Results for "Uwe Sterr"

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Tuning the Thermal Expansion Properties of Optical Reference Cavities with Fused Silica MirrorsFeb 10 2010We investigate the thermal expansion of low thermal noise Fabry-Perot cavities made of Low Thermal Expansion (LTE) glass spacers and Fused Silica (FS) mirrors. The different thermal expansion of mirror and spacer deforms the mirror. This deformation strongly ... More
Thermal noise in optical cavities revisitedNov 21 2011Thermal noise of optical reference cavities sets a fundamental limit to the frequency instability of ultra-stable lasers. Using Levin's formulation of the fluctuation-dissipation theorem we correct the analytical estimate for the spacer contribution given ... More
On the relation between uncertainties of weighted frequency averages and the various types of Allan deviationsApr 02 2015Apr 27 2015The power spectral density in Fourier frequency domain, and the different variants of the Allan deviation (ADEV) in dependence on the averaging time are well established tools to analyse the fluctuation properties and frequency instability of an oscillatory ... More
Wavelength dependent ac-Stark shift of the 1S0 - 3P1 transition at 657 nm in CaJun 04 2004We have measured the ac-Stark shift of the 4s2 1S0 - 4s4p 3P1 line in 40Ca for perturbing laser wavelengths between 780 nm and 1064 nm with a time domain Ramsey-Borde atom interferometer. We found a zero crossing of the shift for the mS = 0 - mP = 0 transition ... More
High accuracy photoassociation of $^{40}$Ca near the ${^3P_1}+{^1S_0}$ asymptote and its Zeeman effectJun 27 2013We report on the first measurement of narrow photoassociation lines of $^{40}$Ca near the ${^3P_1}+{^1S_0}$ asymptote related to the molecular states $^3\Pi_u$ and $^3\Sigma^+_u$. The highly accurate binding energies and Zeeman splittings are well described ... More
Long range transport of ultra cold atoms in a far-detuned 1D optical latticeApr 16 2012We present a novel method to transport ultra cold atoms in a focused optical lattice over macroscopic distances of many Rayleigh ranges. With this method ultra cold atoms were transported over 5 cm in 250 ms without significant atom loss or heating. By ... More
Delivering pulsed and phase stable light to atoms of an optical clockAug 18 2011Feb 10 2012In optical clocks, transitions of ions or neutral atoms are interrogated using pulsed ultra-narrow laser fields. Systematic phase chirps of the laser or changes of the optical path length during the measurement cause a shift of the frequency seen by the ... More
Nonlinear Zeeman effect in photoassociation spectra of $^{40}$Ca near the $^3$P$_1$+$^1$S$_0$ asymptoteJun 12 2015We present calculations of the Zeeman effect of narrow photoassociation lines of $^{40}$Ca near the $^3$P$_1$ + $^1$S$_0$ asymptote. Using a coupled-channel model we find a nonlinear Zeeman effect that even at low fields of a few mT amounts to several ... More
High accuracy correction of blackbody radiation shift in an optical lattice clockAug 14 2012Oct 29 2012We have determined the frequency shift that blackbody radiation is inducing on the $5s^2$ $^1$S$_0$ -- $5s5p$ $^3$P$_0$ clock transition in strontium. Previously its uncertainty limited the uncertainty of strontium lattice clocks to $1\times10^{-16}$. ... More
Bose-Einstein condensation of alkaline earth atoms: $^{40}${Ca}Aug 03 2009Sep 02 2009We have achieved Bose-Einstein condensation of $^{40}$Ca, the first for an alkaline earth element. The influence of elastic and inelastic collisions associated with the large ground state s-wave scattering length of $^{40}$Ca was measured. From these ... More
Lattice-induced photon scattering in an optical lattice clockFeb 08 2018We investigate scattering of lattice laser radiation in a strontium optical lattice clock and its implications for operating clocks at interrogation times up to several ten seconds. Rayleigh scattering does not cause significant decoherence of the atomic ... More
A compact and efficient strontium oven for laser-cooling experimentsSep 25 2012Here we describe a compact and efficient strontium oven well suited for laser-cooling experiments. Novel design solutions allowed us to produce a collimated strontium atomic beam with a flux of 1.0\times10^13 s^-1 cm^-2 at the oven temperature of 450 ... More
Reducing the effect of thermal noise in optical cavitiesDec 14 2012Dec 17 2013Thermal noise in optical cavities imposes a severe limitation in the stability of the most advanced frequency standards at a level of a few 10^(-16) (s/t)^(1/2) for long averaging times t. In this paper we describe two schemes for reducing the effect ... More
Ground-state properties of Ca$_2$ from narrow line two-color photoassociationFeb 02 2017May 23 2017By two-color photoassociation of $^{40}$Ca four weakly bound vibrational levels in the Ca$_2$ \Xpot ground state potential were measured, using highly spin-forbidden transitions to intermediate states of the coupled system $^3\Pi_{u}$ and $^3\Sigma^+ ... More
Demonstration of a Transportable 1 Hz-Linewidth LaserOct 13 2010May 18 2011We present the setup and test of a transportable clock laser at 698 nm for a strontium lattice clock. A master-slave diode laser system is stabilized to a rigidly mounted optical reference cavity. The setup was transported by truck over 400 km from Braunschweig ... More
Noise and instability of an optical lattice clockJul 17 2015Nov 03 2015We present an analysis of the different types of noise from the detection and interrogation laser in our strontium lattice clock. We develop a noise model showing that in our setup quantum projection noise--limited detection is possible if more than 130~atoms ... More
Lattice-induced photon scattering in an optical lattice clockFeb 08 2018Jul 19 2018We investigate scattering of lattice laser radiation in a strontium optical lattice clock and its implications for operating clocks at interrogation times up to several tens of seconds. Rayleigh scattering does not cause significant decoherence of the ... More
Phase- coherent comparison of two optical frequency standards over 146 km using a telecommunication fiber linkJun 18 2009We have explored the performance of two "dark fibers" of a commercial telecommunication fiber link for a remote comparison of optical clocks. The two fibers, linking the Leibniz University of Hanover (LUH) with the Physi-kalisch-Technische Bundesanstalt ... More
Tackling the blackbody shift in a strontium optical lattice clockSep 10 2010A major obstacle for optical clocks is the frequency shift due to black body radiation. We discuss how one can tackle this problem in an optical lattice clock; in our case 87-Sr: firstly, by a measurement of the dc Stark shift of the clock transition ... More
8E-17 fractional laser frequency instability with a long room-temperature cavityFeb 09 2015Mar 31 2015We present a laser system based on a 48 cm long optical glass resonator. The large size requires a sophisticated thermal control and optimized mounting design. A self balancing mounting was essential to reliably reach sensitivities to acceleration of ... More
Ultra-stable laser with average fractional frequency drift rate below $5\times10^{-19}/\mathrm{s}$May 07 2014Cryogenic single-crystal optical cavities have the potential to provide highest dimensional stability. We have investigated the long-term performance of an ultra-stable laser system which is stabilized to a single-crystal silicon cavity operated at 124 ... More
Liaison classes of modulesSep 25 2004We propose a concept of module liaison that extends Gorenstein liaison of ideals and provides an equivalence relation among unmixed modules over a commutative Gorenstein ring. Analyzing the resulting equivalence classes we show that several results known ... More
Comparing Castelnuovo-Mumford regularity and extended degree: the borderline casesNov 28 2003Castelnuovo-Mumford regularity and any extended degree function can be thought of as complexity measures for the structure of finitely generated graded modules. A recent result of Doering, Gunston, Vasconcelos shows that both can be compared in case of ... More
Free Lévy Processes on Dual GroupsMar 23 2002We give a short introduction to the theory of L\'evy processes on dual groups. As examples we consider L\'evy processes with additive increments and L\'evy processes on the dual affine group.
Minimal free resolutions of projective subschemes of small degreeMay 16 2005We discuss the minimal free resolution of an irreducible projective subscheme X. If X is also reduced, we focus on the case when its degree equals two plus the codimension. The set of all possible graded Betti numbers is described if the codimension is ... More
Volume Laws for Boxed Plane Partitions and Area Laws for Ferrers DiagramsApr 28 2008Jan 27 2009We asymptotically analyse the volume-random variables of general, symmetric and cyclically symmetric plane partitions fitting inside a box. We consider the respective symmetry class equipped with the uniform distribution. We also prove area limit laws ... More
Monotone and Boolean Convolutions for Non-compactly Supported Probability MeasuresMar 14 2007Jul 03 2009The equivalence of the characteristic function approach and the probabilistic approach to monotone and boolean convolutions is proven for non-compactly supported probability measures. A probabilistically motivated definition of the multiplicative boolean ... More
LIL type behaviour of multivariate Levy processes at zeroJun 19 2018Jan 14 2019We study the almost sure behaviour of suitably normalised multivariate Levy processes as t goes to zero. Among other results we find necessary and sufficient conditions for a law of a very slowly varying function which includes a general law of the iterated ... More
Orientations of 1-Factorizations and the List Chromatic Index of Small GraphsMay 01 2017As starting point, we formulate a corollary to the Quantitative Combinatorial Nullstellensatz. This corollary does not require the consideration of any coefficients of polynomials, only evaluations of polynomial functions. In certain situations, our corollary ... More
Simple evaluation of one of Malmstén's integralsSep 25 2017The logarithmic integral no. 4.325.7 from Gradshteyn and Ryzhik's tables of integrals was first evaluated by Malmst\'en. Recently, Blagouchine used contour integration methods to evaluate a family of logarithmic integrals that contains this integral. ... More
Influence of the SIPG penalisation on the numerical properties of linear systems for elastic wave propagationDec 15 2017Interior penalty discontinuous Galerkin discretisations (IPDG) and especially the symmetric variant (SIPG) for time-domain wave propagation problems are broadly accepted and widely used due to their advantageous properties. Linear systems with block structure ... More
Determining the geometry of noncircular gears for given transmission functionMay 07 2019A pair of noncircular gears can be used to generate a strictly increasing continuous function $\psi(\varphi)$ whose derivative $\psi'(\varphi) = \mathrm{d}\psi(\varphi)/\mathrm{d}\varphi > 0$ is $2\pi/n$-periodic, where $\varphi$ and $\gamma = \psi(\varphi)$ ... More
Weights in arithmetic geometryMar 03 2010The concept of weights on the cohomology of algebraic varieties was initiated by fundamental ideas and work of A. Grothendieck and P. Deligne. It is deeply connected with the concept of motives and appeared first on the singular cohomology as the weights ... More
On Reasoning with AmbiguitiesFeb 21 1995Feb 22 1995The paper adresses the problem of reasoning with ambiguities. Semantic representations are presented that leave scope relations between quantifiers and/or other operators unspecified. Truth conditions are provided for these representations and different ... More
Trigonometric R Matrices related to `Dilute' Birman--Wenzl--Murakami AlgebraFeb 16 1994Explicit expressions for three series of $R$ matrices which are related to a ``dilute'' generalisation of the Birman--Wenzl--Murakami are presented. Of those, one series is equivalent to the quantum $R$ matrices of the $D^{(2)}_{n+1}$ generalised Toda ... More
Non-degenerate curves with maximal Hartshorne-Rao moduleSep 21 2002Extending results for space curves we establish bounds for the cohomology of a non-degenerate curve in projective $n$-space. As a consequence, for any given $n$ we determine all possible pairs $(d, g)$ where $d$ is the degree and $g$ is the (arithmetic) ... More
Characterization of some projective subschemes by locally free resolutionsDec 16 2002A locally free resolution of a subscheme is by definition an exact sequence consisting of locally free sheaves (except the ideal sheaf) which has uniqueness properties like a free resolution. The purpose of this paper is to characterize certain locally ... More
SDLCQ and String/Field Theory CorrespondencesFeb 05 2001String/Field theory correspondences have been discussed heavily in recent years. Here, we describe a testing scenario involving a non-perturbative field theory calculation using the framework of supersymmetric discrete light-cone quantization (SDLCQ). ... More
Aperiodicity and Disorder - Does it Matter?Oct 25 2000The effects of an aperiodic order or a random disorder on phase transitions in statistical mechanics are discussed. A heuristic relevance criterion based on scaling arguments as well as specific results for Ising models with random disorder or certain ... More
X-Ray Scattering at FeCo(001) Surfaces and the Crossover between Ordinary and Normal TransitionsOct 21 1997In a recent experiment by Krimmel et al. [PRL 78, 3880 (1997)], the critical behavior of FeCo near a (001) surface was studied by x-ray scattering. Here the experimental data are reanalyzed, taking into account recent theoretical results on order-parameter ... More
Limit laws for discrete excursions and meanders and linear functional equations with a catalytic variableMay 26 2011Dec 13 2011We study limit distributions for random variables defined in terms of coefficients of a power series which is determined by a certain linear functional equation. Our technique combines the method of moments with the kernel method of algebraic combinatorics. ... More
The mean width of the oloid and integral geometric applications of itApr 25 2016The oloid is the convex hull of two circles with equal radius in perpendicular planes so that the center of each circle lies on the other circle. We calculate the mean width of the oloid in two ways, first via the integral of mean curvature, and then ... More
Buffon's problem with a pivot needleJan 14 2014Jan 16 2014In this paper, we solve Buffon's needle problem for a needle consisting of two line segments connected in a pivot point.
Probabilistic properties of the elliptic motionMar 31 2017In this paper we consider the plane elliptic motion which occurs if the moving centrode is a circle of radius $r$ and the fixed centrode a circle of radius $2r$. Every point of the moving plane generates an ellipse in the fixed plane. Let a disk of radius ... More
Buffon's problem with a star of needles and a lattice of parallelogramsSep 24 2012A star of n (n greater than or equal to 2) line segments (needles) of equal length with common endpoint and constant angular spacing is randomly placed onto a lattice which is the union of two families of equidistant lines in the plane with angle alpha ... More
Hasse principles for higher-dimensional fieldsOct 15 2009Dec 04 2014For schemes X over global or local fields, or over their rings of integers, K. Kato stated several conjectures on certain complexes of Gersten-Bloch-Ogus type, generalizing the fundamental exact sequence of Brauer groups for a global field. He proved ... More
On Dirichlet Products Evaluated at Fibonacci NumbersJun 06 2016In this work we discuss Dirichlet products evaluated at Fibonacci numbers. As first applications of the results we get a representation of Fibonacci numbers in terms of Euler's totient function, an upper bound on the number of primitive prime divisors ... More
A compact, robust, and transportable ultra-stable laser with a fractional frequency instability of $1\times10^{-15}$Oct 20 2014We present a compact and robust transportable ultra-stable laser system with minimum fractional frequency instability of $1\times10^{-15}$ at integration times between 1 to 10 s. The system was conceived as a prototype of a subsystem of a microwave-optical ... More
Presentations of homotopy skein modules of oriented 3-manifoldsJul 06 2000A new method to derive presentations of skein modules is developed. For the case of homotopy skein modules it will be shown how the topology of a 3-manifold is reflected in the structure of the module. The freeness problem for q-homotopy skein modules ... More
Boolean convolution of probability measures on the unit circleMar 15 2004Dec 13 2006We introduce the boolean convolution for probability measures on the unit circle. Roughly speaking, it describes the distribution of the product of two boolean independent unitary random variables. We find an analogue of the characteristic function and ... More
The Tournament Scheduling Problem with AbsencesSep 01 2015May 20 2016We study time scheduling problems with allowed absences as a new kind of graph coloring problem. One may think of a sport tournament where each player (each team) is permitted a certain number $t$ of absences. We then examine how many rounds are needed ... More
A Note on Adjoint Linear AlgebraMay 02 2019A new proof for adjoint systems of linear equations is presented. The argument is built on the principles of Algorithmic Differentiation. Application to scalar multiplication sets the base line. Generalization yields adjoint inner vector, matrix-vector, ... More
Examples for the improvements in AES Depth Profiling of Multilayer Thin Film Systems by Application of Factor Analysis Data EvaluationFeb 12 2015Factor Analysis has proved to be a powerful tool for the full exploitation of the chemical information included in the peak shapes and peak positions of spectra measured by AES depth profiling. Due to its ability to extract the number of independent chemical ... More
The Benefit of Wide Energy Range Spectrum Acquisition During Sputter Depth Profile MeasurementsNov 26 2017Thin film systems are often analysed by using sputter depth profiling. First the sample gets eroded by inert gas ion impact during sputter depth profiling. Then the elemental composition of the freshly unveiled surface is determined by using a surface ... More
A generalization of Strassen's functional LILJan 25 2006Aug 25 2006Let X_1,X_2, . . . be a sequence of i.i.d. mean zero random variables and let S_n the sum of the first n random variables. We show that whenever lim sup_n |S_n|/c_n is finite with probability one and the normalizing sequence {c_n} is sufficiently regular, ... More
The Theory of Quantum Levy ProcessesJul 28 2004Various recent results on quantum L\'evy processes are presented. The first part provides an introduction to the theory of L\'evy processes on involutive bialgebras. The notion of independence used for these processes is tensor independence, which generalizes ... More
Quantitative Combinatorial NullstellensatzDec 22 2012The main result of this paper is a coefficient formula that sharpens and generalizes Alon and Tarsi's Combinatorial Nullstellensatz, which provides some information about the polynomial map $P|_{\X_1\times...\times\X_n}$ when only incomplete information ... More
Dilute Birman--Wenzl--Murakami Algebra and $D^{(2)}_{n+1}$ modelsFeb 14 1994A ``dilute'' generalisation of the Birman--Wenzl--Murakami algebra is considered. It can be ``Baxterised'' to a solution of the Yang--Baxter algebra. The $D^{(2)}_{n+1}$ vertex models are examples of corresponding solvable lattice models and can be regarded ... More
The roughening transition of interfaces in disordered mediaOct 29 1997Competing pinning effects on a D-dimensional interface by weak impurity disorder and a periodic potential of the underlying crystal lattice are analyzed for $2<D<4$. We use both the Gaussian variational method (GVM) and the functional renormalization ... More
On Cloning Context-FreenessJul 22 1997To Rogers (1994) we owe the insight that monadic second order predicate logic with multiple successors (MSO) is well suited in many respects as a realistic formal base for syntactic theorizing. However, the agreeable formal properties of this logic come ... More
Correlators in N=1 SYM(2+1)Apr 30 2001We present a calculation of the correlator <0|T^{++}(r) T^{++}(0) |0> in N=1 SYM theory in 2+1 dimensions. In the calculation, we use supersymmetric discrete light-cone quantization (SDLCQ), which preserves the supersymmetry at every step of the calculation. ... More
On the Role of the Annihilation Channel in Front Form PositroniumMay 12 1997The annihilation channel is implemented into the front form calculations of the positronium spectrum presented in a previous publication. The effective Hamiltonian is calculated analytically. Its eigensolutions are obtained numerically. A complete separation ... More
Level-spacing distributions of the Gaussian unitary random matrix ensembleNov 14 2002Jun 24 2004Level-spacing distributions of the Gaussian Unitary Ensemble (GUE) of random matrix theory are expressed in terms of solutions of coupled differential equations. Series solutions up to order 50 in the level spacing are obtained, thus providing a very ... More
Co-Indexing Labelled DRSs to Represent and Reason with AmbiguitiesJul 25 1995The paper addresses the problem of representing ambiguities in a way that allows for monotonic disambiguation and for direct deductive computation. The paper focuses on an extension of the formalism of underspecified DRSs to ambiguities introduced by ... More
Deformation of string topology into homotopy skein modulesNov 25 2002Oct 20 2003Relations between the string topology of Chas and Sullivan and the homotopy skein modules of Hoste and Przytycki are studied. This provides new insight into the structure of homotopy skein modules and their meaning in the framework of quantum topology. ... More
Quantum deformations of fundamental groups of oriented 3-manifoldsFeb 27 2002Feb 27 2002We compute two-term skein modules of framed oriented links in oriented 3-manifolds. They contain the self-writhe and total linking number invariants of framed oriented links in a universal way. The relations in a natural presentation of the skein module ... More
Multiplicative monotone convolutionsMar 25 2005Recently, Bercovici has introduced multiplicative convolutions based on Muraki's monotone independence and shown that these convolution of probability measures correspond to the composition of some function of their Cauchy transforms. We provide a new ... More
Random chords and point distances in regular polygonsApr 12 2012Sep 05 2012In this paper we obtain the chord length distribution function for any regular polygon. From this function we conclude the density function and the distribution function of the distance between two uniformly and independently distributed random points ... More
Measures and geometric probabilities for ellipses intersecting circlesDec 06 2016Santal\'o calculated the measures for all positions of a moving line segment in which it lies inside a fixed circle and intersects this circle in one or two points. From these measures he concluded hitting probabilities for a line segment thrown randomly ... More
Hitting probabilities for random convex bodies and lattices of trianglesDec 18 2013In the first part of this paper, we obtain symmetric formulae for the probabilities that a plane convex body hits exactly 1, 2, 3, 4, 5 or 6 triangles of a lattice of congruent triangles in the plane. Furthermore, a very simple formula for the expectation ... More
Dilute Algebras and Solvable Lattice ModelsNov 24 1995The definition of a dilute braid-monoid algebra is briefly reviewed. The construction of solvable vertex and interaction-round-a-face models built on representations of the dilute Temperley-Lieb and Birman-Wenzl-Murakami algebras is discussed.
Representations of Two-Colour BWM Algebras and Solvable Lattice ModelsDec 03 1996Many of the known solutions of the Yang-Baxter equation, which are related to solvable lattice models of vertex- and IRF-type, yield representations of the Birman-Wenzl-Murakami algebra. From these, representations of a two-colour generalization of the ... More
Note on a Positronium Model from Flow Equations in Front Form DynamicsAug 13 1998Jan 16 2001In this note we address the problem of solving for the positronium mass spectrum. We use front-form dynamics together with the method of flow equations. For a special choice of the similarity function, the calculations can be simplified by analytically ... More
SYM Correlators and the Maldacena ConjectureAug 21 2002We report on progress in evaluating quantum filed theories with supersymmetric discrete light-cone quantization (SDLCQ). We compare the method to lattice gauge theory and point out its relevance for lattice calculations. As an exciting application we ... More
Analytical solution to the Schrodinger equation of a laser-driven correlated two-particle systemJan 31 2002The time-dependent quantum system of two laser-driven electrons in a harmonic oscillator potential is analysed, taking into account the repulsive Coulomb interaction between both particles. The Schrodinger equation of the two-particle system is shown ... More
Improved bounds on the number of ternary square-free wordsMay 29 2001Aug 02 2001Improved upper and lower bounds on the number of square-free ternary words are obtained. The upper bound is based on the enumeration of square-free ternary words up to length 110. The lower bound is derived by constructing generalised Brinkhuis triples. ... More
Testing SDLCQ in 2+1 dimensionsMar 13 2000The SDLCQ regularization is known to explicitly preserve supersymmetry in 1+1 dimensions. To test this property in higher dimensions, we consider supersymmetric Yang-Mills theory on R x S^1 x S^1. In particular, we choose one of the compact directions ... More
Basis Invariants in Non--Abelian Gauge TheoriesJan 23 1997Feb 05 1997A basis of Lorentz and gauge-invariant monomials in non--Abelian gauge theories with matter is described, applicable for the inverse mass expansion of effective actions. An algorithm to convert an arbitrarily given invariant expression into a linear combination ... More
Recent HERA Results and Future ProspectsJun 10 1998A few selected HERA results are presented and the prospects for future measurements with high luminosity are discussed, which will become available after the planned luminosity upgrade of the HERA storage ring planned for 2000.
What is Stochastic Independence?Jun 03 2002The notion of a tensor product with projections or with inclusions is defined. It is shown that the definition of stochastic independence relies on such a structure and that independence can be defined in an arbitrary category with a tensor product with ... More
Killing forms on G2 and Spin7 manifoldsOct 04 2004Killing forms on Riemannian manifolds are differential forms whose covariant derivative is totally skew-symmetric. We show that on a compact manifold with holonomy G2 or Spin7 any Killing form has to be parallel. The main tool is a universal Weitzenboeck ... More
The Distribution of Heights of Discrete ExcursionsAug 07 2012Aug 13 2012We compute the limiting distribution of height of a random discrete excursion with step sets consisting of one positive step 1 and arbitrary finite set of non-positive integers. The limit law is the supremum of a Brownian excursion. This is well-known ... More
Geometric probabilities for a cluster of needles and a lattice of rectanglesFeb 14 2018A cluster of $n$ needles ($1\leq n<\infty$) is dropped at random onto a plane lattice of rectangles. Each needle is fixed at one end in the cluster centre and can rotate independently about this centre. The distribution of the relative number of needles ... More
The distribution function of the distance between two random points in a right-angled triangleAug 30 2012Sep 17 2012In this paper we obtain the density function and the distribution function of the distance between two uniformly and independently distributed random points in any right-angled triangle. The density function is derived from the chord length distribution ... More
On Stronger Calculi for QBFsApr 21 2016Quantified Boolean formulas (QBFs) generalize propositional formulas by admitting quantifications over propositional variables. QBFs can be viewed as (restricted) formulas of first-order predicate logic and easy translations of QBFs into first-order formulas ... More
Classification of Polynomial Mappings Between Commutative GroupsDec 21 2012Jan 28 2014Some polynomials $P$ with rational coefficients give rise to well defined maps between cyclic groups, $\Z_q\longrightarrow\Z_r$, $x+q\Z\longmapsto P(x)+r\Z$. More generally, there are polynomials in several variables with tuples of rational numbers as ... More
A strontium lattice clock with $3 \times 10^{-17}$ inaccuracy and its frequencyDec 12 2013Aug 15 2014We have measured the absolute frequency of the optical lattice clock based on $^{87}$Sr at PTB with an uncertainty of $3.9\times 10^{-16}$ using two caesium fountain clocks. This is close to the accuracy of today's best realizations of the SI second. ... More
Crystalline optical cavity at 4 K with thermal noise limited instability and ultralow driftDec 06 2018Crystalline optical cavities are the foundation of today's state-of-the-art ultrastable lasers. Building on our previous silicon cavity effort, we now achieve the fundamental thermal noise-limited stability for a 6 cm long silicon cavity cooled to 4 Kelvin, ... More
A high-performance optical lattice clock based on bosonic atomsMar 08 2018Optical lattice clocks with uncertainty and instability in the $10^{-17}$-range and below have so far been demonstrated exclusively using fermions. Here, we demonstrate a bosonic optical lattice clock with $3\times 10^{-18}$ instability and $2.0\times ... More
An Optical Clock with Ultracold Neutral AtomsMay 16 2002Nov 20 2002We demonstrate how to realize an optical clock with neutral atoms that is competitive to the currently best single ion optical clocks in accuracy and superior in stability. Using ultracold atoms in a Ca optical frequency standard we show how to reduce ... More
Optical frequency transfer via 146 km fiber link with 10^{-19} relative accuracyApr 17 2009We demonstrate the long-distance transmission of an ultra-stable optical frequency derived directly from a state-of-the-art optical frequency standard. Using an active stabilization system we deliver the frequency via a 146 km long underground fiber link ... More
A transportable strontium optical lattice clockSep 16 2014Sep 17 2014We report on a transportable optical clock, based on laser-cooled strontium atoms trapped in an optical lattice. The experimental apparatus is composed of a compact source of ultra-cold strontium atoms including a compact cooling laser set-up and a transportable ... More
The stability of an optical clock laser transferred to the interrogation oscillator for a Cs fountainSep 12 2008We stabilise a microwave oscillator at 9.6 GHz to an optical clock laser at 344 THz by using a fibre-based femtosecond laser frequency comb as a transfer oscillator. With a second frequency comb we measure independently the instability of the microwave ... More
Towards Quantum Simulating QCDSep 25 2014Quantum link models provide an alternative non-perturbative formulation of Abelian and non-Abelian lattice gauge theories. They are ideally suited for quantum simulation, for example, using ultracold atoms in an optical lattice. This holds the promise ... More
High-resolution spectroscopy and high-density monitoring in X-rays of NovaeSep 10 2012The 21st century X-ray observatories XMM-Newton, Chandra, and Swift gave us completely new insights into the X-ray behaviour of nova outbursts. These new-generation X-ray observatories provide particularly high spectral resolution and high density in ... More
Scaling Limit of the Ising Model in a FieldOct 01 1996The dilute A_3 model is a solvable IRF (interaction round a face) model with three local states and adjacency conditions encoded by the Dynkin diagram of the Lie algebra A_3. It can be regarded as a solvable version of an Ising model at the critical temperature ... More
Aperiodic Tilings on the ComputerFeb 28 1999We briefly review the standard methods used to construct quasiperiodic tilings, such as the projection, the inflation, and the grid method. A number of sample Mathematica programs, implementing the different approaches for one- and two-dimensional examples, ... More
Remarks on dimensional reduction of multidimensional cosmological modelsJan 02 2004Mar 09 2004Multidimensional cosmological models with factorizable geometry and their dimensional reduction to effective four-dimensional theories are analyzed on sensitivity to different scalings. It is shown that a non-correct gauging of the effective four-dimensional ... More
Dynamical role of anyonic excitation statistics in rapidly rotating Bose gasesMay 10 2004Oct 06 2004We show that for rotating harmonically trapped Bose gases in a fractional quantum Hall state, the anyonic excitation statistics in the rotating gas can effectively play a {\em dynamical} role. For particular values of the two-dimensional coupling constant ... More
Specific heat of the Kelvin modes in low temperature superfluid turbulenceFeb 01 2001It is pointed out that the specific heat of helical vortex line excitations, in low temperature superfluid turbulence experiments carried out in helium II, can be of the same order as the specific heat of the phononic quasiparticles. The ratio of Kelvin ... More