Results for "Christian Daniel"

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Line defects in Graphene: How doping affects the electronic and mechanical propertiesJan 25 2016Graphene and carbon nanotubes have extraordinary mechanical and electronic properties. Intrinsic line defects such as local non-hexagonal reconstructions or grain boundaries, however, significantly reduce the tensile strength, but feature exciting electronic ... More
Quasi-Variational Inequalities in Banach Spaces: Theory and Augmented Lagrangian MethodsSep 30 2018Dec 03 2018This paper deals with quasi-variational inequality problems (QVIs) in a generic Banach space setting. We provide a theoretical framework for the analysis of such problems which is based on two key properties: the pseudomonotonicity (in the sense of Brezis) ... More
The Falicov-Kimball modelFeb 17 2005Aug 12 2005This is a review for Elsevier's Encyclopedia of mathematical physics.
Hamiltonian actions of unipotent groups on compact Kähler manifoldsMay 07 2018Nov 08 2018We study meromorphic actions of unipotent complex Lie groups on compact K\"ahler manifolds using moment map techniques. We introduce natural stability conditions and show that sets of semistable points are Zariski-open and admit geometric quotients that ... More
Augmented Lagrangian Methods for the Solution of Generalized Nash Equilibrium ProblemsJul 12 2018We propose an augmented Lagrangian-type algorithm for the solution of generalized Nash equilibrium problems (GNEPs). Specifically, we discuss the convergence properties with regard to both feasibility and optimality of limit points. This is done by introducing ... More
Base manifolds for Lagrangian fibrations on hyperkähler manifoldsMar 15 2013Jun 05 2013We show that the base manifold of a Lagrangian fibration on a hyperk\"ahler manifold is isomorphic to complex projective space. This generalises a theorem of J.-M. Hwang to the K\"ahler case.
Erdős-Szekeres and Testing Weak epsilon-Nets are NP-hard in 3 dimensions - and what now?Nov 25 2011We consider the computational versions of the Erd\H os-Szekeres theorem and related problems in 3 dimensions. We show that, in constrast to the planar case, no polynomial time algorithm exists for determining the largest (empty) convex subset (unless ... More
On the perturbation of positive semigroupsJul 17 2013We prove a perturbation result for positive semigroups, thereby extending a heat kernel estimate by Barlow, Grigor'yan and Kumagai for Dirichlet forms (\cite{bgk2009}) to positive semigroups. This also leads to a generalization of domination for semigroups ... More
Numerical integrators for motion under a strong constraining forceMar 17 2014Jul 22 2014This paper deals with the numerical integration of Hamiltonian systems in which a stiff anharmonic potential causes highly oscillatory solution behavior with solution-dependent frequencies. The impulse method, which uses micro- and macro-steps for the ... More
Singular (Lipschitz) homology and homology of integral currentsFeb 23 2009We compare the homology groups $H_n ^{IC}(X)$ of the chain complex of integral currents with compact support of a metric space $X$ with the singular Lipschitz homology $H^L_n (X)$ and with ordinary singular homology. If $X$ satisfies certain cone inequalities ... More
Marginalization in nonlinear mixed-effects models with an application to dose-response analysisJul 08 2017Inference in hierarchical nonlinear models needs careful consideration about targeting parameters that have either a conditional or population-average interpretation. For the special case of mixed-effects nonlinear sigmoidal models we propose a method ... More
On Error Bounds and Multiplier Methods for Variational Problems in Banach SpacesJul 11 2018This paper deals with a general form of variational problems in Banach spaces which encompasses variational inequalities as well as minimization problems. We prove a characterization of local error bounds for the distance to the (primal-dual) solution ... More
Invariant meromorphic functions on Stein spacesOct 14 2010In this paper we develop fundamental tools and methods to study meromorphic functions in an equivariant setup. As our main result we construct quotients of Rosenlicht-type for Stein spaces acted upon holomorphically by complex-reductive Lie groups and ... More
Electromagnetic Potential in Pre-Metric Electrodynamics: Causal Structure, Propagators and QuantizationFeb 02 2016Aug 03 2016An axiomatic approach to electrodynamics reveals that Maxwell electrodynamics is just one instance of a variety of theories for which the name electrodynamics is justified. They all have in common that their fundamental input are Maxwell's equations $\textrm{d} ... More
Some determinants of path generating functions, IIFeb 16 2018Aug 28 2018We evaluate Hankel determinants of matrices in which the entries are generating functions for paths consisting of up-steps, down-steps and level steps with a fixed starting point but variable end point. By specialisation, these determinant evaluations ... More
Computational Analysis of Composition-Structure-Property-Relationships in NZP-type Materials for Li-Ion BatteriesJan 28 2019Compounds crystallizing in the structure of NaZr$_2$(PO$_4$)$_3$ (NZP) are considered as promising materials for solid state electrolytes in Li-ion batteries. Using density functional theory (DFT), a systematic computational screening of 18 NZP compounds, ... More
An Augmented Lagrangian Method for Optimization Problems in Banach SpacesJul 12 2018We propose a variant of the classical augmented Lagrangian method for constrained optimization problems in Banach spaces. Our theoretical framework does not require any convexity or second-order assumptions and allows the treatment of inequality constraints ... More
Infrared Behaviour and Running Couplings in Interpolating Gauges in QCDApr 26 2005Aug 22 2005We consider the class of gauges that interpolates between Landau- and Coulomb-gauge QCD, and show the non-renormalisation of the two independent ghost-gluon vertices. This implies the existence of two RG-invariant running couplings, one of which is interpreted ... More
Lagrangian fibrations on hyperkähler fourfoldsOct 12 2011Nov 07 2012Let X be a projective hyperk\"ahler manifold containing a Lagrangian subtorus L. We study intersections of deformations of L, defining a canonical almost holomorphic map called L-reduction, which is not birational if and only if X admits an almost holomorphic ... More
Magnetoconductance switching in an array of oval quantum dotsApr 24 2009Employing oval shaped quantum billiards connected by quantum wires as the building blocks of a linear quantum dot array, we calculate the ballistic magnetoconductance in the linear response regime. Optimizing the geometry of the billiards, we aim at a ... More
An algebra generated by $x - 2$May 05 2016Jun 13 2016By a theorem of R. Stanley, a graded Cohen-Macaulay domain $A$ is Gorenstein if and only if its Hilbert series satisfies the functional equation \[ \operatorname{Hilb}_A(t^{-1})=(-1)^d t^{-a}\operatorname{Hilb}_A(t), \] where $d$ is the Krull dimension ... More
Hamiltonian and primary constraints of new general relativityNov 27 2018May 03 2019We derive the kinematic Hamiltonian for the so-called "new general relativity" class of teleparallel gravity theories, which is the most general class of theories whose Lagrangian is quadratic in the torsion tensor and does not contain parity violating ... More
Dynamical Decoupling and Homogenization of continuous variable systemsMay 19 2016Mar 08 2017For finite-dimensional quantum systems, such as qubits, a well established strategy to protect such systems from decoherence is dynamical decoupling. However many promising quantum devices, such as oscillators, are infinite dimensional, for which the ... More
Zero measure Cantor spectra for continuum one-dimensional quasicrystalsAug 15 2013We study Schr\"odinger operators on $\R$ with measures as potentials. Choosing a suitable subset of measures we can work with a dynamical system consisting of measures. We then relate properties of this dynamical system with spectral properties of the ... More
Robust classification of salient links in complex networksOct 18 2011May 31 2012Complex networks in natural, social, and technological systems generically exhibit an abundance of rich information. Extracting meaningful structural features from data is one of the most challenging tasks in network theory. Many methods and concepts ... More
On Mordell-Weil groups and congruences between derivatives of twisted Hasse-Weil L-functionsMay 18 2015Let A be an abelian variety defined over a number field k and let F be a finite Galois extension of k. Let p be a prime number. Then under certain not-too-stringent conditions on A and F we compute explicitly the algebraic part of the p-component of the ... More
The MSW Effect in Quantum Field TheoryApr 12 1999We show in detail the general relationship between the Schr\"{o}dinger equation approach to calculating the MSW effect and the quantum field theoretical S-matrix approach. We show the precise form a generic neutrino propagator must have to allow a physically ... More
The Standard Model Higgs as the origin of the hot Big BangApr 13 2016Jun 29 2017If the Standard Model (SM) Higgs is weakly coupled to the inflationary sector, the Higgs is expected to be universally in the form of a condensate towards the end of inflation. The Higgs decays rapidly after inflation - via non-perturbative effects - ... More
Quantum Energy Inequalities in Pre-Metric ElectrodynamicsSep 06 2017Oct 04 2017Pre-metric electrodynamics is a covariant framework for electromagnetism with a general constitutive law. Its lightcone structure can be more complicated than that of Maxwell theory as is shown by the phenomenon of birefringence. We study the energy density ... More
Lagrangian fibrations on hyperkähler manifolds - On a question of BeauvilleMay 17 2011Nov 08 2012Let X be a compact hyperk\"ahler manifold containing a complex torus L as a Lagrangian subvariety. Beauville posed the question whether X admits a Lagrangian fibration with fibre L. We show that this is indeed the case if X is not projective. If X is ... More
Megahertz Schlieren Imaging of Shock Structure and Sound Waves in Under-Expanded, Impinging JetsOct 15 2010The accompanying fluid dynamics videos visualize the temporal evolution of shock structures and sound waves in and around an under-expanded jet that is impinging on a rigid surface at varying pressure ratios. The recordings were obtained at frame rates ... More
A continuous-time diffusion limit theorem for dynamical decoupling and intrinsic decoherenceMay 29 2014Apr 13 2015We discuss a few mathematical aspects of random dynamical decoupling, a key tool procedure in quantum information theory. In particular, we place it in the context of discrete stochastic processes, limit theorems and CPT semigroups on matrix algebras. ... More
Agent-Based Simulation Modelling for Reflecting on Consequences of Digital Mental HealthFeb 05 2019The premise of this working paper is based around agent-based simulation models and how to go about creating them from given incomplete information. Agent-based simulations are stochastic simulations that revolve around groups of agents that each have ... More
Stock prices, inflation and inflation uncertainty in the U.S.: Testing the long-run relationship considering Dow Jones sector indexesMar 03 2016We test for the long-run relationship between stock prices, inflation and its uncertainty for different U.S. sector stock indexes, over the period 2002M7 to 2015M10. For this purpose we use a cointegration analysis with one structural break to capture ... More
Mechanisms for p-type behavior of ZnO, Zn$_{1-x}$Mg$_x$O and related oxide semiconductorsFeb 24 2016Possibilities of turning intrinsically n-type oxide semiconductors like ZnO and Zn$_{1-x}$Mg$_x$O into p-type materials are investigated. Motivated by recent experiments on Zn$_{1-x}$Mg$_x$O doped with nitrogen we analyze the electronic defect levels ... More
Model sets with positive entropy in Euclidean cut and project schemesMay 04 2016We construct model sets arising from cut and project schemes in Euclidean spaces whose associated Delone dynamical systems have positive toplogical entropy. The construction works both with windows that are proper and with windows that have empty interior. ... More
Comment on new physics contributions to Gamma_{12}^sJun 08 2010Jun 29 2010A recent measurement by the D0 collaboration finds a like-sign di-muon charge asymmetry in the B system that is roughly 3 sigma larger than the value predicated by the Standard Model. This suggests new physics contributing to B-Bbar mixing. For the current ... More
Hamiltonian and primary constraints of new general relativityNov 27 2018We derive the kinematic Hamiltonian for the so called "new general relativity" class of teleparallel gravity theories, which is the most general non-parity violating class of theories whose Lagrangian is quadratic in the torsion tensor. Our approach makes ... More
Defect turbulence and generalized statistical mechanicsFeb 28 2003We present experimental evidence that the motion of point defects in thermal convection patterns in an inclined fluid layer is well-described by Tsallis statistics with an entropic index $q \approx 1.5$. The dynamical properties of the defects (anomalous ... More
Algorithmic counting of nonequivalent compact Huffman codesJan 31 2019It is known that the following five counting problems lead to the same integer sequence~$f_t(n)$: the number of nonequivalent compact Huffman codes of length~$n$ over an alphabet of $t$ letters, the number of `nonequivalent' canonical rooted $t$-ary trees ... More
Simulations of Bunch Merging in a Beta Beam Decay RingSep 08 2011To further study neutrino oscillation properties a Beta Beam facility has been proposed. Beta decaying ions with high kinetic energy are stored in a storage ring ("Decay Ring") with straight sections to create pure focused (anti) electron neutrino beams. ... More
Fixed Parameter Complexity and Approximability of Norm MaximizationJul 24 2013The problem of maximizing the $p$-th power of a $p$-norm over a halfspace-presented polytope in $\R^d$ is a convex maximization problem which plays a fundamental role in computational convexity. It has been shown in 1986 that this problem is $\NP$-hard ... More
Control of open quantum systems: Case study of the central spin modelNov 30 2013We study the controllability of a central spin guided by a classical field and interacting with a spin bath, showing that the central spin is fully controllable independently of the number of bath spins. Additionally we find that for unequal system-bath ... More
The Price of Gold: Curiosity?May 02 2019Gold open access as characterised by the payment of an article processing charge (APC) has become one of the dominant models in open access publication. This paper examines an extreme hypothetical case in which the APC model is the only model and the ... More
Algorithmic counting of nonequivalent compact Huffman codesJan 31 2019Aug 02 2019It is known that the following five counting problems lead to the same integer sequence~$f_t(n)$: the number of nonequivalent compact Huffman codes of length~$n$ over an alphabet of $t$ letters, the number of `nonequivalent' canonical rooted $t$-ary trees ... More
Functional error estimators for the adaptive discretization of inverse problemsJul 29 2015Aug 31 2016So-called functional error estimators provide a valuable tool for reliably estimating the discretization error for a sum of two convex functions. We apply this concept to Tikhonov regularization for the solution of inverse problems for partial differential ... More
An Interpolation Procedure for List Decoding Reed--Solomon codes Based on Generalized Key EquationsOct 18 2011The key step of syndrome-based decoding of Reed-Solomon codes up to half the minimum distance is to solve the so-called Key Equation. List decoding algorithms, capable of decoding beyond half the minimum distance, are based on interpolation and factorization ... More
Evolution of holographic entanglement entropy in an anisotropic systemJun 08 2015Jun 19 2015We determine holographically 2-point correlators of gauge invariant operators with large conformal weights and entanglement entropy of strips for a time-dependent anisotropic 5-dimensional asymptotically anti-de Sitter spacetime. At the early stage of ... More
Critical Transitions in Social Network ActivityJul 31 2013Nov 13 2013A large variety of complex systems in ecology, climate science, biomedicine and engineering have been observed to exhibit tipping points, where the internal dynamical state of the system abruptly changes. For example, such critical transitions may result ... More
Dynamical Decoupling and Homogenization of continuous variable systemsMay 19 2016For finite-dimensional quantum systems, such as qubits, a well established strategy to protect such systems from decoherence is dynamical decoupling. However many promising quantum devices, such as oscillators, are infinite dimensional, for which the ... More
The Standard Model Higgs as the origin of the hot Big BangApr 13 2016If the Standard Model (SM) Higgs is weakly coupled to the inflationary sector, the Higgs is expected to be universally in the form of a condensate towards the end of inflation. The Higgs decays rapidly after inflation -- via non-perturbative effects -- ... More
Functional error estimators for the adaptive discretization of inverse problemsJul 29 2015Feb 10 2017So-called functional error estimators provide a valuable tool for reliably estimating the discretization error for a sum of two convex functions. We apply this concept to Tikhonov regularization for the solution of inverse problems for partial differential ... More
On the Galois structure of Selmer groupsMay 18 2015Let A be an abelian variety defined over a number field k and F a finite Galois extension of k. Let p be a prime number. Then under certain not-too-stringent conditions on A and F we investigate the explicit Galois structure of the p-primary Selmer group ... More
Generalized Berezin quantization, Bergman metrics and fuzzy LaplaciansApr 29 2008Sep 09 2008We study extended Berezin and Berezin-Toeplitz quantization for compact Kaehler manifolds, two related quantization procedures which provide a general framework for approaching the construction of fuzzy compact Kaehler geometries. Using this framework, ... More
On the gauge fixing in the Hamiltonian analysis of general teleparallel theoriesMay 03 2019The covariant formulation of teleparallel gravity theories must include the spin connection, which has 6 degrees of freedom. One can, however, always choose a gauge such that the spin connection is put to zero. In principle this gauge may affect counting ... More
On compositions with $x^2/(1-x)$Apr 03 2014In the past, empirical evidence has been presented that Hilbert series of symplectic quotients of unitary representations obey a certain universal system of infinitely many constraints. Formal series with this property have been called \emph{symplectic}. ... More
Using clustering of rankings to explain brand preferences with personality and socio-demographic variablesApr 04 2017The primary aim of market segmentation is to identify relevant groups of consumers that can be addressed efficiently by marketing or advertising campaigns. This paper addresses the issue whether consumer groups can be identified from background variables ... More
Uniformity of hitting times of the contact processApr 29 2017For the supercritical contact process on the hyper-cubic lattice started from a single infection at the origin and conditioned on survival, we establish two uniformity results for the hitting times $t(x)$, defined for each site $x$ as the first time at ... More
The Laurent coefficients of the Hilbert series of a Gorenstein algebraMay 05 2016Nov 01 2017By a theorem of R. Stanley, a graded Cohen-Macaulay domain $A$ is Gorenstein if and only if its Hilbert series satisfies the functional equation \[ \operatorname{Hilb}_A(t^{-1})=(-1)^d t^{-a}\operatorname{Hilb}_A(t), \] where $d$ is the Krull dimension ... More
Fourth generation quark mass limits in CKM-element spaceJan 25 2011We present a reanalysis of CDF data to extend limits on individual fourth-generation quark masses from particular flavor-mixing rates to the entire space of possible mixing values. Measurements from CDF have set individual limits on masses, $m_{b'}$ and ... More
Magnetic field-induced control of transport in multiterminal focusing quantum billiardsDec 19 2010Mar 02 2011By exploring the four-terminal transmission of a semi-elliptic open quantum billiard in dependence of its geometry and an applied magnetic field, it is shown that a controllable switching of currents between the four terminals can be obtained. Depending ... More
Singleton physicsJan 12 1999We review the developments in the past twenty years (which are based on our deformation philosophy of physical theories) dealing with elementary particles composed of singletons in anti De Sitter space-time. The study starts with the kinematical aspects ... More
The Spherically Symmetric Standard Model with GravityDec 21 2004Spherical reduction of generic four-dimensional theories is revisited. Three different notions of "spherical symmetry" are defined. The following sectors are investigated: Einstein-Cartan theory, spinors, (non-)abelian gauge fields and scalar fields. ... More
Generalized Berezin-Toeplitz quantization of Kaehler supermanifoldsNov 28 2008May 15 2009We extend the construction of generalized Berezin and Berezin-Toeplitz quantization to the case of compact Hodge supermanifolds. Our approach is based on certain super-analogues of Rawnsley's coherent states. As applications, we discuss the quantization ... More
Model sets with positive entropy in Euclidean cut and project schemesMay 04 2016Jun 25 2018We construct model sets arising from cut and project schemes in Euclidean spaces whose associated Delone dynamical systems have positive toplogical entropy. The construction works both with windows that are proper and with windows that have empty interior. ... More
Hilbert series associated to symplectic quotients by $\operatorname{SU}_2$Sep 20 2018We compute the Hilbert series of the graded algebra of real regular functions on the symplectic quotient associated to an $\operatorname{SU}_2$-module and give an explicit expression for the first nonzero coefficient of the Laurent expansion of the Hilbert ... More
Relaxation schemes for mathematical programs with switching constraintsSep 07 2018Switching-constrained optimization problems form a difficult class of mathematical programs since their feasible set is almost disconnected while standard constraint qualifications are likely to fail at several feasible points. That is why the application ... More
The A-theoretic Farrell-Jones Conjecture for virtually solvable groupsSep 23 2016We prove the A-theoretic Farrell-Jones Conjecture for virtually solvable groups. As a corollary, we obtain that the conjecture holds for S-arithmetic groups and lattices in almost connected Lie groups.
Fixed-parameter tractability and lower bounds for stabbing problemsJun 21 2009We study the following general stabbing problem from a parameterized complexity point of view: Given a set $\mathcal S$ of $n$ translates of an object in $\Rd$, find a set of $k$ lines with the property that every object in $\mathcal S$ is ''stabbed'' ... More
Pinning of Fermionic Occupation Numbers: General Concepts and One DimensionFeb 16 2016Analytical evidence for the physical relevance of generalized Pauli constraints (GPCs) has recently been provided in [PRL 110, 040404]: Natural occupation numbers $\vec{\lambda}\equiv (\lambda_i)$ of the ground state of a model system in the regime of ... More
On the spectrum of operator families on discrete groups over minimal dynamical systemsJun 27 2016It is well known that, given an equivariant and continuous (in a suitable sense) family of selfadjoint operators in a Hilbert space over a minimal dynamical system, the spectrum of all operators from that family coincides. As shown recently similar results ... More
Finding the Rashba-type spin-splitting from interband scattering in quasiparticle interference mapsJun 27 2013We have studied the BiCu$_2$/Cu(111) surface alloy using low-temperature scanning tunneling microscopy and spectroscopy. We observed standing waves caused by scattering off defects and step edges. Different from previous studies on similar Rashba-type ... More
Strong Homotopy Lie Algebras, Generalized Nahm Equations and Multiple M2-branesJan 26 2009We review various generalizations of the notion of Lie algebras, in particular those appearing in the recently proposed Bagger-Lambert-Gustavsson model, and study their interrelations. We find that Filippov's n-Lie algebras are a special case of strong ... More
Scalable Edge PartitioningAug 20 2018Oct 11 2018Edge-centric distributed computations have appeared as a recent technique to improve the shortcomings of think-like-a-vertex algorithms on large scale-free networks. In order to increase parallelism on this model, edge partitioning - partitioning edges ... More
Long-Duration Autonomy for Small Rotorcraft UAS including RechargingOct 12 2018Many unmanned aerial vehicle surveillance and monitoring applications require observations at precise locations over long periods of time, ideally days or weeks at a time (e.g. ecosystem monitoring), which has been impractical due to limited endurance ... More
Quantum simulation of dark energy candidatesNov 16 2018May 13 2019Additional scalar fields from scalar-tensor, modified gravity or higher dimensional theories beyond general relativity may account for dark energy and the accelerating expansion of the Universe. These theories have lead to proposed models of screening ... More
Saturation of the Quantum Null Energy Condition in Far-From-Equilibrium SystemsOct 26 2017The Quantum Null Energy Condition (QNEC) is a new local energy condition that a general Quantum Field Theory (QFT) is believed to satisfy, relating the classical null energy condition (NEC) to the second functional derivative of the entanglement entropy ... More
Open Set Logo Detection and RetrievalOct 30 2017Current logo retrieval research focuses on closed set scenarios. We argue that the logo domain is too large for this strategy and requires an open set approach. To foster research in this direction, a large-scale logo dataset, called Logos in the Wild, ... More
Efficient High-Speed WPA2 Brute Force Attacks using Scalable Low-Cost FPGA Clustering [Extended Version]May 25 2016WPA2-Personal is widely used to protect Wi-Fi networks against illicit access. While attackers typically use GPUs to speed up the discovery of weak network passwords, attacking random passwords is considered to quickly become infeasible with increasing ... More
Efficient implementation of the Localized Orthogonal Decomposition methodFeb 04 2016Feb 20 2019In this paper we present algorithms for an efficient implementation of the Localized Orthogonal Decomposition method (LOD). The LOD is a multiscale method for the numerical simulation of partial differential equations with a continuum of inseparable scales. ... More
Distinguishing decoherence from alternative quantum theories by dynamical decouplingMay 29 2014Aug 03 2015A longstanding challenge in the foundations of quantum mechanics is the verification of alternative collapse theories despite their mathematical similarity to decoherence. To this end, we suggest a novel method based on dynamical decoupling. Experimental ... More
The Hilbert series and $a$-invariant of circle invariantsJul 11 2017Let $V$ be a finite-dimensional representation of the complex circle $\mathbb{C}^\times$ determined by a weight vector $\mathbf{a}\in\mathbb{Z}^n$. We study the Hilbert series $\operatorname{Hilb}_{\mathbf{a}}(t)$ of the graded algebra $\mathbb{C}[V]^{\mathbb{C}_{\mathbf{a}}^\times}$ ... More
Don't Paint It Black: White-Box Explanations for Deep Learning in Computer SecurityJun 05 2019Jun 06 2019Deep learning is increasingly used as a basic building block of security systems. Unfortunately, deep neural networks are hard to interpret, and their decision process is opaque to the practitioner. Recent work has started to address this problem by considering ... More
A disk-covering problem with application in optical interferometryDec 05 2006Given a disk O in the plane called the objective, we want to find n small disks P_1,...,P_n called the pupils such that $\bigcup_{i,j=1}^n P_i \ominus P_j \supseteq O$, where $\ominus$ denotes the Minkowski difference operator, while minimizing the number ... More
Coarse-Graining Can Beat the Rotating Wave Approximation in Quantum Markovian Master EquationsMar 26 2013We present a first-principles derivation of the Markovian semi-group master equation without invoking the rotating wave approximation (RWA). Instead we use a time coarse-graining approach which leaves us with a free timescale parameter, which we can optimize. ... More
Joint Design of Channel and Network Coding for Star NetworksJan 28 2013Channel coding alone is not sufficient to reliably transmit a message of finite length $K$ from a source to one or more destinations as in, e.g., file transfer. To ensure that no data is lost, it must be combined with rateless erasure correcting schemes ... More
A new algorithm for point spread function subtraction in high-contrast imaging: a demonstration with angular differential imagingFeb 26 2007Direct imaging of exoplanets is limited by bright quasi-static speckles in the point spread function (PSF) of the central star. This limitation can be reduced by subtraction of reference PSF images. We have developed an algorithm to construct an optimized ... More
Efficient Error-Correcting GeocodingFeb 16 2011We study the problem of resolving a perhaps misspelled address of a location into geographic coordinates of latitude and longitude. Our data structure solves this problem within a few milliseconds even for misspelled and fragmentary queries. Compared ... More
Multiplexed Quantum Random Number GenerationJan 22 2018May 06 2019Fast secure random number generation is essential for high-speed encrypted communication, and is the backbone of information security. Generation of truly random numbers depends on the intrinsic randomness of the process used and is usually limited by ... More
Byzantine Fault Tolerant Vector Consensus with Anonymous ProposalsFeb 26 2019In this paper, we introduce the anonymous proposer vector consensus problem in which a set of processes decide on a vector of values, where each value is a proposal made anonymously by a single process. In a distributed survey, for example, a solution ... More
Sparse Models and Methods for Optimal Instruments with an Application to Eminent DomainOct 21 2010Apr 19 2015We develop results for the use of Lasso and Post-Lasso methods to form first-stage predictions and estimate optimal instruments in linear instrumental variables (IV) models with many instruments, $p$. Our results apply even when $p$ is much larger than ... More
Dynamical Decoupling of Unbounded HamiltoniansApr 20 2017We investigate the possibility to suppress interactions between a finite dimensional system and an infinite dimensional environment through a fast sequence of unitary kicks on the finite dimensional system. This method, called dynamical decoupling, is ... More
The Cremmer-Scherk Mechanism in F-theory Compactifications on K3 ManifoldsMar 06 2014Oct 21 2016It is well understood --- through string dualities --- that there are 20 massless vector fields in the spectrum of eight-dimensional F-theory compactifications on smooth elliptically fibered K3 surfaces at a generic point in the K3 moduli space. Such ... More
Bayesian identification of sound sources with the Helmholtz equationMay 29 2018Jan 15 2019In this work we discuss the problem of identifying sound sources from pressure measurements with a Bayesian approach. The acoustics are modelled by the Helmholtz equation and the goal is to get information about the number, strength and position of the ... More
The parameterized complexity of some geometric problems in unbounded dimensionJun 18 2009We study the parameterized complexity of the following fundamental geometric problems with respect to the dimension $d$: i) Given $n$ points in $\Rd$, compute their minimum enclosing cylinder. ii) Given two $n$-point sets in $\Rd$, decide whether they ... More
CO adsorption on neutral iridium clustersSep 27 2010The adsorption of carbon monoxide on neutral iridium clusters in the size range of n = 3 to 21 atoms is investigated with infrared multiple photon dissociation spectroscopy. For each cluster size only a single v(CO) band is present with frequencies in ... More
3D Lyman-alpha radiation transfer. III. Constraints on gas and stellar properties of z~3 Lyman break galaxies (LBG) and implications for high-z LBGs and Lyman-alpha emitters(LAEs)May 23 2008The Aim of our study is to understand the variety of observed Lyman-alpha (Lya) line profiles and strengths in Lyman Break Galaxies (LBGs) and Lya emitters (LAEs), the physical parameters governing them, and hence deriving constraints on the gas and dust ... More
Analysis of Agglomerative ClusteringDec 16 2010Mar 07 2014The diameter $k$-clustering problem is the problem of partitioning a finite subset of $\mathbb{R}^d$ into $k$ subsets called clusters such that the maximum diameter of the clusters is minimized. One early clustering algorithm that computes a hierarchy ... More
B.A.T.Mobile: Leveraging Mobility Control Knowledge for Efficient Routing in Mobile Robotic NetworksJul 05 2016Efficient routing is one of the key challenges of wireless networking for unmanned autonomous vehicles (UAVs) due to dynamically changing channel and network topology characteristics. Various well known mobile-ad-hoc routing protocols, such as AODV, OLSR ... More
Computational efficiency of staggered Wilson fermions: A first lookDec 11 2013Dec 17 2013Results on the computational efficiency of 2-flavor staggered Wilson fermions compared to usual Wilson fermions in a quenched lattice QCD simulation on $16^3\times32$ lattice at $\beta=6$ are reported. We compare the cost of inverting the Dirac matrix ... More