Results for "Sebastian Schöps"

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Stochastic Modeling and Regularity of the Nonlinear Elliptic Curl-Curl EquationJun 24 2016This paper addresses the nonlinear elliptic curl-curl equation with uncertainties in the material law. It is frequently employed in the numerical evaluation of magnetostatic fields, where the uncertainty is ascribed to the so-called B-H curve. A truncated ... More
Modeling of Spatial Uncertainties in the Magnetic ReluctivityOct 10 2016In this paper a computationally efficient approach is suggested for the stochastic modeling of an inhomogeneous reluctivity of magnetic materials. These materials can be part of electrical machines, such as a single phase transformer (a benchmark example ... More
Multiple Right-Hand Side Techniques in Semi-Explicit Time Integration Methods for Transient Eddy Current ProblemsNov 21 2016The spatially discretized magnetic vector potential formulation of magnetoquasistatic field problems is transformed from an infinitely stiff differential algebraic equation system into a finitely stiff ordinary differential equation (ODE) system by application ... 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
A 2-D Finite-Element Model for Electro-Thermal Transients in Accelerator MagnetsOct 03 2017Dec 05 2017Superconducting accelerator magnets require sophisticated monitoring and means of protection due to the large energy stored in the magnetic field. Numerical simulations play a crucial role in understanding transient phenomena occurring within the magnet, ... More
An Application of ParaExp to Electromagnetic Wave ProblemsJul 01 2016Recently, ParaExp was proposed for the time integration of hyperbolic problems. It splits the time interval of interest into sub-intervals and computes the solution on each sub-interval in parallel. The overall solution is decomposed into a particular ... More
Coupling of Magneto-Thermal and Mechanical Superconducting Magnet Models by Means of Mesh-Based InterpolationDec 29 2017In this paper we present an algorithm for the coupling of magneto-thermal and mechanical finite element models representing superconducting accelerator magnets. The mechanical models are used during the design of the mechanical structure as well as the ... More
Waveform Relaxation for the Computational Homogenization of Multiscale Magnetoquasistatic ProblemsJul 19 2016This paper proposes the application of the waveform relaxation method to the homogenization of multiscale magnetoquasistatic problems. In the monolithic heterogeneous multiscale method, the nonlinear macroscale problem is solved using the Newton--Raphson ... More
STEAM: A Hierarchical Co-Simulation Framework for Superconducting Accelerator Magnet CircuitsJan 26 2018Simulating the transient effects occurring in superconducting accelerator magnet circuits requires including the mutual electro-thermo-dynamic interaction among the circuit elements, such as power converters, magnets, and protection systems. Nevertheless, ... More
A Defect Corrected Finite Element Approach for the Accurate Evaluation of Magnetic Fields on Unstructured GridsNov 25 2016In electromagnetic simulations of magnets and machines one is often interested in a highly accurate and local evaluation of the magnetic field uniformity. Based on local post-processing of the solution, a defect correction scheme is proposed as an easy ... More
Automatic Generation of Equivalent Electrothermal SPICE Netlists from 3D Electrothermal Field ModelsOct 14 2016Starting from a 3D electrothermal field problem discretized by the Finite Integration Technique, the equivalence to a circuit description is shown by exploiting the analogy to the Modified Nodal Analysis approach. Using this analogy, an algorithm for ... More
Determination of Bond Wire Failure Probabilities in Microelectronic PackagesSep 18 2016This work deals with the computation of industry-relevant bond wire failure probabilities in microelectronic packages. Under operating conditions, a package is subject to Joule heating that can lead to electrothermally induced failures. Manufacturing ... More
An Application of ParaExp to Electromagnetic Wave ProblemsJul 01 2016Oct 16 2016Recently, ParaExp was proposed for the time integration of hyperbolic problems. It splits the time interval of interest into sub-intervals and computes the solution on each sub-interval in parallel. The overall solution is decomposed into a particular ... More
Isogeometric Simulation of Lorentz Detuning in Superconducting Accelerator CavitiesJun 27 2016Cavities in linear accelerators suffer from eigenfrequency shifts due to mechanical deformation caused by the electromagnetic radiation pressure, a phenomenon known as Lorentz detuning. Estimating the frequency shift up to the needed accuracy by means ... More
Low-Dimensional Stochastic Modeling of the Electrical Properties of Biological TissuesNov 22 2016Uncertainty quantification plays an important role in biomedical engineering as measurement data is often unavailable and literature data shows a wide variability. Using state-of-the-art methods one encounters difficulties when the number of random inputs ... More
An algorithmic comparison of the Hyper-Reduction and the Discrete Empirical Interpolation Method for a nonlinear thermal problemOct 17 2016An algorithmic summary and comparison of the methodological and numerical properties of competing parametric model reduction techniques is presented for a planar nonlinear thermal conduction problem. First, the Galerkin reduced basis (RB) formulation ... More
Electrothermal Simulation of Bonding Wire Degradation under Uncertain GeometriesOct 14 2016In this paper, electrothermal field phenomena in electronic components are considered. This coupling is tackled by multiphysical field simulations using the Finite Integration Technique (FIT). In particular, the design of bonding wires with respect to ... More
XPath Node Selection over Grammar-Compressed TreesNov 21 2013XML document markup is highly repetitive and therefore well compressible using grammar-based compression. Downward, navigational XPath can be executed over grammar-compressed trees in PTIME: the query is translated into an automaton which is executed ... More
Fast and Tiny Structural Self-Indexes for XMLDec 28 2010XML document markup is highly repetitive and therefore well compressible using dictionary-based methods such as DAGs or grammars. In the context of selectivity estimation, grammar-compressed trees were used before as synopsis for structural XPath queries. ... More
Morse theory and higher torsion invariants IIMay 20 2003Let p: M -> B be a family of compact manifolds equipped with a unitarily flat vector bundle F -> M. We generalize Igusa's higher Franz-Reidemeister torsion \tau(M/B;F) to the case that the fibre-wise cohomology H^*(M/B;F) -> B carries a parallel metric. ... More
On the irreducible representations of generalized quantum doublesFeb 20 2012A description of all the irreducible representations of generalized quantum doubles associated to skew pairings of semisimple Hopf algebras is given. In particular a description of the irreducible representations of semisimple Drinfeld doubles is obtained. ... More
Backward-Backward Splitting in Hadamard SpacesSep 23 2013Sep 30 2013The backward-backward algorithm is a tool for finding minima of a regularization of the sum of two convex functions in Hilbert spaces. We generalize this setting to Hadamard spaces and prove the convergence of an error-tolerant version of the backward-backward ... More
Mellin moments of heavy flavor contributions to F_2(x,Q^2) at NNLOOct 16 2009This thesis is concerned with the calculation of fixed moments of the O(a_s^3) heavy flavor contributions to the Wilson coefficients of the structure function F_2(x,Q^2) in the limit Q^2 >> m^2, neglecting power corrections. The massive Wilson coefficients ... More
One-dimensional quantum wires: A pedestrian approach to bosonizationAug 01 2007Sep 08 2009In these lecture notes we will consider systems in which the motion of electrons is confined to one dimension (1D). In these so-called quantum wires electron-electron interaction effects play an important role because the restricted dimensions enhance ... More
Numerical Evidence for Multiplicative Logarithmic Corrections from Marginal OperatorsFeb 06 1996May 28 1996Field theory calculations predict multiplicative logarithmic corrections to correlation functions from marginally irrelevant operators. However, for the numerically most suitable model - the spin-1/2 chain - these corrections have been controversial. ... More
An Accurate Determination of the Exchange Constant in Sr_2CuO_3 from Recent Theoretical ResultsAug 10 1995Feb 08 1996Data from susceptibility measurements on Sr_2CuO_3 are compared with recent theoretical predictions for the magnetic susceptibility of the antiferromagnetic spin-1/2 Heisenberg chain. The experimental data fully confirms the theoretical predictions and ... More
Accurate variational electronic structure calculations with the density matrix renormalization groupMay 06 2014During the past 15 years, the density matrix renormalization group (DMRG) has become increasingly important for ab initio quantum chemistry. The underlying matrix product state (MPS) ansatz is a low-rank decomposition of the full configuration interaction ... More
R-Matrix Poisson Algebras and Their DeformationsJun 03 2007We classify in this paper Poisson structures on modules over semisimple Lie algebras arising from classical r-matrices. We then study their quantizations and the relation to classical invariant theory.
Equivariant Quantizations of Symmetric AlgebrasOct 12 2008Dec 09 2008Let g be a Lie bialgebra and let V be a finite-dimensional g-module. We study deformations of the symmetric algebra of V which are equivariant with respect to an action of the quantized enveloping algebra of g. In particular we investigate such quantizations ... More
Turbulent spectra in real-time gauge field evolutionDec 12 2008We investigate ultraviolet fixed points in the real-time evolution of non-Abelian gauge fields. Classical-statistical lattice simulations reveal equal-time correlation functions with a spectral index 3/2. Analytical understanding of this result is achieved ... More
Validation of credit default probabilities via multiple testing proceduresJun 25 2010We apply multiple testing procedures to the validation of estimated default probabilities in credit rating systems. The goal is to identify rating classes for which the probability of default is estimated inaccurately, while still maintaining a predefined ... More
Supersymmetry beyond minimal flavour violationAug 14 2008Nov 18 2008We review the sources and phenomenology of non-minimal flavour violation in the MSSM. We discuss in some detail the most important theoretical and experimental constraints, as well as promising observables to look for supersymmetric effects at the LHC ... More
On strategies for determination and characterization of the underlying eventSep 04 2010Sep 22 2010We discuss the problem of the separation and description of the underlying event (UE) within two existing approaches to UE measurement: the "traditional" method, widely used at Tevatron, and a recently proposed jet-area/median method. A simple toy model ... More
Wilson Loops, Bianchi Constraints and Duality in Abelian Lattice ModelsAug 05 1998Nov 18 1998We introduce new modified Abelian lattice models, with inhomogeneous local interactions, in which a sum over topological sectors are included in the defining partition function. The dual models, on lattices with arbitrary topology, are constructed and ... More
Bipartite Field Theories: from D-Brane Probes to Scattering AmplitudesJul 03 2012Dec 20 2012We introduce and initiate the investigation of a general class of 4d, N=1 quiver gauge theories whose Lagrangian is defined by a bipartite graph on a Riemann surface, with or without boundaries. We refer to such class of theories as Bipartite Field Theories ... More
Depth Two Hopf Subalgebras of Semisimple Hopf algebrasJul 18 2008Let H be a finite dimensional semisimple Hopf algebra over an algebraically closed field of characteristic zero. In this note we give a short proof of the fact that a Hopf subalgebra of H is a depth two subalgebra if and only if it is normal Hopf subalgebra. ... More
Categorical Hopf kernels and representations of semisimple Hopf algebrasOct 11 2010In the category of semisimple Hopf algebras the Hopf kernels introduced by Andruskiewitsch and Devoto in \cite{AD} coincide with kernels of representation as introduced in \cite{Bker}. Some new results concerning the normality of kernels are also presented. ... More
Fourier multipliers on weighted $L^p$ spacesMar 18 2014May 13 2014The paper provides a complement to the classical results on Fourier multipliers on $L^p$ spaces. In particular, we prove that if $q\in (1,2)$ and a function $m:\mathbb{R} \rightarrow \mathbb{C}$ is of bounded $q$-variation uniformly on the dyadic intervals ... More
Considerations about Chopper Configuration at a time-of-flight SANS Instrument at a Spallation SourceJun 14 2016In any neutron scattering experiment the measurement of the position of the scattered neutrons and their respective velocities is necessary. In order to do so, a position sensitive detector as well as a way to determine the velocities is needed. Measuring ... More
The Chordal Loewner Equation and Monotone Probability TheoryMay 21 2016Jun 21 2016In [5], O. Bauer interpreted the chordal Loewner equation in terms of non-commutative probability theory. We follow this perspective and identify the chordal Loewner equations as the non-autonomous versions of evolution equations for semigroups in monotone ... More
Second-order perturbation theory for 3He and pd scattering in pionless EFTSep 11 2016This work implements pionless effective field theory with the two-nucleon system expanded around the unitarity limit at second order perturbation theory. The expansion is found to converge well. All Coulomb effects are treated in perturbation theory, ... More
A Projection to the Pure Spinor SpaceFeb 02 2012This article is based on a talk given at the Memorial Conference for Maximilian Kreuzer at the ESI in Vienna and contains a compact summary of a recent collaboration with P.A. Grassi. A non-linear projection from the space of SO(10) Weyl spinors to the ... More
The burnside problem for $\text{Diff}_{\text{Vol}}(\mathbb{S}^2)$Jul 15 2016Let $S$ be a closed surface and $\text{Diff}_{\text{Vol}}(S)$ be the group of volume preserving diffeomorphisms of $S$. A finitely generated group $G$ is periodic of bounded exponent if there exists $k \in \mathbb{N}$ such that every element of $G$ has ... More
Distributed Event-based State EstimationNov 16 2015An event-based state estimation approach for reducing communication in a networked control system is proposed. Multiple distributed sensor-actuator-agents observe a dynamic process and sporadically exchange their measurements and inputs over a bus network. ... More
Polylogarithmic Cuts in Models of V^0Mar 25 2013Mar 29 2013We study initial cuts of models of weak two-sorted Bounded Arithmetics with respect to the strength of their theories and show that these theories are stronger than the original one. More explicitly we will see that polylogarithmic cuts of models of $\mathbf{V}^0$ ... More
Invariance Principle for the Random Conductance Model with dynamic bounded ConductancesFeb 03 2012Oct 11 2012We study a continuous time random walk X in an environment of dynamic random conductances. We assume that the conductances are stationary ergodic, uniformly bounded and bounded away from zero and polynomially mixing in space and time. We prove a quenched ... More
Higher genus minimal surfaces in $S^3$ and stable bundlesMar 27 2009Aug 06 2010We consider compact minimal surfaces $f\colon M\to S^3$ of genus 2 which are homotopic to an embedding. We assume that the associated holomorphic bundle is stable. We prove that these surfaces can be constructed from a globally defined family of meromorphic ... More
Asymptotic Rasmussen InvariantFeb 12 2007We use simple properties of the Rasmussen invariant of knots to study its asymptotic behaviour on the orbits of a smooth volume preserving vector field on a compact domain in the 3-space. A comparison with the asymptotic signature allows us to prove that ... More
On the 3-arrow calculus for homotopy categoriesJan 25 2010Mar 30 2011We develop a localisation theory for certain categories, yielding a 3-arrow calculus: Every morphism in the localisation is represented by a diagram of length 3, and two such diagrams represent the same morphism if and only if they can be embedded in ... More
Composition, collimation, contamination: the jet of Cygnus X-1Sep 26 2005We model the observed size and brightness of the VLBA radio core of the jet in Cygnus X-1 to derive an expression for the jet power as a function of basic jet parameters. We apply this expression to recent constraints on the jet power from observations ... More
Chow groups of tensor triangulated categoriesJan 04 2013Oct 01 2015We recall P. Balmer's definition of tensor triangular Chow group for a tensor triangulated category $\mathcal{K}$ and explore some of its properties. We give a proof that for a suitably nice scheme $X$ it recovers the usual notion of Chow group from algebraic ... More
Non-Coexistence of Infinite Clusters in Two-Dimensional Dependent Site PercolationMar 04 2011Jul 20 2011This paper presents three results on dependent site percolation on the square lattice. First, there exists no positively associated probability measure on {0,1}^{Z^2} with the following properties: a) a single infinite 0cluster exists almost surely, b) ... More
Sharpness of the phase transition and lower bounds for the critical intensity in continuum percolation on $\mathbb{R}^d$Jul 21 2016We consider the Boolean model $Z$ on $\mathbb{R}^d$ with random compact grains, i.e. $Z := \bigcup_{i \in \mathbb{N}} (X_i + Z_i)$ where $\eta_t := \{X_1, X_2, \dots\}$ is a Poisson point process of intensity $t$ and $(Z_1, Z_2, \dots)$ is an i.i.d. sequence ... More
Low-dimensional totally geodesic submanifolds in "skew" position in the symmetric spaces of rank 2Oct 30 2017We use the Cartan representations of $SO(3)$ and $SU(3)$, and an irreducible 14-dimensional representation of $Sp(3)$ to construct certain totally geodesic submanifolds in "skew" position in the complex quadrics, the complex 2-Grassmannians and the quaternionic ... More
BEACH 2014 Theory SummaryJan 30 2015I summarize key aspects of the quest for physics beyond the Standard Model in flavour physics as discussed at the BEACH 2014 conference in Birmingham.
A Note on kappa-Diagonal Surface StatesAug 31 2004We classify all twist-even squeezed states in string field theory which are diagonal in the kappa-basis and simultaneously surface states. For this purpose, we derive a consistency condition for the maps defining kappa-diagonal surface states. It restricts ... More
WZ and W+jets production at large transverse momenta beyond NLOMay 28 2013Jun 09 2013We present a study of higher order QCD corrections beyond NLO to processes with electroweak vector bosons. We focus on the regions of high transverse momenta of commonly used differential distributions. We employ the LoopSim method, combined with NLO ... More
The Yang-Mills Vacuum Wave Functional in 2+1 DimensionsApr 28 2014Aug 23 2014We investigate Yang-Mills theory in 2+1 dimensions in the Schroedinger representation. The Schroedinger picture is interesting because it is well suited to explore properties of the vacuum state in the non-perturbative regime. Yet, not much analytical ... More
On a symmetry of Müger's centralizer for the Drinfeld double of a semisimple Hopf algebraDec 11 2013In this paper we prove a formula that relates M\"uger's centralizer in the category of representations of a factorizable Hopf algebra to the notion of Hopf kernel of a representation of the dual Hopf algebra. Using this relation we obtain a complete description ... More
Morse theory and higher torsion invariants INov 20 2001Jan 09 2003We compare the higher analytic torsion of Bismut and Lott of a fibre bundle p: M -> B equipped with a flat vector bundle F -> M and a fibre-wise Morse function h on M with a higher torsion T that is constructed in terms of a families Thom-Smale complex ... More
Adiabatic limits of Seifert fibrations, Dedekind sums, and the diffeomorphism type of certain 7-manifoldsAug 29 2011We extend the adiabatic limit formula for eta-invariants by Bismut-Cheeger and Dai to Seifert fibrations. Our formula contains a new contribution from the singular fibres that takes the form of a generalised Dedekind sum. As an application, we compute ... More
Dirichlet-to-Neumann and Neumann-to-Dirichlet methods for bound states of the Helmholtz equationFeb 25 2011Two methods for computing bound states of the Helmholtz equation in a finite domain are presented. The methods are formulated in terms of the Dirichlet-to-Neumann (DtN) and Neumann-to-Dirichlet (NtD) surface integral operators. They are adapted from the ... More
Scanning Tunneling Microscopy of a Luttinger LiquidAug 31 1999May 02 2000Explicit predictions for Scanning Tunneling Microscopy (STM) on interacting one-dimensional electron systems are made using the Luttinger liquid formalism. The STM current changes with distance from an impurity or boundary in a characteristic way, which ... More
Improved Information Gain Estimates for Decision Tree InductionJun 18 2012Ensembles of classification and regression trees remain popular machine learning methods because they define flexible non-parametric models that predict well and are computationally efficient both during training and testing. During induction of decision ... More
Braided Symmetric Algebras of Simple $U_q(sl_2)$-Modules and Their GeometrySep 15 2010Feb 29 2012In the present paper we prove decomposition formulae for the braided symmetric powers of simple modules over the quantized enveloping algebra $U_q(sl_2)$; natural quantum analogues of the classical symmetric powers of a module over a complex semisimple ... More
Spectroscopic Measurements Using the H1 and ZEUS DetectorsJun 08 2005Results on spectroscopy from the H1 and ZEUS collaborations are presented. The main focus is to search for baryon states which could be interpreted as pentaquarks. This includes states decaying to K^0_sp and K^0_s\bar{p}, \Xi\pi and D*p. In addition an ... More
Normal Hopf subalgebras of semisimple Drinfeld doublesMay 17 2010Jan 30 2013A description of all normal Hopf subalgebras of a semisimple Drinfeld double is given. This is obtained by considering an analogue of Goursat's lemma concerning fusion subcategories of Deligne products of two fusion categories. As an application we show ... More
T-Duality in Lattice Regularized Sigma ModelsMay 29 1998It is shown that when the underlying sigma model of bosonic string theory is written in terms of single-valued fields, which live in the covering space of the target space, Abelian T-duality survives lattice regularization of the world-sheet. The projection ... More
$L^{p}-L^{q}$ theory for holomorphic functions of perturbed first order Dirac operatorsMar 21 2014Sep 09 2014The aim of the article is to prove $L^{p}-L^{q}$ off-diagonal estimates and $L^{p}-L^{q}$ boundedness for operators in the functional calculus of certain perturbed first order differential operators of Dirac type for with $p\le q$ in a certain range of ... More
Predictive and Self Triggering for Event-based State EstimationSep 23 2016Event-based state estimation can achieve estimation quality comparable to traditional time-triggered methods, but with a significantly lower number of samples. In networked estimation problems, this reduction in sampling instants does, however, not necessarily ... More
QCD and Jets at Hadron CollidersNov 30 2015Sep 13 2016We review various aspects of jet physics in the context of hadron colliders. We start by discussing the definitions and properties of jets and recent development in this area. We then consider the question of factorization for processes with jets, in ... More
The S-Matrix of superstring field theoryJul 29 2015We show that the classical S-matrix calculated from the recently proposed superstring field theories give the correct perturbative S-matrix. In the proof we exploit the fact that the vertices are obtained by a field redefinition in the large Hilbert space. ... More
Frustrated polaritonsFeb 05 2016Artificially engineered light-matter systems constitute a novel, versatile architecture for the quantum simulation of driven, dissipative phase transitions and non-equilibrium quantum many-body systems. Here, we review recent experimental as well as theoretical ... More
The Fixed Points of the Multivariate Smoothing TransformSep 03 2013Nov 24 2014Let $N,d > 1$ be fixed integers, let $(T_1, ..., T_N)$ be random d-by-d matrices with nonnegative entries and $Q$ a random d-vector with nonnegative entries. This induces a mapping (the multivariate smoothing transform) on probability laws on the nonnegative ... More
Totally geodesic submanifolds of the complex quadricMar 07 2006In this article, relations between the root space decomposition of a Riemannian symmetric space of compact type and the root space decompositions of its totally geodesic submanifolds (symmetric subspaces) are described. These relations provide an approach ... More
Lawson's genus two minimal surface and meromorphic connectionsSep 28 2010We investigate the Lawson genus $2$ surface by methods from integrable system theory. We prove that the associated family of flat connections comes from a family of flat connections on a $4-$punctured sphere. We describe the symmetries of the holonomy ... More
Lifting SU(3)-structures to nearly parallel G_{2}-structuresJul 13 2007Hitchin shows that half-flat SU(3)-structures on a 6-dimensional manifold M can be lifted to parallel G_{2}-structure on the product $M\times\mathbb{R}$. We show that Hitchin's approach can also be used to construct nearly parallel G_{2}-structures by ... More
A control approach to recover the wave speed (conformal factor) from one measurementJan 27 2014Jan 08 2015In this paper we consider the problem of recovering the conformal factor in a conformal class of Riemannian metrics from the boundary measurement of one wave field. More precisely, using boundary control operators, we derive an explicit equation satisfied ... More
Categorical Green functors arising from group actions on categoriesJul 15 2014In this paper we introduce the notion of a categorical Mackey functor. This categorical notion allows us to obtain new Mackey functors by passing to Quillen's $K$-theory of the corresponding abelian categories. In the case of an action by monoidal autoequivalences ... More
Post-Newtonian approximation of the Vlasov-Nordström systemOct 23 2004We study the Nordstr\"om-Vlasov system which describes the dynamics of a self-gravitating ensemble of collisionless particles in the framework of the Nordstr\"om scalar theory of gravitation. If the speed of light $c$ is considered as a parameter, it ... More
Poisson and quantum geometry of acyclic cluster algebrasOct 22 2012We prove that certain acyclic cluster algebras over the complex numbers are the coordinate rings of holomorphic symplectic manifolds. We also show that the corresponding quantum cluster algebras have no non-trivial prime ideals. This allows us to give ... More
Dynamical sensitivity of recurrence and transience of branching random walksJul 27 2009Dec 07 2009Consider a sequence of i.i.d. random variables $X_n$ where each random variable is refreshed independently according to a Poisson clock. At any fixed time $t$ the law of the sequence is the same as for the sequence at time 0 but at random times almost ... More
Recurrence for branching Markov chainsOct 25 2007Nov 12 2008The question of recurrence and transience of branching Markov chains is more subtle than for ordinary Markov chains; they can be classified in transience, weak recurrence, and strong recurrence. We review criteria for transience and weak recurrence and ... More
Black hole entropy and thermodynamics from symmetriesApr 22 2002Apr 29 2002Given a boundary of spacetime preserved by a Diff(S^{1}) sub-algebra, we propose a systematic method to compute the zero mode and the central extension of the associated Virasoro algebra of charges. Using these values in the Cardy formula, we may derive ... More
A non-relativistic Model of Plasma Physics Containing a Radiation Reaction TermApr 20 2016While a fully relativistic collisionless plasma is modeled by the Vlasov-Maxwell system a good approximation in the non-relativistic limit is given by the Vlasov-Poisson system. We modify the Vlasov-Poisson system so that damping due to the relativistic ... More
Discrete Möbius EnergyNov 13 2013May 19 2014We investigate a discrete version of the M\"obius energy, that is of geometric interest in its own right and is defined on equilateral polygons with $n$ segments. We show that the $\Gamma$-limit regarding $L^{q}$ or $W^{1,q}$ convergence, $q\in [1,\infty]$ ... More
String States on AdS_3 x S^3 from the SupergroupAug 01 2012Oct 24 2012In the hybrid formulation of string theory on AdS_3 x S^3, the compactification-independent physical spectrum at the first massive level is determined. We find that these states transform in representations of the Lie superalgebra psl(2|2) and present ... More
Towards a Data Reduction for the Minimum Flip Supertree ProblemApr 22 2011In computational phylogenetics, the problem of constructing a supertree of a given set of rooted input trees can be formalized in different ways, to cope with contradictory information in the input. We consider the Minimum Flip Supertree problem, where ... More
Determining Aschbacher classes using charactersFeb 26 2014Let $\Delta\colon G \to \mathrm{GL}(n, K)$ be an absolutely irreducible representation of an arbitrary group $G$ over an arbitrary field $K$; let $\chi\colon G \to K\colon g \mapsto \mathrm{tr}(\Delta(g))$ be its character. In this paper, we assume knowledge ... More
Surgery stable curvature conditionsMar 26 2013We give a simple criterion for a pointwise curvature condition to be stable under surgery. Namely, a curvature condition $C$, which is understood to be an open, convex, O(n)-invariant cone in the space of algebraic curvature operators, is stable under ... More
New examples of Green functors arising from representation theory of semisimple Hopf algebrasAug 05 2012Aug 13 2013A general Mackey type decomposition for representations of semisimple Hopf algebras is investigated. We show that such a decomposition occurs in the case that the module is induced from an arbitrary Hopf subalgebra and it is restricted back to a group ... More
Geometric interpretations of a counterexample to Hilbert's 14th problem, and rings of bounded polynomials on semialgebraic setsMay 10 2011Dec 31 2012We interpret a counterexample to Hilbert's 14th problem by S. Kuroda geometrically in two ways: As ring of regular functions on a smooth rational quasiprojective variety over any field K of characteristic 0, and, in the special case where K are the real ... More
An L2-quotient algorithm for finitely presented groups on arbitrarily many generatorsFeb 27 2014We generalize the Plesken-Fabia\'nska $\mathrm{L}_2$-quotient algorithm for finitely presented groups on two or three generators to allow an arbitrary number of generators. The main difficulty lies in a constructive description of the invariant ring of ... More
B_s-B_s-bar mixing and lepton flavor violation in SUSY SO(10)May 27 2005We present a quantitative analysis of the flavor physics of a SUSY SO(10) model proposed by Chang, Masiero, and Murayama, linking b -> s transitions to the large observed atmospheric neutrino mixing. We consider B_s-B_s-bar mixing and tau -> mu gamma ... More
Kernels of representations and coideal subalgebras of Hopf algebrasDec 14 2010We define left and right kernels of representations of Hopf algebras. In the case of group algebras, left and right kernels coincide and they are the usual kernels of modules. In the general case we show that these kernels coincide with the categorical ... More
Tangency properties of sets with finite geometric curvature energiesFeb 02 2012Apr 03 2012We investigate inverse thickness $1/\Delta$ and the integral Menger curvature energies $\mathcal{U}_{p}^{\alpha}$, $\mathcal{I}_{p}^{\alpha}$ and $\mathcal{M}_{p}^{\alpha}$, to find that finite $1/\Delta$ or $\mathcal{U}_{p}^{\alpha}$ implies the existence ... More
Information Theoretic Resources in Quantum TheoryMar 19 2013Resource identification and quantification is an essential element of both classical and quantum information theory. Entanglement is one of these resources, arising when quantum communication and nonlocal operations are expensive to perform. In the first ... More
Quantifying entanglement when measurements are imperfect or restrictedNov 19 2010Oct 30 2012Motivated by the increasing ability of experimentalists to perform detector tomography, we consider how to incorporate the imperfections and restrictions of available measurements directly into the quantification of entanglement. Exploiting the idea that ... More
A simple test for the existence of two accretion modes in Active Galactic NucleiFeb 20 2005By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion ... More
Dimer Models, Integrable Systems and Quantum Teichmuller SpaceMay 09 2011Jul 05 2011We introduce a correspondence between dimer models (and hence superconformal quivers) and the quantum Teichmuller space of the Riemann surfaces associated to them by mirror symmetry. Via the untwisting map, every brane tiling gives rise to a tiling of ... More