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Results for "Henk A. Dijkstra"

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On the state dependency of fast feedback processes in (palaeo) climate sensitivityMar 21 2014Apr 30 2014Palaeo data have been frequently used to determine the equilibrium (Charney) climate sensitivity $S^a$, and - if slow feedback processes (e.g. land ice-albedo) are adequately taken into account - they indicate a similar range as estimates based on instrumental ... More
Effects of Drake Passage on a strongly eddying global oceanOct 14 2015The climate impact of ocean gateway openings during the Eocene-Oligocene transition is still under debate. Previous model studies employed grid resolutions at which the impact of mesoscale eddies has to be parameterized. We present results of a state-of-the-art ... More
Derivation of Delay Equation Climate Models Using the Mori-Zwanzig FormalismFeb 08 2019Models incorporating delay have been frequently used to understand climate variability phenomena, but often the delay is introduced through an ad-hoc physical reasoning, such as the propagation time of waves. In this paper, the Mori-Zwanzig formalism ... More
Dynamic Transitions of Surface Tension Driven ConvectionMay 05 2011We study the well-posedness and dynamic transitions of the surface tension driven convection in a three-dimensional (3D) rectangular box with non-deformable upper surface and with free-slip boundary conditions. It is shown that as the Marangoni number ... More
High-Performance Distributed Multi-Model / Multi-Kernel Simulations: A Case-Study in Jungle ComputingMar 01 2012High-performance scientific applications require more and more compute power. The concurrent use of multiple distributed compute resources is vital for making scientific progress. The resulting distributed system, a so-called Jungle Computing System, ... More
Notes on the roots of Steiner polynomialsMar 13 2007We study the location and the size of the roots of Steiner polynomials of convex bodies in the Minkowski relative geometry. Based on a problem of Teissier on the intersection numbers of Cartier divisors of compact algebraic varieties it was conjectured ... More
A Climate Network Based Stability Index for El Niño VariabilityMar 18 2015Most of the existing prediction methods gave a false alarm regarding the El Ni\~no event in 2014. A crucial aspect is currently limiting the success of such predictions, i.e. the stability of the slowly varying Pacific climate. This property determines ... More
Steiner polynomials via ultra-logconcave sequencesDec 20 2011We investigate structural properties of the cone of roots of relative Steiner polynomials of convex bodies. We prove that they are closed, monotonous with respect to the dimension, and that they cover the whole upper half-plane, except the positive real ... More
Near-infrared observations of water-ice in OH/IR starsJan 27 2006A search for the near-infrared water-ice absorption band was made in a number of very red OH/IR stars which are known to exhibit the 10um silicate absorption. As a by-product, accurate positions of these highly reddened objects are obtained. We derived ... More
On extensions of Minkowski's theorem on successive minimaMay 20 2014Minkowski's 2nd theorem in the Geometry of Numbers provides optimal upper and lower bounds for the volume of a $o$-symmetric convex body in terms of its successive minima. In this paper we study extensions of this theorem from two different points of ... More
Deep ocean early warning signals of an Atlantic MOC collapseMay 06 2014The Atlantic Meridional Overturning Circulation (MOC) is a crucial part of the climate system because of its associated northward heat transport. The present-day MOC is sensitive to freshwater anomalies and may collapse to a state with a strongly reduced ... More
Crisis of the Chaotic Attractor of a Climate Model: A Transfer Operator ApproachJul 08 2015The destruction of a chaotic attractor leading to a rough change in the dynamics of a system as a control parameter is smoothly varied is studied. While bifurcations involving non-chaotic invariant sets, such as fixed points or periodic orbits, can be ... More
An early warning indicator for atmospheric blocking events using transfer operatorsFeb 03 2015Mar 14 2015The existence of persistent midlatitude atmospheric flow regimes with time-scales larger than 5-10 days and indications of preferred transitions between them motivates to develop early warning indicators for such regime transitions. In this paper, we ... More
Free planes in lattice sphere packingsAug 11 2003We show that for every lattice packing of $n$-dimensional spheres there exists an $(n/\log_2(n))$-dimensional affine plane which does not meet any of the spheres in their interior, provided $n$ is large enough. Such an affine plane is called a free plane ... More
Crushing candies on the lineJan 14 2015We investigate stability properties of a probabilistic cellular automaton based on the candy crush game.
The Cerny conjecture and 1-contracting automataJul 22 2015Oct 05 2015A deterministic finite automaton is synchronizing if there exists a word that sends all states of the automaton to the same state. \v{C}ern\'y conjectured in 1964 that a synchronizing automaton with $n$ states has a synchronizing word of length at most ... More
Successive Minima and Lattice PointsApr 12 2002The main purpose of this note is to prove an upper bound on the number of lattice points of a centrally symmetric convex body in terms of the successive minima of the body. This bound improves on former bounds and narrows the gap towards a lattice point ... More
Constraining Reionization with Lyman Alpha Emitting GalaxiesNov 04 2015Neutral diffuse intergalactic gas that existed during the Epoch of Reionization (EoR) suppresses Lyman Alpha (Lya) flux emitted by background galaxies. In this chapter I summarise the increasing observational support for the claim that Lya photons emitted ... More
Structural transitions of skyrmion lattices in synthetic antiferromagnetsDec 19 2018Jan 16 2019Thin magnetic films with Dzyaloshinskii-Moriya interactions are known to host skyrmion crystals, which typically have a hexagonal lattice structure. We investigate skyrmion-lattice configurations in synthetic antiferromagnets, i.e., a bilayer of thin ... More
Creep of Chiral Domain WallsDec 21 2018Recent experimental studies of magnetic domain expansion under easy-axis drive fields in materials with a perpendicular magnetic anisotropy have shown that the domain wall velocity is asymmetric as a function of an external in plane magnetic field. This ... More
Upper and lower bounds for the correlation function via inducing with general return timesApr 20 2015Oct 15 2015For non-uniformly expanding maps inducing with a general return time to Gibbs Markov maps, we provide sufficient conditions for obtaining higher order asymptotics for the correlation function in the infinite measure setting. Along the way, we show that ... More
Topological invariance of the sign of the Lyapunov exponents in one-dimensional mapsSep 06 2004Nov 02 2004We explore some properties of Lyapunov exponents of measures preserved by smooth maps of the interval, and study the behaviour of the Lyapunov exponents under topological conjugacy.
Restricted Successive MinimaFeb 06 2013Mar 13 2013We give bounds on the successive minima of an $o$-symmetric convex body under the restriction that the lattice points realizing the successive minima are not contained in a collection of forbidden sublattices. Our investigations extend former results ... More
On isotopy of self-homeomorphisms of quadratic inverse limit spacesJul 07 2017We prove that every self-homeomorphism on the inverse limit space of a quadratic map is isotopic to some power of the shift map.
On "observable" Li-Yorke tuples for interval mapsJun 23 2014In this paper we study the set of Li-Yorke $d$-tuples and its $d$-dimensional Lebesgue measure for interval maps $T\colon [0,1] \to [0,1]$. If a topologically mixing $T$ preserves an absolutely continuous probability measure 9with respect to Lebesgue), ... More
Three-dimensional polyhedra can be described by three polynomial inequalitiesJul 14 2008Bosse et al. conjectured that for every natural number $d \ge 2$ and every $d$-dimensional polytope $P$ in $\real^d$ there exist $d$ polynomials $p_0(x),...,p_{d-1}(x)$ satisfying $P=\{x \in \mathbb{R}^d : p_0(x) \ge 0, >..., p_{d-1}(x) \ge 0 \}.$ We ... More
Foundations of Descriptive and Inferential StatisticsFeb 11 2013Aug 30 2015These lecture notes were written with the aim to provide an accessible though technically solid introduction to the logic of systematical analyses of statistical data to undergraduate and to postgraduate students, in particular in the Social Sciences ... More
Altmetrics as traces of the computerization of the research processOct 17 2015I propose a broad, multi-dimensional conception of altmetrics, namely as traces of the computerization of the research process. Computerization should be conceived in its broadest sense, including all recent developments in ICT and software, taking place ... More
Fibonacci-like unimodal inverse limit spaces and the core Ingram conjectureMay 20 2013We study the structure of inverse limit space of so-called Fibonacci-like tent maps. The combinatorial constraints implied by the Fibonacci-like assumption allow us to introduce certain chains that enable a more detailed analysis of symmetric arcs within ... More
Note on adelic triangulations and an Adelic Blichfeldt-type inequalityMay 22 2014We introduce a notion of convex hull and polytope into adele space. This allows to consider adelic triangulations which, in particular, lead to an adelic blichfeldt-type inequality, complementing former results.
Natural extensions for piecewise affine maps via Hofbauer towersJun 23 2013We use canonical Markov extensions (Hofbauer towers) to give an explicit construction of the natural extensions of various measure preserving endomorphisms, and present some applications to particular examples.
Representing simple d-dimensional polytopes by d polynomialsSep 13 2007A polynomial representation of a convex d-polytope P is a finite set \{p_1(x),...,p_n(x)\} of polynomials over E^d such that P=\setcond{x \in \E^d}{p_1(x) \ge 0 {for every} 1 \le i \le n}. By s(d,P) we denote the least possible number of polynomials in ... More
Markov extensions and lifting measures for complex polynomialsJul 26 2005Oct 16 2006For polynomials $f$ on the complex plane with a dendrite Julia set we study invariant probability measures, obtained from a reference measure. To do this we follow Keller in constructing canonical Markov extensions. We discuss ``liftability'' of measures ... More
Lower bounds on the coefficients of Ehrhart polynomialsOct 14 2007Feb 26 2008We present lower bounds for the coefficients of Ehrhart polynomials of convex lattice polytopes in terms of their volume. Concerning the coefficients of the Ehrhart series of a lattice polytope we show that Hibi's lower bound is not true for lattice polytopes ... More
Cone-volume measures of polytopesMay 23 2013Nov 27 2013The cone-volume measure of a polytope with centroid at the origin is proved to satisfy the subspace concentration condition. As a consequence a conjectured (a dozen years ago) fundamental sharp affine isoperimetric inequality for the U-functional is completely ... More
Lattice points in vector-dilated polytopesApr 27 2012For $A\in\mathbb{Z}^{m\times n}$ we investigate the behaviour of the number of lattice points in $P_A(b)=\{x\in\mathbb{R}^n:Ax\leq b\}$, depending on the varying vector $b$. It is known that this number, restricted to a cone of constant combinatorial ... More
Iran's scientific dominance and the emergence of South-East Asian countries as scientific collaborators in the Persian Gulf RegionFeb 15 2016Apr 04 2016A longitudinal bibliometric analysis of publications indexed in Thomson Reuters' Incites and Elsevier's Scopus, and published from Persian Gulf States and neighbouring Middle East countries, shows clear effects of major political events during the past ... More
An Introduction to Business MathematicsSep 11 2015Sep 16 2015These lecture notes provide a self-contained introduction to the mathematical methods required in a Bachelor degree programme in Business, Economics, or Management. In particular, the topics covered comprise real-valued vector and matrix algebra, systems ... More
Weak Gravitational Lensing and its Cosmological ApplicationsMay 02 2008Weak gravitational lensing is a unique probe of the dark side of the universe: it provides a direct way to map the distribution of dark matter around galaxies, clusters of galaxies and on cosmological scales. Furthermore, the measurement of lensing induced ... More
Constructing and searching conditioned Galton-Watson treesDec 18 2014We investigate conditioning Galton-Watson trees on general recursive-type events, such as the event that the tree survives until a specific level. It turns out that the conditioned tree is again a type of Galton-Watson tree, with different types of offspring ... More
LLL-reduction for Integer KnapsacksDec 14 2010Jul 29 2011Given an integer mxn matrix A satisfying certain regularity assumptions, a well-known integer programming problem asks to find an integer point in the associated knapsack polytope P(A, b)={x: A x= b, x>=0} or determine that no such point exists. We obtain ... More
On the representation of polyhedra by polynomial inequalitiesMar 26 2002Oct 24 2002A beautiful result of Br\"ocker and Scheiderer on the stability index of basic closed semi-algebraic sets implies, as a very special case, that every $d$-dimensional polyhedron admits a representation as the set of solutions of at most $d(d+1)/2$ polynomial ... More
Equilibrium states for potentials with $\supφ- \infφ< \htop(f)$Aug 02 2007Aug 14 2008In the context of smooth interval maps, we study an inducing scheme approach to prove existence and uniqueness of equilibrium states for potentials $\phi$ with he `bounded range' condition $\sup \phi - \inf \phi < \htop$, first used by Hofbauer and Keller. ... More
Equilibrium states for interval maps: the potential $-t\log |Df|$Apr 17 2007Feb 19 2008Let $f:I \to I$ be a $C^2$ multimodal interval map satisfying polynomial growth of the derivatives along critical orbits. We prove the existence and uniqueness of equilibrium states for the potential $\phi_t:x\mapsto -t\log|Df(x)|$ for $t$ close to 1, ... More
Densest Lattice Packings of 3-PolytopesSep 29 1999Based on Minkowski's work on critical lattices of 3-dimensional convex bodies we present an efficient algorithm for computing the density of a densest lattice packing of an arbitrary 3-polytope. As an application we calculate densest lattice packings ... More
Transience and thermodynamic formalism for infinitely branched interval mapsApr 28 2011We study a one-parameter family of countably piecewise linear interval maps, which, although Markov, fail the `large image property'. This leads to conservative as well as dissipative behaviour for different maps in the family with respect to Lebesgue. ... More
Bias-voltage dependence of the magneto-resistance in ballistic vacuum tunneling: Theory and application to planar Co(0001) junctionsMay 22 2003Motivated by first-principles results for jellium and by surface-barrier shapes that are typically used in electron spectroscopies, the bias voltage in ballistic vacuum tunneling is treated in a heuristic manner. The presented approach leads in particular ... More
Correlated fractal percolation and the Palis conjectureOct 30 2009Let F1 and F2 be independent copies of correlated fractal percolation, with Hausdorff dimensions dimH(F1) and dimH(F2). Consider the following question: does dimH(F1)+dimH(F2)>1 imply that their algebraic difference F1-F2 will contain an interval? The ... More
A critical comparative analysis of five world university rankingsNov 20 2016Dec 05 2016To provide users insight into the value and limits of world university rankings, a comparative analysis is conducted of 5 ranking systems: ARWU, Leiden, THE, QS and U-Multirank. It links these systems with one another at the level of individual institutions, ... More
Admissibility of kneading sequences and structure of Hubbard trees for quadratic polynomialsJan 30 2008Hubbard trees are invariant trees connecting the points of the critical orbits of postcritically finite polynomials. Douady and Hubbard \cite{Orsay} introduced these trees and showed that they encode the essential information of Julia sets in a combinatorial ... More
Constant slope maps and the Vere-Jones classificationFeb 22 2016Jul 07 2016We study continuous countably piecewise monotone interval maps, and formulate conditions under which these are conjugate to maps of constant slope, particularly when this slope is given by the topological entropy of the map. We confine our investigation ... More
Return time statistics for invariant measures for interval maps with positive Lyapunov exponentAug 02 2007Apr 20 2009We prove that multimodal maps with an absolutely continuous invariant measure have exponential return time statistics around a.e. point. We also show a `polynomial Gibbs property' for these systems, and that the convergence to the entropy in the Ornstein-Weiss ... More
Wild attractors and thermodynamic formalismFeb 08 2012Feb 04 2015Fibonacci unimodal maps can have a wild Cantor attractor, and hence be Lebesgue dissipative, depending on the order of the critical point. We present a one-parameter family $f_\lambda$ of countably piecewise linear unimodal Fibonacci maps in order to ... More
Successive Minima and Best Simultaneous Diophantine ApproximationsMar 17 2005We study the problem of best approximations of a vector $\alpha\in{\mathbb R}^n$ by rational vectors of a lattice $\Lambda\subset {\mathbb R}^n$ whose common denominator is bounded. To this end we introduce successive minima for a periodic lattice structure ... More
Optimizing propagating spin wave spectroscopyJan 30 2019The frequency difference between two oppositely propagating spin waves can be used to probe several interesting magnetic properties, such as the Dzyaloshinkii-Moriya interaction (DMI). Propagating spin wave spectroscopy is a technique that is very sensitive ... More
Phase behavior of hard spheres confined between parallel hard plates: Manipulation of colloidal crystal structures by confinementApr 06 2006Jun 11 2006We study the phase behavior of hard spheres confined between two parallel hard plates using extensive computer simulations. We determine the full equilibrium phase diagram for arbitrary densities and plate separations from one to five hard-sphere diameters ... More
The Polarization of Scattered Lyman Alpha Radiation Around High-Redshift GalaxiesNov 15 2007Jul 16 2008The high-redshift Universe contains luminous Lyman Alpha (hereafter Lya) emitting sources such as galaxies and quasars. The emitted Lya radiation is often scattered by surrounding neutral hydrogen atoms. We show that the scattered Lya radiation obtains ... More
Phase behavior and structure of colloidal bowl-shaped particles: simulationsJul 01 2010We study the phase behavior of bowl-shaped particles using computer simulations. These particles were found experimentally to form a meta-stable worm-like fluid phase in which the bowl-shaped particles have a strong tendency to stack on top of each other ... More
VIMOS-VLT spectroscopy of the giant Ly-alpha nebulae associated with three z~2.5 radio galaxiesApr 09 2007The morphological and spectroscopic properties of the giant (>60 kpc) Ly-alpha nebulae associated with three radio galaxies at z~2.5 (MRC 1558-003, MRC 2025-218 and MRC 0140-257) have been investigated using integral field spectroscopic data obtained ... More
On the Lebesgue measure of Li-Yorke pairs for interval mapsNov 10 2009We investigate the prevalence of Li-Yorke pairs for $C^2$ and $C^3$ multimodal maps $f$ with non-flat critical points. We show that every measurable scrambled set has zero Lebesgue measure and that all strongly wandering sets have zero Lebesgue measure, ... More
Monotonicity of entropy for real multimodal mapsMay 20 2009Dec 10 2013In \cite{Mil}, Milnor posed the {\em Monotonicity Conjecture} that the set of parameters within a family of real multimodal polynomial interval maps, for which the topological entropy is constant, is connected. This conjecture was proved for quadratic ... More
Resolving the optical emission lines of Lya blob 'B1' at z=2.38: another hidden quasarMay 13 2013We have used the SINFONI near-infrared integral field unit on the VLT to resolve the optical emission line structure of one of the brightest (L~1e44 erg/s) and nearest (z=2.38) of all Lya blobs (LABs). The target, known in the literature as object 'B1' ... More
Non-Markovian entanglement dynamics in the presence of system-bath coherenceApr 09 2010A complete treatment of the entanglement of two-level systems, which evolves through the contact with a thermal bath, must include the fact that the system and the bath are not fully separable. Therefore, quantum coherent superpositions of system and ... More
Linear, third- and fifth-order nonlinear spectroscopy of a charge transfer system coupled to an underdamped vibrationFeb 23 2015We study hole, electron and exciton transport in a charge transfer system in the presence of underdamped vibrational motion. We analyze the signature of these processes in the linear and third-, and fifth-order nonlinear electronic spectra. Calculations ... More
Large-scale Structure and Dynamics of the Most X-ray Luminous Galaxy Cluster Known -- RX J1347-1145Dec 11 2009We present photometric, spectroscopic and weak lensing analysis of the large-scale structure and dynamics of the most X-ray luminous galaxy cluster known, RX J1347-1145, at z=0.451. We spectroscopically confirmed 47 new members with LDSS3 on the Magellan ... More
Dynamic Transitions of Quasi-Geostrophic Channel FlowFeb 11 2015The main aim of this paper is to describe the dynamic transitions in flows described by the two-dimensional, barotropic vorticity equation in a periodic zonal channel. In \cite{CGSW03}, the existence of a Hopf bifurcation in this model as the Reynolds ... More
Silicon surface with giant spin-splittingMay 06 2009We demonstrate the induction of a giant Rashba-type spin-splitting on a semiconducting substrate by means of a Bi trimer adlayer on a Si(111) wafer. The in-plane inversion symmetry is broken so that the in-plane potential gradient induces a giant spin-splitting ... More
Intrinsic unpredictability of strong El Niño eventsJul 09 2016The El Ni\~no-Southern Oscillation (ENSO) is a mode of interannual variability in the coupled equatorial ocean/atmosphere Pacific. El Ni\~no describes a state in which sea surface temperatures in the eastern Pacific increase and upwelling of colder, deep ... More
The Mid-IR spatially resolved environment of OH26.5+0.6 at maximum luminosityJan 11 2005We present observations of the famous OH/IR star OH26.5+0.6 obtained using the Mid-Infrared Interferometric Instrument MIDI at the European Southern Observatory (ESO) Very Large Telescope Interferometer VLTI. The emission of the dusty envelope, spectrally ... More
Unified functional network and nonlinear time series analysis for complex systems science: The pyunicorn packageJul 02 2015Apr 06 2016We introduce the \texttt{pyunicorn} (Pythonic unified complex network and recurrence analysis toolbox) open source software package for applying and combining modern methods of data analysis and modeling from complex network theory and nonlinear time ... More
Vehicle-to-Vehicle Communications with Urban Intersection Path Loss ModelsOct 10 2016Vehicle-to-vehicle (V2V) communication can improve road safety and traffic efficiency, particularly around critical areas such as intersections. We analytically derive V2V success probability near an urban intersection, based on empirically supported ... More
Pressure function and limit theorems for almost Anosov flowsNov 20 2018We obtain limit theorems (Stable Laws and Central Limit Theorems, both Gaussian and non-Gaussian) and thermodynamic properties for a class of non-uniformly hyperbolic flows: almost Anosov flows, constructed here. The proofs of the limit theorems for these ... More
Synchronization in Networks of Diffusively Coupled Nonlinear Systems: Robustness Against Time-DelaysOct 31 2017In this manuscript, we study the problem of robust synchronization in networks of diffusively time-delayed coupled nonlinear systems. In particular, we prove that, under some mild conditions on the input-output dynamics of the systems and the network ... More
Generalized Frobenius numbers: Bounds and average behaviorMay 04 2011We produce new upper and lower bounds for the s-Frobenius number by relating it to the so called s-covering radius of a certain convex body with respect to a certain lattice; this generalizes a well-known theorem of R. Kannan for the classical Frobenius ... More
Decay of correlations in one-dimensional dynamicsAug 14 2002We consider multimodal C^3 interval maps f satisfying a summability condition on the derivatives D_n along the critical orbits which implies the existence of an absolutely continuous f -invariant probability measure mu. If f is non-renormalizable, mu ... More
A discrete version of Koldobsky's slicing inequalityNov 09 2015Let $\# K$ be a number of integer lattice points contained in a set $K$. In this paper we prove that for each $d\in {\mathbb N}$ there exists a constant $C(d)$ depending on $d$ only, such that for any origin-symmetric convex body $K \subset {\mathbb R}^d$ ... More
Distances to Lattice Points in Knapsack PolyhedraMay 11 2018We give an optimal upper bound for the maximum-norm distance from a vertex of a knapsack polyhedron to its nearest feasible lattice point. In a randomised setting, we show that the upper bound can be significantly improved on average. As a corollary, ... More
Spam filter analysisFeb 19 2004Unsolicited bulk email (aka. spam) is a major problem on the Internet. To counter spam, several techniques, ranging from spam filters to mail protocol extensions like hashcash, have been proposed. In this paper we investigate the effectiveness of several ... More
Spatial Wireless Channel Prediction under Location UncertaintyJan 15 2015Sep 25 2015Spatial wireless channel prediction is important for future wireless networks, and in particular for proactive resource allocation at different layers of the protocol stack. Various sources of uncertainty must be accounted for during modeling and to provide ... More
Fundamental Limits of Wideband Localization - Part II: Cooperative NetworksJun 04 2010The availability of positional information is of great importance in many commercial, governmental, and military applications. Localization is commonly accomplished through the use of radio communication between mobile devices (agents) and fixed infrastructure ... More
A Precipice Below Which Lies Absurdity? Theories without a Spacetime and Scientific UnderstandingJul 07 2018While the relation between visualization and scientific understanding has been a topic of long-standing discussion, recent developments in physics have pushed the boundaries of this debate to new and still unexplored realms. For it is claimed that, in ... More
Hitting and escaping statistics: mixing, targets and holesSep 05 2016Jan 04 2018There is a natural connection between two types of recurrence law: hitting times to shrinking targets, and hitting times to a fixed target (usually seen as escape through a hole). We show that for systems which mix exponentially fast, one can move through ... More
Integer Points in Knapsack Polytopes and s-covering RadiusNov 14 2012Given an integer matrix A satisfying certain regularity assumptions, we consider for a positive integer s the set F_s(A) of all integer vectors b such that the associated knapsack polytope P(A,b)={x: Ax=b, x non-negative} contains at least s integer points. ... More
Two-stage melting induced by dislocations and grain boundaries in Monolayers of Hard SpheresJul 04 2013Jan 26 2014Melting in two-dimensional systems has remained controversial as theory, simulations, and experiments show contrasting results. One issue that obscures this discussion is whether or not theoretical predictions on strictly 2D systems describe those of ... More
Finite-size Scaling and Universality above the Upper Critical DimensionalityJan 26 1996According to renormalization theory, Ising systems above their upper critical dimensionality d_u = 4 have classical critical behavior and the ratio of magnetization moments Q = <m^2>^2 / <m^4> has the universal value 0.456947... However, Monte Carlo simulations ... More
Cooperative Synchronization in Wireless NetworksApr 30 2013Aug 19 2013Synchronization is a key functionality in wireless network, enabling a wide variety of services. We consider a Bayesian inference framework whereby network nodes can achieve phase and skew synchronization in a fully distributed way. In particular, under ... More
Semi-passivity and synchronization of diffusively coupled neuronal oscillatorsMar 20 2009We discuss synchronization in networks of neuronal oscillators which are interconnected via diffusive coupling, i.e. linearly coupled via gap junctions. In particular, we present sufficient conditions for synchronization in these networks using the theory ... More
Integrality Gaps of Integer Knapsack ProblemsNov 11 2016We obtain optimal lower and upper bounds for the (additive) integrality gaps of integer knapsack problems. In a randomised setting, we show that the integrality gap of a "typical" knapsack problem is drastically smaller than the integrality gap that occurs ... More
Joint CMB and Weak Lensing Analysis; Physically Motivated Constraints on Cosmological ParametersFeb 20 2003Feb 23 2003We use Cosmic Microwave Background (CMB) observations together with the Red-sequence Cluster Survey (RCS) weak lensing results to derive constraints on a range of cosmological parameters. This particular choice of observations is motivated by their robust ... More
Existence and convergence properties of physical measures for certain dynamical systems with holesMay 29 2007Sep 24 2008We study two classes of dynamical systems with holes: expanding maps of the interval and Collet-Eckmann maps with singularities. In both cases, we prove that there is a natural absolutely continuous conditionally invariant measure $\mu$ (a.c.c.i.m.) with ... More
The pressure function for infinite equilibrium measuresNov 14 2017Oct 09 2018Assume that $(X,f)$ is a dynamical system and $\phi:X \to [-\infty, \infty)$ is a potential such that the $f$-invariant measure $\mu_\phi$ equivalent to $\phi$-conformal measure is infinite, but that there is an inducing scheme $F = f^\tau$ with a finite ... More
Optimizing Reweighted Belief Propagation for Distributed Likelihood Fusion ProblemsJan 28 2018Feb 07 2018Belief propagation (BP) is a powerful tool to solve distributed inference problems, though it is limited by short cycles in the corresponding factor graph. Such cycles may lead to incorrect solutions or oscillatory behavior. Only for certain types of ... More
Rates of mixing for nonMarkov infinite measure semiflowsJul 29 2016Nov 01 2018We develop an abstract framework for obtaining optimal rates of mixing and higher order asymptotics for infinite measure semiflows. Previously, such results were restricted to the situation where there is a first return Poincar\'e map that is uniformly ... More
Matching for generalised $β$-transformationsOct 06 2016We investigate matching for the family $T_\alpha(x) = \beta x + \alpha \pmod 1$, $\alpha \in [0,1]$, for fixed $\beta > 1$. Matching refers to the property that there is an $n \in \mathbb N$ such that $T_\alpha^n(0) = T_\alpha^n(1)$. We show that for ... More
Uncountably many planar embeddings of unimodal inverse limit spacesMar 12 2016Sep 08 2016For point $x$ in the inverse limit space $X$ with a single unimodal bonding map we construct, with the use of symbolic dynamics, a planar embedding such that $x$ is accessible. It follows that there are uncountably many non-equivalent planar embeddings ... More
The Core Ingram Conjecture for non-recurrent critical pointsDec 22 2015We study inverse limit spaces of tent maps, and the Ingram Conjecture, which states that the inverse limit spaces of tent maps with different slopes are non-homeomorphic. When the tent map is restricted to its core, so there is no ray compactifying on ... More
Cotangent bundle reduction and Poincaré-Birkhoff normal formsNov 25 2012In this paper we study a systematic and natural construction of canonical coordinates for the reduced space of a cotangent bundle with a free Lie group action. The canonical coordinates enable us to compute Poincar{\'e}-Birkhoff normal forms of relative ... More
The Impact of The IGM on High-Redshift Lyman Alpha Emission LinesJan 23 2007May 04 2007We calculate the impact of the intergalactic medium (IGM) on the observed Lyman alpha lines (hereafter Lya) emitted by galaxies in an ionised IGM at z>4. Our model accounts for gas clumping in the IGM and for the fact that high-redshift galaxies reside ... More
On Detecting the X-ray Silhouette of a Damped Lyman alpha SystemSep 22 2004Mar 16 2005We explore the possibility of resolving an image of a damped Lyman alpha (DLA) system in absorption against an extended, diffuse background X-ray source. Typical columns of neutral hydrogen in DLAs are high enough to block out up to ~30% of the soft X-ray ... More
Depletion-induced biaxial nematic states of boardlike particlesNov 17 2011Mar 26 2012With the aim of investigating the stability conditions of biaxial nematic liquid crystals, we study the effect of adding a non-adsorbing ideal depletant on the phase behavior of colloidal hard boardlike particles. We take into account the presence of ... More