Results for "Stefan Funk"

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Comparison of Fermi-LAT and CTA in the region between 10-100 GeVMay 03 2012The past decade has seen a dramatic improvement in the quality of data available at both high (HE: 100 MeV to 100 GeV) and very high (VHE: 100 GeV to 100 TeV) gamma-ray energies. With three years of data from the Fermi Large Area Telescope (LAT) and deep ... More
Escape from Vela XNov 08 2011Whilst the Vela pulsar and its associated nebula are often considered as the archetype of a system powered by a \sim10^4 year old isolated neutron star, many features of the spectral energy distribution of this pulsar wind nebula are both puzzling and ... More
Indirect Detection of Dark Matter with gamma raysOct 10 2013Feb 12 2014The details of what constitutes the majority of the mass that makes up dark matter in the Universe remains one of the prime puzzles of cosmology and particle physics today - eighty years after the first observational indications. Today, it is widely accepted ... More
The status of gamma-ray astronomyApr 20 2012Gamma-ray studies are an essential tool in our search for the origin of cosmic rays. Instruments like the Fermi-LAT, H.E.S.S., MAGIC and VERITAS have revolutionized our understanding of the high energy Universe. This paper describes the status of the ... More
Status of Identification of VHE gamma-ray sourcesSep 20 2006With the recent advances made by Cherenkov telescopes such as H.E.S.S., the field of very high-energy (VHE) gamma-ray astronomy has recently entered a new era in which for the first time populations of Galactic sources such as e.g. Pulsar wind nebulae ... More
Solution to the cosmic ray anisotropy problemAug 15 2014Jan 14 2015In the standard diffusive picture for transport of cosmic rays (CRs), a gradient in the CR density induces a typically small, dipolar anisotropy in their arrival directions. This has been widely advertised as a tool for finding nearby sources. However, ... More
Demystifying an unidentified EGRET source by VHE gamma-ray observationsNov 21 2006Nov 22 2006In a novel approach in observational high-energy gamma-ray astronomy, observations carried out by imaging atmospheric Cherenkov telescopes provide necessary templates to pinpoint the nature of intriguing, yet unidentified EGRET gamma-ray sources. Using ... More
Extended Gamma-ray Emission from the G25.0+0.0 Region: A Star Forming Region Powered by the Newly Found OB Association?Apr 20 2017We report a study of extended $\gamma$-ray emission with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, which is likely to be the second case of a $\gamma$-ray detection from a star-forming region (SFR) in our Galaxy. The ... More
A Multi-Wavelength Investigation of the Unidentified Gamma-Ray Source HESS J1708-410Nov 03 2009We report on recent XMM-Newton observations, archival radio continuum and CO data, and SED modeling of the unidentified Galactic plane source HESS J1708-410. No significant extended X-ray emission is observed, and we place an upper limit of 3.2 x 10{-13} ... More
Towards the First Catalog of Fermi-LAT sources below 100 MeVFeb 08 2018Previous analyses of point sources in the gamma-ray range were done either below 30 MeV or above 100 MeV. Below 30 MeV, the imaging Compton telescope (COMPTEL) onboard NASA's Compton Gamma-Ray Observatory detected 26 steady sources in the energy range ... More
The hunt for axionlike particles with the Cherenkov Telescope ArrayMay 01 2013Gamma-ray photons can convert into axion-like particles (ALPs) and vice versa when interacting with astrophysical magnetic fields. The conversions of ALPs may have important implications for astrophysics since they would imprint characteristic features ... More
Gamma-ray Emission from Crushed Clouds in Supernova RemnantsAug 11 2010Sep 30 2010It is shown that the radio and gamma-ray emission observed from newly-found "GeV-bright" supernova remnants (SNRs) can be explained by a model, in which a shocked cloud and shock-accelerated cosmic rays (CRs) frozen in it are simultaneously compressed ... More
The first catalog of Fermi-LAT sources below 100 MeVJun 28 2018We present the first Fermi Large Area Telescope (LAT) low energy catalog (1FLE) of sources detected in the energy range 30 - 100 MeV. The COMPTEL telescope detected sources below 30 MeV, while catalogs released by the Fermi-LAT and EGRET collaborations ... More
Characterizations of Morita equivalent inverse semigroupsJun 04 2009Jul 26 2010We prove that four different notions of Morita equivalence for inverse semigroups motivated by, respectively, $C^{\ast}$-algebra theory, topos theory, semigroup theory and the theory of ordered groupoids are equivalent. We also show that the category ... More
Prospects for Indirect Detection of Dark Matter with CTAMay 01 2013Sep 20 2013We discuss the prospects for indirect detection of dark matter (DM) with the Cherenkov Telescope Array (CTA), a future ground-based gamma-ray observatory that will be sensitive to gamma rays in the energy range from a few tens of GeV to 100 TeV. We consider ... More
Development of an ASIC for Dual Mirror Telescopes of the Cherenkov Telescope ArrayOct 21 2011We have developed an application-specific integrated circui (ASIC) for photomultipler tube (PMT) waveform digitization which is well-suited for the Schwarzschild-Couder optical system under development for the Cherenkov Telescope Array (CTA) project. ... More
Suzaku observation of the unidentified VHE gamma-ray source HESS J1702-420Jun 02 2011A deep X-ray observation of the unidentified very high energy (VHE) gamma-ray source HESS J1702-420, for the first time, was carried out by Suzaku. No bright sources were detected in the XIS field of view (FOV) except for two faint point-like sources. ... More
Quantum key distribution using non-classical photon number correlations in macroscopic light pulsesSep 14 2001Nov 07 2001We propose a new scheme for quantum key distribution using macroscopic non-classical pulses of light having of the order 10^6 photons per pulse. Sub-shot-noise quantum correlation between the two polarization modes in a pulse gives the necessary sensitivity ... More
A shortcut to (sun)flowers: Kernels in logarithmic space or linear timeApr 30 2015We investigate whether kernelization results can be obtained if we restrict kernelization algorithms to run in logarithmic space. This restriction for kernelization is motivated by the question of what results are attainable for preprocessing via simple ... More
Streaming KernelizationMay 06 2014Kernelization is a formalization of preprocessing for combinatorially hard problems. We modify the standard definition for kernelization, which allows any polynomial-time algorithm for the preprocessing, by requiring instead that the preprocessing runs ... More
On the commutability of homogenization and linearization in finite elasticityNov 16 2010May 16 2011We study non-convex elastic energy functionals associated to (spatially) periodic, frame indifferent energy densities with a single non-degenerate energy well at SO(n). Under the assumption that the energy density admits a quadratic Taylor expansion at ... More
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
Superstability of the yeast cell cycle dynamics: Ensuring causality in the presence of biochemical stochasticityMay 05 2006Gene regulatory dynamics is governed by molecular processes and therefore exhibits an inherent stochasticity. However, for the survival of an organism it is a strict necessity that this intrinsic noise does not prevent robust functioning of the system. ... More
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
HESS J1825-137: A pulsar wind nebula associated with PSR B1823-13?Oct 15 2005HESS J1825-137 was detected with a significance of 8.1 $\sigma$ in the Galactic Plane survey conducted with the H.E.S.S. instrument in 2004. Both HESS J1825-137 and the X-ray pulsar wind nebula G18.0--0.7 (associated with the Vela-like pulsar PSR B1823-13) ... More
Complementarity of Dark Matter Searches in the pMSSMMay 26 2014As is well known, the search for and eventual identification of dark matter in supersymmetry requires a simultaneous, multi-pronged approach with important roles played by the LHC as well as both direct and indirect dark matter detection experiments. ... More
Fermi-LAT Discovery of GeV Gamma-ray Emission from the Vicinity of SNR W44Mar 14 2012We report the detection of GeV gamma-ray emission from the molecular cloud complex that surrounds the supernova remnant (SNR) W44 using the Large Area Telescope (LAT) onboard Fermi. While the previously reported gamma-ray emission from SNR W44 is likely ... More
The midpoint between dipole and parton showersJun 16 2015Sep 19 2015We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A ... More
VHE Gamma-ray supernova remnantsJan 16 2007Increasing observational evidence gathered especially in X-rays and gamma-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ``knee'' in the energy ... More
Homology Classes of Semi-Algebraic Sets and Mass MinimizationApr 18 2014Nov 06 2014We associate to any compact semi-algebraic set $X \subset \mathbb R^n$ a chain complex of currents $S_\ast (X)$ generated by integration along semi-algebraic submanifolds and we analyze the corresponding homology groups. In particular, we show that these ... More
Space- and Ground-Based Gamma-Ray AstrophysicsAug 21 2015In recent years, observational $\gamma$-ray astronomy has seen a remarkable range of exciting new results in the high-energy and very-high energy regimes. Coupled with extensive theoretical and phenomenological studies of non-thermal processes in the ... More
Co-detection of micro seismic activity as early warning of gravitational slope failureDec 13 2018We developed a new strategy for Disaster Risk Reduction for gravitational slope failure: We propose a simple method for real-time early warning of gravity-driven failures that considers and exploits both the heterogeneity of natural media and characteristics ... More
$C^0$-characterization and $C^0$-rigidity of symplectic and contact embeddingsJul 11 2016Jul 25 2016We present a novel C^0-characterization of symplectic embeddings and diffeomorphisms in terms of Lagrangian embeddings. Our approach is based on the shape invariant, which was discovered by J. C. Sikorav and Y. Eliashberg, intersection theory and the ... More
HS06 Benchmark for an ARM ServerNov 15 2013We benchmarked an ARM cortex-A9 based server system with a four-core CPU running at 1.1 GHz. The system used Ubuntu 12.04 as operating system and the HEPSPEC 2006 (HS06) benchmarking suite was compiled natively with gcc-4.4 on the system. The benchmark ... More
Power Corrections in Electron-Positron Annihilation: Experimental ReviewJun 20 2006Experimental studies of power corrections with e+e- data are reviewed. An overview of the available data for jet and event shape observables is given and recent analyses based on the Dokshitzer-Marchesini-Webber (DMW) model of power corrections are summarised. ... More
D-branes in a marginally deformed WZW modelDec 17 2002In this talk we discuss symmetry preserving D-branes on a line of a marginally deformed SU(2) WZW model. A semiclassical and a quantum theoretical approach are presented.
D-branes on a Deformation of SU(2)Dec 20 2001Jan 04 2002We discuss D-branes on a line of conformal field theories connected by an exact marginal deformation. The line contains an SU(2) WZW model and two mutually T-dual SU(2)/U(1) cosets times a free boson. We find the D-branes preserving a U(1) isometry, an ... More
Membrany corrections to the string anti-string potential in M5-brane theoryFeb 10 1999Mar 06 2000We study the potential between a string and an anti-string source in M5-theory by using the adS/CFT duality conjecture. We find that the next to leading order corrections in a saddle point approximation renormalize the classical result.
Measurement of the Pion Polarizability at COMPASSJan 20 2014Feb 12 2014The value of the pion polarizability is predicted with high precision by Chiral Perturbation Theory. However, the existing experimental values are at tension with this prediction as well as among themselves. The COMPASS experiment at the CERN SPS accesses ... More
Rho meson properties from combining QCD-based modelsMar 04 2003Aiming at the calculation of the properties of rho-mesons, non-perturbative QCD-based methods are discussed concerning their potentials as well as their short-comings. The latter are overcome by combining these techniques. The utilized methods are (i) ... More
Life time of resonances in transport simulationsAug 21 2000We calculate the life time of a resonance in our recently developed framework for a test-particle description of transport processes for states with continuous mass spectra. The result differs from the expression commonly used in transport simulations ... More
Information on the structure of the rho meson from the pion form-factorJul 01 2009The electromagnetic pion form-factor is calculated in a Bethe-Salpeter approach which accounts for pion rescattering. In the scattering kernel the pion-pion contact interaction from lowest-order chiral perturbation theory is considered together with an ... More
Spin Path Integrals, Berry phase, and the Quantum Phase Transition in the sub-Ohmic Spin-boson ModelJul 26 2010The quantum critical properties of the sub-Ohmic spin-1/2 spin-boson model and of the Bose-Fermi Kondo model have recently been discussed controversially. The role of the Berry phase in the breakdown of the quantum-to-classical mapping of quantum criticality ... More
A Rigidity Phenomenon for the Hardy-Littlewood Maximal FunctionOct 02 2014Nov 13 2015The Hardy-Littlewood maximal function $\mathcal{M}$ and the trigonometric function $\sin{x}$ are two central objects in harmonic analysis. We prove that $\mathcal{M}$ characterizes $\sin{x}$ in the following way: let $f \in C^{\alpha}(\mathbb{R}, \mathbb{R})$ ... More
A geometric uncertainty principle with an application to Pleijel's estimateJun 13 2013Nov 04 2013Consider partitions of an open, bounded domain in $\mathbb{R}^n$. Then an average element of the partition has either its Fraenkel asymmetry or its deviation from the smallest element in the partition bounded away from 0 by a universal constant. As an ... More
Period -- mass-loss rate relation of Miras with and without technetiumNov 05 2014We present the discovery that Mira variables separate in two distinct sequences in a near- to mid-IR color versus pulsation period diagram, if a distinction is made with respect to the presence of technetium (Tc) in the stars. Tc is an indicator of recent ... More
Period -- mass-loss rate relation of Miras with and without technetiumJun 23 2013Aims: We report the discovery that Mira variables with and without absorption lines of the element technetium (Tc) occupy two different regions in a diagram of near- to mid-infrared colour versus pulsation period. Tc is an indicator of a recent or ongoing ... More
Dynamical properties of a randomly diluted neural network with variable activityMar 08 1999The subject of study is a neural network with binary neurons, randomly diluted synapses and variable pattern activity. We look at the system with parallel updating using a probabilistic approach to solve the one step dynamics with one condensed pattern. ... More
The coherent states: old geometrical methods in new quantum clothesAug 02 1994A geometric characterization of transition amplitudes between coherent states, or equivalently, of the hermitian scalar product of holomorphic cross sections in the associated D - M tilda - module, in terms of the embedding of the cohe- rent state manifold ... More
Phase Diagram of Interacting Bosons on the Honeycomb LatticeJan 15 2007We study the ground state properties of repulsively interacting bosons on the honeycomb lattice using large-scale quantum Monte Carlo simulations. In the hard-core limit the half-filled system develops long ranged diagonal order for sufficiently strong ... More
Periods and Hodge structures in perturbative quantum field theoryFeb 04 2013Jul 06 2013There is a fruitful interplay between algebraic geometry on the one side and perturbative quantum field theory on the other side. I review the main relevant mathematical concepts of periods, Hodge structures and Picard-Fuchs equations and discuss the ... More
Feynman GraphsJan 29 2013In these lectures I discuss Feynman graphs and the associated Feynman integrals. Of particular interest are the classes functions, which appear in the evaluation of Feynman integrals. The most prominent class of functions is given by multiple polylogarithms. ... More
Introduction to Feynman IntegralsMay 11 2010In these lectures I will give an introduction to Feynman integrals. In the first part of the course I review the basics of the perturbative expansion in quantum field theories. In the second part of the course I will discuss more advanced topics: Mathematical ... More
Status of NNLO 3-jet calculationsAug 25 2004The process e+ e- -> 3 jets offers the opportunity to measure the strong coupling constant. For an accurate determination, precise theoretical calculations are necessary. I will give an overview on the status of the next-to-next-to-leading order calculations. ... More
Subtraction terms for one-loop amplitudes with one unresolved partonJun 25 2003Fully differential next-to-next-to-leading order calculations require a method to cancel infrared singularities. In a previous publication, I discussed the general setup for the subtraction method at NNLO. In this paper I give all subtraction terms for ... More
gTybalt - a free computer algebra systemApr 29 2003This article documents the free computer algebra system "gTybalt". The program is build on top of other packages, among others GiNaC, TeXmacs and Root. It offers the possibility of interactive symbolic calculations within the C++ programming language. ... More
Computer Algebra in Particle PhysicsSep 20 2002These lectures given to graduate students in theoretical particle physics, provide an introduction to the ``inner workings'' of computer algebra systems. Computer algebra has become an indispensable tool for precision calculations in particle physics. ... More
Theoretical overview on top pair production and single top productionJan 19 2012In this talk I will give an overview on theoretical aspects of top quark physics. The focus lies on top pair production and single top production.
Symmetry breaking of gauge theories down to Abelian sub-groupsFeb 14 2008I re-derive the lowest order effective Lagrangian for electro-weak symmetry breaking without the use of Goldstone's theorem for spontaneously broken global symmetries and without the assumption of a custodial symmetry. I consider the breaking of a local ... More
Automated computation of spin- and colour-correlated Born matrix elementsOct 12 2005I report on an implementation of an algorithm for the automated numerical calculation of spin- and colour-correlated Born matrix elements in QCD. These spin- and colour-correlated matrix elements are needed for NLO calculations in combination with the ... More
Algebraic Algorithms in Perturbative CalculationsMay 30 2003I discuss algorithms for the evaluation of Feynman integrals. These algorithms are based on Hopf algebras and evaluate the Feynman integral to (multiple) polylogarithms.
Flavour-Dependent Type II LeptogenesisApr 12 2007Sep 11 2008We reanalyse leptogenesis via the out-of-equilibrium decay of the lightest right-handed neutrino in type II seesaw scenarios, taking into account flavour-dependent effects. In the type II seesaw mechanism, in addition to the type I seesaw contribution, ... More
Renormalization Group Analysis of Neutrino Mass ParametersAug 20 2002Tools for calculating the Renormalization Group Equations for renormalizable and non-renormalizable operators in various theories are reviewed, which are essential for comparing experimental results with predictions from models beyond the Standard Model. ... More
Effective descent maps for schemesJun 11 2001Feb 01 2003The paper is withdrawn due to mistakes in the proofs for Proposition 1.2 and Theorem 2.2.
Simulation of Z plus Graviton/Unparticle Production at the LHCSep 27 2008Feb 09 2009Theories with extra dimensions have gained much interest in recent years as candidates for a possible extension of the SM. The observation of large extra dimensions through real graviton emission is one of the most popular related new phenomena. The main ... More
Status of the Forward Physics Projects in ATLASJun 05 2007The ATLAS experiment at the LHC is building several detector systems for forward physics studies and to determine the luminosity. The main forward systems consist of a Cerenkov detector called LUCID, a Zero Degree Calorimeter (ZDC) and Roman Pots which ... More
Recent developments in deformation quantizationJan 31 2015In this review an overview on some recent developments in deformation quantization is given. After a general historical overview we motivate the basic definitions of star products and their equivalences both from a mathematical and a physical point of ... More
Deformation Quantization: Observable Algebras, States and Representation TheoryMar 10 2003In these lecture notes I give an introduction to deformation quantization. The quantization problem is discussed in some detail thereby motivating the notion of star products. Starting from a deformed observable algebra, i.e. the star product algebra, ... More
A Nuclear Weyl AlgebraSep 25 2012Jun 13 2013A bilinear form on a possibly graded vector space $V$ defines a graded Poisson structure on its graded symmetric algebra together with a star product quantizing it. This gives a model for the Weyl algebra in an algebraic framework, only requiring a field ... More
Positivity in Rieffel's strict deformation quantizationSep 15 2009We review a recent result on Rieffel's deformation quantization by actions of R^d: it is shown that for every state omega_0 of the undeformed C*-algebra A_0 there is a continuous section of states omega(hbar) through omega_0. We outline the physical interpretation ... More
Introduction to parton-shower event generatorsNov 14 2014Jun 18 2015This lecture discusses the physics implemented by Monte Carlo event generators for hadron colliders. It details the construction of parton showers and the matching of parton showers to fixed-order calculations at higher orders in perturbative QCD. It ... More
Stochastic Methods for Quantum ScatteringFeb 25 1994Quantum scattering at zero energy is studied with stochastic methods. A path integral representation for the scattering cross section is developed. It is demonstrated that Monte Carlo simulation can be used to compare effective potentials which are frequently ... More
Off-shell effects in Higgs decays to heavy gauge bosons and signal-background interference in Higgs decays to photons at a linear colliderMar 26 2015We discuss off-shell contributions in Higgs decays to heavy gauge bosons $H\rightarrow VV^{(*)}$ with $V\in\lbrace Z,W\rbrace$ for a standard model (SM) Higgs boson for both dominant production processes $e^+e^-\rightarrow ZH\rightarrow ZVV^{(*)}$ and ... More
Neutral Higgs production at proton colliders in the CP-conserving NMSSMFeb 27 2015May 21 2015We discuss neutral Higgs boson production through gluon fusion and bottom-quark annihilation in the CP-conserving $\mathbb{Z}_3$-invariant Next-to-Minimal Supersymmetric Standard Model (NMSSM) at proton colliders. For gluon fusion we adapt known asymptotic ... More
Flavour Physics in the Littlest Higgs Model with T-Parity: Effects in the K, B_d/s and D systemsAug 21 2009The Littlest Higgs Model with T parity (LHT) is an interesting alternative model for New Physics at the TeV scale. Although Flavour Physics was not the reason for creating the LHT model, significant effects (such as large CP violation where not predicted ... More
Electron-ion merged-beam experiments at heavy-ion storage ringsJul 24 2014In the past two decades, the electron-ion merged-beams technique has extensively been exploited at heavy-ion storage rings equipped with electron coolers for spectroscopic studies of highly charged ions as well as for measuring absolute cross sections ... More
Not So Easy Problems for Tree Decomposable GraphsJul 06 2011We consider combinatorial problems that can be solved in polynomial time for graphs of bounded treewidth but where the order of the polynomial that bounds the running time is expected to depend on the treewidth bound. First we review some recent results ... More
Permanents in linear optical networksJun 18 2004We develop an abstract look at linear optical networks from the viewpoint of combinatorics and permanents. In particular we show that calculation of matrix elements of unitarily transformed photonic multi-mode states is intimately linked to the computation ... More
Electronic Structure Methods Exhibiting Linear Scaling of the Computational Effort with Respect to the Size of the SystemJun 05 1998Oct 29 1998Methods exhibiting linear scaling with respect to the size of the system, so called O(N) methods, are an essential tool for the calculation of the electronic structure of large systems containing many atoms. They are based on algorithms which take advantage ... More
Renormalized Quantum Yang-Mills Fields in Curved SpacetimeMay 23 2007Feb 28 2008We present a proof that quantum Yang-Mills theory can be consistently defined as a renormalized, perturbative quantum field theory on an arbitrary globally hyperbolic curved, Lorentzian spacetime. To this end, we construct the non-commutative algebra ... More
Black hole uniqueness theorems and new thermodynamic identities in eleven dimensional supergravityApr 16 2012Aug 30 2012We consider stationary, non-extremal black holes in 11-dimensional supergravity having isometry group $\mathbb{R} \times U(1)^8$. We prove that such a black hole is uniquely specified by its angular momenta, its electric charges associated with the various ... More
Valuation theoretic methods in the birational geometry of algebraic varietiesOct 31 2016In this paper, we give a valuation formula for rational top differential forms of function fields in characteristic zero for arbitrary Abhyankar places generalizing the classical valuation at prime divisors. This enables us to define log discrepancies ... More
QCD sum rules as applied to heavy baryonsJun 08 2000We give an overview over recent calculations of baryonic correlator functions with finite mass quarks in view on their applicability for QCD sum rules. The QCD sum rule method is then demonstrated within the Heavy Quark Effective Theory.
Baryon chiral perturbation theoryOct 02 2009We provide an introduction to the power-counting issue in baryon chiral perturbation theory and discuss some recent developments in the manifestly Lorentz-invariant formulation of the one-nucleon sector. As explicit applications we consider the chiral ... More
Chiral perturbation theory - Success and challengeDec 22 2005Chiral perturbation theory is the effective field theory of the strong interactions at low energies. We will give a short introduction to chiral perturbation theory for mesons and will discuss, as an example, the electromagnetic polarizabilities of the ... More
Quantitative Homogenization and Convergence of Moving AveragesOct 31 2018We study homogenization it its most basic form $$-\left(a\left(\frac{x}{\varepsilon}\right) u_{\varepsilon}'(x)\right)' = f(x) \quad \mbox{for} ~x \in (0,1),$$ where $a(\cdot)$ is a positive $1-$periodic continuous function, $f$ is smooth and $u_{\varepsilon}$ ... More
Relative entropy close to the edgeMay 25 2018We show that the relative entropy between the reduced density matrix of the vacuum state in some region $A$ and that of an excited state created by a unitary operator localized at a small distance $\ell$ of a boundary point $p$ is insensitive to the global ... More
An Endpoint Alexandrov Bakelman Pucci Estimate in the PlaneApr 25 2018Jul 31 2018The classical Alexandrov-Bakelman-Pucci estimate for the Laplacian states $$ \max_{x \in \Omega}{ |u(x)|} \leq \max_{x \in \partial \Omega}{|u(x)|} + c_{s,n} \mbox{diam}(\Omega)^{2-\frac{n}{s}} \left\| \Delta u\right\|_{L^s(\Omega)}$$ where $\Omega \subset ... More
Fast multigrid solvers for conforming and non-conforming multi-patch Isogeometric AnalysisFeb 05 2019Isogeometric Analysis allows high-order discretizations of boundary value problems using a number of degrees of freedom which is as small as for a low-order method. To be able to choose high spline degrees in practice, suitable numerical solvers are required. ... More
Differential forms on singular spaces, the minimal model program, and hyperbolicity of moduli stacksJul 21 2011Dec 20 2011This survey discusses hyperbolicity properties of moduli stacks and generalisations of the Shafarevich Hyperbolicity Conjecture to higher dimensions. It concentrates on methods and results that relate moduli theory with recent progress in higher dimensional ... More
The Process of price formation and the skewness of asset returnsMar 02 2006Distributions of assets returns exhibit a slight skewness. In this note we show that our model of endogenous price formation \cite{Reimann2006} creates an asymmetric return distribution if the price dynamics are a process in which consecutive trading ... More
Quantum Approximation I. Embeddings of Finite Dimensional L_p SpacesMay 06 2003We study approximation of embeddings between finite dimensional L_p spaces in the quantum model of computation. For the quantum query complexity of this problem matching (up to logarithmic factors) upper and lower bounds are obtained. The results show ... More
Stably irrational hypersurfaces of small slopesJan 16 2018Sep 11 2018Let k be an uncountable field of characteristic different from two. We show that a very general hypersurface of dimension N>2 and degree at least $\log_2N +2$ is not stably rational over the algebraic closure of k.
A Framework for Bottom-Up Simulation of SLD-ResolutionMay 15 2014This paper introduces a framework for the bottom-up simulation of SLD-resolution based on partial evaluation. The main idea is to use database facts to represent a set of SLD goals. For deductive databases it is natural to assume that the rules defining ... More
Zoomable telescope by rotation of toroidal lensesJul 20 2018A novel type of a continuously zoomable telescope is based on two pairs of adjacent toroidal lenses ("saddle lenses") in combination with standard optical components. Its variable magnification is adjusted by a mere rotation of the four saddle lenses ... More
A quasi-robust discretization error estimate for discontinuous Galerkin Isogeometric AnalysisJan 10 2019Isogeometric Analysis is a spline-based discretization method to partial differential equations which shows the approximation power of a high-order method. The number of degrees of freedom, however, is as small as the number of degrees of freedom of a ... More
Heterotic supersymmetry, anomaly cancellation and equations of motionAug 20 2009Jan 15 2010We show that the heterotic supersymmetry (Killing spinor equations) and the anomaly cancellation imply the heterotic equations of motion in dimensions five, six, seven, eight if and only if the connection on the tangent bundle is an instanton. For heterotic ... More
Genetic algorithm dynamics on a rugged landscapeMar 04 1999The genetic algorithm is an optimization procedure motivated by biological evolution and is successfully applied to optimization problems in different areas. A statistical mechanics model for its dynamics is proposed based on the parent-child fitness ... More