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Results for "Martijn N. de Vries"

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On the number of unique expansions in non-integer basesMay 14 2008Jun 13 2009Let $q > 1$ be a real number and let $m=m(q)$ be the largest integer smaller than $q$. It is well known that each number $x \in J_q:=[0, \sum_{i=1}^{\infty} m q^{-i}]$ can be written as $x=\sum_{i=1}^{\infty}{c_i}q^{-i}$ with integer coefficients $0 \le ... More
A two-dimensional univoque setMar 28 2010Dec 16 2010Let $\mathbf{J} \subset \mathbb{R}^2$ be the set of couples $(x,q)$ with $q>1$ such that $x$ has at least one representation of the form $x=\sum_{i=1}^{\infty} c_i q^{-i}$ with integer coefficients $c_i$ satisfying $0 \leq c_i < q$, $i \ge 1$. In this ... More
Unique expansions of real numbersSep 25 2006Dec 18 2008It was discovered some years ago that there exist non-integer real numbers $q>1$ for which only one sequence $(c_i)$ of integers $c_i \in [0,q)$ satisfies the equality $\sum_{i=1}^\infty c_iq^{-i}=1$. The set of such "univoque numbers" has a rich topological ... More
Evidence for a TDE origin of the radio transient Cygnus A-2Apr 12 2019In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with the Very Large Array. Because of its radio brightness ($\nu F_{\nu} \approx 6 \times 10^{39}$ erg s$^{-1}$), this transient likely represents a secondary black hole in orbit around ... More
Optimal expansions in non-integer basesNov 23 2010May 15 2011For a given positive integer $m$, let $A=\set{0,1,...,m}$ and $q \in (m,m+1)$. A sequence $(c_i)=c_1c_2 ...$ consisting of elements in $A$ is called an expansion of $x$ if $\sum_{i=1}^{\infty} c_i q^{-i}=x$. It is known that almost every $x$ belonging ... More
Simulations of the merging cluster of galaxies Cygnus ADec 13 2018The archetype FR-II galaxy Cygnus A lies in a moderately rich cluster about to undergo a major merger. We study the pre-merger Cygnus cluster environment using smoothed particle hydrodynamics simulations constrained by 2Ms of Chandra observations of the ... More
Univoque bases and Hausdorff dimensionsJun 13 2016Given a positive integer $M$ and a real number $q >1$, a \emph{$q$-expansion} of a real number $x$ is a sequence $(c_i)=c_1c_2\ldots$ with $(c_i) \in \{0,\ldots,M\}^\infty$ such that \[x=\sum_{i=1}^{\infty} c_i q^{-i}.\] It is well known that if $q \in ... More
Univoque bases and Hausdorff dimensionJun 13 2016Apr 02 2017Given a positive integer $M$ and a real number $q >1$, a \emph{$q$-expansion} of a real number $x$ is a sequence $(c_i)=c_1c_2\cdots$ with $(c_i) \in \{0,\ldots,M\}^\infty$ such that \[x=\sum_{i=1}^{\infty} c_iq^{-i}.\] It is well known that if $q \in ... More
An overview of dynamical models for outflows in BALQSOs and SeyfertsApr 23 1997This paper reviews the dynamical models that have been proposed for the outflows that are responsible for the broad blue-shifted absorption features observed in broad absorption line quasars and in some Seyfert galaxies.
HST STIS Observations of PG 0946+301: the Highest Quality UV Spectrum of a BALQSOJul 20 2001We describe deep (40 orbits) HST/STIS observations of the BALQSO PG 0946+301 and make them available to the community. These observations are the major part of a multi-wavelength campaign on this object aimed at determining the ionization equilibrium ... More
Equilibrated adaptive learning rates for non-convex optimizationFeb 15 2015Aug 29 2015Parameter-specific adaptive learning rate methods are computationally efficient ways to reduce the ill-conditioning problems encountered when training large deep networks. Following recent work that strongly suggests that most of the critical points encountered ... More
Parity violation in proton-proton scattering from chiral effective field theorySep 18 2013Nov 27 2013We present a calculation of the parity-violating longitudinal asymmetry in proton-proton scattering. The calculation is performed in the framework of chiral effective field theory which is applied systematically to both the parity-conserving and parity-violating ... More
Four-Quark Effective Operators at Hadron CollidersSep 16 2014Mar 25 2015The robustness of translating effective operator constraints to BSM theories crucially depends on the mass and coupling of BSM particles. This is especially relevant for hadron colliders where the partonic centre of mass energy is around the typical energy ... More
Algebraic hierarchy of logics unifying fuzzy logic and quantum logicJul 14 2007In this paper, a short survey about the concepts underlying general logics is given. In particular, a novel rigorous definition of a fuzzy negation as an operation acting on a lattice to render it into a fuzzy logic is presented. According to this definition, ... More
The Z2 Two Higgs Doublet Model and the hierarchy problemSep 02 2011Nov 01 2013The hierarchy problem is investigated in the $\mathbb{Z}_2$ Two Higgs Doublet extension of the Standard Model. From the quadratic divergences of the Higgs field propagators fine-tuning constraints are extracted and solved. This leads to the mass relation ... More
Many-valued logics inside λ-calculus: Church's rescue of Russell with B{\"}ohm treesOct 17 2018We extend the Church encoding of the Booleans and two-valued Boolean Logic in $\lambda$-calculus to encodings of $n$-valued sequential propositional logic (for $3\leq n\leq 5$) in well-chosen infinitary extensions in $\lambda$-calculus. In case of three-valued ... More
A property of algebraic univoque numbersDec 20 2006Mar 07 2007Consider the set $\uu$ of real numbers $q \ge 1$ for which only one sequence $(c_i)$ of integers $0 \le c_i \le q$ satisfies the equality $\sum_{i=1}^{\infty} c_i q^{-i} = 1$. In this note we show that the set of algebraic numbers in $\uu$ is dense in ... More
Thermal Instability and Evaporation of Accretion Disc AtmospheresMar 10 1999We investigate the thermal stability of the outer layers of accretion discs in which the local viscous energy dissipation rate scales with the pressure as for standard Shakura-Sunyaev discs. By solving for the accretion disc vertical structure using the ... More
Massive galaxies with very young AGNAug 20 2007Gigahertz Peaked Spectrum (GPS) radio galaxies are generally thought to be the young counterparts of classical extended radio sources and live in massive ellipticals. GPS sources are vital for studying the early evolution of radio-loud AGN, the trigger ... More
Parity violation in neutron capture on the proton: determining the weak pion-nucleon couplingJan 08 2015Jun 12 2015We investigate the parity-violating analyzing power in neutron capture on the proton at thermal energies in the framework of chiral effective field theory. By combining this analysis with a previous analysis of parity violation in proton-proton scattering, ... More
A study of the parity-odd nucleon-nucleon potentialApr 06 2014Jul 16 2014We investigate the parity-violating nucleon-nucleon potential as obtained in chiral effective field theory. By using resonance saturation we compare the chiral potential to the more traditional one-meson exchange potential. In particular, we show how ... More
Team Delft's Robot Winner of the Amazon Picking Challenge 2016Oct 18 2016This paper describes Team Delft's robot, which won the Amazon Picking Challenge 2016, including both the Picking and the Stowing competitions. The goal of the challenge is to automate pick and place operations in unstructured environments, specifically ... More
Effective photons in weakly absorptive dielectric media and the Beer-Lambert-Bouguer lawDec 14 2013Apr 18 2014We derive effective photon modes that facilitate an intuitive and convenient picture of photon dynamics in a structured Kramers-Kronig dielectric in the limit of weak absorption. Each mode is associated with an effective line-width which determines the ... More
Schur and Fourier multipliers of an amenable group acting on non-commutative Lp-spacesMar 01 2013Sep 18 2013Consider a completely bounded Fourier multiplier phi of a locally compact group G, and take 1 <= p <= infinity. One can associate to phi a Schur multiplier on the Schatten classes S_p(L^2 G), as well as a Fourier multiplier on Lp(LG), the non-commutative ... More
Complete identification of the Parkes half-Jansky sample of GHz peaked spectrum radio galaxiesJan 10 2007Gigahertz Peaked Spectrum (GPS) radio galaxies are generally thought to be the young counterparts of classical extended radio sources. Statistically complete samples of GPS sources are vital for studying the early evolution of radio-loud AGN and the trigger ... More
Hyperbolic metamaterials: nonlocal response regularizes broadband super-singularityApr 24 2012Nov 16 2012We study metamaterials known as hyperbolic media that in the usual local-response approximation exhibit hyperbolic dispersion and an associated broadband singularity in the density of states. Instead, from the more microscopic hydrodynamic Drude theory ... More
Green function surface-integral method for nonlocal response of plasmonic nanowires in arbitrary dielectric environmentsJul 26 2013We develop a nonlocal-response generalization to the Green-function surface-integral method (GSIM), also known as the boundary-element method (BEM). This numerically light method can accurately describe the linear hydrodynamic nonlocal response of arbitrarily ... More
Projected-Dipole Model for Quantum PlasmonicsApr 27 2015Quantum effects of plasmonic phenomena have been explored through ab-initio studies, but only for exceedingly small metallic nanostructures, leaving most experimentally relevant structures too large to handle. We propose instead an effective description ... More
Bayesian Approach for Counting Experiment Statistics applied to a Neutrino Point Source AnalysisDec 10 2012Oct 02 2013In this paper we present a model independent analysis method following Bayesian statistics to analyse data from a generic counting experiment and apply it to the search for neutrinos from point sources. We discuss a test statistic defined following a ... More
Evaluating e-voting: theory and practiceFeb 08 2016In the Netherlands as well as many other countries, the use of electronic voting solutions is a recurrent topic of discussion. While electronic voting certainly has advantages over paper voting, there are also important risks involved. This paper presents ... More
Quantum optical effective-medium theory for loss-compensated metamaterialsAug 02 2012Mar 13 2013A central aim in metamaterial research is to engineer sub-wavelength unit cells that give rise to desired effective-medium properties and parameters, such as a negative refractive index. Ideally one can disregard the details of the unit cell and employ ... More
Hyperbolic metamaterial lens with hydrodynamic nonlocal responseFeb 15 2013We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths ... More
Evidence for radiative generation of lepton massesMar 11 2005We present a fit to the experimental charged lepton masses as coming from radiative corrections in QED.
Locally Nameless Permutation TypesOct 23 2017We define "Locally Nameless Permutation Types", which fuse permutation types as used in Nominal Isabelle with the locally nameless representation. We show that this combination is particularly useful when formalizing programming languages where bound ... More
Can deep learning help you find the perfect match?May 02 2015Jun 20 2015Is he/she my type or not? The answer to this question depends on the personal preferences of the one asking it. The individual process of obtaining a full answer may generally be difficult and time consuming, but often an approximate answer can be obtained ... More
Towards an automated query modification assistantApr 01 2011Users who need several queries before finding what they need can benefit from an automatic search assistant that provides feedback on their query modification strategies. We present a method to learn from a search log which types of query modifications ... More
VLBI observations of the CORALZ sample: young radio sources at low redshiftJan 14 2009Young radio-loud active galactic nuclei form an important tool to investigate the evolution of extragalactic radio sources. To study the early phases of expanding radio sources, we have constructed CORALZ, a sample of 25 compact ($\theta<2"$) radio sources ... More
A Bayesian binary classification approach to pure tone audiometryNov 27 2015Mar 16 2016The pure tone hearing threshold is usually estimated from responses to stimuli at a set of standard frequencies. This paper describes a probabilistic approach to the estimation problem in which the hearing threshold is modelled as a smooth continuous ... More
Electricity markets regarding the operational flexibility of power plantsJan 31 2015Electricity market mechanisms designed to steer sustainable generation of electricity play an important role for the energy transition intended to mitigate climate change. One of the major problems is to complement volatile renewable energy sources by ... More
Invariant densities for random $β$-expansionsDec 20 2006Let $\beta >1$ be a non-integer. We consider expansions of the form $\sum_{i=1}^{\infty} d_i \beta^{-i}$, where the digits $(d_i)_{i \geq 1}$ are generated by means of a Borel map $K_{\beta}$ defined on $\{0,1\}^{\N}\times [ 0, \lfloor \beta \rfloor /(\beta ... More
The metal contents of two groups of galaxiesMar 31 2011The hot gas in clusters and groups of galaxies is continuously being enriched with metals from supernovae and stars. It is well established that the enrichment of the gas with elements from oxygen to iron is mainly caused by supernova explosions. The ... More
A Probabilistic Modeling Approach to Hearing Loss CompensationFeb 03 2016Sep 06 2016Hearing Aid (HA) algorithms need to be tuned ("fitted") to match the impairment of each specific patient. The lack of a fundamental HA fitting theory is a strong contributing factor to an unsatisfying sound experience for about 20% of hearing aid patients. ... More
The Astrophysical Multipurpose Software EnvironmentJul 11 2013We present the open source Astrophysical Multi-purpose Software Environment (AMUSE, www.amusecode.org), a component library for performing astrophysical simulations involving different physical domains and scales. It couples existing codes within a Python ... More
Photoionization Models for BALQSO PG 0946+301Jul 20 2001This is a companion paper to the manuscript entitled: ``HST STIS Observations Of PG 0946+301: The Highest Quality UV Spectrum of a BALQSO'' (Arav et al. 2001; accepted for publication in ApJ). Here we present photoionization-modeling results for ALL the ... More
A Click Sequence Model for Web SearchMay 09 2018Getting a better understanding of user behavior is important for advancing information retrieval systems. Existing work focuses on modeling and predicting single interaction events, such as clicks. In this paper, we for the first time focus on modeling ... More
On the Column Density of AGN Outflows: the Case of NGC 5548Jul 25 2001Apr 04 2002We re-analyze the HST high resolution spectroscopic data of the intrinsic absorber in NGC 5548 and find that the C IV absorption column density is at least four times larger than previously determined. This increase arises from accounting for the kinematical ... More
Accretion disk reversal and the spin-up/spin-down of accreting pulsarsOct 07 1998We numerically investigate the hydrodynamics of accretion disk reversal and relate our findings to the observed spin-rate changes in the accreting X-ray pulsar GX~1+4. In this system, which accretes from a slow wind, the accretion disk contains two dynamically ... More
Search for high-energy neutrinos from dust obscured BlazarsNov 09 2015Nov 15 2016The recent discovery of high-energy cosmic neutrinos by the IceCube neutrino observatory opens up a new field in physics, the field of neutrino astronomy. Using the IceCube neutrino detector we plan to search for high-energy neutrinos emitted from Active ... More
Little Higgs Model Limits from LHC - Input for Snowmass 2013Jul 18 2013Sep 05 2013The status of several prominent model implementations of the Little Higgs paradigm, the Littlest Higgs with and without discrete T-parity as well as the Simplest Little Higgs are reviewed. For this, we are taking into account a fit of 21 electroweak precision ... More
K-tree: Large Scale Document ClusteringJan 06 2010We introduce K-tree in an information retrieval context. It is an efficient approximation of the k-means clustering algorithm. Unlike k-means it forms a hierarchy of clusters. It has been extended to address issues with sparse representations. We compare ... More
Violations of discrete space-time symmetries in chiral effective field theorySep 24 2015Apr 28 2016We review recent progress in the theoretical description of the violation of discrete space-time symmetries in hadronic and nuclear systems. We focus on parity-violating and time-reversal-conserving interactions which are induced by the Standard Model ... More
Localized plasmons in graphene-coated nanospheresDec 22 2014We present an analytical derivation of the electromagnetic response of a spherical object coated by a conductive film, here exemplified by a graphene coating. Applying the framework of Mie-Lorenz theory augmented to account for a conductive boundary condition, ... More
Littlest Higgs with T-parity: Status and ProspectsOct 10 2013Feb 20 2014The Littlest Higgs model with T-parity is providing an attractive solution to the fine-tuning problem. This solution is only entirely natural if its intrinsic symmetry breaking scale f is relatively close to the electroweak scale. We examine the constraints ... More
Temperature dependence of the energy barrier and switching field of sub-micron permanent magnetsNov 15 2016Nov 24 2016Using the highly sensitive anomalous Hall effect (AHE) we have been able to measure the reversal of a single magnetic island, of diameter 220nm, in an array consisting of more than 80 of those islands. By repeatedly traversing the hysteresis loop, we ... More
Long Term Variability of SDSS QuasarsJun 12 2003We use a sample of 3791 quasars from the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR), and compare their photometry to historic plate material for the same set of quasars in order to study their variability properties. The time base-line we ... More
Automatic segmentation of MR brain images with a convolutional neural networkApr 11 2017Automatic segmentation in MR brain images is important for quantitative analysis in large-scale studies with images acquired at all ages. This paper presents a method for the automatic segmentation of MR brain images into a number of tissue classes using ... More
Casimir forces in multilayer magnetodielectrics with both gain and lossApr 08 2011A path-integral approach to the quantization of the electromagnetic field in a linearly amplifying magnetodielectric medium is presented. Two continua of inverted harmonic oscillators are used to describe the polarizability and magnetizability of the ... More
Nonlocal study of ultimate plasmon hybridizationJun 19 2014Within our recently proposed generalized nonlocal optical response (GNOR) model, we revisit the fundamental problem of an optically excited plasmonic dimer. The dimer consists of two identical cylinders separated by a nanometre-sized gap. We consider ... More
A hybridizable discontinuous Galerkin method for solving nonlocal optical response modelsNov 24 2016We propose Hybridizable Discontinuous Galerkin (HDG) methods for solving the frequency-domain Maxwell's equations coupled to the Nonlocal Hydrodynamic Drude (NHD) and Generalized Nonlocal Optical Response (GNOR) models, which are employed to describe ... More
Nonlocal optical response in metallic nanostructuresDec 02 2014This review provides a broad overview of the studies and effects of nonlocal response in metallic nanostructures. In particular, we thoroughly present the nonlocal hydrodynamic model and the recently introduced generalized nonlocal optical response (GNOR) ... More
The Cocoon Shocks of Cygnus A: Pressures and Their Implications for the Jets and LobesFeb 27 2018We use 2.0 Msec of Chandra observations to investigate the cocoon shocks of Cygnus A and some implications for its lobes and jet. Measured shock Mach numbers vary in the range 1.18-1.66 around the cocoon. We estimate a total outburst energy of $\simeq ... More
Physical properties of amorphous solid interstellar material from X-ray absorption spectroscopy of Sco X-1Jan 20 2009High quality, high resolution X-ray spectra were obtained of Sco X-1 with the Reflection Grating Spectrometer (RGS) on board the XMM-Newton satellite. The spectrum around the Oxygen K-edge is searched for signatures indicative for EXAFS. Analysis shows ... More
Uniqueness Typing for Resource Management in Message-Passing ConcurrencyMar 29 2010We view channels as the main form of resources in a message-passing programming paradigm. These channels need to be carefully managed in settings where resources are scarce. To study this problem, we extend the pi-calculus with primitives for channel ... More
Temperature dependence of the energy barrier and switching field of sub-micron permanent magnetsNov 15 2016Using the highly sensitive anomalous Hall effect (AHE) we have been able to measure the reversal of a single magnetic island, of diameter 220nm, in an array consisting of more than 80 of those islands. By repeatedly traversing the hysteresis loop, we ... More
Beyond-the-Standard-Model matrix elements with the gradient flowSep 09 2014Sep 10 2014At the Forschungszentrum Juelich (FZJ) we have started a long-term program that aims to determine beyond-the-Standard-Model (BSM) matrix elements using the gradient flow, and to understand the impact of BSM physics in nucleon and nuclear observables. ... More
The nucleon electric dipole moment with the gradient flow: the $θ$-term contributionJul 09 2015Oct 27 2015We propose a new method to calculate electric dipole moments induced by the strong QCD $\theta$-term. The method is based on the gradient flow for gauge fields and is free from renormalization ambiguities. We test our method by computing the nucleon electric ... More
Supersymmetric Quantum Mechanics of Magnetic Monopoles: A Case StudyNov 13 2008Feb 04 2009We study, in detail, the supersymmetric quantum mechanics of charge-(1,1) monopoles in N=2 supersymmetric Yang-Mills-Higgs theory with gauge group SU(3) spontaneously broken to U(1) x U(1). We use the moduli space approximation of the quantised dynamics, ... More
TopSig: Topology Preserving Document SignaturesApr 24 2012Performance comparisons between File Signatures and Inverted Files for text retrieval have previously shown several significant shortcomings of file signatures relative to inverted files. The inverted file approach underpins most state-of-the-art search ... More
Document Clustering with K-treeJan 06 2010This paper describes the approach taken to the XML Mining track at INEX 2008 by a group at the Queensland University of Technology. We introduce the K-tree clustering algorithm in an Information Retrieval context by adapting it for document clustering. ... More
Radiative bound-state-formation cross-sections for dark matter interacting via a Yukawa potentialNov 04 2016We calculate the cross-sections for the radiative formation of bound states by dark matter whose interactions are described in the non-relativistic regime by a Yukawa potential. These cross-sections are important for cosmological and phenomenological ... More
Supercharges, Quantum States and Angular Momentum for N=4 Supersymmetric MonopolesApr 04 2010May 20 2010We revisit the moduli space approximation to the quantum mechanics of monopoles in N=4 supersymmetric Yang-Mills-Higgs theory with maximal symmetry breaking. Starting with the observation that the set of fermionic zero-modes in N=4 supersymmetric Yang-Mills-Higgs ... More
Coherent transition radiation from the geomagnetically-induced current in cosmic-ray air showers: Implications for the anomalous events observed by ANITAMar 20 2019We show that coherent transition radiation (CTR) from the electrically-neutral transverse geomagnetic current (CTR-GM) has to be included in the radio emission models to understand the radio emission from a high-energy cosmic-ray air shower traversing ... More
Molecular Line Profile Fitting with Analytic Radiative Transfer ModelsOct 29 2004We present a study of analytic models of starless cores whose line profiles have ``infall asymmetry,'' or blue-skewed shapes indicative of contracting motions. We compare the ability of two types of analytical radiative transfer models to reproduce the ... More
Report on TBAS 2012: Workshop on Task-Based and Aggregated SearchApr 06 2017The ECIR half-day workshop on Task-Based and Aggregated Search (TBAS) was held in Barcelona, Spain on 1 April 2012. The program included a keynote talk by Professor Jarvelin, six full paper presentations, two poster presentations, and an interactive discussion ... More
Dynamics of a stochastically driven running sandpileJul 11 1994We analyze in detail a one-dimensional stochastically driven running sandpile. The dynamics shows three different phases, depending on the on-site relaxation rate and stochastic driving rate. Two phases are characterized by the presence of travelling ... More
The O VII X-ray forest toward Markarian 421: Consistency between XMM-Newton and ChandraApr 25 2006Recently the first detections of highly ionised gas associated with two Warm-Hot Intergalactic Medium (WHIM) filaments have been reported. The evidence is based on X-ray absorption lines due to O VII and other ions observed by Chandra towards the bright ... More
Dusty wind of W Hya. Multi-wavelength modelling of the present-day and recent mass-lossMar 16 2015Low- and intermediate-mass stars go through a period of intense mass-loss at the end of their lives in a phase known as the asymptotic giant branch (AGB). During the AGB a significant fraction of their initial mass is expelled in a stellar wind. This ... More
Random Indexing K-treeJan 06 2010Feb 02 2010Random Indexing (RI) K-tree is the combination of two algorithms for clustering. Many large scale problems exist in document clustering. RI K-tree scales well with large inputs due to its low complexity. It also exhibits features that are useful for managing ... More
A Factor Graph Approach to Automated Design of Bayesian Signal Processing AlgorithmsNov 08 2018The benefits of automating design cycles for Bayesian inference-based algorithms are becoming increasingly recognized by the machine learning community. As a result, interest in probabilistic programming frameworks has much increased over the past few ... More
Two-photon exchange and elastic scattering of electrons/positrons on the proton. (Proposal for an experiment at VEPP-3)Aug 18 2004It has been suggested that two-photon exchange corrections could explain the discrepancy between Rosenbluth extractions of the proton form factors and recent polarization transfer measurements. We propose a precise comparison of electron-proton and positron-proton ... More
Obscured flat spectrum radio AGN as sources of high-energy neutrinosJul 29 2016Active Galactic Nuclei (AGN) are believed to be one of the main source candidates for the high-energy (TeV-PeV) cosmic neutrino flux recently discovered by the IceCube neutrino observatory. Nevertheless, several correlation studies between AGN and the ... More
Towards the understanding of the origin of charge-current-induced spin voltage signals in the topological insulator Bi$_2$Se$_3$Oct 28 2015Nov 04 2015Topological insulators provide a new platform for spintronics due to the spin texture of the surface states that are topologically robust against elastic backscattering. Here, we report on an investigation of the measured voltage obtained from efforts ... More
Obscured flat spectrum radio AGN as sources of high-energy neutrinosJul 29 2016Oct 31 2016Active Galactic Nuclei (AGN) are believed to be one of the main source candidates for the high-energy (TeV-PeV) cosmic neutrino flux recently discovered by the IceCube neutrino observatory. Nevertheless, several correlation studies between AGN and the ... More
Coexistence of bulk and surface states probed by Shubnikov-de Haas oscillations in Bi$_2$Se$_3$ with high charge-carrier densityJul 27 2017Topological insulators are ideally represented as having an insulating bulk with topologically protected, spin-textured surface states. However, it is increasingly becoming clear that these surface transport channels can be accompanied by a finite conducting ... More
Instantaneous coherent destruction of tunneling and fast quantum state preparation for strongly pulsed spin qubits in diamondJan 26 2010Nov 22 2010Qubits driven by resonant strong pulses are studied and a parameter regime is explored in which the dynamics can be solved in closed form. Instantaneous coherent destruction of tunneling can be seen for longer pulses, whereas shorter pulses allow a fast ... More
Geometry of Particle PhysicsMar 06 2007Aug 23 2007We explain how to construct a large class of new quiver gauge theories from branes at singularities by orientifolding and Higgsing old examples. The new models include the MSSM, decoupled from gravity, as well as some classic models of dynamical SUSY ... More
Large Volume Perspective on Branes at SingularitiesDec 03 2002Jan 12 2004In this paper we consider a somewhat unconventional approach for deriving worldvolume theories for D3 branes probing Calabi-Yau singularities. The strategy consists of extrapolating the calculation of F-terms to the large volume limit. This method circumvents ... More
Top Quark Mass Measurements at the TevatronJun 12 2005In the year 2004 several milestones in the measurement of the top quark mass were reached. The DO collaboration published a significant improvement of their Run I measurement of the top quark mass, and both Tevatron experiments released preliminary measurements ... More
Weight theory for ultraproductsMay 24 2016May 30 2016For a family of von Neumann algebras $\mathcal{M}_j$ equipped with normal weights $\varphi_j$ we define the ultraproduct weight $(\varphi_j)_\omega$ on the Groh--Raynaud ultrapower $\prod_{j, \omega} \mathcal{M}_j$. We prove results about Tomita-Takesaki ... More
Connes embeddability of graph productsJun 05 2015We prove that the Connes embedding problem is stable under graph products.
Absence of Cartan subalgebras for Hecke von Neumann algebrasJan 04 2016For a right-angled Coxeter system $(W,S)$ and $q>0$, let $\mathcal{M}_q$ be the associated Hecke von Neumann algebra, which is generated by self-adjoint operators $T_s, s \in S$ satisfying the Hecke relation $(\sqrt{q}\: T_s - q) (\sqrt{q} \: T_s + 1) ... More
On the Role of Cylindrical Functions in Kantorovich dualityApr 10 2015We study the dual formulation of the Monge-Kantorovich optimal transportation problem, in particular under what circumstances it is permitted in an infinite dimensional setting to use cylindrical functions, i.e. functions of the form $\varphi\circ P$ ... More
Fixed point loci of moduli spaces of sheaves on toric varietiesOct 02 2008Mar 22 2014Extending work of Klyachko and Perling, we develop a combinatorial description of pure equivariant sheaves of any dimension on an arbitrary nonsingular toric variety $X$. Using geometric invariant theory (GIT), this allows us to construct explicit moduli ... More
On Curvature-Squared Corrections for D-brane ActionsJan 07 2003Curvature-squared corrections for D-brane actions in type II string theory were derived by Bachas, Bain and Green. Here we write down a generalisation of these corrections to all orders in $F$, the field strength of the U(1) gauge field on the brane. ... More
Higgs Bundles and String PhenomenologyJan 12 2012String phenomenology is the branch of string theory concerned with making contact with particle physics. The original models involved compactifying ten-dimensional supersymmetric Yang-Mills theory on an internal Calabi-Yau three-fold. In recent years, ... More
The L^p-Fourier transform on locally compact quantum groupsAug 16 2010Jul 24 2011Using interpolation properties of non-commutative L^p-spaces associated with an arbitrary von Neumann algebra, we define a L^p-Fourier transform 1 <= p <= 2 on locally compact quantum groups. We show that the Fourier transform determines a distinguished ... More
The continued spectral evolution of the neutron star RX J0720.4-3125May 20 2004We observed the isolated neutron star RX J720.4-3125 with Chandra's Low Energy Transmission Grating Spectrometer, following the XMM-Newton discovery of long term spectral evolution of this source. The new observation shows that the spectrum of RX J720.4-3125 ... More
AO Observations of Three Powerful Radio GalaxiesSep 12 2002The host galaxies of powerful radio sources are ideal laboratories to study active galactic nuclei (AGN). The galaxies themselves are among the most massive systems in the universe, and are believed to harbor supermassive black holes (SMBH). If large ... More
A Realistic Treatment of Geomagnetic Cherenkov Radiation from Cosmic Ray Air ShowersJan 21 2012Aug 29 2012We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from three-dimensional Monte Carlo simulations of air showers in a realistic geo-magnetic ... More
Is there room for CP violation in the top-Higgs sector?Mar 09 2016Aug 02 2016We discuss direct and indirect probes of chirality-flipping couplings of the top quark to Higgs and gauge bosons, considering both CP-conserving and CP-violating observables, in the framework of the Standard Model effective field theory. In our analysis ... More