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Results for "Stefan Klein"

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Radiative neutrino masses and successful $SU(5)$ unificationJul 11 2019Minimal $SU(5)$ Grand Unified models predict massless neutrinos and struggle to achieve gauge coupling unification compatible with the observed lower limit on the proton lifetime. Both of these issues can be resolved by embedding minimal radiative neutrino ... More
Improving students' understanding of rotating frames of reference using videos from different perspectivesFeb 26 2019The concepts of the Coriolis and the centrifugal force are essential in various scientific fields and they are standard components of introductory physics lectures. In this paper we explore how students understand and apply concepts of rotating frames ... More
Bayesian Effect Selection in Structured Additive Distributional Regression ModelsFeb 27 2019We propose a novel spike and slab prior specification with scaled beta prime marginals for the importance parameters of regression coefficients to allow for general effect selection within the class of structured additive distributional regression. This ... More
Disease Progression Timeline Estimation for Alzheimer's Disease using Discriminative Event Based ModelingAug 10 2018Alzheimer's Disease (AD) is characterized by a cascade of biomarkers becoming abnormal, the pathophysiology of which is very complex and largely unknown. Event-based modeling (EBM) is a data-driven technique to estimate the sequence in which biomarkers ... More
Event-Based Modeling with High-Dimensional Imaging Biomarkers for Estimating Spatial Progression of DementiaMar 08 2019Event-based models (EBM) are a class of disease progression models that can be used to estimate temporal ordering of neuropathological changes from cross-sectional data. Current EBMs only handle scalar biomarkers, such as regional volumes, as inputs. ... More
First supra-THz Heterodyne Array Receivers for Astronomy with the SOFIA ObservatoryDec 09 2015We present the upGREAT THz heterodyne arrays for far-infrared astronomy. The Low Frequency Array (LFA) is designed to cover the 1.9-2.5 THz range using 2x7-pixel waveguide-based HEB mixer arrays in a dual polarization configuration. The High Frequency ... More
Localization for quasiperiodic Schrodinger operators with multivariable Gevrey potential functionsApr 13 2012May 29 2013We consider an integer lattice quasiperiodic Schrodinger operator. The underlying dynamics is either the skew-shift or the multi-frequency shift by a Diophantine frequency. We assume that the potential function belongs to a Gevrey class on the multi-dimensional ... More
A spectral theory for simply periodic solutions of the sinh-Gordon equationJul 29 2016In this work a spectral theory for 2-dimensional, simply periodic, complex-valued solutions u of the sinh-Gordon equation is developed. Spectral data for such solutions are defined (following Hitchin and Bobenko) and the space of spectral data is described ... More
BOHB: Robust and Efficient Hyperparameter Optimization at ScaleJul 04 2018Modern deep learning methods are very sensitive to many hyperparameters, and, due to the long training times of state-of-the-art models, vanilla Bayesian hyperparameter optimization is typically computationally infeasible. On the other hand, bandit-based ... More
Inverting the spherical Radon transform for physically meaningful functionsJul 28 2003In this paper we refer to the reconstruction formulas given in L.-E. Andersson's On the determination of a function from spherical averages, which are often used in applications such as SAR and SONAR. We demonstrate that the first one of these formulas ... More
Hamiltonian spectral invariants, symplectic spinors and Frobenius structures IIJan 17 2019Feb 02 2019In this article, we continue our study of 'Frobenius structures' and symplectic spectral invariants in the context of symplectic spinors. By studying the case of $C^1$-small Hamiltonian mappings on symplectic manifolds $M$ admitting a metaplectic structure ... More
Multimodal Machine Learning-based Knee Osteoarthritis Progression Prediction from Plain Radiographs and Clinical DataApr 12 2019May 06 2019Knee osteoarthritis (OA) is the most common musculoskeletal disease without a cure, and current treatment options are limited to symptomatic relief. Prediction of OA progression is a very challenging and timely issue, and it could, if resolved, accelerate ... More
Spectral data for simply-periodic solutions of the sinh-Gordon equationJan 11 2017This note summarizes results that were obtained by the author in his habilitation thesis (arXiv:1607.08792) concerning the development of a spectral theory for simply periodic, 2-dimensional, complex-valued solutions of the sinh-Gordon equation. Spectral ... More
Hamiltonian spectral invariants, symplectic spinors and Frobenius structures INov 16 2014Jan 24 2016This is the first of two articles aiming to introduce symplectic spinors into the field of symplectic topology and the subject of Frobenius structures. After exhibiting a (tentative) axiomating setting for Frobenius structures resp. 'Higgs pairs' in the ... More
Future Deep Inelastic Scattering with the LHeCFeb 12 2018For nearly a decade, Guido Altarelli accompanied the Large Hadron electron Collider project, as invited speaker, referee and member of the International Advisory Committee. This text summarises the status and prospects of the development of the LHeC, ... More
Anderson localization for the discrete one-dimensional quasi-periodic Schroedinger operator with potential defined by a Gevrey-class functionDec 30 2003In this paper we consider the discrete one-dimensional Schroedinger operator with quasi-periodic potential v_n = \lambda v (x + n \omega). We assume that the frequency \omega satisfies a strong Diophantine condition and that the function v belongs to ... More
Market free lunch and large financial marketsFeb 14 2007The main result of the paper is a version of the fundamental theorem of asset pricing (FTAP) for large financial markets based on an asymptotic concept of no market free lunch for monotone concave preferences. The proof uses methods from the theory of ... More
Low-dimensional totally geodesic submanifolds in "skew" position in the symmetric spaces of rank 2Oct 30 2017We use the Cartan representations of $SO(3)$ and $SU(3)$, and an irreducible 14-dimensional representation of $Sp(3)$ to construct certain totally geodesic submanifolds in "skew" position in the complex quadrics, the complex 2-Grassmannians and the quaternionic ... More
Symplectic Spinors, Holonomy and Maslov IndexNov 17 2008Jun 22 2011In this note it is shown that the Maslov Index for pairs of Lagrangian Paths as introduced by Cappell, Lee and Miller appears by parallel transporting elements of (a certain complex line-subbundle of) the symplectic spinorbundle over Euclidean space, ... More
Maximal Fermi charts and geometry of inflationary universesOct 29 2012Jul 09 2015A proof is given that the maximal Fermi coordinate chart for any comoving observer in a broad class of Robertson-Walker spacetimes consists of all events within the cosmological event horizon, if there is one, or is otherwise global. Exact formulas for ... More
From Koopman-von Neumann Theory to Quantum TheoryMay 21 2017May 18 2018Koopman and von Neumann (KvN) extended the Liouville equation by introducing a phase space function $S^{(K)}(q,p,t)$ whose physical meaning is unknown. We show that a different $S(q,p,t)$, with well-defined physical meaning, may be introduced without ... More
Chow groups of tensor triangulated categoriesJan 04 2013Oct 01 2015We recall P. Balmer's definition of tensor triangular Chow group for a tensor triangulated category $\mathcal{K}$ and explore some of its properties. We give a proof that for a suitably nice scheme $X$ it recovers the usual notion of Chow group from algebraic ... More
Hamiltonian fixed points, symplectic spinors and Frobenius structuresJun 10 2013Nov 16 2014This article announces a series of articles aiming at introducing the concept of symplectic spinors into symplectic topology resp. the concept of Frobenius structures. We will give lower bounds for the number of fixed points of a Hamiltonian diffeomorphism ... More
Asynchronous Stochastic Gradient MCMC with Elastic CouplingDec 02 2016We consider parallel asynchronous Markov Chain Monte Carlo (MCMC) sampling for problems where we can leverage (stochastic) gradients to define continuous dynamics which explore the target distribution. We outline a solution strategy for this setting based ... More
A Discriminative Event Based Model for Alzheimer's Disease Progression ModelingFeb 21 2017The event-based model (EBM) for data-driven disease progression modeling estimates the sequence in which biomarkers for a disease become abnormal. This helps in understanding the dynamics of disease progression and facilitates early diagnosis by staging ... More
Asynchronous Stochastic Gradient MCMC with Elastic CouplingDec 02 2016Dec 08 2016We consider parallel asynchronous Markov Chain Monte Carlo (MCMC) sampling for problems where we can leverage (stochastic) gradients to define continuous dynamics which explore the target distribution. We outline a solution strategy for this setting based ... More
Towards Automated Deep Learning: Efficient Joint Neural Architecture and Hyperparameter SearchJul 18 2018While existing work on neural architecture search (NAS) tunes hyperparameters in a separate post-processing step, we demonstrate that architectural choices and other hyperparameter settings interact in a way that can render this separation suboptimal. ... More
TADPOLE Challenge: Prediction of Longitudinal Evolution in Alzheimer's DiseaseMay 10 2018Aug 30 2018The Alzheimer's Disease Prediction Of Longitudinal Evolution (TADPOLE) Challenge compares the performance of algorithms at predicting future evolution of individuals at risk of Alzheimer's disease. TADPOLE Challenge participants train their models and ... More
Bayesian structured additive distributional regression with an application to regional income inequality in GermanySep 17 2015We propose a generic Bayesian framework for inference in distributional regression models in which each parameter of a potentially complex response distribution and not only the mean is related to a structured additive predictor. The latter is composed ... More
Fast Bayesian Optimization of Machine Learning Hyperparameters on Large DatasetsMay 23 2016Bayesian optimization has become a successful tool for hyperparameter optimization of machine learning algorithms, such as support vector machines or deep neural networks. But it is still costly if each evaluation of the objective requires training and ... More
Fast Bayesian Optimization of Machine Learning Hyperparameters on Large DatasetsMay 23 2016Mar 07 2017Bayesian optimization has become a successful tool for hyperparameter optimization of machine learning algorithms, such as support vector machines or deep neural networks. Despite its success, for large datasets, training and validating a single configuration ... More
Pre-big bang geometric extensions of inflationary cosmologiesApr 21 2016Jan 22 2018Robertson-Walker spacetimes within a large class are geometrically extended to larger cosmologies that include spacetime points with zero and negative cosmological times. In the extended cosmologies, the big bang is lightlike, and though singular, it ... More
Poincare Complex DiagonalsNov 01 2006Nov 13 2006Let M be a Poincare duality space of dimension at least four. In this paper we describe a complete obstruction to realizing the diagonal map M -> M x M by a Poincare embedding. The obstruction group depends only on the fundamental group and the parity ... More
The Dualizing Spectrum, IIOct 01 2006Jan 02 2007To an inclusion topological groups H->G, we associate a naive G-spectrum. The special case when H=G gives the dualizing spectrum D_G introduced by the author in the first paper of this series. The main application will be to give a purely homotopy theoretic ... More
On closed finite gap curves in spaceforms IJan 22 2018Jun 12 2019We show that the spaces of closed finite gap curves in $R^3$ and $S^3$ are dense with respect to the Sobolev $W^{1,2}$-norm in the spaces of closed curves in $R^3$ respectively $S^3$.
Fourth order time-stepping for Kadomtsev-Petviashvili and Davey-Stewartson equationsAug 16 2011Dec 06 2011Purely dispersive partial differential equations as the Korteweg-de Vries equation, the nonlinear Schr\"odinger equation and higher dimensional generalizations thereof can have solutions which develop a zone of rapid modulated oscillations in the region ... More
Gröbner bases and the Cohen-Macaulay property of Li's double determinantal varietiesJun 17 2019Jul 08 2019We consider double determinantal varieties, a special case of Nakajima quiver varieties. Li conjectured that double determinantal varieties are normal, irreducible, Cohen-Macaulay varieties whose defining ideals have a Gr\"obner basis given by their natural ... More
Biased halfspaces, noise sensitivity, and relative Chernoff inequalities (extended version)Oct 20 2017Nov 01 2017In analysis of Boolean functions, a halfspace is a function $f:\{-1,1\}^n \rightarrow \{0,1\}$ of the form $f(x)=1_{\{a\cdot x>t\}}$, where $\sum_i a_i^2=1$. We show that if $f$ is a halfspace with $\mathbb{E}[f]=\epsilon$, then the degree-1 Fourier weight ... More
Reactive Synthesis: Towards Output-Sensitive AlgorithmsMar 27 2018Reactive synthesis is a technology for the automatic construction of reactive systems from logical specifications. In these lecture notes, we study different algorithms for the reactive synthesis problem of linear-time temporal logic (LTL). The classic ... More
Testing the Markov condition in ion channel recordingsMar 04 1997A statistical test is presented to decide whether data are adequately described by probabilistic functions of finite state Markov chains (''hidden Markov models'') as applied in the analysis of ion channel data. Particularly, the test can be used to decide ... More
What are Strategies in Delay Games? Borel Determinacy for Games with LookaheadApr 10 2015We investigate determinacy of delay games with Borel winning conditions, infinite-duration two-player games in which one player may delay her moves to obtain a lookahead on her opponent's moves. First, we prove determinacy of such games with respect to ... More
Gender Gap Through Time and Space: A Journey Through Wikipedia Biographies and the "WIGI" IndexFeb 10 2015In this study we investigate how quantification of Wikipedia biographies can shed light on worldwide longitudinal gender inequality trends. We present an academic index allowing comparative study of gender inequality through space and time, the Wikipedia ... More
Uncertainty and causal emergence in complex networksJul 08 2019The connectivity of a network conveys information about the dependencies between nodes. We show that this information can be analyzed by measuring the uncertainty (and certainty) contained in paths along nodes and links in a network. Specifically, we ... More
Tunneling for a class of Difference Operators: Complete AsymptoticsJun 20 2017We analyze a general class of difference operators $H_\varepsilon = T_\varepsilon + V_\varepsilon$ on $\ell^2(\varepsilon\mathbf{Z}^d)$, where $V_\varepsilon$ is a multi-well potential and $\varepsilon$ is a small parameter. We derive full asymptotic ... More
Probing high-energy interactions of atmospheric and astrophysical neutrinosJun 05 2019Astrophysical and atmospheric neutrinos are important probes of the powerful accelerators that produce cosmic-rays with EeV energies. Understanding these accelerators is a key goal of neutrino observatories, along with searches for neutrinos from supernovae, ... More
The Liouville equation for singular ergodic magnetic Schrödinger operatorsNov 24 2008Oct 08 2009We study the time evolution of a density matrix in a quantum mechanical system described by an ergodic magnetic Schr\"odinger operator with singular magnetic and electric potentials, the electric field being introduced adiabatically. We construct a unitary ... More
The two-edge connectivity survivable-network design problem in planar graphsFeb 09 2013Sep 30 2015Consider the following problem: given a graph with edge costs and a subset Q of vertices, find a minimum-cost subgraph in which there are two edge-disjoint paths connecting every pair of vertices in Q. The problem is a failure-resilient analog of the ... More
Relative tensor triangular Chow groups for coherent algebrasJul 12 2016Feb 04 2019We apply the machinery of relative tensor triangular Chow groups to the action of the derived category of quasi-coherent sheaves on a noetherian scheme $X$ on the derived category of quasi-coherent $\mathcal{A}$-modules, where $\mathcal{A}$ is a (not ... More
The transition to the ultimate regime of thermal convection from a stochastic one-dimensional turbulence perspectiveJun 15 2019The Rayleigh number $Ra$ dependence of the Nusselt number $Nu$ in turbulent Rayleigh--B\'enard convection is numerically investigated for a moderate and low Prandtl number, $Pr=0.7$ and $0.021$, respectively. Here we specifically address the case of a ... More
Exact Relativistic Gravitational Field of a Stationary Counterrotating Dust DiskAug 13 1999Disks of collisionless particles are important models for certain galaxies and accretion disks in astrophysics. We present here a solution to the stationary axisymmetric Einstein equations which represents an infinitesimally thin dust disk consisting ... More
Physically Realistic Solutions to the Ernst Equation on Hyperelliptic Riemann SurfacesJun 10 1998Oct 07 1998We show that the class of hyperelliptic solutions to the Ernst equation (the stationary axisymmetric Einstein equations in vacuum) previously discovered by Korotkin and Neugebauer and Meinel can be derived via Riemann-Hilbert techniques. The present paper ... More
A structure theorem for almost low-degree functions on the sliceJan 25 2019The Fourier-Walsh expansion of a Boolean function $f \colon \{0,1\}^n \rightarrow \{0,1\}$ is its unique representation as a multilinear polynomial. The Kindler-Safra theorem (2002) asserts that if in the expansion of $f$, the total weight on coefficients ... More
Velocity addition formulas in Robertson-Walker spacetimesMar 17 2015Universal velocity addition formulas analogous to the well-known formula in special relativity are found for four geometrically defined relative velocities in a large class of Robertson-Walker spacetimes. Explicit examples are given. The special relativity ... More
Moduli of suspension spectraOct 17 2002Jan 03 2003For a 1-connected spectrum E, we study the moduli space of suspension spectra which come equipped with a weak equivalence to E. We construct a spectral sequence converging to the homotopy of the moduli space in positive degrees. In the metastable range, ... More
Agmon-Type Estimates for a Class of Difference OperatorsJun 20 2017We analyze a general class of self-adjoint difference operators $H_\varepsilon = T_\varepsilon + V_\varepsilon$ on $\ell^2(\varepsilon\mathbb{Z}^d)$, where $V_\varepsilon$ is a one-well potential and $\varepsilon$ is a small parameter. We construct a ... More
A block Hankel generalized confluent Vandermonde matrixMar 23 2013Vandermonde matrices are well known. They have a number of interesting properties and play a role in (Lagrange) interpolation problems, partial fraction expansions, and finding solutions to linear ordinary differential equations, to mention just a few ... More
New Results on Hard Probes in Heavy-Ion Collisions with ALICESep 13 2018Sep 17 2018Hard probes - final state particles related to an interaction with large momentum transfer or mass scale - play a distinguished role in the discovery and the study of the Quark-Gluon Plasma (QGP), a phase of deconfined quarks and gluons reached at high ... More
Bootstrap multiscale analysis and localization for multi-particle continuous Anderson HamiltoniansNov 17 2013Apr 15 2014We extend the bootstrap multiscale analysis developed by Germinet and Klein to the multi-particle continuous Anderson Hamiltonian, obtaining Anderson localization with finite multiplicity of eigenvalues, decay of eigenfunction correlations, and a strong ... More
Phonon-induced artificial magnetic fieldsAug 14 2008Jan 22 2009We investigate the effect of a rotating Bose-Einstein condensate on a system of immersed impurity atoms trapped by an optical lattice. We analytically show that for a one-dimensional, ring-shaped setup the coupling of the impurities to the Bogoliubov ... More
Application of the Kerman-Klein method to the solution of a spherical shell model for a deformed rare-earth nucleusFeb 19 1997Core-particle coupling models are made viable by assuming that core properties such as matrix elements of multipole and pairing operators and excitation spectra are known independently. From the completeness relation, it is seen, however, that these quantities ... More
Simulating high-temperature superconductivity model Hamiltonians with atoms in optical latticesJan 12 2006May 30 2006We investigate the feasibility of simulating different model Hamiltonians used in high-temperature superconductivity. We briefly discuss the most common models and then focus on the simulation of the so-called t-J-U Hamiltonian using ultra-cold atoms ... More
The largest small polytopesDec 19 2002The aim of this paper is the determination of the largest $n$-dimensional polytope with $n+3$ vertices of unit diameter. This is a special case of a more general problem proposed by Graham.
Constituency Parsing with a Self-Attentive EncoderMay 02 2018We demonstrate that replacing an LSTM encoder with a self-attentive architecture can lead to improvements to a state-of-the-art discriminative constituency parser. The use of attention makes explicit the manner in which information is propagated between ... More
Absolutely Continuous Spectrum for Random Schroedinger Operators on the Bethe StripJan 22 2011Jan 03 2012The Bethe Strip of width $m$ is the cartesian product $\B\times\{1,...,m\}$, where $\B$ is the Bethe lattice (Cayley tree). We prove that Anderson models on the Bethe strip have "extended states" for small disorder. More precisely, we consider Anderson-like ... More
Goldman flows on a nonorientable surfaceOct 28 2007Given an embedded cylinder in an arbitrary surface, we give a gauge theoretic definition of the associated Goldman flow, which is a circle action on a dense open subset of the moduli space of equivalence classes of flat SU(2)-connections over the surface. ... More
Asymptotic Eigenfunctions for a class of Difference OperatorsFeb 03 2017We analyze a general class of difference operators $H_\varepsilon = T_\varepsilon + V_\varepsilon$ on $\ell^2(\varepsilon \mathbb{Z}^d)$, where $V_\varepsilon$ is a one-well potential and $\varepsilon$ is a small parameter. We construct formal asymptotic ... More
Fermi coordinates, simultaneity, and expanding space in Robertson-Walker cosmologiesOct 04 2010Mar 05 2011Explicit Fermi coordinates are given for geodesic observers comoving with the Hubble flow in expanding Robertson-Walker spacetimes, along with exact expressions for the metric tensors in Fermi coordinates. For the case of non inflationary cosmologies, ... More
Numerical study of a multiscale expansion of KdV and Camassa-Holm equationFeb 12 2007We study numerically solutions to the Korteweg-de Vries and Camassa-Holm equation close to the breakup of the corresponding solution to the dispersionless equation. The solutions are compared with the properly rescaled numerical solution to a fourth order ... More
Kinetic Pathways of the DNA Melting TransitionOct 09 2012Mar 28 2013We investigate kinetic pathways of the DNA melting transition using variable-range versions of the Poland-Scheraga (PS) and Peyrard-Dauxois-Bishop (PDB) models of DNA. In the PS model, we construct a phi^4-field theory to calculate the critical droplet ... More
On the numerical evaluation of algebro-geometric solutions to integrable equationsJul 11 2011Dec 06 2011Physically meaningful periodic solutions to certain integrable partial differential equations are given in terms of multi-dimensional theta functions associated to real Riemann surfaces. Typical analytical problems in the numerical evaluation of these ... More
The Bezoutian and Fisher's information matrix of an ARMA processMay 11 2005In this paper we derive some properties of the Bezout matrix and relate the Fisher information matrix for a stationary ARMA process to the Bezoutian. Some properties are explained via realizations in state space form of the derivatives of the white noise ... 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
Reliability of regulatory networks and its evolutionMay 27 2008The problem of reliability of the dynamics in biological regulatory networks is studied in the framework of a generalized Boolean network model with continuous timing and noise. Using well-known artificial genetic networks such as the repressilator, we ... More
Reliability of genetic networks is evolvableJul 10 2007Control of the living cell functions with remarkable reliability despite the stochastic nature of the underlying molecular networks -- a property presumably optimized by biological evolution. We here ask to what extent the property of a stochastic dynamical ... More
On Semigroups of Two-Dimensional Upper-Triangular Integer MatricesMay 13 2019We analyze algorithmic problems in finitely generated semigroups of two-dimensional upper-triangular integer matrices. These semigroup problems are tightly connected with problems about compositions of affine functions over one variable. Building on a ... More
Finite-Size Corrections for Ground States of Edwards-Anderson Spin GlassesOct 28 2011May 30 2012Extensive computations of ground state energies of the Edwards-Anderson spin glass on bond-diluted, hypercubic lattices are conducted in dimensions d=3,..,7. Results are presented for bond-densities exactly at the percolation threshold, p=p_c, and deep ... 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
On the homotopy invariance of configuration spacesOct 31 2003Oct 15 2004For a closed PL manifold M, we consider the configuration space F(M,k) of ordered k-tuples of distinct points in M. We show that a suitable iterated suspension of F(M,k) is a homotopy invariant of M. The number of suspensions we require depends on three ... More
Simulating Radial Velocity Observations of Trappist-1 with SPIRouJul 12 2019We simulate a radial velocity (RV) follow-up of the TRAPPIST-1 system, a faithful representative of M dwarfs hosting transiting Earth-sized exoplanets to be observed with SPIRou in the months to come. We generate a RV curve containing the signature of ... More
Grand canonical ensembles in general relativitySep 20 2010Feb 29 2012We develop a formalism for general relativistic, grand canonical ensembles in space-times with timelike Killing fields. Using that formalism we derive ideal gas laws, and show how they depend on the geometry of the particular space-times. A systematic ... More
A chain rule in the calculus of homotopy functorsJan 09 2003We formulate and prove a chain rule for the derivative, in the sense of Goodwillie, of compositions of weak homotopy functors from simplicial sets to simplicial sets. The derivative spectrum dF(X) of such a functor F at a simplicial set X can be equipped ... More
Multiple-source single-sink maximum flow in directed planar graphs in $O(n^{1.5} \log n)$ timeAug 31 2010Sep 14 2010We give an $O(n^{1.5} \log n)$ algorithm that, given a directed planar graph with arc capacities, a set of source nodes and a single sink node, finds a maximum flow from the sources to the sink . This is the first subquadratic-time strongly polynomial ... More
Relative velocities for radial motion in expanding Robertson-Walker spacetimesJun 20 2011Feb 03 2012The expansion of space, and other geometric properties of cosmological models, can be studied using geometrically defined notions of relative velocity. In this paper, we consider test particles undergoing radial motion relative to comoving (geodesic) ... More
Contact real hypersurfaces in the complex hyperbolic quadricOct 27 2017Nov 16 2017We give a new proof of the classification of contact real hypersurfaces with constant mean curvature in the complex hyperbolic quadric ${Q^m}^* = SO_{m,2}^o/SO_mSO_2$, where $m\geq 3$. We show that a contact real hypersurface $M$ in ${Q^m}^*$ for $m\geq ... More
Progress in modeling magnetic white dwarfsFeb 04 2003First satisfactory fits to the flux spectrum and circular polarization of the DAP Grw +70 8247 are presented, as well as a first model of the DBP GD 229 with consistent helium line data.
The combinatorial multitude of fatty acids can be described by Fibonacci numbersMar 28 2013The famous series of Fibonacci numbers is defined by a recursive equation saying that each number is the sum of its two predecessors, with the initial condition that the first two numbers are equal to unity. Here, we show that the numbers of fatty acids ... More
Beyond the Second Generation of Laser-Interferometric Gravitational Wave ObservatoriesNov 27 2011This article gives an overview of potential upgrades of second generation gravitational wave detectors and the required key technologies to improve the limiting noise sources. In addition the baseline design of the Einstein Telescope, a European third ... More
Centralizers in 3-manifold groupsMay 10 2012Using the Geometrization Theorem we prove a result on centralizers in fundamental groups of 3-manifolds. This result had been obtained by Jaco and Shalen and by Johannson using different techniques.
$L^2$--eta--invariants and their approximation by unitary eta--invariantsMay 28 2003Cochran, Orr and Teichner introduced $L^2$--eta--invariants to detect highly non--trivial examples of non slice knots. Using a recent theorem by L\"uck and Schick we show that their metabelian $L^2$--eta--invariants can be viewed as the limit of finite ... More
A note on the growth of Betti numbers and ranks of 3-manifold groupsJan 17 2013Apr 18 2013Let N be an irreducible, compact 3-manifold with empty or toroidal boundary which is not a closed graph manifold. Using recent work of Agol, Kahn-Markovic and Przytycki-Wise we will show that pi_1(N) admits a cofinal filtration with `fast' growth of Betti ... More
Extremal Optimization: Heuristics via Co-Evolutionary AvalanchesJun 23 2000An introduction to Extremal Optimization written for the Computer Simulation Column in ``Computing in Science and Engineering'' (CISE).
Extremal Optimization for Sherrington-Kirkpatrick Spin GlassesJul 06 2004Mar 24 2005Extremal Optimization (EO), a new local search heuristic, is used to approximate ground states of the mean-field spin glass model introduced by Sherrington and Kirkpatrick. The implementation extends the applicability of EO to systems with highly connected ... More
Mode-by-mode hydrodynamics: ideas and conceptsJan 10 2014The main ideas, technical concepts and perspectives for a mode resolved description of the hydrodynamical regime of relativistic heavy ion collisions are discussed. A background-fluctuation splitting and a Bessel-Fourier expansion for the fluctuating ... More
Sneutrino Hybrid InflationAug 23 2006We review the scenario of sneutrino hybrid inflation, where one of the singlet sneutrinos, the superpartners of the right-handed neutrinos, plays the role of the inflaton. In a minimal model of sneutrino hybrid inflation, the spectral index is given by ... More
Models for Neutrino Masses and MixingsJan 23 2013We review recent developments towards models for neutrino masses and mixings.
The bottomonium spectrum from lattice QCD with 2+1 flavors of domain wall fermionsMar 18 2009Apr 21 2009Recently, realistic lattice QCD calculations with 2+1 flavors of domain wall fermions and the Iwasaki gauge action have been performed by the RBC and UKQCD collaborations. Here, results for the bottomonium spectrum computed on their gauge configurations ... More
Scaling and Decoherence in the Out-of-Equilibrium Kondo ModelOct 13 2004Oct 26 2004We study the Kondo effect in quantum dots in an out-of-equilibrium state due to an applied dc-voltage bias. Using the method of infinitesimal unitary transformations (flow equations), we develop a perturbative scaling picture that naturally contains both ... More
Calculation of Massless Feynman Integrals using Harmonic SumsMay 19 2005Jul 10 2006A method for the evaluation of the epsilon expansion of multi-loop massless Feynman integrals is introduced. This method is based on the Gegenbauer polynomial technique and the expansion of the Gamma function in terms of harmonic sums. Algorithms for ... More
Combining optical spectroscopy and interferometryDec 13 2013Modern optical spectrographs and optical interferometers push the limits in the spectral and spatial regime, providing important new tools for the exploration of the universe. In this contribution I outline the complementary nature of spectroscopic & ... More
H-äquivariante Morita-Äquivalenz und DeformationsquantisierungApr 09 2010English abstract: This work contains of five chapters: The first one deals with Morita equivalence of star algebras. In particular star algebras which are equipped with a symmetry given by a Hopf (star-) algebra. In the second chapter we describe the ... More