, for every trade, ... More
Strongly Polynomial 2-Approximations of Discrete Wasserstein BarycentersApr 18 2017Oct 23 2018Wasserstein barycenters correspond to optimal solutions of transportation problems for several marginals, which arise in a wide range of fields. In many applications, data is given as a set of probability measures with finite support. The discrete barycenters ... More
Intersecting 1-factors and nowhere-zero 5-flowsJun 24 2013Let $G$ be a bridgeless cubic graph, and $\mu_2(G)$ the minimum number $k$ such that two 1-factors of $G$ intersect in $k$ edges. A cyclically $n$-edge-connected cubic graph $G$ has a nowhere-zero 5-flow if (1) $n \geq 6$ and $\mu_2(G) \leq 2$ or (2) ... More
Gauge techniques in time and frequency domain TLMJun 13 2000Mar 22 2009Typical features of the Transmission Line Matrix (TLM) algorithm in connection with stub loading techniques and prone to be hidden in common frequency domain formulations are elucidated within the propagator approach to TLM. In particular, the latter ... More
Dual Scattering Channel Schemes Extending the Johns AlgorithmSep 16 2003Apr 17 2006Dual scattering channel schemes extend the transmission line matrix numerical method (JOHNS' TLM algorithm) in two directions. For one point, transmission line links are replaced by abstract scattering channels in terms of paired distributions (characteristic ... More
mu-Stability of 2-immersions of prescribed mean curvature and flat normal bundle in Euclidean spaces of higher codimensionJan 22 2007We present three ways to establish general stability inequalities for various classes of 2-immersions in Euclidean spaces of higher codimension
Area estimates for two-dimensional immersions of mean curvature type in Euclidean spaces of higher codimensionMar 12 2007We establish area bounds for two-dimensional immersions in R^3 and R^n. Namely, for \mu-stable immersions in R^3 (R^n), for graphs in $\mathbb R^3$ which solve quasilinear equations in divergence form, and for graphs which are critical for Fermat-type ... More
Residual based Error Estimate and Quasi-Interpolation on Polygonal Meshes for High Order BEM-based FEMNov 29 2015Only a few numerical methods can treat boundary value problems on polygonal and polyhedral meshes. The BEM-based Finite Element Method is one of the new discretization strategies, which make use of and benefits from the flexibility of these general meshes ... More
Arveson dichotomy and essential fractalityJul 26 2011The notions of fractal and essentially fractal algebras of approximation sequences and of the Arveson dichotomy have proved extremely useful for several spectral approximation problems. The purpose of this short note is threefold: to present a short new ... More
Curvature Bounds for Neighborhoods of Self-Similar SetsOct 11 2010In some recent work, fractal curvatures C^f_k(F) and fractal curvature measures C^f_k(F, .), k = 0, ..., d, have been determined for all self-similar sets F in R^d, for which the parallel neighborhoods satisfy a certain regularity condition and a certain ... More
The quantization complexity of diffusion processesNov 26 2004We investigate the high resolution coding problem for solutions of stochastic differential equations in the L^p[0,1]- and the C[0,1]-space. Tight asymptotic estimates are found under weak regularity assumptions. The main technical tool is a decoupling ... More
DG-algebras and derived A-infinity algebrasNov 28 2007Jul 21 2009A differential graded algebra can be viewed as an A-infinity algebra. By a theorem of Kadeishvili, a dga over a field admits a quasi-isomorphism from a minimal A-infinity algebra. We introduce the notion of a derived A-infinity algebra and show that any ... More
2D Numerical Simulation of Stellar ConvectionMar 06 2000The dynamics and thermal structure of the surface layers of stars with outer convection zones can be studied in some detail by means of numerical simulations of time-dependent compressible convection. In an effort to investigate the properties of ``stellar ... More
Kinetic induced phase transitionJul 27 1999An Ising model with local Glauber dynamics is studied under the influence of additional kinetic restrictions for the spin-flip rates depending on the orientation of neighboring spins. Even when the static interaction between the spins is completely eliminated ... More
On the stability of the tangent bundle of Fano manifoldsJul 10 1994By using the classification of Fano 3-folds we prove: Let $X$ be Fano 3-fold. Assume that the tangent bundle $T_X$ of $X$ is not stable (i.e. semi-stable or unstable). Then $b_2\geq 2$ and a relative tangent sheaf $T_{X/Y}$ of a contraction $f:X\longrightarrow ... More
Kernel Regression by Mode Calculation of the Conditional Probability DistributionNov 21 2008The most direct way to express arbitrary dependencies in datasets is to estimate the joint distribution and to apply afterwards the argmax-function to obtain the mode of the corresponding conditional distribution. This method is in practice difficult, ... More
On the Iterated Hairpin CompletionOct 18 2010Mar 09 2011The (bounded) hairpin completion and its iterated versions are operations on formal lan- guages which have been inspired by the hairpin formation in DNA-biochemistry. The paper answers two questions asked in the literature about the iterated hairpin completion. ... More
Dynamical modeling and the interactions with the ISMSep 22 2011This paper is a review of some of the recent modeling efforts to improve our understanding of structure formation and evolution of planetary nebulae including their interaction with the interstellar medium. New propositions have been made for the formation ... More
2-point functions in quantum cosmologyAug 30 2011We discuss the path-integral formulation of quantum cosmology with a massless scalar field as a sum-over-histories, with particular reference to loop quantum cosmology. Exploiting the analogy with the relativistic particle, we give a complete overview ... More
Asymptotic normality of integer compositions inside a rectangleMar 03 2012Among all restricted integer compositions with at most $m$ parts, each of which has size at most $l$, choose one uniformly at random. Which integer does this composition represent? In the current note, we show that underlying distribution is, for large ... More
Classical GR as a topological theory with linear constraintsNov 24 2010Sep 23 2011We investigate a formulation of continuum 4d gravity in terms of a constrained topological (BF) theory, in the spirit of the Plebanski formulation, but involving only linear constraints, of the type used recently in the spin foam approach to quantum gravity. ... More
Directional H2-matrix compression for high-frequency problemsOct 23 2015Jun 11 2016Standard numerical algorithms like the fast multipole method or $\mathcal{H}$-matrix schemes rely on low-rank approximations of the underlying kernel function. For high-frequency problems, the ranks grow rapidly as the mesh is refined, and standard techniques ... More
Epistemic extensions of combined classical and intuitionistic propositional logicNov 04 2016Logic L was introduced by Lewitzka [8] as a modal system that combines intuitionistic and classical logic: L is a conservative extension of CPC and it contains a copy of IPC via embedding $\varphi\mapsto\square\varphi$. In this article, we consider L3, ... More
W+jets as a background to top physics: the quest for many jetsJul 20 2010The latest progress in calculating electroweak gauge boson production in association with QCD jets at hadron colliders is summarized. Particular emphasis is given to the recently completed QCD one-loop calculations of W+3jets and Wb final states. Furthermore ... More
Fermions coupled to Skyrmions on S^3Apr 30 2003This paper discusses Skyrmions on the 3-sphere coupled to fermions. The resulting Dirac equation commutes with a generalized angular momentum G. For G = 0 the Dirac equation can be solved explicitly for a constant Skyrme configuration and also for a SO(4) ... More
Benchmarking cross-project defect prediction approaches with costs metricsJan 12 2018Defect prediction can be a powerful tool to guide the use of quality assurance resources. In recent years, many researchers focused on the problem of Cross-Project Defect Prediction (CPDP), i.e., the creation of prediction models based on training data ... More
Normal Products and Zimmermann Identities in Configuration Space BPHZ RenormalizationAug 14 2017The notion of normal products, a generalization of Wick products, is derived with respect to BPHZ renormalization formulated entirely in configuration space. If inserted into time-ordered products, they admit the limit of coinciding field operators, which ... More
Configuration Space BPHZ Renormalization on Analytic SpacetimesAug 14 2017A configuration space version of BPHZ renormalization is proved in the realm of perturbative algebraic quantum field theory. All arguments are formulated entirely in configuration space so that the range of application is extended to analytic spacetimes. ... More
Niebur-Poincaré Series and Traces of Singular ModuliApr 26 2017Apr 17 2018We compute the Fourier coefficients of analogues of Kohnen and Zagier's modular forms $f_{k,D}$ of weight $2$ and negative discriminant. These functions can also be written as twisted traces of certain weight $2$ Poincar\'e series with evaluations of ... More
The Combinatorics of Weighted Vector CompositionsApr 17 2017Aug 25 2018A vector composition of a vector $\mathbf{\ell}$ is a matrix $\mathbf{A}$ whose rows sum to $\mathbf{\ell}$. We define a weighted vector composition as a vector composition in which the column values of $\mathbf{A}$ may appear in different colors. We ... More
Graph Transformation Planning via AbstractionJul 30 2014Modern software systems increasingly incorporate self-* behavior to adapt to changes in the environment at runtime. Such adaptations often involve reconfiguring the software architecture of the system. Many systems also need to manage their architecture ... More
Quantum cosmology of (loop) quantum gravity condensates: An exampleApr 10 2014Jul 04 2014Spatially homogeneous universes can be described in (loop) quantum gravity as condensates of elementary excitations of space. Their treatment is easiest in the second-quantised group field theory formalism which allows the adaptation of techniques from ... More
Vizing's independence number conjecture is true asymptoticallySep 03 2016In 1965, Vizing conjectured that the independence ratio of edge-chromatic critical graphs is at most $\frac{1}{2}$. We prove that for every $\epsilon > 0$ this conjecture is equivalent to its restriction on a specific set of edge-chromatic critical graphs ... More
Identities for partial Bell polynomials derived from identities for weighted integer compositionsJan 06 2016We discuss closed-form formulas for the (n; k)-th partial Bell polynomials derived in Cvijovic. We show that partial Bell polynomials are special cases of weighted integer compositions, and demonstrate how the identities for partial Bell polynomials easily ... More
Combining intermediate propositional logics with classical logicOct 19 2015In [17], we introduced a modal logic, called $L$, which combines intuitionistic propositional logic $IPC$ and classical propositional logic $CPC$ and is complete w.r.t. an algebraic semantics. However, $L$ seems to be too weak for Kripke-style semantics. ... More
Identifying cosmological perturbations in group field theory condensatesMay 27 2015Aug 03 2015One proposal for deriving effective cosmological models from theories of quantum gravity is to view the former as a mean-field (hydrodynamic) description of the latter, which describes a universe formed by a 'condensate' of quanta of geometry. This idea ... More
Hierarchical matrix arithmetic with accumulated updatesMar 27 2017Jul 31 2018Hierarchical matrices can be used to construct efficient preconditioners for partial differential and integral equations by taking advantage of low-rank structures in triangular factorizations and inverses of the corresponding stiffness matrices. The ... More
1-factor and cycle covers of cubic graphsSep 20 2012Jan 29 2015Let $G$ be a bridgeless cubic graph. Consider a list of $k$ 1-factors of $G$. Let $E_i$ be the set of edges contained in precisely $i$ members of the $k$ 1-factors. Let $\mu_k(G)$ be the smallest $|E_0|$ over all lists of $k$ 1-factors of $G$. Any list ... More
Denotational semantics for modal systems S3--S5 extended by axioms for propositional quantifiers and identityDec 29 2012Sep 07 2014There are logics where necessity is defined by means of a given identity connective: $\square\varphi := \varphi\equiv\top$ ($\top$ is a tautology). On the other hand, in many standard modal logics the concept of propositional identity (PI) $\varphi\equiv\psi$ ... More
Large eddy approximation of turbulent flow in DSC schemesMar 30 2006Aug 28 2008Large eddy approximation of turbulent flow is given a natural setting within the DSC framework of computational fluid dynamics. Periodic cellular coarse-graining prevents the nodal flow from piling up and preserves its large patterns. The coarsening operations ... More
Adaptive compression of large vectorsMay 31 2015Apr 09 2017Numerical algorithms for elliptic partial differential equations frequently employ error estimators and adaptive mesh refinement strategies in order to reduce the computational cost. We can extend these techniques to general vectors by splitting the vectors ... More
On Sharpness of Error Bounds for Single Hidden Layer Feedforward Neural NetworksNov 13 2018Mar 14 2019A new non-linear variant of a quantitative extension of the uniform boundedness principle is used to show sharpness of error bounds for approximation by sums of sigmoid and ReLU functions. Single hidden layer feedforward neural networks perform such operations. ... More
Adaptive compression of large vectorsMay 31 2015Numerical algorithms for elliptic partial differential equations frequently employ error estimators and adaptive mesh refinement strategies in order to reduce the computational cost. We can extend these techniques to general vectors by splitting the vectors ... More
Master Equation and Two Heat ReservoirsAug 16 2006We analyze a simple spin-flip process under the presence of two heat reservoirs. While one flip process is triggered by a bath at temperature $T$, the inverse process is activated by a bath at a different temperature $T ^{\prime}$. The situation can be ... More
On the stability of dual scattering channel schemesMay 06 2004Jun 08 2004Dual scattering channel (DSC) schemes generalize Johns' TLM algorithm in replacing transmission lines with abstract scattering channels in terms of paired distributions. A well known merit of TLM schemes is unconditional stability, a property that is ... More
The Anderson impurity model with a narrow-band host: from orbital physics to the Kondo effectMay 10 2011A particle-hole symmetric Anderson impurity model with a metallic host of narrow bandwidth is studied within the framework of the local moment approach. The resultant single-particle spectra are compared to unrestricted Hartree-Fock, second order perturbation ... More
Generalized Prediction Intervals for Arbitrary Distributed High-Dimensional DataSep 19 2008This paper generalizes the traditional statistical concept of prediction intervals for arbitrary probability density functions in high-dimensional feature spaces by introducing significance level distributions, which provides interval-independent probabilities ... More
Boltzmann Collision TermOct 31 2005We derive the Boltzmann equation for scalar fields using the Schwinger-Keldysh formalism. The focus lies on the derivation of the collision term. We show that the relevant self-energy diagrams have a factorization property. The collision term assumes ... More
Dynamical dark energy and variation of fundamental "constants"Dec 17 2008In this thesis we study the influence of a possible variation of fundamental "constants" on the process of Big Bang Nucleosynthesis (BBN). Our findings are combined with further studies on variations of constants in other physical processes to constrain ... More
Quantization of SkyrmionsOct 16 2006The Skyrme model is a nonlinear classical field theory which models the strong interaction between atomic nuclei. In order to compare the predictions of the Skyrme model with nuclear physics, it has to be quantized. We show, summarizing earlier work, ... More
S^3 Skyrmions and the Rational Map AnsatzJun 19 2000Oct 28 2002This paper discusses multi-skyrmions on the 3-sphere with variable radius L using the rational map ansatz. For baryon number B = 3,...,9 this ansatz produces the lowest energy solutions known so far. By considering the geometry of the model we find an ... More
Occupants in simplicial complexesNov 19 2017Let $M$ be a smooth manifold and $K\subset M$ be a simplicial complex of codimension at least 3. Functor calculus methods lead to a homotopical formula of $M\setminus K$ in terms of spaces $M\setminus T$ where $T$ is a finite subset of $K$. This is a ... More
A BPHZ Theorem in Configuration SpaceJun 21 2017The concept of BPHZ renormalization is translated into configuration space. A new version of the convergence theorem by means of Zimmermann's forest formula is proved and a sufficient condition for the existence of the constant coupling limit is derived ... More
A systematic mapping study on cross-project defect predictionMay 18 2017Cross-Project-Defect Prediction as a sub-topic of defect prediction in general has become a popular topic in research. In this article, we present a systematic mapping study with the focus on CPDP, for which we found 50 publications. We summarize the ... More
Deriving Faà di Bruno's formula for the derivative of a composite function via compositions of integersMar 03 2014We give yet another proof for Fa\`{a} di Bruno's formula for higher derivatives of composite functions. Our proof technique relies on reinterpreting the composition of two power series as the generating function for weighted integer compositions, for ... More