Results for "Roland Wiesendanger"

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Pattern formation in skyrmionic materials with anisotropic environmentsMar 03 2016Magnetic skyrmions have attracted broad attention during recent years because they are regarded as promising candidates as bits of information in novel data storage devices. A broad range of theoretical and experimental investigations have been conducted ... More
STM study of the preparation of clean Ta(110) and the subsequent growth of two-dimensional Fe islandsApr 07 2016Jun 07 2016This report deals with the preparation of a clean Ta(110) surface, investigated by means of scanning tunneling microscopy/spectroscopy as well as by low-energy electron diffraction and Auger electron spectroscopy. The surface initially exhibits a surface ... More
A millikelvin all-fiber cavity optomechanical apparatus for merging with ultra-cold atoms in a hybrid quantum systemNov 10 2016Feb 13 2017We describe the construction of an apparatus designed to realize a hybrid quantum system comprised of a cryogenically cooled mechanical oscillator and ultra-cold $^{87}$Rb atoms coupled via light. The outstanding feature of our instrument is an in-situ ... More
Multi-scale RenormalizationDec 18 1996The Standard MS renormalization prescription is inadequate for dealing with multi-scale problems. To illustrate this we consider the computation of the effective potential in the Higgs-Yukawa model. It is argued that it is natural to employ a two-scale ... More
Computing with spins and magnetsNov 25 2014The possible use of spin and magnets in place of charge and capacitors to store and process information is well known. Magnetic tunnel junctions are being widely investigated and developed for magnetic random access memories. These are two terminal devices ... More
Long spin relaxation times in a transition metal atom in direct contact to a metal substrateDec 14 2017Long spin relaxation times are a prerequisite for the use of spins in data storage or nanospintronics technologies. An atomic-scale solid-state realization of such a system is the spin of a transition metal atom adsorbed on a suitable substrate. For the ... More
Engineering the spin couplings in atomically crafted spin chains on an elemental superconductorAug 14 2018Magnetic atoms on a superconductor give rise to Yu-Shiba-Rusinov (YSR) states within the superconducting energy gap. A spin chain of magnetic adatoms on an s-wave superconductor may lead to topological superconductivity accompanied by the emergence of ... More
Pinning and movement of individual nanoscale magnetic skyrmions via defectsJan 20 2016An understanding of the pinning of magnetic skyrmions to defects is crucial for the development of future spintronic applications. While pinning is desirable for a precise positioning of magnetic skyrmions it is detrimental when they are to be moved through ... More
Domain imaging across the magneto-structural phase transition in Fe$_{1+y}$TeNov 30 2017The investigation of the magnetic phase transitions in the parent compounds of Fe-based superconductors is regarded essential for an understanding of the pairing mechanism in the related superconducting compounds. Even though the chemical and electronic ... More
Tuning non-collinear magnetic states by hydrogenationDec 17 2018Two different superstructures form when atomic H is incorporated in the Fe monolayer on Ir(111). Depending on the amount of H provided, either a highly ordered p(2x2) hexagonal superstructure or an irregular roughly square structure is created. We present ... More
Coupling of Coexisting Non-Collinear Spin States in the Fe Monolayer on Re(0001)May 17 2016Jun 22 2016Spin-polarized scanning tunneling microscopy is used to investigate the magnetic state of the Fe monolayer on Re(0001). Two coexisting atomic-scale non-collinear spin textures are observed with a sharp transition between them on the order of one atomic ... More
Probing weakly hybridized magnetic molecules by spin-polarized tunnelingJun 11 2019Advances in molecular spintronics rely on the in-depth characterization of the molecular building blocks in terms of their electronic and, more importantly, magnetic properties. For this purpose, inert substrates that interact only weakly with adsorbed ... More
Probing the Nanoskyrmion Lattice on Fe/Ir(111) with Magnetic Exchange Force MicroscopyApr 10 2017We demonstrate that the magnetic nanoskyrmion lattice on the Fe monolayer on Ir(111) and the positions of the Fe atoms can be resolved simultaneously using magnetic exchange force microscopy. Thus, the relation between magnetic and atomic structure can ... More
Impact of the skyrmion spin texture on magnetoresistanceJan 31 2017We investigate the impact of the local spin texture on the differential conductance by scanning tunneling microscopy. In the focus is the previously found non-collinear magnetoresistance, which originates from spin mixing effects upon electron hopping ... More
Effective damping enhancement in noncollinear spin structuresMay 04 2018Oct 15 2018Damping mechanisms in magnetic systems determine the lifetime, diffusion and transport properties of magnons, domain walls, magnetic vortices, and skyrmions. Based on the phenomenological Landau-Lifshitz-Gilbert equation, here the effective damping parameter ... More
Analysis of the inelastic contribution to atomic spin excitation spectroscopyFeb 18 2011We investigate the dependence of the inelastic spin excitation contribution to scanning tunneling spectroscopy recorded above Fe adsorbates on the InSb(110) surface at subkelvin temperatures, on bulk doping and tunnel junction resistance. To explain our ... More
Localized spin waves in isolated $kπ$ skyrmionsOct 15 2018The localized magnon modes of isolated $k\pi$ skyrmions on a field-polarized background are analyzed based on the Landau-Lifshitz-Gilbert equation within the terms of an atomistic classical spin model, with system parameters based on the Pd/Fe biatomic ... More
Final State Interactions and Khuri-Treiman Equations in $η\to 3π$ decaysSep 23 1995Using extended Khuri-Treiman equations, we evaluate the final state interactions due to two-pion rescatterings to the decays $\eta\to \pi^0 \pi^+ \pi^-$ and $\eta\to \pi^0 \pi^0 \pi^0$. As subtraction to the dispersion relation we take the one-loop chiral ... More
Magnetic domain walls in strain-patterned ultrathin filmsAug 24 2018We present a comparison of the characteristics of the magnetic domain walls in an atomic monolayer of Co on Pt(111) and a Ni/Fe atomic bilayer on Ir(111), based on spin-polarized scanning tunneling microscopy measurements. In both cases, the films exhibit ... More
Controlling the Local Spin-Polarization at the Organic-Ferromagnetic InterfaceMay 28 2010By means of ab initio calculations and spin-polarized scanning tunneling microscopy experiments we show how to manipulate the local spin-polarization of a ferromagnetic surface by creating a complex energy dependent magnetic structure. We demonstrate ... More
Evidence for a two-fold symmetric superconducting gap in a monolayer of FeSe$_{0.5}$Te$_{0.5}$ on a topological insulatorAug 12 2016We present our investigations on the superconducting properties of monolayers of FeSe$_{0.5}$Te$_{0.5}$ grown on the 3D topological insulator Bi$_{2}$Se$_{1.2}$Te$_{1.8}$ using low temperature scanning tunneling spectroscopy (STS). While the morphology ... More
Tailoring non-collinear magnetism by misfit dislocation linesOct 21 2016The large epitaxial stress induced by the misfit between a triple atomic layer Fe film and an Ir(111) substrate is relieved by the formation of a dense dislocation line network. Spin-polarized scanning tunneling microscopy (SP-STM) investigations show ... More
Atomic-Scale Interface Engineering of Majorana Edge Modes in a 2D Magnet-Superconductor Hybrid SystemSep 12 2018Topological superconductors are predicted to harbor exotic boundary states - Majorana zero-energy modes - whose non-Abelian braiding statistics present a new paradigm for the realization of topological quantum computing. Using low-temperature scanning ... More
Field-Dependent Size and Shape of Single Magnetic SkyrmionsApr 07 2015The atomic-scale spin structure of individual isolated skyrmions in an ultrathin film is investigated in real space by spin-polarized scanning tunneling microscopy. Their axial symmetry as well as their unique rotational sense is revealed by using both ... More
Symmetry breaking in spin spirals and skyrmions by in-plane and canted magnetic fieldsMar 18 2016The influence of in-plane and canted magnetic fields on spin spirals and skyrmions in atomic bilayer islands of palladium and iron on an Ir(111) substrate is investigated by scanning tunnelling microscopy at low temperatures. It is shown that the spin ... More
Report on imaging of individual skyrmions of MML systems made by different techniquesSep 27 2016Deliverable 1.1 is a report on imaging of individual skyrmions of MML systems made by different techniques. This deliverable falls within work package 1 (WP1:Static equilibrium properties of interface induced skyrmions in magnetic films and multilayers) ... More
Isolated zero field sub-10 nm skyrmions in ultrathin Co filmsMar 06 2019Due to their exceptional topological and dynamical properties magnetic skyrmions - localized stable spin structures on the nanometre scale - show great promise for future spintronic applications. To become technologically competitive, isolated skyrmions ... More
Set-up of a High-Resolution 300 mK Atomic Force Microscope in an Ultra-High Vacuum Compatible 3He/10T CryostatJun 20 2016The design of an atomic force microscope with an all-fiber interferometric detection scheme capable of atomic resolution at about 500 mK is presented. The microscope body is connected to a small pumped 3He reservoir with a base temperature of about 300 ... More
Revealing Sub-Surface Vibrational Modes by Atom-Resolved Damping Force SpectroscopyApr 17 2009We propose to use the damping signal of an oscillating cantilever in dynamic atomic force microscopy as a noninvasive tool to study the vibrational structure of the substrate. We present atomically resolved maps of damping in carbon nanotube peapods, ... More
Stochastic dynamics and pattern formation of geometrically confined skyrmionsMay 10 2019Ensembles of magnetic skyrmions in confined geometries are shown to exhibit thermally driven motion on two different time scales. The intrinsic fluctuating dynamics ($t\sim 1~$ps) is governed by short-range symmetric and antisymmetric exchange interactions, ... More
Temperature-induced increase of spin spiral periodsMar 31 2017Spin-polarized scanning tunneling microscopy investigations reveal a significant increase of the magnetic period of spin spirals in three-atomic-layer-thick Fe films on Ir(111), from about 4nm at 8K to about 65nm at room temperature. We attribute this ... More
Combined feedback and sympathetic cooling of a mechanical oscillator coupled to ultracold atomsJun 13 2018A promising route to novel quantum technologies are hybrid quantum systems, which combine the advantages of several individual quantum systems. We have realized a hybrid atomic-mechanical experiment consisting of a SiN membrane oscillator cryogenically ... More
Electric field driven switching of individual magnetic skyrmionsJan 12 2016Controlling magnetism with electric fields is a key challenge to develop future energy-efficient devices, however, the switching between inversion symmetric states, e.g. magnetization up and down as used in current technology, is not straightforward, ... More
Controlled creation and stability of kπ-skyrmions on a discrete latticeFeb 26 2018We determine sizes and activation energies of k{\pi}-skyrmions on a discrete lattice using the Landau- Lifshitz-Gilbert equation and the geodesic nudged elastic band method. The employed atomic material parameters are based on the skyrmionic material ... More
Nano-scale magnetic skyrmions and target states in confined geometriesJan 21 2019Research on magnetic systems with broken inversion symmetry has been stimulated by the experimental proof of particle-like configurations known as skyrmions, whose non-trivial topological properties make them ideal candidates for spintronic technology. ... More
Giant magnetization canting due to symmetry breaking in zigzag Co chains on Ir(001)Sep 24 2013We demonstrate a canted magnetization of biatomic zigzag Co chains grown on the 5 x 1 reconstructed Ir(001) surface using density functional theory calculations and spin-polarized scanning tunneling microscopy (SP-STM) experiments. Biatomic Co chains ... More
Spin-polarization of platinum (111) induced by the proximity to cobalt nanostripesOct 11 2010We measured a spin polarization above a Pt (111) surface in the vicinity of a Co nanostripe by spin-polarized scanning tunneling spectroscopy. The spin polarization is exponentially decaying away from the Pt/Co interface and is detectable at distances ... More
Electrical detection of magnetic skyrmions by non-collinear magnetoresistanceJul 15 2015Magnetic skyrmions are localised non-collinear spin textures with high potential for future spintronic applications. Skyrmion phases have been discovered in a number of materials and a focus of current research is the preparation, detection, and manipulation ... More
Domain walls and Dzyaloshinskii-Moriya interaction in epitaxial Co/Ir(111) and Pt/Co/Ir(111)Feb 06 2018We use spin-polarized scanning tunneling microscopy and density functional theory (DFT) to study domain walls (DWs) and the Dzyaloshinskii-Moriya interaction (DMI) in epitaxial films of Co/Ir(111) and Pt/Co/Ir(111). Our measurements reveal DWs with fixed ... More
Spin- and energy-dependent tunneling through a single molecule with intramolecular spatial resolutionMay 26 2010We investigate the spin- and energy dependent tunneling through a single organic molecule (CoPc) adsorbed on a ferromagnetic Fe thin film, spatially resolved by low-temperature spin-polarized scanning tunneling microscopy. Interestingly, the metal ion ... More
Imaging correlated wave functions of few-electron quantum dots: Theory and scanning tunneling spectroscopy experimentsAug 02 2007We show both theoretically and experimentally that scanning tunneling spectroscopy (STS) images of semiconductor quantum dots may display clear signatures of electron-electron correlation. We apply many-body tunneling theory to a realistic model which ... More
Correlation Effects in Wave Function Mapping of Molecular Beam Epitaxy Grown Quantum DotsJul 31 2007We investigate correlation effects in the regime of a few electrons in uncapped InAs quantum dots by tunneling spectroscopy and wave function (WF) mapping at high tunneling currents where electron-electron interactions become relevant. Four clearly resolved ... More
Non-collinear spin states in bottom-up fabricated atomic chainsOct 10 2017Jan 23 2018Non-collinear spin states with unique rotational sense, such as chiral spin-spirals, are recently heavily investigated because of advantages for future applications in spintronics and information technology and as potential hosts for Majorana Fermions ... More
Stabilizing spin systems via symmetrically tailored RKKY interactionsNov 07 2018The spin of a single atom adsorbed on a substrate is a promising building block for future spintronics and quantum computation schemes. To process spin information and also for increased magnetic stability, these building blocks have to be coupled. For ... More
Spin spirals in ultra-thin films driven by frustration of exchange interactions: Rh/Fe/Ir(111)Oct 25 2016Numerous complex non-collinear spin structures such as spin spirals and skyrmions have been observed recently in ultrathin transition-metal films at surfaces. In these systems the interfacial Dzyaloshinskii-Moriya interaction (DMI) plays a decisive role ... More
Enhanced spin ordering temperature in ultrathin FeTe films grown on a topological insulatorNov 28 2017Nov 30 2017We studied the temperature dependence of the diagonal double-stripe spin order in one and two unit cell thick layers of FeTe grown on the topological insulator Bi_2Te_3 via spin-polarized scanning tunneling microscopy. The spin order persists up to temperatures ... More
Nano-scale magnetic skyrmions and target states in confined geometriesJan 21 2019May 17 2019Research on magnetic systems with broken inversion symmetry has been stimulated by the experimental proof of particle-like configurations known as skyrmions, whose non-trivial topological properties make them ideal candidates for spintronic technology. ... More
Itinerant Nature of Atom-Magnetization Excitation by Tunneling ElectronsOct 06 2010Nov 04 2010We have performed single-atom magnetization curve (SAMC) measurements and inelastic scanning tunneling spectroscopy (ISTS) on individual Fe atoms on a Cu(111) surface. The SAMCs show a broad distribution of magnetic moments with $\unit[3.5]{\mu_{\rm B}}$ ... More
Magnetism and in-gap states of 3d transition metal atoms on superconducting ReMar 25 2019Magnetic atoms on heavy-element superconducting substrates are potential building blocks for realizing topological superconductivity in one- and two-dimensional atomic arrays. Their localized magnetic moments induce so-called Yu-Shiba-Rusinov (YSR) states ... More
Correction of systematic errors in scanning tunnelling spectra on semiconductor surfaces: the energy gap of Si(111)-7x7 at 0.3 KAug 19 2009The investigation of the electronic properties of semiconductor surfaces using scanning tunnelling spectroscopy (STS) is often hindered by non-equilibrium transport of the injected charge carriers. We propose a correction method for the resulting systematic ... More
Non-equilibrium finite temperature dynamics of magnetic quantum systems: Applications to spin-polarized scanning tunneling microscopyAug 13 2013We calculate the real time non-equilibrium dynamics of quantum spin systems at finite temperatures. The mathematical framework originates from the $C^*$-approach to quantum statistical mechanics and is applied to samples investigated by means of spin-polarized ... More
The Quantum Theory of Gravitation: I Quantization of Free Fields - II Proof of RenormalizabilityMay 17 2019Quantization of Free Fields: The non-interacting field belonging to a new {\bf SO(1,3)\/} gauge field theory equivalent to General Relativity is canonically quantized in the Lorentz gauge and the physical Fock space for free gauge particles is constructed. ... More
Reconstructions and faceting of H-covered Al(111)Jul 14 1996Jul 19 1996First principles calculations show that H overlayers induce a honeycomb vacancy reconstruction on Al(111). Above one ML H coverage, Al(111) facets into surfaces vicinal to (111), with {100} faceted single and double steps and vacancies on the {111} terraces. ... More
The ultrarelativistic Reissner-Nordstrom field in the Colombeau algebraJun 19 1996Feb 24 1997The electromagnetic field of the ultrarelativistic Reissner-Nordstrom solution shows the physically highly unsatisfactory property of a vanishing field tensor but a nonzero, i.e., delta-like, energy density. The aim of this work is to analyze this situation ... More
Gamma-Ray Line AstronomySep 28 2004Gamma-ray lines from radioactive isotopes, ejected into interstellar space by cosmic nucleosynthesis events, are observed with new space telescopes. The Compton Observatory had provided a sky survey for the isotopes 56Co, 22Na, 44Ti, and 26Al, detecting ... More
Decoherence : An irreversible ProcessJun 01 2001A wide-ranging theory of decoherence is derived from the quantum theory of irreversible processes, with specific results having for their main limitation the assumption of an exact pointer basis.
Almost sure asymptotics for the maximum local time in Brownian environmentMar 02 2010Jun 15 2011We study the asymptotic behaviour of the maximum local time L*(t) of the Brox's process, the diffusion in Brownian environment. Shi proved that the maximum speed of L*(t) is surprisingly, at least t log(log(log t)) whereas in the discrete case it is t. ... More
Cones of ball-ball separable elementsMar 24 2005Let B_1,B_2 be balls in finite-dimensional real vector spaces E_1,E_2, centered around unit length vectors v_1,v_2 and not containing zero. An element in the tensor product space E_1 \otimes E_2 is called B_1 \otimes B_2-separable if it is contained in ... More
Heavy-Ion Physics at the LHC with the Compact Muon Solenoid DetectorMay 18 2004Hadron collisions at the LHC offer a unique opportunity to study strong interactions. The exciting data collected by the four RHIC experiments suggest that in heavy-ion collisions at sqrt(s_NN) = 200 GeV, an equilibrated, strongly-coupled partonic system ... More
Stability-preserving model order reduction for linear stochastic Galerkin systemsMay 03 2019Mathematical modeling often yields linear dynamical systems in science and engineering. We change physical parameters of the system into random variables to perform an uncertainty quantification. The stochastic Galerkin method yields a larger linear dynamical ... More
Categorical crepant resolutions for quotient singularitiesJun 17 2014Jun 19 2014We discuss some "folklore" results on categorical crepant resolutions for varieties with quotient singularities.
Développements limités et la transformée inverseMar 18 2003The generating series associated to a certain sequence of limited Taylor expansions coincides with the continuously iterated Invert Transform and displays thus a nice functional equality.
An explicit André-Oort type result for P^1(C) x G_m(C)Mar 10 2014Using class field theory we prove an explicit result of Andr\'e-Oort type for $\mathbb{P}^1(\mathbb{C}) \times \mathbb{G}_m(\mathbb{C})$. In this variation the special points of $\mathbb{P}^1(\mathbb{C})$ are the singular moduli, while the special points ... More
The Hilbert's class field and the p-class group of the cyclotomic fieldsJan 23 2011Jan 27 2011Let $p$ be an irregular prime and $K=\Q(\zeta)$ the $p$-cyclotomic field. Let $\sigma$ be a $\Q$-isomorphism of $K$ generating $Gal(K/\Q)$. Let $S/K$ be a cyclic unramified extension of degree $p$, defined by $S= K(A^{1/p})$ where $A\in K\backslash K^p$, ... More
Sur le groupe d'interpolationSep 26 2006Oct 30 2006We study the interpolation group whose elements are suitable pairs of formal power series. This group has a faithful representation into infinite lower triangular matrices and carries thus a natural structure as a Lie group. The matrix exponential between ... More
Some congruences on prime factors of class number of finite algebraic extensions K/QApr 25 2003This paper is a contribution to the description of some congruences on the odd prime factors of the class number of the number fields. An example of results obtained is: Let L/Q be a finite Galois solvable extension with [L:Q]=N, where N > 1 is odd. Let ... More
Paperfolding and Catalan numbersJun 17 2004We reprove a few results concerning paperfolding sequences using properties of Catalan numbers modulo 2.
Nonlinear stability of self-similar solutions for semilinear wave equationsNov 12 2008Dec 08 2009We prove nonlinear stability of the fundamental self--similar solution of the wave equation with a focusing power nonlinearity $\psi_{tt}-\Delta \psi=\psi^p$ for $p=3,5,7,...$ in the radial case. The proof is based on a semigroup formulation of the wave ... More
Application of Multihomogeneous Covariants to the Essential Dimension of Finite GroupsNov 24 2008We investigate essential dimension of finite groups over arbitrary fields and give a systematic treatment of multihomogenization, introduced by H.Kraft, G.Schwarz and the author. We generalize the central extension theorem of Buhler and Reichstein and ... More
Universal convex coveringsDec 18 2008Jul 01 2009In every dimension $d\ge1$, we establish the existence of a constant $v_d>0$ and of a subset $\mathcal U_d$ of $\mathbb R^d$ such that the following holds: $\mathcal C+\mathcal U_d=\mathbb R^d$ for every convex set $\mathcal C\subset \mathbb R^d$ of volume ... More
Convergence of metric two-level measure spacesMay 02 2018Jun 14 2018In this article we extend the notion of metric measure spaces to so-called metric two-level measure spaces (m2m spaces): An m2m space $(X, r, \nu)$ is a Polish metric space $(X, r)$ equipped with a two-level measure $\nu \in \mathcal{M}_f(\mathcal{M}_f(X))$, ... More
Copositive matrices with circulant zero support setMar 16 2016Nov 08 2016Let $n \geq 5$ and let $u^1,\dots,u^n$ be nonnegative real $n$-vectors such that the indices of their positive elements form the sets $\{1,2,\dots,n-2\},\{2,3,\dots,n-1\},\dots,\{n,1,\dots,n-3\}$, respectively. Here each index set is obtained from the ... More
Stability preservation in Galerkin-type projection-based model order reductionNov 08 2017We consider linear dynamical systems consisting of ordinary differential equations with high dimensionality. The aim of model order reduction is to construct an approximating system of a much lower dimension. Therein, the reduced system may be unstable, ... More
Model order reduction and sparse orthogonal expansions for random linear dynamical systemsMay 23 2016We consider linear dynamical systems of ordinary differential equations or differential algebraic equations. Physical parameters are substituted by random variables for an uncertainty quantification. We expand the state variables as well as a quantity ... More
Stability-preserving model order reduction for linear stochastic Galerkin systemsMay 03 2019Sep 16 2019Mathematical modeling often yields linear dynamical systems in science and engineering. We change physical parameters of the system into random variables to perform an uncertainty quantification. The stochastic Galerkin method yields a larger linear dynamical ... More
Le cocycle du vergerDec 03 2003We define and prove uniqueness of a natural homomorphism (called the Orchard morphism) from some groups associated naturally to a finite set $E$ to the group ${\mathcal E}(E)$ of two-partitions of $E$ representing equivalence relations having at most ... More
Chebyshev polynomials, quadratic surds and a variation of Pascal's triangleSep 30 2015Using Chebyshev polynomialsof both kinds, we construct rational fractions which are convergents of the smallest root of $x^2-\alpha x+1$ for $\alpha=3,4,5,\dots$.Some of the underlying identities suggest an identity involving binomialcoefficients which ... More
The Ring of Support-Classes of $\mathrm{SL}\_2(\mathbb F\_q)$Jun 04 2015We introduce and study a subring $\mathcal{SC}$ of $\mathbb Z[\mathrm{SL}\_2(\mathbb F\_q)]$ obtained by summing elements of $\mathrm{SL}\_2(\mathbb F\_q)$ according to their support. The ring $\mathcal SC$ can be used for the construction of several ... More
Local properties of entanglement and application to collapseSep 13 2013Sep 26 2013When a quantum system is macroscopic and becomes entangled with a microscopic one, this entanglement is not immediately total, but gradual and local. A study of this locality is the starting point of the present work and shows unexpected and detailed ... More
B meson decays and CP (and T) violationJan 11 2013Jan 14 2013The prolific field of B meson decays and CP violation is illustrated in a few examples of recent results: The measurement of the CKM unitarity angle $\beta = \phi_1$, the measurement of a significant violation of time reversal symmetry, an unexplained ... More
Effect of non-magnetic impurities on the gap of a $d_{x^2-y^2}$ superconductor as seen by angle-resolved photoemissionMar 15 1996An analysis of angle-resolved photoemission (ARPES) experiments in the superconducting state of the high \tc copper-oxides is presented. It is based on a phenomenological weak-coupling BCS model which incorporates the experimental normal state dispersion ... More
ALTRO and TPC Performance of ALICEJan 11 2005Nov 25 2005The extraction and optimisation of the ALTRO Parameters out of the ALICE TPC data is described, including the performance measurment of this set. The ion tail of a signal pulse and the variation is firstly measured and quantified.
A Note on Distributional Semi-Riemannian GeometryNov 30 2008We discuss some basic concepts of semi-Riemannian geometry in low-regularity situations. In particular, we compare the settings of (linear) distributional geometry in the sense of L. Schwartz and nonlinear distributional geometry in the sense of J.F. ... More
Geodesics and geodesic deviation for impulsive gravitational wavesOct 28 1997Mar 27 1998The geometry of impulsive pp-waves is explored via the analysis of the geodesic and geodesic deviation equation using the distributional form of the metric. The geodesic equation involves formally ill-defined products of distributions due to the nonlinearity ... More
Model order reduction for random nonlinear dynamical systems and low-dimensional representations for their quantities of interestApr 07 2017We examine nonlinear dynamical systems of ordinary differential equations or differential algebraic equations. In an uncertainty quantification, physical parameters are replaced by random variables. The inner variables as well as a quantity of interest ... More
Scalar self-force on eccentric geodesics in Schwarzschild spacetime: a time-domain computationApr 05 2007Jul 06 2007We calculate the self-force acting on a particle with scalar charge moving on a generic geodesic around a Schwarzschild black hole. This calculation requires an accurate computation of the retarded scalar field produced by the moving charge; this is done ... More
A geometric approach to full Colombeau algebrasOct 10 2007Sep 17 2008We present a geometric approach to diffeomorphism invariant full Colombeau algebras which allows a particularly clear view on the construction of the intrinsically defined algebra $\hat{\mathcal G}(M)$ on the manifold $M$ given in (Grosser et al., Adv. ... More
Massive-Star Nucleosynthesis and INTEGRALJul 25 2011Products from massive-star nucleosynthesis have been measured with SPI on INTEGRAL: Characteristic gamma-ray lines from radioactive decays of long-lived 26Al and 60Fe isotopes, and from 44Ti decay (decay time 89y). Detections of both these isotopes has ... More
Deeply Virtual Compton Scattering at HERA II (H1 results)May 22 2006New results on the Deeply Virtual Compton Scattering process $\gamma^* p \to \gamma p$ (DVCS) from H1 experiment at the $e p$ collider HERA are presented, using data collected during the year 2004 and corresponding to an integrated luminosity of 39.7 ... More
Limits of Thompson's group FJan 22 2007Mar 07 2010Let F be the Thompson's group. We study the structure of F-limit groups. Consider a sequence of groups marked by three elements, each isomorphic to F. Assume that the this sequence is convergent in the space of marked groups. We prove that no HNN-extension ... More
Old and New Advances in Black Hole Accretion Disk TheoryFeb 15 1999A summary is given of the high-lights during the Reykjavik Midsummer Symposium on Non-Linear Phenomena in Accretion Discs around Black Holes. Such high-lights include the recent advances on understanding: 1) the accretion disc solution branch dominated ... More
Models of X-ray and gamma-ray emission from Seyfert galaxiesMay 15 1996May 17 1996X-ray and gamma-ray observations of Seyfert 1 galaxies are briefly reviewed. Both thermal and non-thermal model for X-ray and gamma-ray emission are discussed. Particular attention is given to various disc-corona models including both homogeneous and ... More
Hodge numbers and Hodge structures for Calabi-Yau categories of dimension threeJul 08 2018Let $\mathcal{A}$ be a smooth proper C-linear triangulated category Calabi-Yau of dimension 3 endowed with a (non-trivial) rank function. Using the homological unit of $\mathcal{A}$ with respect to the given rank function, we define Hodge numbers for ... More
Scheme-theoretic Whitney conditions and applications to tangency of projective varietiesApr 11 2017Nov 21 2018We investigate a scheme-theoretic variant of Whitney condition a. If X is a projec-tive variety over the field of complex numbers and Y $\subset$ X a subvariety, then X satisfies generically the scheme-theoretic Whitney condition a along Y provided that ... More
On the number of perfect latticesApr 07 2017Aug 30 2017We show that the number $p\_d$ of non-similar perfect $d$-dimensional lattices satisfies eventually the inequalities$e^{d^{1-\epsilon}}<p\_d<e^{d^{3+\epsilon}}$ for arbitrary smallstrictly positive $\epsilon$.
On the minimal degree of morphisms between algebraic curvesAug 30 2016Given smooth, projective, geometrically integral algebraic curves $X$ and $Y$ defined over a number field $K$, assuming that there is a non-constant $K$-morphism $\varphi \colon X \to Y$, we give an upper bound on the minimum of the degrees of such morphisms. ... More
Scheme of a Derivation of Collapse from Quantum DynamicsJan 06 2016Feb 29 2016Two categories of results regarding quantum measurements are derived in this work and applied to the problem of collapse. The first category is concerned with local and transient features of the entanglement between a macroscopic measuring system and ... More
Executing Arbitrary Code in the Context of the Smartcard System ServiceJan 21 2016This report summarizes our findings regarding a severe weakness in implementations of the Open Mobile API deployed on several Android devices. The vulnerability allows arbitrary code coming from a specially crafted Android application package (APK) to ... More
Astrophysics with radioactive isotopesNov 26 2018Radioactivity was discovered as a by-product of searching for elements with suitable chemical properties. Understanding its characteristics led to the development of nuclear physics, understanding that unstable configurations of nucleons transform into ... More
Centro-affine hypersurface immersions with parallel cubic formAug 06 2012Jan 04 2013We consider non-degenerate centro-affine hypersurface immersions in R^n whose cubic form is parallel with respect to the Levi-Civita connection of the affine metric. There exists a bijective correspondence between homothetic families of proper affine ... More