Results for "Hans Peter Büchler"

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Topological states in a microscopic model of interacting fermionsApr 16 2015We present a microscopic model of interacting fermions where the ground state degeneracy is topologically protected. The model is based on a double-wire setup with local interactions in a particle number conserving setting. A compelling property of this ... More
Full Counting Statistics for Interacting Fermions with Determinantal Quantum Monte Carlo SimulationsJun 27 2017We present a method for computing the full probability distribution function of quadratic observables for the Fermi-Hubbard model within the framework of determinantal quantum Monte Carlo. Especially, in cold atoms experiments with single site resolution, ... More
Minimal instances for toric code ground statesJun 29 2012A decade ago Kitaev's toric code model established the new paradigm of topological quantum computation. Due to remarkable theoretical and experimental progress, the quantum simulation of such complex many-body systems is now within the realms of possibility. ... More
Quantum theory of Kerr nonlinearity with Rydberg slow light polaritonsApr 18 2016We study the propagation of Rydberg slow light polaritons through an atomic medium for intermediate interactions. Then, the dispersion relation for the polaritons is well described by the slow light velocity alone, which allows for an analytical solution ... More
In situ measurement of the dynamic structure factor in ultracold quantum gasesJul 13 2011Apr 09 2012We propose an experimental setup to efficiently measure the dynamic structure factor of ultracold quantum gases. Our method uses the interaction of the trapped atomic system with two different cavity modes, which are driven by external laser fields. By ... More
Two-Stage Melting in Systems of Strongly Interacting Rydberg AtomsJul 13 2010Feb 04 2011We analyze the ground state properties of a one-dimensional cold atomic system in a lattice, where Rydberg excitations are created by an external laser drive. In the classical limit, the ground state is characterized by a complete devil's staircase for ... More
The Role of Quantum Fluctuations in the Hexatic Phase of Cold Polar MoleculesJan 22 2014Two dimensional crystals melt via an intermediate \textit{hexatic} phase which is characterized by an anomalous scaling of spatial and orientational correlation functions and the absence of an attraction between dislocations. We propose a protocol to ... More
Ising anyonic topological phase of interacting Fermions in one dimensionMay 04 2017Oct 06 2017We study a microscopic model of interacting fermions in a ladder setup, where the total number of particles is conserved. At a special point, the ground state is known and gives rise to a topological state of matter with edge modes obeying the statistics ... More
Quantum Crystals and Laughlin Droplets of Cavity Rydberg PolaritonsJun 01 2015Synthetic quantum materials offer an exciting opportunity to explore quantum many-body physics and novel states of matter under controlled conditions. In particular, they provide an avenue to exchange the short length scales and large energy scales of ... More
Beyond-mean-field corrections for dipolar bosons in an optical latticeJan 09 2019Mar 29 2019Recent experiments with ultracold lanthanide atoms which are characterized by a large magnetic moment have revealed the crucial importance of beyond-mean-field corrections in understanding the dynamics of the gas. We study how the presence of an external ... More
Quasiparticles in quantum spin chains with long-range interactionsJan 02 2018Aug 28 2018We study quasiparticle excitations for quantum spin chains with long-range interactions using variational matrix product state techniques. It is confirmed that the local quasiparticle ansatz is able to capture those excitations very accurately, even when ... More
Collective many-body interaction in Rydberg dressed atomsApr 14 2010Sep 17 2010We present a method to control the shape and character of the interaction potential between cold atomic gases by weakly dressing the atomic ground state with a Rydberg level. For increasing particle densities, a crossover takes place from a two-particle ... More
Quantum critical behavior in strongly interacting Rydberg gasesJun 24 2008Dec 16 2008We study the appearance of correlated many-body phenomena in an ensemble of atoms driven resonantly into a strongly interacting Rydberg state. The ground state of the Hamiltonian describing the driven system exhibits a second order quantum phase transition. ... More
Topological bands with Chern number C=2 by dipolar exchange interactionsOct 21 2014May 19 2015We demonstrate the realization of topological band structures by exploiting the intrinsic spin-orbit coupling of dipolar interactions in combination with broken time-reversal symmetry. The system is based on polar molecules trapped in a deep optical lattice, ... More
A Rydberg Quantum SimulatorJul 10 2009Apr 09 2012Following Feynman and as elaborated on by Lloyd, a universal quantum simulator (QS) is a controlled quantum device which reproduces the dynamics of any other many particle quantum system with short range interactions. This dynamics can refer to both coherent ... More
Dipolar dephasing of Rydberg D-state polaritonsMay 14 2015Jun 23 2016We experimentally study the effects of the anisotropic Rydberg-interaction on $D$-state Rydberg polaritons slowly propagating through a cold atomic sample. In addition to the few-photon nonlinearity known from similar experiments with Rydberg $S$-states, ... More
Dimensional crossover for the beyond-mean-field correction in Bose gasesJun 05 2018Nov 28 2018We present a detailed beyond-mean-field analysis of a weakly interacting Bose gas in the crossover from three to low dimensions. We find an analytical solution for the energy and provide a clear qualitative picture of the crossover in the case of a box ... More
Fractional Excitations in Cold Atomic GasesOct 04 2012We study the behavior of excitations in the tilted one-dimensional Bose-Hubbard model. In the phase with broken symmetry, fundamental excitations are domain-walls which show fractional statistics. Using perturbation theory, we derive an analytic model ... More
Majorana modes and $p$-wave superfluids for fermionic atoms in optical latticesMar 03 2014We present a simple approach to create a strong $p$-wave interaction for fermions in an optical lattice. The crucial step is that the combination of a lattice setup with different orbital states and $s$-wave interactions can give rise to a strong induced ... More
An experimental and theoretical guide to strongly interacting Rydberg gasesFeb 10 2012We review experimental and theoretical tools to excite, study and understand strongly interacting Rydberg gases. The focus lies on the excitation of dense ultracold atomic samples close to, or within quantum degeneracy, to high lying Rydberg states. The ... More
Accurate mapping of multilevel Rydberg atoms on interacting spin-$1/2$ particles for the quantum simulation of Ising modelsOct 17 2017We study a system of atoms that are laser-driven to $nD_{3/2}$ Rydberg states and assess how accurately they can be mapped onto spin-$1/2$ particles for the quantum simulation of anisotropic Ising magnets. Using non-perturbative calculations of the pair ... More
Artificial atoms can do more than atoms: Deterministic single photon subtraction from arbitrary light fieldsMar 07 2011We study the interplay of photons interacting with an artificial atom in the presence of a controlled dephasing. Such artifical atoms consisting of several independent scatterer can exhibit remarkable properties superior to single atoms with a prominent ... More
The low-energy Goldstone mode in a trapped dipolar supersolidJun 11 2019A supersolid is a counter-intuitive state of matter that combines the frictionless flow of a superfluid with the crystal-like periodic density modulation of a solid. Since the first prediction in the 1950s, experimental efforts to realize this state have ... More
Experimental realization of a symmetry protected topological phase of interacting bosons with Rydberg atomsOct 31 2018The concept of topological phases is a powerful framework to characterize ground states of quantum many-body systems that goes beyond the paradigm of symmetry breaking. While a few topological phases appear in condensed matter systems, a current challenge ... More
Universal scaling in a strongly interacting Rydberg gasFeb 26 2009Nov 25 2009We study a gas of ultracold atoms resonantly driven into a strongly interacting Rydberg state. The long distance behavior of the spatially frozen effective pseudospin system is determined by a set of dimensionless parameters, and we find that the experimental ... More
Observation of three-body correlations for photons coupled to a Rydberg superatomMay 31 2018We report on the experimental observation of non-trivial three-photon correlations imprinted onto initially uncorrelated photons through interaction with a single Rydberg superatom. Exploiting the Rydberg blockade mechanism, we turn a cold atomic cloud ... More
Learning to Control Highly Accelerated Ballistic Movements on Muscular RobotsApr 07 2019High-speed and high-acceleration movements are inherently hard to control. Applying learning to the control of such motions on anthropomorphic robot arms can improve the accuracy of the control but might damage the system. The inherent exploration of ... More
Preparation and spectroscopy of a metastable Mott insulator state with attractive interactionsJan 04 2012We prepare and study a metastable attractive Mott insulator state formed with bosonic atoms in a three-dimensional optical lattice. Starting from a Mott insulator with Cs atoms at weak repulsive interactions, we use a magnetic Feshbach resonance to tune ... More
Strictly local one-dimensional topological quantum error correction with symmetry-constrained cellular automataNov 22 2017Jan 12 2018Active quantum error correction on topological codes is one of the most promising routes to long-term qubit storage. In view of future applications, the scalability of the used decoding algorithms in physical implementations is crucial. In this work, ... More
Topological networks for quantum communication between distant qubitsMay 19 2017Nov 22 2017Efficient communication between qubits relies on robust networks which allow for fast and coherent transfer of quantum information. It seems natural to harvest the remarkable properties of systems characterized by topological invariants to perform this ... More
Exploring quantum phases by driven dissipationAug 20 2014Ever since the insight spreaded that tailored dissipation can be employed to control quantum systems and drive them towards pure states, the field of non-equilibrium quantum mechanics gained remarkable momentum. So far research focussed on emergent phenomena ... More
Time averages of polynomialsNov 29 2007We define and study when a polynomial mapping has a local or global time average. We conjecture that a polynomial f in the complex plane has a time average near a point z if and only if z is eventually mapped into a Siegel-disc of f. We prove that the ... More
Perturbed Basins of AttractionNov 15 2004Let F be an automorphism of C^k which has a fixed point. It is well known that the basin of attraction is biholomorphically equivalent to C^k. We will show that the basin of attraction of a sequence of automorphisms is also biholomorphic to C^k if all ... More
On Bayes' theorem for improper mixturesDec 14 2011Although Bayes's theorem demands a prior that is a probability distribution on the parameter space, the calculus associated with Bayes's theorem sometimes generates sensible procedures from improper priors, Pitman's estimator being a good example. However, ... More
Non-autonomous dynamics of holomorphic mappings in projective spaceJan 16 2004We study the dynamics of compositions of a sequence of holomorphic mappings in projective space. We define ergodicity and mixing for non-autonomous dynamical systems, and we construct totally invariant measures for which our sequence satisfies these properties. ... More
Ferroelectric quantum phase transition with cold polar moleculesDec 01 2014We analyze a system of polar molecules in a one-dimensional optical lattice. By controlling the internal structure of the polar molecules with static electric and microwave fields, we demonstrate the appearance of a quantum phase transition into a ferroelectric ... More
Dipole Interaction Mediated Laser Cooling of Polar Molecules to Ultra-cold TemperaturesDec 02 2011May 13 2012We present a method to design a finite decay rate for excited rotational states in polar molecules. The setup is based on a hybrid system of polar molecules with atoms driven into a Rydberg state. The atoms and molecules are coupled via the strong dipolar ... More
Three-body interaction of Rydberg slow light polaritonsApr 13 2016Aug 08 2016We study a system of three photons in an atomic medium coupled to Rydberg states near the conditions of electromagnetically induced transparency. Based on the analytical analysis of the microscopic set of equations in the far-detuned regime, the effective ... More
Beyond-mean-field corrections for dipolar bosons in an optical latticeJan 09 2019Recent experiments with ultracold lanthanide atoms which are characterized by a large magnetic moment have revealed the crucial importance of beyond-mean-field corrections in understanding the dynamics of the gas. We study how the presence of an external ... More
Emergent universal dynamics for an atomic cloud coupled to an optical wave-guideMar 23 2018Jul 16 2018We study the dynamics of a single collective excitation in a cold ensemble of atoms coupled to a one-dimensional waveguide. The coupling between the atoms and the photonic modes provides a coherent and a dissipative dynamics for this collective excitation. ... More
Discrete Laplace Cycles of Period FourApr 19 2011We study discrete conjugate nets whose Laplace sequence is of period four. Corresponding points of opposite nets in this cyclic sequence have equal osculating planes in different net directions, that is, they correspond in an asymptotic transformation. ... More
Triggering at High Luminosity CollidersApr 19 2007Jun 02 2007This article discusses the techniques used to select online promising events at high energy and high luminosity colliders. After a brief introduction, explaining some general aspects of triggering, the more specific implementation options for well established ... More
Fatou components of elliptic polynomial skew productsAug 31 2016Jan 27 2017We investigate the description of Fatou components for polynomial skew-products in two complex variables. The non-existence of wandering domains near a super-attracting invariant fiber was shown in [L], and the geometrically-attracting case was studied ... More
Unconstrained Hamiltonian formulation of low energy QCDMay 08 2014Using a generalized polar decomposition of the gauge fields into gauge-rotation and gauge-invariant parts, which Abelianises the Non-Abelian Gauss-law constraints, an unconstrained Hamiltonian formulation of QCD can be achieved. The exact implementation ... More
QCD in terms of gauge-invariant dynamical variablesMar 15 2013For a complete description of the physical properties of low-energy QCD, it might be advantageous to first reformulate QCD in terms of gauge-invariant dynamical variables, before applying any approximation schemes. Using a canonical transformation of ... More
Fatou components of elliptic polynomial skew productsAug 31 2016We investigate the description of Fatou components for polynomial skew-products in two complex variables. The non-existence of wandering domains near a super-attracting invariant fiber was shown in [L], and the geometrically-attracting case was studied ... More
Orthologic Tetrahedra with Intersecting EdgesOct 08 2009Oct 19 2009Two tetrahedra are called orthologic if the lines through vertices of one and perpendicular to corresponding faces of the other are intersecting. This is equivalent to the orthogonality of non-corresponding edges. We prove that the additional assumption ... More
A 3d Gauge Theory/Quantum K-Theory CorrespondenceAug 06 2018Sep 27 2018The 2d gauged linear sigma model (GLSM) gives a UV model for quantum cohomology on a Kahler manifold X, which is reproduced in the IR limit. We propose and explore a 3d lift of this correspondence, where the UV model is the N=2 supersymmetric 3d gauge ... More
The Bäcklund Transform of Principal Contact Element NetsOct 16 2010We investigate geometric aspects of the the B\"acklund transform of principal contact element nets. A B\"acklund transform exists if and only if it the principal contact element net is of constant negative Gaussian curvature (a pseudosphere). We describe ... More
Polynomial maps that are roots of power seriesJun 06 2007We introduce a class of polynomial maps that we call polynomial roots of powerseries, and show that automorphisms with this property generate the automorphism group in any dimension. In particular we determine generically which polynomial maps that preserve ... More
Discrete Gliding Along Principal CurvesApr 08 2010We consider $n$-dimensional discrete motions such that any two neighbouring positions correspond in a pure rotation ("rotating motions"). In the Study quadric model of Euclidean displacements these motions correspond to quadrilateral nets with edges contained ... More
Julia sets of complex Hénon mapsJun 01 2017Sep 07 2017There are two natural definitions of the Julia set for complex H\'enon maps: the sets $J$ and $J^\star$. Whether these two sets are always equal is one of the main open questions in the field. We prove equality when the map acts hyperbolically on the ... More
Random local complex dynamicsMar 16 2018The study of the dynamics of an holomorphic map near a fixed point is a central topic in complex dynamical systems. In this paper we will consider the corresponding random setting: given a probability measure $\nu$ with compact support on the space of ... More
SU(3) Yang-Mills Hamiltonian in the flux-tube gauge: Strong coupling expansion and glueball dynamicsNov 20 2016It is shown that the formulation of the SU(3) Yang-Mills quantum Hamiltonian in the "flux-tube gauge" A_{a1}=0 for all a=1,2,4,5,6,7 and A_{a2}=0 for all a=5,7 allows for a systematic and practical strong coupling expansion of the Hamiltonian in \lambda\equiv ... More
Blocks of monodromy groups in Complex DynamicsJan 28 2009May 20 2010Motivated by a problem in complex dynamics, we examine the block structure of the natural action of monodromy groups on the tree of preimages of a generic point. We show that in many cases, including when the polynomial has prime power degree, there are ... More
Polynomials constant on a hyperplane and CR maps of hyperquadricsOct 14 2009Dec 21 2010We prove a sharp degree bound for polynomials constant on a hyperplane with a fixed number of distinct monomials for dimensions 2 and 3. We study the connection with monomial CR maps of hyperquadrics and prove similar bounds in this setup with emphasis ... More
From geometry to invertibility preserversMar 31 2013We characterize bijections on matrix spaces (operator algebras) preserving full rank (invertibility) of differences of matrix (operator) pairs in both directions.
Anomalous Behavior of Spin Systems with Dipolar InteractionsMar 07 2012Jul 11 2012We study the properties of spin systems realized by cold polar molecules interacting via dipole-dipole interactions in two dimensions. Using a spin wave theory, that allows for the full treatment of the characteristic long-distance tail of the dipolar ... More
Driving Dipolar Fermions into the Quantum Hall Regime by Spin-Flip Induced Insertion of Angular MomentumFeb 06 2013Apr 03 2013A new method to drive a system of neutral dipolar fermions into the lowest Landau level regime is proposed. By employing adiabatic spin-flip processes in combination with a diabatic transfer, the fermions are pumped to higher orbital angular momentum ... More
The topological susceptibility in finite temperature QCD and axion cosmologyJun 09 2016We study the topological susceptibility in 2+1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings, corresponding to temporal extent of the lattice, $N_\tau=6,8,10$ and ... More
Fatou components of attracting skew productsAug 26 2015We investigate the existence of wandering Fatou components for polynomial skew-products in two complex variables. In 2004 the non-existence of wandering domains near a super-attracting invariant fiber was shown in [8]. In 2014 it was shown in [1] that ... More
Adaptive trains for attracting sequences of holomorphic automorphismsAug 03 2014Consider a holomorphic automorphism acting hyperbolically on an invariant compact set. It has been conjectured that the arising stable manifolds are all biholomorphic to Euclidean space. Such a stable manifold is always equivalent to the basin of a uniformly ... More
Condensation of MgS in outflows from carbon starsMar 20 2008The basic mechanism responsible for the widespread condensation of MgS in the outflows from carbon rich stars on the tip of the AGB is discussed with the aim of developing a condensation model that can be applied in model calculations of dust formation ... More
Random Neighbor Theory of the Olami-Feder-Christensen Earthquake ModelJul 11 1997Sep 16 1997We derive the exact equations of motion for the random neighbor version of the Olami-Feder-Christensen earthquake model in the infinite-size limit. We solve them numerically, and compare with simulations of the model for large numbers of sites. We find ... More
A polynomial skew-product with a wandering Fatou-diskMay 06 2014Little is known about the existence of wandering Fatou components for rational maps in two complex variables. In 2003 Lilov proved the non-existence of wandering Fatou components for polynomial skew-products in the neighborhood of an invariant super-attracting ... More
Generalized string compactifications with spontaneously broken supersymmetryJun 22 1996Aug 04 1996The Narain lattice construction of string compactifications is generalized to include spontaneously broken supersymmetry. Consistency conditions from modular invariance and Lorentz symmetry are solved in full generality. This framework incorporates models ... More
Self-Induced Compactness in Banach SpacesMar 28 1994The question which led to the title of this note is the following: {\it If $X$ is a Banach space and $K$ is a compact subset of $X$, is it possible to find a compact, or even approximable, operator $v:X\to X$ such that $K\subset\ol{v(B_X)}$?} This question ... More
Non-Autonomous Basins of Attraction With 4-Dimensional BoundariesOct 07 2004We study whether the basin of attraction of a sequence of automorphisms of $\mathbb{C}^k$ is biholomorphic to $\mathbb{C}^k$. In particular we show that given any sequence of automorphisms with the same attracting fixed point, the basin is biholomorphic ... More
Lyapunov Conditions for Differentiability of Markov Chain Expectations: the Absolutely Continuous CaseJul 12 2017We consider a family of Markov chains whose transition dynamics are affected by model parameters. Understanding the parametric dependence of (complex) performance measures of such Markov chains is often of significant interest. The derivatives of the ... More
Quark number susceptibilities at finite chemical potential from fugacity expansionSep 16 2014Generalized quark number susceptibilities are expected to be good probes for the phase transitions in QCD and the search of a possible critical point. However, their computation in lattice QCD is plagued by the complex action problem which appears at ... More
The Bak-Chen-Tang Forest Fire Model RevisitedJun 23 1997We reconsider a model introduced by Bak, Chen, and Tang (Phys. Rev. A 38, 364 (1988)) as a supposedly self-organized critical model for forest fires. We verify again that the model is not critical in 2 dimensions, as found also by previous authors. But ... More
Mean Field Behaviour in a Local Low-Dimensional ModelSep 16 1994We point out a new mechanism which can lead to mean field type behaviour in nonequilibrium critical phenomena. We demonstrate this mechanism on a two-dimensional model which can be understood as a stochastic and non-conservative version of the abelian ... More
Gravitational divergences as a mediator of supersymmetry breakingJul 04 1997Gravitational divergences associated with singlet fields in supersymmetric theories are reexamined, and their possible contributions to the low-energy effective theory are pointed out. We demonstrate that such divergences are not necessarily harmful and ... More
Supersymmetric Neutrino Masses, R Symmetries, and The Generalized mu ProblemJun 20 1996In supersymmetric models a tree-level neutrino mass could originate from the (weak-scale) superpotential. We propose and examine a realization of that idea, which arises naturally in the framework of a spontaneously broken U(1) R-symmetry. The solution ... More
Bifurcating vortex solutions of the complex Ginzburg-Landau equationJun 25 1999It is shown that the complex Ginzburg-Landau (CGL) equation on the real line admits nontrivial $2\pi$-periodic vortex solutions that have $2n$ simple zeros (``vortices'') per period. The vortex solutions bifurcate from the trivial solution and inherit ... More
Quantitative analysis of galaxy-galaxy lensingJan 31 1996In this paper we explore a quantitative and efficient method to constrain the halo properties of distant galaxy populations through ``galaxy--galaxy" lensing and show that the mean masses and sizes of halos can be estimated accurately, without excessive ... More
The LPM effect in sequential bremsstrahlung: 4-gluon verticesAug 19 2016The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue study ... More
A transcendental Hénon map with an oscillating wandering Short $\mathbb{C}^2$Jan 22 2019Short $\mathbb{C}^2$'s were constructed in [F] as attracting basins of a sequence of holomorphic automorphisms whose rate of attraction increases superexponentially. The goal of this paper is to show that such domains also arise naturally as autonomous ... More
(Semi)classical limit of the Hartree equation with harmonic potentialMay 19 2004Nonlinear Schrodinger Equations (NLS) of the Hartree type occur in the modeling of quantum semiconductor devices. Their "semiclassical" limit of vanishing (scaled) Planck constant is both a mathematical challenge and practically relevant when coupling ... More
The LPM effect in sequential bremsstrahlung: dimensional regularizationJun 28 2016The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent interest is the case ... More
Scalable Density-Based Distributed ClusteringSep 22 2014Clustering has become an increasingly important task in analysing huge amounts of data. Traditional applications require that all data has to be located at the site where it is scrutinized. Nowadays, large amounts of heterogeneous, complex data reside ... More
The LPM effect in sequential bremsstrahlung: 4-gluon verticesAug 19 2016Oct 19 2016The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. In this paper, we continue study ... More
The LPM effect in sequential bremsstrahlung: dimensional regularizationJun 28 2016Oct 19 2016The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent interest is the case ... More
Simulation of infinitely divisible random fieldsOct 14 2009Two methods to approximate infinitely divisible random fields are presented. The methods are based on approximating the kernel function in the spectral representation of such fields, leading to numerical integration of the respective integrals. Error ... More
Infinite divisibility of random fields admitting an integral representation with an infinitely divisible integratorOct 08 2009Aug 12 2010We consider random fields that can be represented as integrals of deterministic functions with respect to infinitely divisible random measures and show that these random fields are infinitely divisible.
Kempe's Universality Theorem for Rational Space CurvesSep 29 2015Feb 11 2017We prove that every bounded rational space curve of degree d and circularity c can be drawn by a linkage with 9/2 d - 6c + 1 revolute joints. Our proof is based on two ingredients. The first one is the factorization theory of motion polynomials. The second ... More
The Theory of Bonds: A New Method for the Analysis of LinkagesJun 18 2012Jul 19 2013In this paper we introduce a new technique, based on dual quaternions, for the analysis of closed linkages with revolute joints: the theory of bonds. The bond structure comprises a lot of information on closed revolute chains with a one-parametric mobility. ... More
A new approach to unbiased estimation for SDE'sJul 10 2012In this paper, we introduce a new approach to constructing unbiased estimators when computing expectations of path functionals associated with stochastic differential equations (SDEs). Our randomization idea is closely related to multi-level Monte Carlo ... More
Thermal evolution and sintering of chondritic planetesimals II. Improved treatment of the compaction processNov 11 2014Reconstruction of the thermal history of individual meteorites which can be assigned to the same parent body allows to derive general characteristics of the parent body, which hold important clues on the planetary formation process. This requires to construct ... More
String Dualities in the Presence of Anomalous U(1) SymmetriesMar 18 1999Anomalous U(1) gauge symmetries in type II orientifold theories show some unexpected properties. In contrast to the heterotic case, the masses of the gauge bosons are in general of order of the string scale even in the absence of large Fayet-Iliopoulos ... More
Coupled fields in external background with application to nonthermal production of gravitinosMar 23 2001May 03 2001We provide the formalism for the quantization of systems of coupled bosonic and fermionic fields in a time dependent classical background. The occupation numbers of the particle eigenstates can be clearly defined and computed, through a generalization ... More
Tunneling dynamics of few bosons in a double wellJan 07 2008We study few-boson tunneling in a one-dimensional double well. As we pass from weak interactions to the fermionization limit, the Rabi oscillations first give way to highly delayed pair tunneling (for medium coupling), whereas for very strong correlations ... More
Silicate condensation in Mira variablesApr 15 2016We study whether the condensation of silicate dust in Mira envelopes could be caused by cluster formation by the abundant SiO molecules. For a simplified model of the pulsational motions of matter in the the outer layers of a Mira variable which is guided ... More
A Survey on the Theory of BondsJul 30 2018Many researchers tried to understand/explain the geometric reasons for paradoxical mobility of a mechanical linkage, i.e. the situation when a linkage allows more motions than expected from counting parameters and constraints. Bond theory is a method ... More
750 GeV Diphotons and Supersymmetric Grand UnificationApr 12 2016We investigate the 750 GeV diphoton excess in terms of supersymmetric models which preserve grand unification in the ultraviolet. We show that minimal extensions of the MSSM by a singlet and a vector-like 5-plet or 10-plet of SU(5) can explain the observed ... More
Spatial Straight Line Linkages by Factorization of Motion PolynomialsOct 10 2014Oct 13 2014We use the recently introduced factorization of motion polynomials for constructing overconstrained spatial linkages with a straight line trajectory. Unlike previous examples, the end-effector motion is not translational and the link graph is a cycle. ... More
Optimal Synthesis of Overconstrained 6R Linkages by Curve EvolutionJan 31 2017Mar 10 2017The paper presents an optimal synthesis of overconstrained linkages, based on the factorization of rational curves (representing one parametric motions) contained in Study's quadric. The group of Euclidean displacements is embedded in a affine space where ... More
Minimal area ellipses in the hyperbolic planeJan 25 2011Jul 06 2011We present uniqueness results for enclosing ellipses of minimal area in the hyperbolic plane. Uniqueness can be guaranteed if the minimizers are sought among all ellipses with prescribed axes or center. In the general case, we present a sufficient and ... More
Davis' Convexity Theorem and Extremal EllipsoidsJul 07 2009Aug 25 2009We give a variety of uniqueness results for minimal ellipsoids circumscribing and maximal ellipsoids inscribed into a convex body. Uniqueness follows from a convexity or concavity criterion on the function used to measure the size of the ellipsoid. Simple ... More
On visualisation scaling, subeigenvectors and Kleene stars in max algebraAug 14 2008Mar 29 2009The purpose of this paper is to investigate the interplay arising between max algebra, convexity and scaling problems. The latter, which have been studied in nonnegative matrix theory, are strongly related to max algebra. One problem is strict visualisation ... More