Results for "Stefan Heun"

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Impact of electron heating on the equilibration between quantum Hall edge channelsDec 12 2011When two separately contacted quantum Hall (QH) edge channels are brought into interaction, they can equilibrate their imbalance via scattering processes. In the present work we use a tunable QH circuit to implement a junction between co-propagating edge ... More
Ohmic contact engineering in few-layer black Phosphorus field effect transistorsMay 14 2019Achieving good quality Ohmic contacts to van der Waals materials is a challenge, since at the interface between metal and van der Waals material, different conditions can occur, ranging from the presence of a large energy barrier between the two materials ... More
Quantum Hall Effect in a Josephson JunctionMay 08 2018Hybrid superconductor/semiconductor devices constitute a powerful platform where intriguing topological properties can be investigated. Here we present fabrication methods and analysis of Josephson junctions formed by a high-mobility InAs quantum-well ... More
Aharonov-Bohm interferometer based on n-p junction in graphene nanoribbonsOct 15 2015Aug 20 2016We demonstrate that the phenomenon of current confinement along graphene n-p junctions at high magnetic fields can be used to form an Aharonov-Bohm interferometer. The interference system exploits a closed n-p junction that can be induced by a floating ... More
Tuning hydrogen adsorption on graphene by gate voltageMay 06 2019In order to realize applications of hydrogen-adsorbed graphene, a main issue is how to control hydrogen adsorption/desorption at room temperature. In this study, we demonstrate the possibility to tune hydrogen adsorption on graphene by applying a gate ... More
Black Phosphorus/Palladium Nanohybrid: Unraveling the Nature of P-Pd Interaction and Application in Selective HydrogenationMar 06 2019The burgeoning interest in 2D black phosphorus (bP) contributes to expand its applications in countless fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical ... More
Hydrogen storage with titanium-functionalized grapheneDec 05 2013We report on hydrogen adsorption and desorption on titanium-covered graphene in order to test theoretical proposals to use of graphene functionalized with metal atoms for hydrogen storage. At room temperature titanium islands grow with an average diameter ... More
Low-temperature quantum transport in CVD-grown single crystal grapheneMar 24 2016Chemical vapor deposition (CVD) has been proposed for large-scale graphene synthesis for practical applications. However, the inferior electronic properties of CVD graphene are one of the key problems to be solved. In this study, we present a detailed ... More
Manipulating quantum Hall edge channels in graphene through Scanning Gate MicroscopyJul 10 2017Oct 12 2017We show evidence of the backscattering of quantum Hall edge channels in a narrow graphene Hall bar, induced by the gating effect of the conducting tip of a Scanning Gate Microscope, which we can position with nanometer precision. We show full control ... More
Li-intercalated Graphene on SiC(0001): an STM studyJun 05 2017We present a systematical study via scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) on the effect of the exposure of Lithium (Li) on graphene on silicon carbide (SiC). We have investigated Li deposition both on epitaxial ... More
Tuning of quantum interference in top-gated graphene on SiCNov 28 2013We report on quantum-interference measurements in top-gated Hall bars of monolayer graphene epitaxially grown on the Si face of SiC, in which the transition from negative to positive magnetoresistance was achieved varying temperature and charge density. ... More
Layer-resolved imaging of domain wall interactions in magnetic tunnel junction-like trilayersFeb 27 2007Nov 08 2007We have performed a layer-resolved, microscopic study of interactions between domain walls in two magnetic layers separated by a non-magnetic one, using high-resolution x-ray photoemission electron microscopy. Domain walls in the hard magnetic Co layer ... More
Decoration of exfoliated black phosphorus with nickel nanoparticles and application in catalysisSep 16 2016Aug 28 2017Nickel nanoparticles were dispersed on the surface of exfoliated black phosphorus and the resulting nanohybrid Ni/2DBP showed an improved stability respect to pristine 2D BP when kept in ambient conditions in the darkness. Ni/2DBP was applied as catalyst ... More
The Influence of Graphene Curvature on Hydrogen Adsorption: Towards Hydrogen Storage DevicesNov 28 2013The ability of atomic hydrogen to chemisorb on graphene makes the latter a promising material for hydrogen storage. Based on scanning tunneling microscopy techniques, we report on site-selective adsorption of atomic hydrogen on convexly curved regions ... More
A sensitive calorimetric technique to study energy (heat) exchange at the nano-scaleApr 29 2019Every time a chemical reaction occurs, an energy exchange between reactants and environment exists, which is defined as the enthalpy of the reaction. In the last decades, research has resulted in an increasing number of devices at the micro- or nano-scale. ... More
Correlation between morphology and transport properties of quasi-free-standing monolayer grapheneSep 01 2014Nov 19 2014We investigate the morphology of quasi-free-standing monolayer graphene (QFMLG) formed at several temperatures by hydrogen intercalation and discuss its relationship with transport properties. Features corresponding to incomplete hydrogen intercalation ... More
The role of water in the preparation and stabilization of high quality phosphorene flakesNov 13 2015Water is believed to be harmful for the stability of phosphorene.On the contrary, the presence of small amount of water allows the synthesis of high-quality material in liquid exfoliation of black phosphorus using dimethylsulfoxide as solvent. A phosphorus/water ... More
Hybrid 2D Black Phosphorus/Polymer Materials: New Platforms for Device FabricationFeb 04 2018Hybrid materials, containing a 2D filler embedded in a polymeric matrix, are an interesting platform for several applications, because of the variety of properties that the filler can impart to the polymer matrix when dispersed at the nanoscale. Moreover, ... More
Surface structures of graphene covered Cu (103)Sep 04 2018We studied the surface structures of chemical vapor deposited (CVD) graphene on Cu(103). The graphene covered Cu surface had (103) facets parallel to the Cu[010] direction, on which triangular patterns were formed. In contrast, the bare Cu surface showed ... More
Full electrostatic control of quantum interference in an extended trenched Josephson junctionMar 07 2019Hybrid semiconductor/superconductor devices constitute an important platform for a wide range of applications, from quantum computing to topological-state-based architectures. Here, we demonstrate full modulation of the interference pattern in a superconducting ... More
Non-equilibrium steady-states in a driven-dissipative superfluidJul 17 2015We experimentally study a driven-dissipative Josephson junction array, realized with a weakly interacting Bose Einstein condensate residing in a one-dimensional optical lattice. Engineered losses on one site act as a local dissipative process, while tunneling ... More
Revealing the multi-bonding state between hydrogen and graphene-supported Ti clustersAug 03 2016Hydrogen adsorption on graphene-supported metal clusters has brought much controversy due to the complex nature of the bonding between hydrogen and metal clusters. The bond types of hydrogen and graphene-supported Ti clusters are experimentally and theoretically ... More
Atomic and Electronic Structure of Si Dangling Bonds in Quasi-Free-Standing Monolayer GrapheneJun 05 2017Si dangling bonds without H termination at the interface of quasi-free standing monolayer graphene (QFMLG) are known scattering centers that can severely affect carrier mobility. In this report, we study the atomic and electronic structure of Si dangling ... More
Noncovalent functionalization of few-layer black phosphorus with metal nanoparticles and its application in catalysisSep 16 2016Transition metal nanoparticles of Ni, Pd, Ru and Au, each of them stabilized by a suitable capping agent, were dispersed on the surface of few-layer black phosphorus (2D BP) achieving new nanocomposite 2D materials. Ni nanoparticles supported on 2D BP ... More
Imaging fractional incompressible stripes in integer quantum Hall systemsMay 02 2012Transport experiments provide conflicting evidence on the possible existence of fractional order within integer quantum Hall systems. In fact integer edge states sometimes behave as monolithic objects with no inner structure, while other experiments clearly ... More
Scanning Gate Imaging of quantum point contacts and the origin of the 0.7 AnomalyNov 25 2013Sep 04 2014The origin of the anomalous transport feature appearing at conductance G \approx 0.7 x (2e2/h) in quasi-1D ballistic devices - the so-called 0.7 anomaly - represents a long standing puzzle. Several mechanisms were proposed to explain it, but a general ... More
Spatially-resolved analysis of edge-channel equilibration in quantum Hall circuitsFeb 21 2011We demonstrate an innovative quantum Hall circuit with variable geometry employing the moveable electrostatic potential induced by a biased atomic force microscope tip. We exploit this additional degree of freedom to identify the microscopic mechanisms ... More
Imaging backscattering through impurity-induced antidots in quantum Hall constrictionsSep 11 2012We exploit the biased tip of a scanning gate microscope (SGM) to induce a controlled backscattering between counter-propagating edge channels in a wide constriction in the quantum Hall regime. We compare our detailed conductance maps with a numerical ... More
Rapid CVD growth of millimetre-sized single crystal graphene using a cold-wall reactorJan 26 2015In this work we present a simple pathway to obtain large single-crystal graphene on copper (Cu) foils with high growth rates using a commercially available cold-wall chemical vapour deposition (CVD) reactor. We show that graphene nucleation density is ... More
Revealing the atomic structure of the buffer layer between SiC(0001) and epitaxial grapheneNov 21 2011Aug 02 2013On the SiC(0001) surface (the silicon face of SiC), epitaxial graphene is obtained by sublimation of Si from the substrate. The graphene film is separated from the bulk by a carbon-rich interface layer (hereafter called the buffer layer) which in part ... More
Bilayer-induced asymmetric quantum Hall effect in epitaxial grapheneOct 08 2014Oct 14 2014The transport properties of epitaxial graphene on SiC(0001) at quantizing magnetic fields are investigated. Devices patterned perpendicularly to SiC terraces clearly exhibit bilayer inclusions distributed along the substrate step edges. We show that the ... More
MBE growth of self-assisted InAs nanowires on grapheneOct 03 2016Self-assisted growth of InAs nanowires on graphene by molecular beam epitaxy is reported. Nanowires with diameter of ~50 nm and aspect ratio of up to 100 were achieved. The morphological and structural properties of the nanowires were carefully studied ... More
Inter-Edge Backscattering in Buried Split-Gate-Defined Graphene Quantum Point ContactsAug 26 2016Quantum Hall effects offer a formidable playground for the investigation of quantum transport phenomena. Edge modes can be detected, branched, and mixed by designing a suitable potential landscape in a two-dimensional conducting system subject to a strong ... More
Polymer-based black phosphorus (bP) hybrid materials by in situ radical polymerization: an effective tool to exfoliate bP and stabilize bP nanoflakesApr 11 2018Black phosphorus (bP) has been recently investigated for next generation nanoelectronic multifunctional devices. However, the intrinsic instability of exfoliated bP (the bP nanoflakes) towards both moisture and air has so far overshadowed its practical ... More
Weak Limit of the 3-State Quantum Walk on the LineApr 04 2014May 21 2014We revisit the one dimensional discrete time quantum walk with 3 states and the Grover coin. We derive analytic expressions for observed the localization, an long time approximation for the probability density function (PDF). We also connect the time ... 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
Efficient n-type Doping in Epitaxial Graphene through Strong Lateral Orbital Hybridization of Ti AdsorbateMar 18 2016Aug 23 2016In recent years, various doping methods for epitaxial graphene have been demonstrated through atom substitution and adsorption. Here we observe by angle-resolved photoemission spectroscopy (ARPES) a coupling-induced Dirac cone renormalization when depositing ... 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
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
Interactive Natural Language Acquisition in a Multi-modal Recurrent Neural ArchitectureMar 24 2017Feb 07 2018For the complex human brain that enables us to communicate in natural language, we gathered good understandings of principles underlying language acquisition and processing, knowledge about socio-cultural conditions, and insights about activity patterns ... More
The H-Covariant Strong Picard GroupoidSep 08 2004Apr 25 2005The notion of H-covariant strong Morita equivalence is introduced for *-algebras over C = R(i) with an ordered ring R which are equipped with a *-action of a Hopf *-algebra H. This defines a corresponding H-covariant strong Picard groupoid which encodes ... 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
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
Non-Classical Longitudinal Magneto-Resistance in Anisotropic Black PhosphorusAug 02 2018Dec 05 2018Resistivity measurements of a few-layer black phosphorus (bP) crystal in parallel magnetic fields up to 45 T are reported as a function of the angle between the in-plane field and the source-drain (S-D) axis of the device. The crystallographic directions ... More
A Perspective on Recent Advances in Phosphorene Functionalization and its Application in DevicesMar 28 2019Phosphorene, the 2D material derived from black phosphorus, has recently attracted a lot of interest for its properties, suitable for applications in material science. In particular, the physical features and the prominent chemical reactivity on its surface ... More
Subsampling Extremes: From Block Maxima to Smooth Tail EstimationApr 02 2012Oct 19 2014We study a new estimator for the tail index of a distribution in the Frechet domain of attraction that arises naturally by computing subsample maxima. This estimator is equivalent to taking a U-statistic over a Hill estimator with two order statistics. ... 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
Sharp L^1 Poincare inequalities correspond to optimal hypersurface cutsSep 24 2013Jun 19 2015Let $\Omega \subset \mathbb{R}^n$ be a convex. If $u: \Omega \rightarrow \mathbb{R}$ has mean 0, then we have the classical Poincar\'{e} inequality $$ \|u \|_{L^p} \leq c_p \mbox{diam}(\Omega) \| \nabla u \|_{L^p}$$ with sharp constants $c_2 = 1/\pi$ ... More
Lower bounds on nodal sets of eigenfunctions via the heat flowJan 15 2013Jul 03 2015We study the size of nodal sets of Laplacian eigenfunctions on compact Riemannian manifolds without boundary and recover the currently optimal lower bound by comparing the heat flow of the eigenfunction with that of an artifically constructed diffusion ... 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
GPU-based visualization of domain-coloured algebraic Riemann surfacesJul 16 2015Nov 10 2015We examine an algorithm for the visualization of domain-coloured Riemann surfaces of plane algebraic curves. The approach faithfully reproduces the topology and the holomorphic structure of the Riemann surface. We discuss how the algorithm can be implemented ... More
Hopf algebras and Dyson-Schwinger equationsJun 30 2015Jan 28 2016In these lectures I discuss Hopf algebras and Dyson-Schwinger equations. The lectures start with an introduction to Hopf algebras, followed by a review where Hopf algebras occur in particles physics. The final part of these lectures is devoted to the ... More
On the solutions of the scattering equationsFeb 11 2014Mar 13 2014This paper addresses the question, whether the solutions of the scattering equations in four space-time dimensions can be expressed as rational functions of the momentum twistor variables. This is the case for $n\le5$ external particles. For general $n$ ... More
NNLO predictions for event shapes and jet rates in electron-positron annihilationJan 08 2010The strong coupling constant is a fundamental parameter of nature. It can be extracted from experiments measuring three-jet events in electron-positron annihilation. For this extraction precise theoretical calculations for jet rates and event shapes are ... More
The infrared structure of e+ e- --> 3 jets at NNLO reloadedApr 07 2009Jun 16 2009This paper gives detailed information on the structure of the infrared singularities for the process e+ e- --> 3 jets at next-to-next-to-leading order in perturbation theory. Particular emphasis is put on singularities associated to soft gluons. The knowledge ... More
Symbolic Expansion of Transcendental FunctionsJan 04 2002Feb 25 2002Higher transcendental function occur frequently in the calculation of Feynman integrals in quantum field theory. Their expansion in a small parameter is a non-trivial task. We report on a computer program which allows the systematic expansion of certain ... More
The forward-backward asymmetry at NNLO revisitedSep 04 2006Nov 16 2006I reconsider the forward-backward asymmetry for flavoured quarks in electron-positron annihilation. I suggest an infrared-safe definition of this observable, such that the asymmetry may be computed in perturbative QCD with massless quarks. With this definition, ... More
Infrared finite cross sections at NNLOJun 29 2004I discuss methods for the cancellation of infrared divergences at NNLO.
A general algorithm to generate unweighted events for next-to-leading order calculations in electron-positron annihilationJun 14 2001Sep 27 2001Given a next-to-leading order calculation, we show how to set up a computer program, which generates a sequence of unweighted momentum configurations, each configuration containing either n or n+1 four-vectors, such that for any infrared safe observable ... 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
Exploring Level Statistics from Quantum Chaos to Localization with the Autocorrelation Function of Spectral DeterminantsJun 30 1998The autocorrelation function of spectral determinants (ASD) is used to characterize the discrete spectrum of a phase coherent quasi- 1- dimensional, disordered wire as a function of its length L in a finite, weak magnetic field. An analytical function ... 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.
Statistical Analysis of Multiwavelength Light curvesJul 05 2012Since its launch in 2008 the Fermi Large Area Telescope provides regular monitoring of a large sample of gamma-ray sources on time scales from hours to years. Together with observations at other wavelengths it is now possible to study variability and ... More
Measurement of Dijet Production in Diffractive Deep-Inelastic Scattering at HERAAug 19 2015The production of dijets is measured in diffractive deep-inelastic scattering at HERA. The data were recorded with the H1 detector at DESY in the years 2003-2007. Diffractive events are selected by requiring a gap in the rapidity distribution of the hadronic ... More
Lower estimates of random unconditional constants of Walsh-Paley martingales with values in banach spacesFeb 28 1992For a Banach space X we define RUMD_n(X) to be the infimum of all c>0 such that (AVE_{\epsilon_k =\pm 1} || \sum_1^n epsilon_k (M_k - M_{k-1} )||_{L_2^X}^2 )^{1/2} <= c || M_n ||_{L_2^X} holds for all Walsh-Paley martingales {M_k}_0^n subset L_2^X with ... More
Filling invariants at infinity and the Euclidean rank of Hadamard spacesDec 25 2005Jul 26 2006In this paper we study a homological version of the higher-dimensional divergence invariants defined by Brady and Farb. We show that they are quasi-isometry invariants in the class of proper cocompact Hadamard spaces in the sense of Alexandrov and that ... More
Storage-ring ionization and recombination experiments with multiply charged ions relevant to astrophysical and fusion plasmasAug 04 2011Past and ongoing research activities at the Heidelberg heavy-ion storage-ring TSR are reviewed which aim at providing accurate absolute rate coefficients and cross sections of atomic collision processes for applications in astrophysics and magnetically ... More
Storage-Ring Measurements of Hyperfine Induced Transition Rates in Berylliumlike IonsNov 06 2012The status of experimental measurements and theoretical calculations of the hyperfine induced 2s2p 3P0 -> 2s2 1S0 transition rate in Be-like ions is reviewed. Possible reasons, such as external electromagnetic fields and competing E1M1 two-photon transitions, ... More
Morita Theory in Deformation QuantizationDec 21 2010Various aspects of Morita theory of deformed algebras and in particular of star product algebras on general Poisson manifolds are discussed. We relate the three flavours ring-theoretic Morita equivalence, $^*$-Morita equivalence, and strong Morita equivalence ... More
Morita Equivalence, Picard Groupoids and Noncommutative Field TheoriesApr 01 2003Apr 03 2003In this article we review recent developments on Morita equivalence of star products and their Picard groups. We point out the relations between noncommutative field theories and deformed vector bundles which give the Morita equivalence bimodules.
A Remark on the Deformation of GNS Representations of *-AlgebrasDec 11 2000Motivated by deformation quantization we investigate the algebraic GNS construction of *-representations of deformed *-algebras over ordered rings and compute their classical limit. The question if a GNS representation can be deformed leads to the deformation ... More
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
Anisotropically Weighted and Nonholonomically Constrained Evolutions on ManifoldsSep 01 2016We present evolution equations for a family of paths that results from anisotropically weighting curve energies in non-linear statistics of manifold valued data. This situation arise when performing inference on data that have non-trivial covariance and ... More
Variance estimation for Brier Score decompositionMar 25 2013Jul 18 2013The Brier Score is a widely-used criterion to assess the quality of probabilistic predictions of binary events. The expectation value of the Brier Score can be decomposed into the sum of three components called reliability, resolution, and uncertainty ... More
Adiabatic limit interference effects for two energy level transition amplitudes and Nikitin - Umanskii formula studied by fundamental solution methodJul 18 2002Apr 04 2003A method of fundamental solutions has been used to study adiabatic transition amplitudes in two energy level systems for a class of Hamiltonians allowing some simplifications of Stokes graphs corresponding to such transitions. It has been shown that for ... More
The Schrödinger functional in QCDNov 28 1994The Schr\"odinger functional in Wilson's lattice QCD leads to a sensible classical continuum theory which can be taken as starting point for a perturbative analysis. In dimensional regularization, the saddle point expansion of the Schr\"odinger functional ... More
Properties of the renormalized quark mass in the Schrodinger functional with a non-vanishing background fieldNov 28 2001We compute the current quark mass in the Schrodinger functional with a non-vanishing background field at one loop order of perturbation theory. The results are used to obtain the critical mass at which the renormalized quark mass vanishes, and some lattice ... 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
Projective Wellorders and the Nonstationary IdealOct 13 2016We show that, under the assumption of the existence of $M_1^{\#}$, there exists a model on which the restricted nonstationary ideal $\hbox{NS} \upharpoonright A$ is $\aleph_2$-saturated, for $A$ a stationary co-stationary subset of $\omega_1$, while the ... More
Valuation Theory, Riemann Varieties and the Structure of integral PreschemesOct 25 2016In this work we show that the classical subject of general valuation theory and Zariski-Riemann varieties has a much wider scope than commutative algebra and desingularization theory. We construct and investigate birational projective limit objects appropriate ... More
On panel-regular ~A_2 latticesAug 25 2016We study lattices on ~A_2 buildings that preserve types, act regularly on each type of edge, and whose vertex stabilizers are cyclic. We show that several of their properties, such as their automorphism group and isomorphism class, can be determined from ... More
Fast Escape in Incompressible Vector FieldsMay 09 2016Swimmers caught in a rip current flowing away from the shore are advised to swim orthogonally to the current to escape it. We describe a mathematical principle in a similar spirit. More precisely, we consider flows $\gamma$ in the plane induced by incompressible ... More
The japanese closure of local noetherian ringsOct 27 2016Given a local noetherian ring $R$ whose formal completion is integral, we introduce and study the japanese closure $R^\text{jpn}$. Roughly speaking, this is the largest purely inseparable $R$-subalgebra inside the formal completion $\hat{R}$. It turns ... More
Well-distributed great circles on S^2Jul 13 2016Let $C_1, \dots, C_n$ denote the $1/n-$neighborhood of $n$ great circles on $\mathbb{S}^2$. We are interested in how much these areas have to overlap and prove the sharp bounds $$ \sum_{i, j = 1 \atop i \neq j}^{n}{|C_i \cap C_j|^s} \gtrsim_s \begin{cases} ... More
Localization of Quantum States and Landscape FunctionsOct 21 2015Eigenfunctions in inhomogeneous media can have strong localization properties. Filoche \& Mayboroda showed that the function $u$ solving $(-\Delta + V)u = 1$ controls the behavior of eigenfunctions $(-\Delta + V)\phi = \lambda\phi$ via the inequality ... More