Results for "Hannes Federrath"

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QUICker connection establishment with out-of-band validation tokensApr 12 2019QUIC is a secure transport protocol and aims to improve the performance of HTTPS traffic. It is a design goal of QUIC to reduce the delay overhead of its connection establishment. However, an initial handshake enforcing strict validation of the client's ... More
IPv6 Prefix Alteration: An Opportunity to Improve Online PrivacyNov 20 2012This paper is focused on privacy issues related to the prefix part of IPv6 addresses. Long-lived prefixes may introduce additional tracking opportunities for communication partners and third parties. We outline a number of prefix alteration schemes that ... More
Evaluating the Security of a DNS Query Obfuscation Scheme for Private Web SurfingMar 21 2016The Domain Name System (DNS) does not provide query privacy. Query obfuscation schemes have been proposed to overcome this limitation, but, so far, they have not been evaluated in a realistic setting. In this paper we evaluate the security of a random ... More
The origin of physical variations in the star formation lawJul 04 2013Dec 10 2013Observations of external galaxies and of local star-forming clouds in the Milky Way have suggested a variety of star formation laws, i.e., simple direct relations between the column density of star formation (Sigma_SFR: the amount of gas forming stars ... More
The turbulent formation of starsJun 14 2018Nov 30 2018How stars are born from clouds of gas is a rich physics problem whose solution will inform our understanding of not just stars but also planets, galaxies, and the universe itself. Star formation is stupendously inefficient. Take the Milky Way. Our galaxy ... More
On the universality of supersonic turbulenceJun 17 2013Sep 24 2013Compressible turbulence shapes the structure of the interstellar medium of our Galaxy and likely plays an important role also during structure formation in the early Universe. The density PDF and the power spectrum of such compressible, supersonic turbulence ... More
Magnetic field amplification in turbulent astrophysical plasmasOct 26 2016Magnetic fields play an important role in astrophysical accretion discs, and in the interstellar and intergalactic medium. They drive jets, suppress fragmentation in star-forming clouds and can have a significant impact on the accretion rate of stars. ... More
Enhanced Performance for the encrypted Web through TLS Resumption across HostnamesFeb 07 2019TLS can resume previous connections via abbreviated resumption handshakes that significantly decrease the delay and save expensive cryptographic operations. For that, cryptographic TLS state from previous connections is reused. TLS version 1.3 recommends ... More
Tracking Users across the Web via TLS Session ResumptionOct 16 2018User tracking on the Internet can come in various forms, e.g., via cookies or by fingerprinting web browsers. A technique that got less attention so far is user tracking based on TLS and specifically based on the TLS session resumption mechanism. To the ... More
Relationship between turbulence energy and density variance in the Solar neighbourhood molecular cloudsNov 05 2017[abridged] We determine the relationship between turbulence energy and gas density variance for 15 molecular clouds in the Solar neighbourhood. We use the linewidths of the CO molecule as the probe of the turbulence energy (sonic Mach number, $\cal{M}_\mathrm{s}$) ... More
The density structure and star formation rate of non-isothermal polytropic turbulenceDec 08 2014Jan 27 2015The interstellar medium of galaxies is governed by supersonic turbulence, which likely controls the star formation rate (SFR) and the initial mass function (IMF). Interstellar turbulence is non-universal, with a wide range of Mach numbers, magnetic fields ... More
A Fluid-Dynamical Subgrid Scale Model for Highly Compressible Astrophysical TurbulenceOct 21 2010We formulate and implement the Euler equations with SGS dynamics and provide numerical tests of an SGS turbulence energy model that predicts the turbulent pressure of unresolved velocity fluctuations and the rate of dissipation for highly compressible ... More
K->pipie+e- decays and chiral low-energy constantsOct 25 2000Mar 21 2001The branching ratios of the measured decay $K_L\to\pi^+\pi^-e^+e^-$ and of the still unmeasured decay $K^+\to\pi^+\pi^0e^+e^-$ are calculated to next-to-leading order in Chiral Perturbation Theory (CHPT). Recent experimental results are used to determine ... More
The generator rank for C*-algebrasOct 24 2012The invariant that assigns to a C*-algebra its minimal number of generators lacks natural permanence properties. In particular, it may increase when passing to ideals or inductive limits. It is therefore hard to compute this invariant directly. To obtain ... More
Inductive limits of semiprojective C*-algebrasApr 13 2018Feb 18 2019We prove closure properties for the class of C*-algebras that are inductive limits of semiprojective C*-algebras. Most importantly, we show that this class is closed under shape domination, and so in particular under shape and homotopy equivalence. It ... More
The topological dimension of type I C*-algebrasOct 16 2012Feb 05 2013While there is only one natural dimension concept for separable, metric spaces, the theory of dimension in noncommutative topology ramifies into different important concepts. To accommodate this, we introduce the abstract notion of a noncommutative dimension ... More
Inductive limits of projective C*-algebrasMay 10 2011Dec 14 2017We show that a separable C*-algebra is an inductive limits of projective C*-algebras if and only if it has trivial shape, that is, if it is shape equivalent to the zero C*-algebra. In particular, every contractible C*-algebra is an inductive limit of ... More
Preduals for spaces of operators involving Hilbert spaces and trace-class operatorsMar 03 2017Mar 27 2018Continuing the study of preduals of spaces $\mathcal{L}(H,Y)$ of bounded, linear maps, we consider the situation that $H$ is a Hilbert space. We establish a natural correspondence between isometric preduals of $\mathcal{L}(H,Y)$ and isometric preduals ... More
On the Hamilton-Jacobi Equation and Infimal Convolution in the Framework of Sobolev-functionsAug 20 2012We study the regularity properties of the Hamilton-Jacobi flow equation and infimal convolution in the case where initial datum function is continuous and lies in given Sobolev-space $W^{1,p}(\rn)$. We prove that under suitable assumptions it holds for ... More
Church's thesis is questioned by new calculation paradigmOct 07 2006Church's thesis claims that all effecticely calculable functions are recursive. A shortcoming of the various definitions of recursive functions lies in the fact that it is not a matter of a syntactical check to find out if an entity gives rise to a function. ... More
Fraud detection with statistics: A comment on "Evidential Value in ANOVA-Regression Results in Scientific Integrity Studies" (Klaassen, 2015)Jun 24 2015Jul 15 2015Klaassen in (Klaassen 2015) proposed a method for the detection of data manipulation given the means and standard deviations for the cells of a oneway ANOVA design. This comment critically reviews this method. In addition, inspired by this analysis, an ... More
On the uniqueness of quasihyperbolic geodesicsApr 08 2015In this work we solve a couple of well known open problems related to the quasihyperbolic metric. In the case of planar domains, our first main result states that quasihyperbolic geodesics are unique in simply connected domains. As the second main result, ... More
Hopf bifurcation and time periodic orbits in reaction-diffusion systems with pde2path - algorithms and applicationsApr 06 2016Aug 28 2017We describe the algorithms used in the Matlab continuation and bifurcation package pde2path for Hopf bifurcation and continuation of branches of periodic orbits in systems of PDEs in 1, 2, and 3 spatial dimensions, including the computation of Floquet ... More
The variation of the maximal function of a radial functionFeb 02 2017We study the problem concerning the variation of the Hardy-Littlewood maximal function in higher dimensions. As the main result, we prove that the variation of the non-centered Hardy-Littlewood maximal function of a radial function is comparable to the ... More
Three-Element Min-Sol and Conservative Min-Cost-HomDec 31 2012Sep 29 2013Thapper and Zivny [STOC'13] recently classified the complexity of VCSP for all finite-valued constraint languages. However, the complexity of VCSPs for constraint languages that are not finite-valued remains poorly understood. In this paper we study the ... More
Electromagnetic radiative corrections to pionic beta decay π^+ to π^0 e^+ ν_eSep 25 2002Pionic beta decay \pi^+ to \pi^0 e^+ \nu_e is analyzed in chiral perturbation theory with virtual photons and leptons. All electromagnetic corrections up to order e^2 p^2 are taken into account. Theoretical results are confronted with preliminary data ... More
Evaluation and selection of models for out-of-sample prediction when the sample size is small relative to the complexity of the data-generating processFeb 22 2008Oct 24 2008In regression with random design, we study the problem of selecting a model that performs well for out-of-sample prediction. We do not assume that any of the candidate models under consideration are correct. Our analysis is based on explicit finite-sample ... More
The distribution of a linear predictor after model selection: Unconditional finite-sample distributions and asymptotic approximationsNov 07 2006We analyze the (unconditional) distribution of a linear predictor that is constructed after a data-driven model selection step in a linear regression model. First, we derive the exact finite-sample cumulative distribution function (cdf) of the linear ... More
Recent results from CCFM evolutionDec 04 2003Recent developments of the small $x$ CCFM evolution are described, including improvements of the splitting function. The resulting unintegrated gluon densities are used for predictions of hadronic final state measurements like jet production at HERA and ... More
Vector meson cross sections at HERAJan 13 2008Inelastic and elastic (exclusive) cross section measurements of vector meson production at HERA are discussed.
Semiprojectivity and semiinjectivity in different categoriesFeb 14 2018Projectivity and injectivity are fundamental notions in category theory. We consider natural weakenings termed semiprojectivity and semiinjectivity, and study these concepts in different categories. For example, in the category of metric spaces, (semi)injective ... More
The Role of Magnetic Fields in Setting the Star Formation Rate and the Initial Mass FunctionFeb 07 2019Star-forming gas clouds are strongly magnetized, and their ionization fractions are high enough to place them close to the regime of ideal magnetohydrodyamics on all but the smallest size scales. In this review we discuss the effects of magnetic fields ... More
Un-integrated PDFs in CCFMNov 22 2004The un-integrated parton distribution functions (uPDFs) obtained from a CCFM evolution are studied in terms of the intrinsic transverse momentum distribution at low scales. The uPDFs are studied for variations of the renormalization and factorization ... More
Conditional predictive inference post model selectionAug 25 2009We give a finite-sample analysis of predictive inference procedures after model selection in regression with random design. The analysis is focused on a statistically challenging scenario where the number of potentially important explanatory variables ... More
On the differentiability of directionally differentiable functions and applicationsAug 20 2012May 10 2013In the first part of this paper we establish, in terms of so called k-tangential sets, a kind of optimal estimate for the size and structure of the set of non-differentiability of Lipshitz functions with one-sided directional derivatives. These results ... More
The Star Formation Rate of Turbulent Magnetized Clouds: Comparing Theory, Simulations, and ObservationsSep 13 2012Nov 07 2012We derive and compare six theoretical models for the star formation rate (SFR) - the Krumholz & McKee (KM), Padoan & Nordlund (PN), and Hennebelle & Chabrier (HC) models, and three multi-freefall versions of these, suggested by HC - all based on integrals ... More
Integrating Privacy-Enhancing Technologies into the Internet InfrastructureNov 20 2017The AN.ON-Next project aims to integrate privacy-enhancing technologies into the internet's infrastructure and establish them in the consumer mass market. The technologies in focus include a basis protection at internet service provider level, an improved ... More
An Observational Method to Measure the Relative Fractions of Solenoidal and Compressible Modes in Interstellar CloudsMay 06 2014We introduce a new method for observationally estimating the fraction of momentum density (${\rho}{\mathbf{v}}$) power contained in solenoidal modes (for which $\nabla \cdot {\rho}{\mathbf{v}} = 0$) in molecular clouds. The method is successfully tested ... More
The role of turbulence during the formation of circumbinary discsOct 23 2018Most stars form in binaries and the evolution of their discs remains poorly understood. To shed light on this subject, we carry out 3D ideal MHD simulations with the AMR code FLASH of binary star formation for separations of $10-20\,\mathrm{AU}$. We run ... More
Nonanalytic quantum oscillator image of complete replica symmetry breakingMay 16 2011We describe the effect of replica symmetry breaking in the field distribution function P(h) of the T=0 SK-model as the difference between a split Gaussian and the first excited state $\psi_1$ of a weakly anharmonic oscillator with nonanalytic shift by ... More
NJL model of homogeneous neutral quark matter: Pseudoscalar diquark condensates revisitedDec 17 2009Apr 19 2010We use a Nambu-Jona Lasinio type model to investigate the phase diagram of dense quark matter under neutron star conditions in mean field approximation. The model contains selfconsistently determined quark masses and allows for diquark condensation in ... More
Lattice QCD Green's functions in maximally Abelian gauge: infrared Abelian dominance and the quark sectorApr 21 2015Nov 03 2015On lattice gauge field configurations with 2+1 dynamical quark flavors, we investigate the momentum space quark and gluon propagators in the combined maximally Abelian plus $U(1)_3\times U(1)_8$ Landau gauge. We extract the gluon fields from the lattice ... More
Gravitational Light Bending Prevents $γγ$ Absorption in Gravitational LensesSep 05 2016The magnification effect due to gravitational lensing enhances the chances of detecting moderate-redshift ($z \sim 1$) sources in very-high-energy (VHE; $E > 100$ GeV) $\gamma$-rays by ground-based Atmospheric Cherenkov Telescope facilities. It has been ... More
Banach algebras generated by an invertible isometry of an $L^p$-spaceMay 22 2014Dec 18 2014We provide a complete description of those Banach algebras that are generated by an invertible isometry of an $L^p$-space together with its inverse. Examples include the algebra $PF_p(\mathbb{Z})$ of $p$-pseudofunctions on $\mathbb{Z}$, the commutative ... More
Brown measure and iterates of the Aluthge transform for some operators arising from measurable actionsDec 09 2005Feb 05 2008We consider the Aluthge transform $|T|^{1/2}U|T|^{1/2}$ of a Hilbert space operator $T$, where $T=U|T|$ is the polar decomposition of $T$. We prove that the map that sends $T$ to its Aluthge transform is continuous with respect to the norm topology and ... More
Admissibility of the usual confidence set for the mean of a univariate or bivariate normal population: The unknown-variance caseSep 20 2018Sep 21 2018In the Gaussian linear regression model (with unknown mean and variance), we show that the standard confidence set for one or two regression coefficients is admissible in the sense of Joshi (1969). This solves a long-standing open problem in mathematical ... More
Optimal management and spatial patterns in a distributed shallow lake modelMar 18 2015Jun 10 2015We present a numerical framework to treat infinite time horizon spatially distributed optimal control problems via the associated canonical system derived by Pontryagin's Maximum Principle. The basic idea is to consider the canonical system in two steps. ... More
Saturation effects in final states due to CCFM with absorptive boundaryDec 22 2008Jan 26 2009We apply the absorptive boundary prescription to include saturation effects in CCFM evolution equation. We are in particular interested in saturation effects in exclusive processes which can be studied using Monte Carlo event generator CASCADE. We calculate ... More
A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and testsJan 15 2011Apr 27 2011The ideal MHD equations are a central model in astrophysics, and their solution relies upon stable numerical schemes. We present an implementation of a new method, which possesses excellent stability properties. Numerical tests demonstrate that the theoretical ... More
Magnetic field tomography in two clouds towards Ursa Major using HI fibersSep 29 2018Mar 18 2019The atomic interstellar medium (ISM) is observed to be full of linear structures that are referred to as "fibers". Fibers exhibit similar properties to linear structures found in molecular clouds known as striations. Suggestive of a similar formation ... More
The Fractal Density Structure in Supersonic Isothermal Turbulence: Solenoidal versus Compressive Energy InjectionOct 06 2007Feb 03 2009In a systematic study, we compare the density statistics in high resolution numerical experiments of supersonic isothermal turbulence, driven by the usually adopted solenoidal (divergence-free) forcing and by compressive (curl-free) forcing. We find that ... More
Connection between dense gas mass fraction, turbulence driving, and star formation efficiency of molecular cloudsApr 18 2013We examine the physical parameters that affect the accumulation of gas in molecular clouds to high column densities where the formation of stars takes place. In particular, we analyze the dense gas mass fraction (DGMF) in a set of self-gravitating, isothermal, ... More
On underwater sound reflection from layered ice sheetsApr 08 2016Reflection of sound from ice sheets floating on water is simulated using Thomson and Haskell's method of matrix propagation. The reflection coefficient is computed as a function of incidence angle and frequency for selected ice parameters of a uniform ... More
Advanced superconducting circuits and devicesFeb 27 2014Apr 02 2014Short review on advanced superconducting circuits and devices.
List and Probabilistic Unique Decoding of Folded Subspace CodesApr 21 2015A new class of folded subspace codes for noncoherent network coding is presented. The codes can correct insertions and deletions beyond the unique decoding radius for any code rate $R\in[0,1]$. An efficient interpolation-based decoding algorithm for this ... More
Coulomb, Landau and Maximally Abelian Gauge Fixing in Lattice QCD with Multi-GPUsDec 20 2012Apr 15 2013A lattice gauge theory framework for simulations on graphic processing units (GPUs) using NVIDIA's CUDA is presented. The code comprises template classes that take care of an optimal data pattern to ensure coalesced reading from device memory to achieve ... More
Multiple Kernel Learning: A Unifying Probabilistic ViewpointMar 04 2011Jun 07 2012We present a probabilistic viewpoint to multiple kernel learning unifying well-known regularised risk approaches and recent advances in approximate Bayesian inference relaxations. The framework proposes a general objective function suitable for regression, ... More
Photonic Quantum Circuits with Time DelaysOct 15 2015We study the dynamics of photonic quantum circuits consisting of nodes coupled by quantum channels. We are interested in the regime where time delay in communication between the nodes is significant. This includes the problem of quantum feedback, where ... More
Reversible Work Transiton State Theory: Application to Dissociative Adsorption of HydrogenNov 16 1994Nov 18 1994A practical method for finding free energy barriers for transitions in high-dimensional classical and quantum systems is presented and used to calculate the dissociative sticking probability of H2 on a metal surface within transition state theory (TST). ... More
Implementing Default and Autoepistemic Logics via the Logic of GKMay 05 2014The logic of knowledge and justified assumptions, also known as logic of grounded knowledge (GK), was proposed by Lin and Shoham as a general logic for nonmonotonic reasoning. To date, it has been used to embed in it default logic (propositional case), ... More
Boundary value problems for the Lorentzian Dirac operatorApr 11 2017Jul 14 2017On a compact globally hyperbolic Lorentzian spin manifold with smooth spacelike Cauchy boundary the (hyperbolic) Dirac operator is known to be Fredholm when Atiyah-Patodi-Singer boundary conditions are imposed. In this paper we investigate to what extent ... More
Preduals and complementation of spaces of bounded linear operatorsSep 17 2016Mar 21 2018For Banach spaces X and Y, we establish a natural bijection between preduals of Y and preduals of L(X,Y) that respect the right L(X)-module structure. If X is reflexive, it follows that there is a unique predual making L(X) into a dual Banach algebra. ... More
Invariant Subspaces for Operators in a General II_1-factorNov 09 2006It is shown that to every operator T in a general von Neumann factor M of type II_1 and to every Borel set B in the complex plane, one can associate a largest, closed, T-invariant subspace, K = K_T(B), affiliated with M, such that the Brown measure of ... More
Extending representations of Banach algebras to their bidualsMar 02 2017Mar 23 2018We show that a representation of a Banach algebra $A$ on a Banach space $X$ can be extended to a canonical representation of $A^{**}$ on $X$ if and only if certain orbit maps $A\to X$ are weakly compact. When this is the case, we show that the essential ... More
A measurement of the turbulence-driven density distribution in a non-star-forming molecular cloudOct 02 2013Oct 04 2013Molecular clouds are supersonically turbulent. This turbulence governs the initial mass function and the star formation rate. In order to understand the details of star formation, it is therefore essential to understand the properties of turbulence, in ... More
Unfolding the Laws of Star Formation: The Density Distribution of Molecular CloudsApr 10 2014The formation of stars shapes the structure and evolution of entire galaxies. The rate and efficiency of this process are affected substantially by the density structure of the individual molecular clouds in which stars form. The most fundamental measure ... More
On the shape and completeness of the column density probability distribution function of molecular cloudsNov 07 2018Both observational and theoretical research over the past decade has demonstrated that the probability distribution function (PDF) of the gas density in turbulent molecular clouds is a key ingredient for understanding star formation. It has recently been ... More
cuLGT: Lattice Gauge Fixing on GPUsDec 11 2014We adopt CUDA-capable Graphic Processing Units (GPUs) for Landau, Coulomb and maximally Abelian gauge fixing in 3+1 dimensional SU(3) and SU(2) lattice gauge field theories. A combination of simulated annealing and overrelaxation is used to aim for the ... More
Representations of $p$-convolution algebras on $L^q$-spacesSep 27 2016For a nontrivial locally compact group $G$, and $p\in [1,\infty)$, consider the Banach algebras of $p$-pseudofunctions, $p$-pseudomeasures, $p$-convolvers, and the full group $L^p$-operator algebra. We show that these Banach algebras are operator algebras ... More
Eigenvalue placement for regular matrix pencils with rank one perturbationsApr 12 2016A regular matrix pencil sE-A and its rank one perturbations are considered. We determine the sets in the extended complex plane which are the eigenvalues of the perturbed pencil. We show that the largest Jordan chains at each eigenvalue of sE-A may disappear ... More
Gauge fixing using overrelaxation and simulated annealing on GPUsSep 18 2012We adopt CUDA-capable Graphic Processing Units (GPUs) for Coulomb, Landau and maximally Abelian gauge fixing in 3+1 dimensional SU(3) lattice gauge field theories. The local overrelaxation algorithm is perfectly suited for highly parallel architectures. ... More
Role of two-flavor color superconductor pairing in a three-flavor Nambu--Jona-Lasinio model with axial anomalyJul 29 2010Oct 18 2010The phase diagram of strongly interacting matter is studied within a three-flavor Nambu--Jona-Lasinio model, which contains the coupling between chiral and diquark condensates through the axial anomaly. Our results show that it is essential to include ... More
Quantum Critical Dynamics Simulation of Dirty Boson SystemsSep 14 2011Nov 23 2011Recently the scaling result $z=d$ for the dynamic critical exponent at the Bose glass to superfluid quantum phase transition has been questioned both on theoretical and numerical grounds. This motivates a careful evaluation of the critical exponents in ... More
Statistics for surface modes of nanoparticles with shape fluctuationsFeb 23 2010We develop a numerical method for approximating the surface modes of sphere-like nanoparticles in the quasi-static limit, based on an expansion of (the angular part of) the potentials into spherical harmonics. Comparisons of the results obtained in this ... More
Interdisciplinary patterns of a university: Investigating collaboration using co-publication network analysisMar 22 2010We investigate collaborative and interdisciplinary research features of University College Dublin, using methods from social network analysis to analyze and visualize (co-)publications covered by the Web of Science from 1998 through 2007. We account for ... More
Pairing an arbitrary regressor with an artificial neural network estimating aleatoric uncertaintyJul 23 2017Sep 03 2018We suggest a general approach to quantification of different forms of aleatoric uncertainty in regression tasks performed by artificial neural networks. It is based on the simultaneous training of two neural networks with a joint loss function and a specific ... More
An integral boundary layer equation for film flow over inclined wavy bottomsNov 20 2008Aug 25 2009We study the flow of an incompressible liquid film down a wavy incline. Applying a Galerkin method with only one ansatz function to the Navier-Stokes equations we derive a second order weighted residual integral boundary layer equation, which in particular ... More
Density functional theory calculation and thermodynamic analysis of the bridgmanite surface structureOct 24 2018Nov 01 2018Bridgmanite, a high temperature and pressure form of $MgSiO_3$, is believed to be Earth's most abundant mineral and responsible for the observed seismic anisotropy in the mantle. Little is known about surfaces of bridgmanite but knowledge of the most ... More
Shrinkage estimators for prediction out-of-sample: Conditional performanceSep 05 2012Nov 29 2013We find that, in a linear model, the James-Stein estimator, which dominates the maximum-likelihood estimator in terms of its in-sample prediction error, can perform poorly compared to the maximum-likelihood estimator in out-of-sample prediction. We give ... More
Brown Measures of Unbounded Operators Affiliated with a Finite von Neumann AlgebraMay 10 2006In this paper we generalize Brown's spectral distribution measure to a large class of unbounded operators affiliated with a finite von Neumann algebra. Moreover, we compute the Brown measure of all unbounded R-diagonal operators in this class. As a particular ... More
Quotients of Banach algebras acting on $L^p$-spacesDec 12 2014Mar 29 2016We show that the class of Banach algebras that can be isometrically represented on an $L^p$-space, for $p\neq 2$, is not closed under quotients. This answers a question asked by Le Merdy 20 years ago. Our methods are heavily reliant on our earlier study ... More
Global weak solutions for an Newtonian Fluid interacting with a Koiter Type Shell under natural boundary conditionsJul 19 2018We consider an viscous, incompressible Newtonian fluid flowing through a thin elastic structure. The motion of the structure is described by the equations of a linearised Koiter shell, whose motion is restricted to transverse displacements. The fluid ... More
Gradient walk and $p$-harmonic functionsMay 18 2016We consider a class of stochastic processes and establish its connection to $p$-harmonic functions. In particular, we obtain stochastic approximations that converge uniformly to a $p$-harmonic function, with an explicit convergence rate, and also obtain ... More
Regularity for nonlinear stochastic gamesSep 24 2015Aug 11 2016We establish regularity for functions satisfying a dynamic programming equation, which may arise for example from stochastic games or discretization schemes. Our results can also be utilized in obtaining regularity and existence results for the corresponding ... More
A feasible second order bundle algorithm for nonsmooth, nonconvex optimization problems with inequality constraints: I. Derivation and convergenceJun 26 2015This paper extends the SQP-approach of the well-known bundle-Newton method for nonsmooth unconstrained minimization to the nonlinearly constrained case. Instead of using a penalty function or a filter or an improvement function to deal with the presence ... More
Is the Scaling of Supersonic Turbulence Universal?Oct 08 2008The statistical properties of turbulence are considered to be universal at sufficiently small length scales, i. e., independent of boundary conditions and large-scale forces acting on the fluid. Analyzing data from numerical simulations of supersonic ... More
The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive ForcingAug 05 2008Nov 06 2008The probability density function (PDF) of the gas density in turbulent supersonic flows is investigated with high-resolution numerical simulations. In a systematic study, we compare the density statistics of compressible turbulence driven by the usually ... More
The origin of kinematically distinct cores and misaligned gas discs in galaxies from cosmological simulationsMay 31 2018Integral field spectroscopy surveys provide spatially resolved gas and stellar kinematics of galaxies. They have unveiled a range of atypical kinematic phenomena, which require detailed modelling to understand. We present results from a cosmological simulation ... More
Preduals and complementation of spaces of bounded linear operatorsSep 17 2016For Banach spaces X and Y, we establish a natural bijection between preduals of Y and preduals of L(X,Y) that respect the right L(X)-module structure. If X is reflexive, it follows that there is a unique predual making L(X) into a dual Banach algebra. ... More
On the Ambiguity of Interaction and Nonlinear Main Effects in a Regime of Dependent CovariatesDec 09 2015Frequently the analysis of large experimental datasets reveals significant interactions that are difficult to interpret within the theoretical framework guiding the research. Some of these interactions are actually spurious artifacts arising from the ... More
Conditional predictive inference for high-dimensional stable algorithmsSep 05 2018We investigate generically applicable and intuitively appealing prediction intervals based on leave-one-out residuals. The conditional coverage probability of the proposed interval, given the observations in the training sample, is close to the nominal ... More
Density functional theory calculations and thermodynamic analysis of the forsterite $Mg_{2}SiO_{4}$(010) surfaceAug 30 2018Sep 13 2018The stability of possible termination structures for the (010) surface of forsterite, $ Mg_2SiO_4 $, is studied using a density functional theory (DFT) based thermodynamic approach. The DFT calculations are used to estimate the surface Gibbs free energy ... More
Necessary subspace concentration conditions for the even dual Minkowski problemMar 30 2017We prove tight subspace concentration inequalities for the dual curvature measures $\widetilde{\mathrm{C}}_q(K,\cdot)$ of an $n$-dimensional origin-symmetric convex body for $q\geq n+1$. This supplements former results obtained in the range $q\leq n$. ... More
The generator problem for Z-stable C*-algebrasJan 18 2012The generator problem was posed by Kadison in 1967, and it remains open until today. We provide a solution for the class of C*-algebras absorbing the Jiang-Su algebra Z tensorially. More precisely, we show that every unital, separable, Z-stable C*-algebras ... More
Need for fully unintegrated parton densitiesAug 27 2005Associated with the use of conventional integrated parton densities are kinematic approximations on parton momenta which result in unphysical differential distributions for final-state particles. We argue that it is important to reformulate perturbative ... More
Towards precision determination of uPDFsJul 29 2007The unintegrated Parton Density Function of the gluon is obtained from a fit to dijet production in DIS as measured at HERA. Reasonable descriptions of the measurements are obtained, and a first attempt to constrain the intrinsic transverse momentum distribution ... More
Small-x Physics and Forward Jet Production at THERAMay 14 2001We discuss some aspects of forward jet production as a signature for small $x$ physics at THERA energies.
Group algebras acting on $L^p$-spacesAug 24 2014Apr 18 2015For $p\in [1,\infty)$ we study representations of a locally compact group $G$ on $L^p$-spaces and $QSL^p$-spaces. The universal completions $F^p(G)$ and $F^p_{\mathrm{QS}}(G)$ of $L^1(G)$ with respect to these classes of representations (which were first ... More
Numerical results for snaking of patterns over patterns in some 2D Selkov-Schnakenberg Reaction-Diffusion systemsApr 05 2013Oct 15 2013For a Selkov--Schnakenberg model as a prototype reaction-diffusion system on two dimensional domains we use the continuation and bifurcation software pde2path to numerically calculate branches of patterns embedded in patterns, for instance hexagons embedded ... More
Bernstein-von Mises theorems and uncertainty quantification for linear inverse problemsNov 09 2018We consider the statistical inverse problem of approximating an unknown function $f$ from a linear measurement corrupted by additive Gaussian white noise. We employ a nonparametric Bayesian approach with standard Gaussian priors, for which the posterior-based ... More