Results for "Tor Arne Johansen"

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Multi-agent formation control for circumnavigation of dynamic shapesMay 07 2018Sep 22 2018The problem of multi-agent formation control for target tracking is considered in this paper. The target is an irregular dynamic shape approximated by a circle with moving centre and varying radius. It is assumed that there are n agents and one of them ... More
Fault-Tolerant Control Allocation: an Unknown Input Observer based approachJun 23 2013This paper focuses on the use of unknown input observers for detection and isolation of actuator and effector faults with control reconfiguration in overactuated systems. The control allocation actively uses input redundancy in order to make relevant ... More
eXogenous Kalman Filter for Lithium-Ion Batteries State-of-Charge Estimation in Electric VehiclesOct 21 2018This paper presents a novel framework for state-of-charge estimation of rechargeable batteries in electric vehicles using a two-stage nonlinear estimator called the eXogenous Kalman filter (XKF). The nonlinear estimator consists of a cascade of nonlinear ... More
CubeSat testing of Coulomb drag propulsionApr 28 2016In Coulomb drag propulsion, a long high voltage tether or system of tethers gathers momentum from a natural plasma stream such as solar wind or ionospheric plasma ram flow. A positively polarised tether in the solar wind can be used for efficient general-purpose ... More
Cooperative decentralized circumnavigation with application to algal bloom trackingMar 14 2019Harmful algal blooms occur frequently and deteriorate water quality. A reliable method is proposed in this paper to track algal blooms using a set of autonomous surface robots. A satellite image indicates the existence and initial location of the algal ... More
Decay of light baryons by soft photon emissionJun 11 2008Jun 17 2008A possible reason for the emission of soft photons in high energy pp-collisions is discussed.
A Scale Free Algorithm for Stochastic Bandits with Bounded KurtosisMar 27 2017Existing strategies for finite-armed stochastic bandits mostly depend on a parameter of scale that must be known in advance. Sometimes this is in the form of a bound on the payoffs, or the knowledge of a variance or subgaussian parameter. The notable ... More
Regret Analysis of the Finite-Horizon Gittins Index Strategy for Multi-Armed BanditsNov 18 2015May 27 2016I analyse the frequentist regret of the famous Gittins index strategy for multi-armed bandits with Gaussian noise and a finite horizon. Remarkably it turns out that this approach leads to finite-time regret guarantees comparable to those available for ... More
The Pareto Regret Frontier for BanditsOct 30 2015Given a multi-armed bandit problem it may be desirable to achieve a smaller-than-usual worst-case regret for some special actions. I show that the price for such unbalanced worst-case regret guarantees is rather high. Specifically, if an algorithm enjoys ... More
Some Relations between Hadron MassesFeb 22 2005The mass of some hadrons are reproduced in terms of the mass of the nucleon. A possible reason for emission of soft gammas is proposed.
Cohomological Degrees, Dilworth Numbers and Linear ResolutionAug 22 2010This thesis is a study of various ways of measuring the size and complexity of finitely generated modules over a Noetherian local ring. The classical example is the multiplicity or degree. Here we investigate several variants of the degree function: the ... More
Regret Analysis of the Anytime Optimally Confident UCB AlgorithmMar 29 2016May 06 2016I introduce and analyse an anytime version of the Optimally Confident UCB (OCUCB) algorithm designed for minimising the cumulative regret in finite-armed stochastic bandits with subgaussian noise. The new algorithm is simple, intuitive (in hindsight) ... More
Optimally Confident UCB: Improved Regret for Finite-Armed BanditsJul 28 2015Feb 24 2016I present the first algorithm for stochastic finite-armed bandits that simultaneously enjoys order-optimal problem-dependent regret and worst-case regret. Besides the theoretical results, the new algorithm is simple, efficient and empirically superb. ... More
The role of magnetic fields for planetary formationMay 15 2009The role of magnetic fields for the formation of planets is reviewed. Protoplanetary disc turbulence driven by the magnetorotational instability has a huge influence on the early stages of planet formation. Small dust grains are transported both vertically ... More
Response time of internautsMar 01 2001A new experiment measuring the dynamical response of the Internet population to a ``point-like'' perturbation has been performed. The nature of the perturbation was that of an announcement, specifically a web-interview on stock market crashes, which contained ... More
On Flow Equivalence of Sofic ShiftsOct 10 2012The flow equivalence of sofic shifts is examined using results about the structure of the corresponding covers. A canonical cover generalising the left Fischer cover to arbitrary sofic shifts is introduced and used to prove that the left Krieger cover ... More
Towards autonomous ocean observing systems using Miniature Underwater Gliders with UAV deployment and recovery capabilitiesFeb 08 2019This paper presents preliminary results towards the development of an autonomous ocean observing system using Miniature Underwater Gliders (MUGs) that can operate with the support of Unmanned Aerial Vehicles (UAVs) and Unmanned Surface Vessels (USVs) ... More
Comment on "Are financial crashes predictable?"May 13 2002May 15 2002Comment on "Are financial crashes predictable?", L. Laloux, M. Potters, R. Cont, J.P Aguilar and J.-P. Bouchaud, Europhys. Lett. 45, 1-5 (1999)
Anomalous Currents in SCFT$_4$Jun 12 1996We analyse the critical behaviour of anomalous currents in N=1 four-dimensional supersymmetric gauge theories in the context of electric-magnetic duality. We show that the anomalous dimension of the Konishi superfield is related to the slope of the beta ... More
Origin of Crashes in 3 US stock markets: Shocks and BubblesJan 13 2004This paper presents an exclusive classification of the largest crashes in Dow Jones Industrial Average (DJIA), SP500 and NASDAQ in the past century. Crashes are objectively defined as the top-rank filtered drawdowns (loss from the last local maximum to ... More
Infinite Conformal Algebras in Supersymmetric Theories on Four ManifoldsJul 18 1994We study a supersymmetric theory twisted on a K\"ahler four manifold $M=\Sigma_1 \times \Sigma_2 ,$ where $\Sigma_{1,2}$ are 2D Riemann surfaces. We demonstrate that it possesses a "left-moving" conformal stress tensor on $\Sigma_1$ ($\Sigma_2$) in a ... More
Comment on A.-L. Barabasi, Nature 435 207-211 (2005)Feb 04 2006The purpose of this communication is twofold. First, it clarifies the origin of the power law obtained in the computer simulations presented in A.-L. Barabasi, Nature 435 207-211 (2005) as well as presenting a statistically more sound analysis of the ... More
Holomorphic Currents and Duality in N=1 Supersymmetric TheoriesSep 12 2003Sep 30 2003Twisted supersymmetric theories on a product of two Riemann surfaces possess non-local holomorphic currents in a BRST cohomology. The holomorphic currents act as vector fields on the chiral ring. The OPE's of these currents are invariant under the renormalization ... More
Characterization of large price variations in financial marketsOct 25 2002Statistics of drawdowns (loss from the last local maximum to the next local minimum) plays an important role in risk assessment of investment strategies. As they incorporate higher ($>$ two) order correlations, they offer a better measure of real market ... More
Comment on recent claims by Sornette and ZhouFeb 07 2003Comment on recent claims by Sornette and Zhou: D. Sornette and W. Zhou, Quantitative Finance 2 (6), 468-481 (2002); Evidence of a Worldwide Stock Market Log-Periodic Anti-Bubble Since Mid-2000, cond-mat/0212010; Renormalization Group Analysis of the 2000-2002 ... More
Realization of $W_{1+\infty}$ and Virasoro Algebras in Supersymmetric Theories on Four ManifoldsJun 23 1994Jul 18 1994We demonstrate that a supersymmetric theory twisted on a K\"ahler four manifold $M=\Sigma_1 \times \Sigma_2 ,$ where $\Sigma_{1,2}$ are 2D Riemann surfaces, possesses a "left-moving" conformal stress tensor on $\Sigma_1$ ($\Sigma_2$) in the BRST cohomology. ... More
Making GDPR Usable: A Model to Support Usability Evaluations of PrivacyAug 09 2019We introduce a new perspective on the evaluation of privacy, where rights of the data subjects, privacy principles, and usability criteria are intertwined. This new perspective is visually represented through a cube where each of its three axes of variability ... More
New Permutation Trinomials From Niho Exponents over Finite Fields with Even CharacteristicJun 12 2016In this paper, a class of permutation trinomials of Niho type over finite fields with even characteristic is further investigated. New permutation trinomials from Niho exponents are obtained from linear fractional polynomials over finite fields, and it ... More
Experiments on Internet ResponseSep 01 2005This paper suggests a generalized distribution of response times to new information $\sim t^{-b}$ for human populations in the absence of deadlines. This has important implications for psychological and social studies as well the study of dynamical networks ... More
Positivity Constraints on Anomalies and SupersymmetryJul 29 1998The relation between the trace and R-current anomalies in 4D supersymmetric theories implies that the U(1)$_R$F$^2$, U(1)$_R$ and U(1)$^3_R$ anomalies which matched in studies of N=1 Seiberg duality satisfy positivity constraints. These constraints are ... More
Remarks on reply to Johansen's commentJun 25 2002Remarks on reply (cond-mat/0206368) to Johansen's comment (cond-mat/0205249)
Twisting of N=1 SUSY Gauge Theories and Heterotic Topological TheoriesMar 03 1994Mar 18 1994It is shown that $D=4$ $N=1$ SUSY Yang-Mills theory with an appropriate supermultiplet of matter can be twisted on compact K\"ahler manifold. The conditions of cancellation of anomalies of BRST charge are found. The twisted theory has an appropriate BRST ... More
Spin Pumping and Inverse Spin Hall Voltages from Dynamical AntiferromagnetsFeb 13 2017Dynamical antiferromagnets pump spins efficiently into adjacent conductors as ferromagnets. The high antiferromagnetic resonance frequencies represent a challenge for experimental detection, but magnetic fields can reduce these resonance frequencies. ... More
Refined Lower Bounds for Adversarial BanditsMay 24 2016We provide new lower bounds on the regret that must be suffered by adversarial bandit algorithms. The new results show that recent upper bounds that either (a) hold with high-probability or (b) depend on the total lossof the best arm or (c) depend on ... More
Ground Motion Model of the SLAC SiteAug 19 2000We present a ground motion model for the SLAC site. This model is based on recent ground motion studies performed at SLAC as well as on historical data. The model includes wave-like, diffusive and systematic types of motion. An attempt is made to relate ... More
On First-Order Bounds, Variance and Gap-Dependent Bounds for Adversarial BanditsMar 19 2019Jun 29 2019We make three contributions to the theory of k-armed adversarial bandits. First, we prove a first-order bound for a modified variant of the INF strategy by Audibert and Bubeck [2009], without sacrificing worst case optimality or modifying the loss estimators. ... More
An Information-Theoretic Approach to Minimax Regret in Partial MonitoringFeb 01 2019May 29 2019We prove a new minimax theorem connecting the worst-case Bayesian regret and minimax regret under partial monitoring with no assumptions on the space of signals or decisions of the adversary. We then generalise the information-theoretic tools of Russo ... More
Interior-point algorithms for convex optimization based on primal-dual metricsNov 08 2014We propose and analyse primal-dual interior-point algorithms for convex optimization problems in conic form. The families of algorithms we analyse are so-called short-step algorithms and they match the current best iteration complexity bounds for primal-dual ... More
Exploration by Optimisation in Partial MonitoringJul 12 2019Jul 24 2019We provide a simple and efficient algorithm for adversarial $k$-action $d$-outcome non-degenerate locally observable partial monitoring game for which the $n$-round minimax regret is bounded by $6(d+1) k^{3/2} \sqrt{n \log(k)}$, matching the best known ... More
Cleaning up the neighborhood: A full classification for adversarial partial monitoringMay 23 2018Partial monitoring is a generalization of the well-known multi-armed bandit framework where the loss is not directly observed by the learner. We complete the classification of finite adversarial partial monitoring to include all games, solving an open ... More
The End of Optimism? An Asymptotic Analysis of Finite-Armed Linear BanditsOct 14 2016Stochastic linear bandits are a natural and simple generalisation of finite-armed bandits with numerous practical applications. Current approaches focus on generalising existing techniques for finite-armed bandits, notably the optimism principle and Thompson ... More
On First-Order Bounds, Variance and Gap-Dependent Bounds for Adversarial BanditsMar 19 2019Jul 24 2019We make three contributions to the theory of k-armed adversarial bandits. First, we prove a first-order bound for a modified variant of the INF strategy by Audibert and Bubeck [2009], without sacrificing worst case optimality or modifying the loss estimators. ... More
Non-local coupling between antiferromagnets and ferromagnets in cavitiesMar 09 2018Microwaves couple to magnetic moments in both ferromagnets and antiferromagnets. Although the magnons in ferromagnets and antiferromagnets radically differ, they can become entangled via strong coupling to the same microwave mode in a cavity. The equilibrium ... More
PAC Bounds for Discounted MDPsFeb 17 2012We study upper and lower bounds on the sample-complexity of learning near-optimal behaviour in finite-state discounted Markov Decision Processes (MDPs). For the upper bound we make the assumption that each action leads to at most two possible next-states ... More
No Free Lunch versus Occam's Razor in Supervised LearningNov 16 2011The No Free Lunch theorems are often used to argue that domain specific knowledge is required to design successful algorithms. We use algorithmic information theory to argue the case for a universal bias allowing an algorithm to succeed in all interesting ... More
On the Equation $x^{2^l+1}+x+a=0$ over $\mathrm{GF}(2^k)$ (Extended Version)Oct 22 2008Oct 07 2009In this paper, the polynomials $P_a(x)=x^{2^l+1}+x+a$ with $a\in\mathrm{GF}(2^k)$ are studied. New criteria for the number of zeros of $P_a(x)$ in $\mathrm{GF}(2^k)$ are proved. In particular, a criterion for $P_a(x)$ to have exactly one zero in $\mathrm{GF}(2^k)$ ... More
Linear dependence of bivariate Minimal Support and LR B-splines over LR-meshesNov 12 2018The focus on locally refined spline spaces has grown rapidly in recent years due to the need in Isogeoemtric analysis (IgA) of spline spaces with local adaptivity: a property not offered by the strict regular structure of tensor product B-spline spaces. ... More
Time Consistent DiscountingJul 27 2011A possibly immortal agent tries to maximise its summed discounted rewards over time, where discounting is used to avoid infinite utilities and encourage the agent to value current rewards more than future ones. Some commonly used discount functions lead ... More
Bounded Regret for Finite-Armed Structured BanditsNov 11 2014We study a new type of K-armed bandit problem where the expected return of one arm may depend on the returns of other arms. We present a new algorithm for this general class of problems and show that under certain circumstances it is possible to achieve ... More
Optimal Ternary Cyclic Codes from MonomialsMay 01 2013Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems, and communication systems as they have efficient encoding and decoding algorithms. Perfect nonlinear monomials were employed to construct ... More
Linear dependence of bivariate Minimal Support and Locally Refined B-splines over LR-meshesNov 12 2018Apr 26 2019The focus on locally refined spline spaces has grown rapidly in recent years due to the need in Isogeoemtric analysis (IgA) of spline spaces with local adaptivity: a property not offered by the strict regular structure of tensor product B-spline spaces. ... More
Information Systems Development and Evolution: A replication study on work distribution in Norwegian OrganizationsJan 01 2019The information systems landscape is at first sight very different from how it was 20 years ago. On the other hand, it seems that we are still struggling with many of the same problems, including late or abandoned projects and unfilled customer demands. ... More
Analysis of the Forward Search using some new results for martingales and empirical processesFeb 02 2016The Forward Search is an iterative algorithm for avoiding outliers in a regression analysis suggested by Hadi and Simonoff (J. Amer. Statist. Assoc. 88 (1993) 1264-1272), see also Atkinson and Riani (Robust Diagnostic Regression Analysis (2000) Springer). ... More
Ice condensation as a planet formation mechanismFeb 15 2013Feb 22 2013We show that condensation is an efficient particle growth mechanism, leading to growth beyond decimeter-sized pebbles close to an ice line in protoplanetary discs. As coagulation of dust particles is frustrated by bouncing and fragmentation, condensation ... More
Rapid growth of gas-giant cores by pebble accretionMay 14 2012Jun 13 2012The observed lifetimes of gaseous protoplanetary discs place strong constraints on gas and ice giant formation in the core accretion scenario. The approximately 10-Earth-mass solid core responsible for the attraction of the gaseous envelope has to form ... More
Quantum theory of successive projective measurementsMay 02 2007We show that a quantum state may be represented as the sum of a joint probability and a complex quantum modification term. The joint probability and the modification term can both be observed in successive projective measurements. The complex modification ... More
Reconstructing weak values without weak measurementsMay 01 2007I propose a scheme for reconstructing the weak value of an observable without the need for weak measurements. The post-selection in weak measurements is replaced by an initial projector measurement. The observable can be measured using any form of interaction, ... More
Significance of log-periodic precursors to financial crashesJun 26 2001We clarify the status of log-periodicity associated with speculative bubbles preceding financial crashes. In particular, we address Feigenbaum's [2001] criticism and show how it can be rebuked. Feigenbaum's main result is as follows: ``the hypothesis ... More
Critical RupturesMar 29 2000Apr 03 2000The fracture of materials is a catastrophic phenomenon of considerable technological and scientific importance. Here, we analysed experiments designed for industrial applications in order to test the concept that, in heterogeneous materials such as fiber ... More
What is the value of an observable between pre- and postselection?Aug 26 2003Feb 07 2004Hall's recent derivation of an exact uncertainty relation [Phys. Rev. A64, 052103 (2001)] is revisited. It is found that the Bayes estimator of an observable between pre- and postselection equals the real part of the weak value. The quadratic loss function ... More
Acoustic radiation controls friction: Evidence from a spring-block experimentJan 29 1999Apr 27 1999Brittle failures of materials and earthquakes generate acoustic/seismic waves which lead to radiation damping feedbacks that should be introduced in the dynamical equations of crack motion. We present direct experimental evidence of the importance of ... More
Critical CrashesJan 06 1999We argue that the word ``critical'' in the title is not purely literary. Based on our and other previous work on nonlinear complex dynamical systems, we summarize present evidence, on the Oct. 1929, Oct. 1987, Oct. 1987 Hong-Kong, Aug. 1998 global market ... More
Large N limit of orbifold field theoriesMar 30 1998May 28 1998We consider certain orbifoldization of the ${\cal N}=4$ field theories that leads to ${\cal N}=2,1,0$ field theories in 4 dimensions. These theories were recently analyzed using the string theory perturbation technique. It was found that in the large ... More
Stock market crashes are outliersNov 30 1997Dec 16 1997We call attention against what seems to a widely held misconception according to which large crashes are the largest events of distributions of price variations with fat tails. We demonstrate on the Dow Jones Industrial index that with high probability ... More
On the Optical Role of Randomness for Structured SurfacesOct 03 2013It has been known for years how random height variations of a repeated nano-scale structure can give rise to smooth angular color variations instead of the well-known diffraction pattern experienced if no randomization is present. However, until now there ... More
Bell's inequality for the Mach-Zehnder interferometerJun 04 1996We show that no local, hidden variable model can be given for two-channel states exhibiting both a sufficiently high interference visibility and a sufficient degree of anticorrelation in a Mach-Zehnder interferometer.
Liouville theory and special coadjoint Virasoro orbitsNov 09 1993We describe the Hamiltonian reduction of the coajoint Kac-Moody orbits to the Virasoro coajoint orbits explicitly in terms of the Lagrangian approach for the Wess-Zumino-Novikov-Witten theory. While a relation of the coajoint Virasoro orbit $Diff \; S^1 ... More
Current driven spin-orbit torque oscillator: ferromagnetic and antiferromagnetic couplingJun 08 2016Sep 23 2016We consider theoretically the impact of Rashba spin-orbit coupling on spin torque oscillators (STOs) in synthetic ferromagnets and antiferromagnets that have either a bulk multilayer or a thin film structure. The synthetic magnets consist of a fixed polarizing ... More
Prograde rotation of protoplanets by accretion of pebbles in a gaseous environmentOct 08 2009Jan 07 2010We perform hydrodynamical simulations of the accretion of pebbles and rocks onto protoplanets of a few hundred kilometres in radius, including two-way drag force coupling between particles and the protoplanetary disc gas. Particle streams interacting ... More
Large Stock Market Price Drawdowns Are OutliersOct 03 2000Jul 25 2001Drawdowns are essential aspects of risk assessment in investment management. They offer a more natural measure of real market risks than the variance or other cumulants of daily (or some other fixed time scale) distributions of returns. Here, we extend ... More
Evaluation of the quantitative prediction of a trend reversal on the Japanese stock market in 1999Feb 03 2000In January 1999, the authors published a quantitative prediction that the Nikkei index should recover from its 14 year low in January 1999 and reach $\approx 20500$ a year later. The purpose of the present paper is to evaluate the performance of this ... More
Download relaxation dynamics on the WWW following newspaper publication of URLJul 23 1999Jul 24 1999A few key properties of the World-Wide-Web (WWW) has been established indicating the lack of any characteristic scales for the WWW, both in its topology and in its dynamics. Here, we report an experiment which quantifies another power law describing the ... More
Equivalence between Bell's inequality and a constraint on stochastic field theories for EPR statesApr 17 1997A generalized form of EPR state is defined, embracing both classical and nonclassical states. It is shown that for such states, Bell's inequality is equivalent to a constraint on stochastic field theories. Thus, violation of Bell's inequality can be observed ... More
Incremental Natural Language Processing: Challenges, Strategies, and EvaluationMay 31 2018Jun 14 2018Incrementality is ubiquitous in human-human interaction and beneficial for human-computer interaction. It has been a topic of research in different parts of the NLP community, mostly with focus on the specific topic at hand even though incremental systems ... More
Logarithmic good reduction, monodromy and the rational volumeFeb 23 2015Oct 17 2016Let $R$ be a strictly local ring complete for a discrete valuation, with fraction field $K$ and residue field of characteristic $p > 0$. Let $X$ be a smooth, proper variety over $K$. Nicaise conjectured that the rational volume of $X$ is equal to the ... More
3-Colourability of Dually Chordal Graphs in Linear TimeJun 01 2012Nov 13 2012A graph G is dually chordal if there is a spanning tree T of G such that any maximal clique of G induces a subtree in T. This paper investigates the Colourability problem on dually chordal graphs. It will show that it is NP-complete in case of four colours ... More
Generalized Complexity of ALC SubsumptionMay 03 2012The subsumption problem with respect to terminologies in the description logic ALC is EXPTIME-complete. We investigate the computational complexity of fragments of this problem by means of allowed Boolean operators. Hereto we make use of the notion of ... More
High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamoAug 26 2008Hydromagnetic stresses in accretion discs have been the subject of intense theoretical research over the past one and a half decades. Most of the disc simulations have assumed a small initial magnetic field and studied the turbulence that arises from ... More
The Nasdaq crash of April 2000: Yet another example of log-periodicity in a speculative bubble ending in a crashApr 17 2000May 21 2000The Nasdaq Composite fell another $\approx 10 %$ on Friday the 14'th of April 2000 signaling the end of a remarkable speculative high-tech bubble starting in spring 1997. The closing of the Nasdaq Composite at 3321 corresponds to a total loss of over ... More
Financial ``Anti-Bubbles'': Log-Periodicity in Gold and Nikkei collapsesJan 25 1999We propose that imitation between traders and their herding behaviour not only lead to speculative bubbles with accelerating over-valuations of financial markets possibly followed by crashes, but also to ``anti-bubbles'' with decelerating market devaluations ... More
Hydrodynamical quantum state reconstructionMay 15 1998The density matrix of a nonrelativistic wave-packet in an arbitrary, one-dimensional and time-dependent potential can be reconstructed by measuring hydrodynamical moments of the Wigner distribution. An n-th order Taylor polynomial in the off-diagonal ... More
Weak Measurements with Arbitrary Pointer StatesFeb 05 2004The exact conditions on valid pointer states for weak measurements are derived. It is demonstrated that weak measurements can be performed with any pointer state with vanishing probability current density. This condition is found both for weak measurements ... More
Endogenous versus Exogenous Crashes in Financial MarketsOct 23 2002We perform an extended analysis of the distribution of drawdowns in the two leading exchange markets (US dollar against the Deutsmark and against the Yen), in the major world stock markets, in the U.S. and Japanese bond market and in the gold market, ... More
EPR correlations and EPW distributions revisitedSep 02 1997It is shown that Bell's proof of violation of local realism in phase space is incorrect. Using Bell's approach, a violation can be derived also for nonnegative Wigner distributions. The error is found to lie in the use of an unnormalizable Wigner function. ... More
Weighted inequalities and uncertainty principles for the $\boldsymbol{(k,a)}$-generalized Fourier transformFeb 17 2015Jan 15 2016We obtain several versions of the Hausdorff-Young and Hardy-Littlewood inequalities for the $(k,a)$-generalized Fourier transform recently investigated at length by Ben Sa\"i d, Kobayashi, and {\O} rsted. We also obtain a number of weighted inequalities ... More
Hardy--Littlewood inequalities for the Heckman--Opdam transformJan 26 2015We establish Hardy--Littlewood inequalities for the Heckman--Opdam transform associated to a general root datum $(\mathfrak{a},\Sigma,m)$ that generalizes an analogous result for the spherical Fourier transform on a Riemannian symmetric space of the non-compact ... More
State symmetries in matrices and vectors on finite state spacesSep 15 2004State symmetries are defined as permutations which act on vector spaces of column vectors and square matrices, resulting in isotropy groups for specific vector spaces. A large number of properties for such objects is shown, to provide a rigorous basis ... More
Finite genome size can halt Muller's ratchetSep 21 2001We study the accumulation of deleterious mutations in a haploid, asexually reproducing population, using analytical models and computer simulations. We find that Muller's ratchet can come to a halt in small populations as a consequence of a finite genome ... More
Dynamic Structural Operational SemanticsDec 02 2016Jul 20 2018We introduce Dynamic SOS as a framework for describing semantics of programming languages that include dynamic software upgrades, for upgrading software code during run-time. Dynamic SOS (DSOS) is built on top of the Modular SOS of P. Mosses, with an ... More
Almost Everywhere Convergence of the inverse Jacobi Transform and Endpoint Results for a Disc MultiplierJan 03 2011Jul 06 2011We introduce a maximal operator for the natural analogue of the disc multiplier in the framework of Jacobi analysis and determine the mapping properties of said maximal operator, including weak type endpoint results. In particular we obtain sharp information ... More
A unique quasi-probability for projective yes-no measurementsApr 28 2008From an analysis of projective measurements, it is shown that the Wigner rule is the unique operational quasi-probability for the post-measurement state. A unique pre-measurement quasi-probability is derived from a principle of invariance of measurement ... More
Dust diffusion in protoplanetary discs by magnetorotational turbulenceJan 28 2005Aug 17 2005We measure the turbulent diffusion coefficient of dust grains embedded in magnetorotational turbulence in a protoplanetary disc directly from numerical simulations and compare it to the turbulent viscosity of the flow. The simulations are done in a local ... More
On a Class of Non-Integrable Multipliers for the Jacobi TransformAug 18 2011We show that a bounded function $m$ on $\R$ not necessarily integrable at infinity may still yield $L^p$-bounded convolution operators for the Jacobi transform if the nontangential boundary values of $\omega m$ along the edges of a certain strip in $\C$ ... More
Protoplanetary Disk Turbulence Driven by the Streaming Instability: Non-Linear Saturation and Particle ConcentrationFeb 23 2007We present simulations of the non-linear evolution of streaming instabilities in protoplanetary disks. The two components of the disk, gas treated with grid hydrodynamics and solids treated as superparticles, are mutually coupled by drag forces. We find ... More
Nonclassical Properties of Coherent StatesSep 02 2003Feb 07 2004It is demonstrated that a weak measurement of the squared quadrature observable may yield negative values for coherent states. This result cannot be reproduced by a classical theory where quadratures are stochastic $c$-numbers. The real part of the weak ... More
Log-periodic power law bubbles in Latin-American and Asian markets and correlated anti-bubbles in Western stock markets: An empirical studyJul 19 1999Twenty-two significant bubbles followed by large crashes or by severe corrections in the Argentinian, Brazilian, Chilean, Mexican, Peruvian, Venezuelan, Hong-Kong, Indonesian, Korean, Malaysian, Philippine and Thai stock markets indices are identified ... More
Nonclassical evolution of a free particleApr 01 1998A conditional kinetic energy is defined in terms of the Wigner distribution. It is shown that this kinetic energy may become negative for negative Wigner distributions. A free particle wave packet with negative kinetic energy will spread in a nonclassical ... More
Evidence of discrete scale invariance in DLA and time-to-failure by canonical averagingMar 15 1998Discrete scale invariance, which corresponds to a partial breaking of the scaling symmetry, is reflected in the existence of a hierarchy of characteristic scales l0, c l0, c^2 l0,... where c is a preferred scaling ratio and l0 a microscopic cut-off. Signatures ... More
Colliding Singularities in F-theory and Phase TransitionsOct 16 1996Oct 27 1996We study F-theory on elliptic threefold Calabi-Yau near colliding singularities. We demonstrate that resolutions of those singularities generically correspond to transitions to phases characterized by new tensor multiplets and enhanced gauge symmetry. ... More
Forming the cores of giant planets from the radial pebble flux in protoplanetary discsAug 26 2014Apr 04 2016The formation of planetary cores must proceed rapidly in order for the giant planets to accrete their gaseous envelopes before the dissipation of the protoplanetary gas disc (<3 Myr). In orbits beyond 10 AU, direct accumulation of planetesimals by the ... More