Results for "Niklas Georg"

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Designing Sound Collaboratively - Perceptually Motivated Audio SynthesisJun 23 2014In this contribution, we will discuss a prototype that allows a group of users to design sound collaboratively in real time using a multi-touch tabletop. We make use of a machine learning method to generate a mapping from perceptual audio features to ... More
On Yangian Symmetry in Planar N=4 SYMApr 30 2010Apr 10 2011Planar N=4 supersymmetric Yang-Mills theory appears to be perturbatively integrable. This work reviews integrability in terms of a Yangian algebra and compares the application to the problems of anomalous dimensions and scattering amplitudes.
Review of AdS/CFT Integrability, Chapter VI.1: Superconformal SymmetryDec 17 2010Mar 20 2011Aspects of the D=4, N=4 superconformal symmetry relevant to the AdS/CFT duality and integrability are reviewed. These include the Lie superalgebra psu(2,2|4), its representations, conformal transformations and correlation functions in N=4 super Yang-Mills ... More
Uncertainty quantification for an optical grating coupler with an adjoint-based Leja adaptive collocation methodJul 19 2018This paper addresses uncertainties arising in the nano-scale fabrication of optical devices. The stochastic collocation method is used to propagate uncertainties in material and geometry to the scattering parameters of the system. A dimension-adaptive ... More
Uncertainty Quantification for Maxwell's Eigenproblem using Isogeometric AnalysisFeb 08 2018May 30 2018The electromagnetic field distribution as well as the resonating frequency of various modes in superconducting cavities used in particle accelerators for example are sensitive to small geometry deformations. The occurring variations are motivated by measurements ... More
Eta-eta' mixing in U(3) chiral perturbation theoryJul 16 2001We investigate eta-eta' mixing in infrared regularized U(3) chiral perturbation theory by calculating the eta and eta' masses up to one-loop order. From this analysis it becomes obvious that even at leading order eta-eta' mixing does not obey the usually ... More
Phragmén-Lindelöf theorems and p-harmonic measures for sets near low-dimensional hyperplanesMar 18 2015Dec 03 2015We prove estimates of a $p$-harmonic measure, $p \in (n-m, \infty]$, for sets in $\mathbf{R}^n$ which are close to an $m$-dimensional hyperplane $\Lambda \subset \mathbf{R}^n$, $m \in [0,n-1]$. Using these estimates, we derive results of Phragm\'en-Lindel\"of ... More
Uncertainty Quantification for Geometry Deformations of Superconducting Cavities using Eigenvalue TrackingFeb 08 2018The electromagnetic field distribution as well as the resonating frequency of various modes in superconducting cavities are sensitive to small geometry deformations. The occurring variations are motivated by measurements of an available set of resonators ... More
Consistent boundary conditions for cosmological topologically massive gravity at the chiral pointAug 19 2008Oct 28 2010We show that cosmological topologically massive gravity at the chiral point allows not only Brown-Henneaux boundary conditions as consistent boundary conditions, but slightly more general ones which encompass the logarithmic primary found in 0805.2610 ... More
Parameterization of the Angular Distribution of Gamma Rays Produced by p-p Interaction in Astronomical EnvironmentSep 03 2007Dec 12 2007We present the angular distribution of gamma rays produced by proton-proton interactions in parameterized formulae to facilitate calculations in astrophysical environments. The parameterization is derived from Monte Carlo simulations of the up-to-date ... More
On linear representation of $\ast$-regular rings having representable ortholattice of projectionsNov 04 2018This paper aims at the following results: \begin{enumerate} \item The class of all $*$-regular rings forms a variety. \item A subdirectly irreducible $*$-regular ring $R$ is faithfully representable (i.e. isomorphic to a subring of an endomorphisms ring ... More
Graded and Geometric Parabolic Induction for Category $\mathcal{O}$Mar 01 2016Sep 13 2018We prove that the parabolic induction functor on BGG-category $\mathcal{O}$ associated to a complex reductive Lie algebra is gradable, that is, lifts to graded category $\mathcal{O}$ as constructed by Beilinson-Ginzburg-Soergel. Graded category $\mathcal{O}$ ... More
A Fault-Tolerant Sequentially Consistent DSM With a Compositional Correctness ProofAug 08 2016We present the SC-ABD algorithm that implements sequentially consistent distributed shared memory (DSM). The algorithm tolerates that less than half of the processes are faulty (crash-stop). Compared to the multi-writer ABD algorithm, SC-ABD requires ... More
Universal Quantum Computing with Spin and ValleyMar 22 2012We investigate a two-electron double quantum dot with both spin and valley degrees of freedom as they occur in graphene, carbon nanotubes, or silicon, and regard the 16-dimensional space with one electron per dot as a four-qubit logic space. In the spin-only ... More
Searching for degeneracies of real Hamiltonians using homotopy classification of loops in SO($n$)Jun 15 2004Jan 25 2005Topological tests to detect degeneracies of Hamiltonians have been put forward in the past. Here, we address the applicability of a recently proposed test [Phys. Rev. Lett. {\bf 92}, 060406 (2004)] for degeneracies of real Hamiltonian matrices. This test ... More
Asymmetric Dark Matter StarsJul 03 2015We study the possibility of asymmetric dark matter with self-interactions forming compact stable objects. We solve the Tolman-Oppenheimer-Volkoff equation and find the mass-radius relation of such "dark stars", their density profile and their Chandrasekhar ... More
Daily modulation and gravitational focusing in direct dark matter search experimentsMay 11 2015Nov 05 2015We study the effect of gravitational focusing of the earth on dark matter. We find that the effect can produce a detectable diurnal modulation in the dark matter signal for part of the parameter space which for high dark matter masses is larger than the ... More
The RTT-Realization for the Deformed gl(2|2) YangianJan 29 2014In this paper we work out the RTT-realization for the Yangian algebra of the Hubbard model and AdS/CFT correspondence. We find that this Yangian algebra is of a non-standard type in which the levels of the Yangian mix. The crucial feature that allows ... More
A simple and accurate approximation for the Q stability parameter in multi-component and realistically thick discsFeb 18 2013May 08 2013In this paper, we propose a Q stability parameter that is more realistic than those commonly used, and is easy to evaluate [see Eq. (19)]. Using our Q_N parameter, you can take into account several stellar and/or gaseous components as well as the stabilizing ... More
Mixed Motives and Geometric Representation Theory in Equal CharacteristicSep 19 2016Let $\mathbb{k}$ be a field of characteristic $p$. We introduce a formalism of mixed sheaves with coefficients in $\mathbb{k}$ and showcase its use in representation theory. More precisely, we construct for all quasi-projective schemes $X$ over an algebraic ... More
Is it ethical to avoid error analysis?Jun 30 2017Machine learning algorithms tend to create more accurate models with the availability of large datasets. In some cases, highly accurate models can hide the presence of bias in the data. There are several studies published that tackle the development of ... More
Exchange Currents in Radiative Hyperon DecaysJun 15 1998A short overview of motivations and successes of two-body exchange currents between constituent quarks for electromagnetic hadron observables like charge radii, magnetic and quadrupole moments is given. We then predict and analyze exchange current effects ... More
SU(r,L) is separably unirationalOct 22 2008We show that the moduli space of SU_X(r,L) of rank r bundles of fixed determinant L on a smooth projective curve X is separably unirational.
Raynaud vector bundlesJun 27 2007We construct vector bundles $R^r_\mu$ on a smooth projective curve $X$ having the property that for all sheaves $E$ of slope $\mu$ and rank $r$ on $X$ we have an equivalence: $E$ is a semistable vector bundle $\iff$ $Hom(R^r_\mu,E)=0$. As a byproduct ... More
Climate Modelling of Mass-Extinction Events: A ReviewJun 18 2009Despite tremendous interest in the topic and decades of research, the origins of the major losses of biodiversity in the history of life on Earth remain elusive. A variety of possible causes for these mass-extinction events have been investigated, including ... More
On the Throughput/Bit-Cost Tradeoff in CSMA Based Cooperative NetworksJun 05 2009Nov 04 2009Wireless local area networks (WLAN) still suffer from a severe performance discrepancy between different users in the uplink. This is because of the spatially varying channel conditions provided by the wireless medium. Cooperative medium access control ... More
Particle production sources at LHC energiesJan 09 2013Feb 18 2013Particle production sources at RHIC and LHC energies are investigated in pseudorapidity space. A nonequilibrium-statistical relativistic diffusion model (RDM) with three sources is applied to the analysis of charged-hadron distributions in AuAu collisions ... More
Optimal Non-Uniform Mapping for Probabilistic ShapingAug 06 2012Jul 07 2014The construction of optimal non-uniform mappings for discrete input memoryless channels (DIMCs) is investigated. An efficient algorithm to find optimal mappings is proposed and the rate by which a target distribution is approached is investigated. The ... More
An approach to computing downward closuresMar 03 2015Jun 01 2015The downward closure of a word language is the set of all (not necessarily contiguous) subwords of its members. It is well-known that the downward closure of any language is regular. While the downward closure appears to be a powerful abstraction, algorithms ... More
EXPODE -- Advanced Exponential Time Integration Toolbox for MATLABApr 17 2014We present a MATLAB toolbox for five different classes of exponential integrators for solving (mildly) stiff ordinary differential equations or time-dependent partial differential equations. For the efficiency of such exponential integrators it is essential ... More
Probabilistic Signal Shaping for Bit-Metric DecodingJan 23 2014Apr 20 2014A scheme is proposed that combines probabilistic signal shaping with bit-metric decoding. The transmitter generates symbols according to a distribution on the channel input alphabet. The symbols are labeled by bit strings. At the receiver, the channel ... More
The complexity of downward closure comparisonsMay 10 2016The downward closure of a language is the set of all (not necessarily contiguous) subwords of its members. It is well-known that the downward closure of every language is regular. Moreover, recent results show that downward closures are computable for ... More
On the Relation between Solar Activity and Clear-Sky Terrestrial IrradianceSep 04 2012Oct 09 2012The Mauna Loa Observatory record of direct-beam solar irradiance measurements for the years 1958-2010 is analysed to investigate the variation of clear-sky terrestrial insolation with solar activity over more than four solar cycles. The raw irradiance ... More
Limits on a CP-violating scalar axion-nucleon interactionMay 08 2012Jul 29 2012Axions or similar hypothetical pseudoscalar bosons may have a small CP-violating scalar Yukawa interaction g_s(N) with nucleons, causing macroscopic monopole-dipole forces. Torsion-balance experiments constrain g_p(e) g_s(N), whereas g_p(N) g_s(N) is ... More
Neutrinos and the starsJan 08 2012May 19 2012The role of neutrinos in stars is introduced for students with little prior astrophysical exposure. We begin with neutrinos as an energy-loss channel in ordinary stars and conversely, how stars provide information on neutrinos and possible other low-mass ... More
CP violation in $B^0_s$ mixing with LHCbDec 05 2011The determination of the CP-violating phase $\phi_s$ in $B^0_s \rightarrow J/\psi \phi$ decays is one of the key goals of the LHCb experiment. Its value is predicted to be very small in the Standard Model but can be significantly enhanced in many models ... More
Ultraviolet energy dependence of particle production sources in relativistic heavy-ion collisionsJan 13 2015The energy dependence of particle production sources in relativistic heavy-ion collisions is investigated from RHIC to LHC energies. Whereas charged-hadron production in the fragmentation sources follows a ln(s_NN/s_0) law, particle production in the ... More
Supersymmetry on the lattice and the status of the Super-Yang-Mills simulationsNov 03 2010Supersymmetry (SUSY) and supersymmetric field theories are an interesting topic for numerical lattice simulations. Similar to the chiral symmetry there is also no local realization of (interacting) supersymmetry on the lattice. I briefly review the basic ... More
The Relative Chern Character and RegulatorsJul 08 2010In this thesis we construct a modified version of Karoubi's relative Chern character for smooth varieties over the complex numbers or the ring of integers in a p-adic number field. Comparison results with the Deligne-Beilinson Chern character and the ... More
Curvature of higher direct images and applications (Curvature of $R^{n-p}f_*Ω^p_{X/S}(K_{X/S}^{\otimes m})$ and applications)Feb 25 2010May 19 2010Given an effectively parameterized family $f:X\to S$ of canonically polarized manifolds, the K\"ahler-Einstein metrics on the fibers induce a hermitian metric on the relative canonical bundle $K_{X/S}$. We use a global elliptic equation to show that this ... More
Gromov-Witten theory of K3 x P1 and quasi-Jacobi formsMay 17 2016Let $S$ be a K3 surface with primitive curve class $\beta$. We completely solve the relative Gromov-Witten theory of $S \times \mathbb{P}^1$ in classes $(\beta,1)$ and $(\beta,2)$. The generating series are quasi-Jacobi forms and equal to a corresponding ... More
The approach of Otto-Reznikoff revisitedSep 03 2013Apr 10 2014In this article we consider a lattice system of unbounded continuos spins. Otto & Reznikoff used the two-scale approach to show that exponential decay of correlations yields a logarithmic Sobolev inequality (LSI) with uniform constant in the system size. ... More
Minimal bundles and fine moduli spacesMar 13 2009We study sheaves E on a smooth projective curve X which are minimal with respect to the property that $h^0(E \otimes L) >0$ for all line bundles L of degree zero. We show that these sheaves define ample divisors D(E) on the Picard torus Pic(X). Next we ... More
Residual intersection theory with reducible schemesNov 07 2001We develop a formula (Theorem 5.1) which allows to compute top Chern classes of vector bundles on the vanishing locus $V(s)$ of a section of this bundle. This formula particularly applies in the case when $V(s)$ is the union of locally complete intersections ... More
On the homotopy theory of n-typesApr 24 2006An n-truncated model structure on simplicial (pre-)sheaves is described having as weak equivalences maps that induce isomorphisms on certain homotopy sheaves only up to degree n. Starting from one of Jardine's intermediate model structures we construct ... More
Risk aggregation with empirical margins: Latin hypercubes, empirical copulas, and convergence of sum distributionsAug 11 2015This paper studies convergence properties of multivariate distributions constructed by endowing empirical margins with a copula. This setting includes Latin Hypercube Sampling with dependence, also known as the Iman--Conover method. The primary question ... More
Explicit thermostatics of certain classical one-dimensional lattice models by harmonic analysisMar 28 1994A certain class of one-dimensional classical lattice models is considered. Using the method of abstract harmonic analysis explicit thermostatic properties of such models are derived. In particular, we discuss the low-temperature behavior of some of these ... More
Injective completion with respect to homologyDec 19 2004Generalizing F-nilpotent completion for a ring spectrum F we first define the notion of completion with respect to a thick subcategory in a monogenic stable homotopy category. Specializing this to the thick subcategory generated by F-injectives gives ... More
An extension theorem for hermitian line bundlesJul 22 2015May 11 2016We prove a general extension theorem for holomorphic line bundles on reduced complex spaces, equipped with singular hermitian metrics, whose curvature currents can be extended as positive, closed currents. The result has applications to various moduli ... More
Complex-Valued Random Vectors and Channels: Entropy, Divergence, and CapacityMay 04 2011Recent research has demonstrated significant achievable performance gains by exploiting circularity/non-circularity or propeness/improperness of complex-valued signals. In this paper, we investigate the influence of these properties on important information ... More
A note on random samples of Lie algebrasJul 09 2014Recently, Paiva and Teixeira (arXiv:1108.4396) showed that the structure constants of a Lie algebra are the solution of a system of linear equations provided a certain subset of the structure constants are given a-priori. Here it is noted that Lie algebras ... More
Silent Transitions in Automata with StorageFeb 15 2013We consider the computational power of silent transitions in one-way automata with storage. Specifically, we ask which storage mechanisms admit a transformation of a given automaton into one that accepts the same language and reads at least one input ... More
On the capabilities of grammars, automata, and transducers controlled by monoidsMar 17 2011During the last decades, classical models in language theory have been extended by control mechanisms defined by monoids. We study which monoids cause the extensions of context-free grammars, finite automata, or finite state transducers to exceed the ... More
A Brascamp-Lieb type covariance estimateFeb 20 2014In this article, we derive a new covariance estimate. The estimate has a similar structure as the Brascamp-Lieb inequality and is optimal for ferromagnetic Gaussian measures. It can be naturally applied to deduce decay of correlations of lattice systems ... More
Abstract tropical linear programmingDec 06 2016Dec 04 2017In this paper we develop a combinatorial abstraction of tropical linear programming. This generalizes the search for a feasible point of a system of min-plus-inequalities. It is based on the polyhedral properties of triangulations of the product of two ... More
Dynamics of a Continuous Piecewise Affine Map of the SquareMay 18 2013We present a one-parameter family of continuous, piecewise affine, area preserving maps of the square, which are inspired by a dynamical system in game theory. Interested in the coexistence of stochastic and (quasi-)periodic behaviour, we investigate ... More
AXIONS IN ASTROPHYSICS AND COSMOLOGYFeb 21 1995Mar 23 1995If axions exist they are efficiently produced in the hot and dense interior of stars, providing a novel energy-loss mechanism. In order to avoid a conflict with the observed properties of stars, one can derive a lower limit on the Peccei-Quinn scale (an ... More
Positivity of relative canonical bundles for families of canonically polarized manifoldsAug 25 2008Oct 19 2010Given an effectively parameterized family of canonically polarized manifolds the Kaehler-Einstein metrics on the fibers induce a hermitian metric on the relative canonical bundle. We use a global elliptic equation to show that this metric is strictly ... More
Truncated resolution model structuresFeb 25 2006Using the dual of Bousfield-Friedlander localization we colocalize resolution model structures on cosimplicial objects over a left proper model category to get truncated resolution model structures. These are useful to study realization and moduli problems ... More
Achievable Rates for Shaped Bit-Metric DecodingOct 29 2014May 28 2016A new achievable rate for bit-metric decoding (BMD) is derived using random coding arguments. The rate expression can be evaluated for any input distribution, and in particular the bit-levels of binary input labels can be stochastically dependent. Probabilistic ... More
Arithmetics with multiple testing proceduresJul 14 2016Statistical discoveries are often obtained through multiple hypothesis testing. A variety of procedures exists to evaluate multiple hypotheses, for instance the ones of Benjamini-Hochberg, Bonferroni, Holm or Sidak. We are particularly interested in multiple ... More
Lecture Notes on Channel CodingJul 04 2016These lecture notes on channel coding were developed for a one-semester course for graduate students of electrical engineering. Chapter 1 reviews the basic problem of channel coding. Chapters 2-5 are on linear block codes, cyclic codes, Reed-Solomon codes, ... More
On an analytic version of Lazard's isomorphismAug 19 2014Apr 06 2015We prove a comparison theorem between locally analytic group cohomology and Lie algebra cohomology for locally analytic representations of a Lie group over a nonarchimedean field of characteristic 0. The proof is similar to that of van-Est's isomorphism ... More
Importance sampling for the simulation of reinsurance lossesMar 30 2013Importance sampling is a well developed method in statistics. Given a random variable $X$, the problem of estimating its expected value $\mu$ is addressed. The standard approach is to use the sample mean as an estimator $\bar x$. In importance sampling, ... More
Karoubi's relative Chern character, the rigid syntomic regulator, and the Bloch-Kato exponential mapNov 17 2011Jul 21 2014We construct a variant of Karoubi's relative Chern character for smooth, separated schemes over the ring of integers in a p-adic field and prove a comparison with the rigid syntomic regulator. For smooth projective schemes we further relate the relative ... More
Deciding Monotone Duality and Identifying Frequent Itemsets in Quadratic LogspaceDec 09 2012Aug 22 2013The monotone duality problem is defined as follows: Given two monotone formulas f and g in iredundant DNF, decide whether f and g are dual. This problem is the same as duality testing for hypergraphs, that is, checking whether a hypergraph H consists ... More
On Minimal Constraint NetworksMar 08 2011Jul 25 2012In a minimal binary constraint network, every tuple of a constraint relation can be extended to a solution. The tractability or intractability of computing a solution to such a minimal network was a long standing open question. Dechter conjectured this ... More
L-stable functorsApr 19 2007We generalize and greatly simplify the approach of Lydakis and Dundas-R\"ondigs-{\O}stv{\ae}r to construct an L-stable model structure for small functors from a closed symmetric monoidal model category V to a V-model category M, where L is a small cofibrant ... More
Duality Construction of Moduli SpacesAug 29 1997We show for the moduli space of rank-2 coherent sheaves on an algebraic surface that there exists a 'dual' moduli space. This dual space allows a construction of the first one without using the GIT construction. Furthermore, we obtain a Barth-morphism, ... More
Weyl Groups with Coxeter Presentation and Presentation by ConjugationJul 22 2006We investigate which Weyl groups have a Coxeter presentation and which of them at least have the presentation by conjugation with respect to their root system. For most concepts of root systems the Weyl group has both. In the context of extended affine ... More
Accelerated Portfolio Optimization with Conditional Value-at-Risk Constraints using a Cutting-Plane MethodAug 12 2014Financial portfolios are often optimized for maximum profit while subject to a constraint formulated in terms of the Conditional Value-at-Risk (CVaR). This amounts to solving a linear problem. However, in its original formulation this linear problem has ... More
Symbols and exact regularity of symmetric pseudo-splines of any arityNov 02 2016Pseudo-splines form a family of subdivision schemes that provide a natural blend between interpolating schemes and approximating schemes, including the Dubuc-Deslauriers schemes and B-spline schemes. Using a generating function approach, we derive expressions ... More
Fixed Point Theorem for Non-Self Maps of Regions in the PlaneDec 15 2011May 03 2013Let X and Y be compact, simply connected and locally connected subsets of R^2, and let f : X -> Y be a homeomorphism isotopic to the identity on X. Generalizing Brouwer's plane translation theorem for self-maps of the plane, we prove that f has no recurrent ... More
Path-Integral Aspects of Supersymmetric Quantum MechanicsSep 02 1996In this talk we briefly review the concept of supersymmetric quantum mechanics using a model introduced by Witten. A quasi-classical path-integral evaluation for this model is performed, leading to a so-called supersymmetric quasi-classical quantization ... More
Recent Developments in Supersymmetric Quantum MechanicsMar 29 1994Apr 05 1994Some recent results in supersymmetric quantum mechanics are presented. New semi-classical approximation formulas for Witten's realization of supersymmetric quantum mechanics are discussed. Implications of the supersymmetric structure of Pauli's Hamiltonian ... More
Acceleration of GRB outflows by Poynting flux dissipationDec 21 2001Jun 24 2002We study magnetically powered relativistic outflows in which a part of the magnetic energy is dissipated internally by reconnection. For GRB parameters, and assuming that the reconnection speed scales with the Alfven speed, significant dissipation can ... More
Pseudorapidity distributions of produced charged hadrons in pp collisions at RHIC and LHC energiesJun 18 2011The energy dependence of charged-hadron production in proton-proton collisions at RHIC and LHC energies is investigated in a nonequilibrium-statistical relativistic diffusion model (RDM) with three sources for particle production. Calculated charged-hadron ... More
Beyond the thermal model in relativistic heavy-ion collisionsMay 31 2016Jun 27 2016Deviations from thermal distribution functions of produced particles in relativistic heavy-ion collisions are discussed as indicators for nonequilibrium processes. The focus is on rapidity distributions of produced charged hadrons as functions of collision ... More
On the Expressive Power of Kleene Algebra with DomainJul 26 2015Aug 02 2015It is shown that antidomain semirings are more expressive than test semirings and that Kleene algebras with domain are more expressive than Kleene algebras with tests. It is also shown that Kleene algebras with domain are expressive for propositional ... More
Rooted Trees with Probabilities RevisitedFeb 04 2013Rooted trees with probabilities are convenient to represent a class of random processes with memory. They allow to describe and analyze variable length codes for data compression and distribution matching. In this work, the Leaf-Average Node-Sum Interchange ... More
The faint young Sun problemApr 19 2012For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the `faint young Sun problem'. For the early Earth, models of stellar evolution predict a solar energy input to the ... More
Motion of inertial particles in Gaussian fields driven by an infinite-dimensional fractional Brownian motionMar 18 2012We study the motion of an inertial particle in a fractional Gaussian random field. The motion of the particle is described by Newton's second law, where the force is proportional to the difference between a background fluid velocity and the particle velocity. ... More
Interpolation categories for homology theoriesDec 19 2004Feb 25 2006For a homological functor from a triangulated category to an abelian category satisfying some technical assumptions we construct a tower of interpolation categories. These are categories over which the functor factorizes and which capture more and more ... More
Positivity of relative canonical bundles and applicationsJan 13 2012Given a family $f:\mathcal X \to S$ of canonically polarized manifolds, the unique K\"ahler-Einstein metrics on the fibers induce a hermitian metric on the relative canonical bundle $\mathcal K_{\mathcal X/S}$. We use a global elliptic equation to show ... More
Pymanopt: A Python Toolbox for Optimization on Manifolds using Automatic DifferentiationMar 10 2016Sep 08 2016Optimization on manifolds is a class of methods for optimization of an objective function, subject to constraints which are smooth, in the sense that the set of points which satisfy the constraints admits the structure of a differentiable manifold. While ... More
Hybrid spin and valley quantum computing with singlet-triplet qubitsMar 27 2014Oct 29 2014The valley degree of freedom in the electronic band structure of silicon, graphene, and other materials is often considered to be an obstacle for quantum computing (QC) based on electron spins in quantum dots. Here we show that control over the valley ... More
Quantum Stability for the Heisenberg FerromagnetApr 02 2008Highly spinning classical strings on RxS^3 are described by the Landau-Lifshitz model or equivalently by the Heisenberg ferromagnet in the thermodynamic limit. The spectrum of this model can be given in terms of spectral curves. However, it is a priori ... More
Enumeration of derangements with descents in prescribed positionsNov 12 2008We enumerate derangements with descents in prescribed positions. A generating function was given by Guo-Niu Han and Guoce Xin in 2007. We give a combinatorial proof of this result, and derive several explicit formulas. To this end, we consider fixed point ... More
Invariant Causal Prediction for Sequential DataJun 25 2017May 28 2018We investigate the problem of inferring the causal predictors of a response $Y$ from a set of $d$ explanatory variables $(X^1,\dots,X^d)$. Classical ordinary least squares regression includes all predictors that reduce the variance of $Y$. Using only ... More
Bonus Yangian Symmetry for the Planar S-Matrix of N=4 Super Yang-MillsMar 03 2011Jun 08 2011Recent developments in the determination of the planar S-matrix of N=4 Super Yang-Mills are closely related to its Yangian symmetry. Here we provide evidence for a yet unobserved additional symmetry: the Yangian level-one helicity operator.
Discovery of VHE Gamma-ray Emission from the Starburst Galaxy M82Dec 18 2009Dec 23 2009The galaxy M82 has long been considered a promising target for VHE gamma-ray observations because of the compact starburst region in its core. Theoretical predictions have suggested it should be detectable by ground-based imaging Cherenkov telescopes ... More
Linking a genetic defect in migraine to spreading depression in a computational modelMar 26 2014Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura. A mutation causing FHM type 3 (FHM3) has been identified in SCN1A encoding the Nav1.1 Na$^+$ channel. This genetic defect affects the inactivation gate. While the Na$^+$ tail ... More
Chiral magnetic effect and anomalous transport from real-time lattice simulationsJun 01 2016Sep 26 2016We present a first-principle study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian $SU(N_c)$ and Abelian $U(1)$ gauge fields. Investigating the behavior of ... More
Long-Range Deformations for Integrable Spin ChainsFeb 05 2009Mar 05 2013We present a recursion relation for the explicit construction of integrable spin chain Hamiltonians with long-range interactions. Based on arbitrary short-range (e.g. nearest-neighbor) integrable spin chains, it allows to construct an infinite set of ... More
Getting drowned in a swirl: deformable bead-spring model microswimmers in external flow fieldsOct 08 2015Dec 27 2015Deformability is a central feature of many types of microswimmers, e.g. for artificially generated self-propelled droplets. Here, we analyze deformable bead-spring microswimmers in an externally imposed solvent flow field as simple theoretical model systems. ... More
Finite Element Error Estimates for Optimal Control Problems with Pointwise TrackingFeb 08 2018We consider a linear-quadratic elliptic optimal control problem with point evaluations of the state variable in the cost functional. The state variable is discretized by conforming linear finite elements. For control discretization, three different approaches ... More
Boosting Nearest-Neighbour to Long-Range Integrable Spin ChainsJul 31 2008Aug 27 2012We present an integrability-preserving recursion relation for the explicit construction of long-range spin chain Hamiltonians. These chains are generalizations of the Haldane-Shastry and Inozemtsev models and they play an important role in recent advances ... More
On Yangian-invariant regularisation of deformed on-shell diagrams in N=4 super-Yang-Mills theoryJan 28 2014Aug 26 2014We investigate Yangian invariance of deformed on-shell diagrams with D=4, N=4 superconformal symmetry. We find that invariance implies a direct relationship between the deformation parameters and the permutation associated to the on-shell graph. We analyse ... More
Full-counting statistics of time-dependent conductorsAug 29 2016We develop a scheme for the computation of the full-counting statistics of transport described by Markovian master equations with an arbitrary time dependence. It is based on a hierarchy of generalized density operators, where the trace of each operator ... More
More on coupling coefficients for the most degenerate representations of SO(n)Mar 18 1999Apr 14 1999We present explicit closed-form expressions for the general group-theoretical factor appearing in the alpha-topology of a high-temperature expansion of SO(n)-symmetric lattice models. This object, which is closely related to 6j-symbols for the most degenerate ... More