Results for "Jes Kristian Jørgensen"

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Resolved images of a protostellar outflow launched by an extended disk windDec 15 2016Young stars are associated with prominent outflows of molecular gas. The ejection of gas via these outflows is believed to remove angular momentum from the protostellar system, thus permitting young stars to grow by accretion of material from the protostellar ... More
The Earliest Stages of Star and Planet Formation: Core Collapse, and the Formation of Disks and OutflowsJan 10 2014(Abridged) In this review we focus on the observations and theory of the formation of early disks and outflows, and their connections with the first phases of planet formation. Large rotationally supported circumstellar disks, although common around more ... More
Detection of Infall in the Protostar B335 with ALMAOct 12 2015Observations of the isolated globule B335 with ALMA have yielded absorption features against the continuum that are redshifted from the systemic velocity in both HCN and HCO$^+$ lines. These features provide unambiguous evidence for infall toward a central ... More
Evidence for the start of planet formation in a young circumstellar diskJun 25 2018The growth of dust grains in protoplanetary disks is a necessary first step towards planet formation. This growth has been inferred via observations of thermal dust emission towards mature protoplanetary systems (age >2 million years) with masses that ... More
The chemical connection between 67P/C-G and IRAS 16293-2422Feb 08 2018The chemical evolution of a star- and planet-forming system begins in the prestellar phase and proceeds across the subsequent evolutionary phases. The chemical trail from cores to protoplanetary disks to planetary embryos can be studied by comparing distant ... More
The ALMA-PILS survey: The sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-GerasimenkoFeb 08 2018Feb 21 2018The evolutionary past of our Solar System can be pieced together by comparing analogous low-mass protostars with remnants of our Protosolar Nebula - comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory ... More
Interplay between chemistry and dynamics in embedded protostellar disksSep 25 2013A fundamental part of the study of star formation is to place young stellar objects in an evolutionary sequence. Establishing a robust evolutionary classification scheme allows us not only to understand how the Sun was born but also to predict what kind ... More
Runge-Kutta methods for third order weak approximation of SDEs with multidimensional additive noiseOct 06 2009May 21 2010A new class of third order Runge-Kutta methods for stochastic differential equations with additive noise is introduced. In contrast to Platen's method, which to the knowledge of the author has been up to now the only known third order Runge-Kutta scheme ... More
Decoherence and Quantum Measurement of Josephson-Junction QubitsDec 09 2005This work deals with two pressing issues in the design and operation of Josephson qubits -- loss of coherence and measurement. (Longer abstract follows in the work.)
A forward-backward splitting algorithm for the minimization of non-smooth convex functionals in Banach spaceJul 04 2008Oct 14 2008We consider the task of computing an approximate minimizer of the sum of a smooth and non-smooth convex functional, respectively, in Banach space. Motivated by the classical forward-backward splitting method for the subgradients in Hilbert space, we propose ... More
Solving Stress and Compliance Constrained Volume Minimization using Anisotropic Mesh Adaptation, the Method of Moving Asymptotes and a Global p-normOct 28 2014Aug 04 2015The p-norm often used in stress constrained topology optimisation supposedly mimics a delta function and it is thus characterised by a small length scale and ideally one would also prefer to have the solid-void transition occur over a small length scale, ... More
On some generalizations of skew-shifts on $\mathbb{T}^2$Oct 11 2016In this paper we investigate maps of the two-torus $\mathbb{T}^2$ of the form $T(x,y)=(x+\omega,g(x)+f(y))$ for Diophantine $\omega\in\mathbb{T}$ and for a class of maps $f,g:\mathbb{T}\to\mathbb{T}$, where each $g$ is strictly monotone and of degree ... More
The dynamics of a class of quasi-periodic Schrödinger cocyclesNov 21 2013Let $f:\mathbb{T}\to\mathbb{R}$ be a Morse function of class $C^2$ with exactly two critical points, let $\omega\in\mathbb{T}$ be Diophantine, and let $\lambda>0$ be sufficiently large (depending on $f$ and $\omega$). For any value of the parameter $E\in ... More
Zeros of functions in Hilbert spaces of Dirichlet seriesJun 13 2012Oct 11 2012The Dirichlet--Hardy space $\Ht$ consists of those Dirichlet series $\sum_n a_n n^{-s}$ for which $\sum_n |a_n|^2<\infty$. It is shown that the Blaschke condition in the half-plane $\operatorname{Re} s>1/2$ is a necessary and sufficient condition for ... More
Encounters with AlexApr 21 2017In the 80th anniversary book for Alex M\"uller I wrote a story of our scientific collaboration, Shared Fascinations. This time I will be more personal, about the human side of our collaboration and encounters, while also referring to episodes mentioned ... More
A short review and primer on eye tracking in human computer interaction applicationsSep 23 2016The application of psychophysiologicy in human-computer interaction is a growing field with significant potential for future smart personalised systems. Working in this emerging field requires comprehension of an array of physiological signals and analysis ... More
Large-scale numerical simulations of star formation put to the test: Comparing synthetic images and actual observations for statistical samples of protostarsOct 27 2015Dec 14 2015(abridged) Context: Both observations and simulations of embedded protostars have progressed rapidly in recent years. Bringing them together is an important step in advancing our knowledge about the earliest phases of star formation. Aims: To compare ... More
Compactly generated homotopy categoriesSep 11 2006Over an associative ring we consider a class $\mathbb{X}$ of left modules which is closed under set-indexed coproducts and direct summands. We investigate when the triangulated homotopy category $\mathsf{K}(\mathbb{X})$ is compactly generated, and give ... More
The solar system mimics a hydrogen atomMar 28 2014The solar system and the hydrogen atom are two well known systems on different scales and look unrelated: The former is a classical system on the scale of about billions of kilometers and the latter a quantum system of about tens of picometers. Here we ... More
Normally Regular DigraphsOct 30 2014A normally regular digraph with parameters $(v,k,\lambda,\mu)$ is a directed graph on $v$ vertices whose adjacency matrix $A$ satisfies the equation $AA^t=k I+\lambda (A+A^t)+\mu(J-I-A-A^t)$. This means that every vertex has out-degree $k$, a pair of ... More
Linking interstellar and cometary O$_2$: a deep search for $^{16}$O$^{18}$O in the solar-type protostar IRAS 16293--2422May 31 2018Recent measurements carried out at comet 67P/C-G with the ${\it Rosetta}$ probe revealed that molecular oxygen, O$_2$, is the fourth most abundant molecule in comets. Models show that O$_2$ is likely of primordial nature, coming from the interstellar ... More
Alignment Between Protostellar Outflows and Filamentary StructureJul 25 2017We present new Submillimeter Array (SMA) observations of CO(2-1) outflows toward young, embedded protostars in the Perseus molecular cloud as part of the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. For 57 Perseus ... More
Viewpoint: Opportunities and challenges of two-dimensional magnetic van der Waals materials: magnetic graphene?Apr 29 2016There has been a huge increase of interests in two-dimensional van der Waals materials over the past ten years or so with the conspicuous absence of one particular class of materials: magnetic van der Waals systems. In this Viewpoint, we point it out ... More
The Structural Biology and Critical Evaluation of Bacterial Proteases as Targets in New Drug DesignJun 03 2014Bacteria produce a range of proteolytic enzymes, for which a number human equivalent or structurally similar examples exist and the primary focus of this study was to analyse the published literature to find proteolytic enzymes, specifically endoproteses ... More
The homological content of the Jones representations at $q = -1$Feb 25 2014We generalize a discovery of Kasahara and show that the Jones representations of braid groups, when evaluated at $q = -1$, are related to the action on homology of a branched double cover of the underlying punctured disk. As an application, we prove for ... More
Multivariate Covariance Generalized Linear ModelsApr 07 2015We propose a general framework for non-normal multivariate data analysis called multivariate covariance generalized linear models (McGLMs), designed to handle multivariate response variables, along with a wide range of temporal and spatial correlation ... More
Partition functions 1: Improved partition functions and thermodynamic quantities for normal, equilibrium, and ortho and para molecular hydrogenJul 15 2016Aims. In this work we rigorously show the shortcomings of various simplifications that are used to calculate the total internal partition function. These shortcomings can lead to errors of up to 40 percent or more in the estimated partition function. ... More
Casimir Effect in a Supersymmetry-Breaking Brane-World as Dark EnergySep 10 2004Mar 25 2005A new model for the origin of dark energy is proposed based on the Casimir effect in a supersymmetry-breaking brane-world. Supersymmetry is assumed to be preserved in the bulk while broken on a 3-brane. Due to the boundary conditions imposed on the compactified ... More
Adaptable Radiative Transfer Innovations for Submillimeter Telescopes (ARTIST)Feb 23 2011Submillimeter observations are a key for answering many of the big questions in modern-day astrophysics, such as how stars and planets form, how galaxies evolve, and how material cycles through stars and the interstellar medium. With the upcoming large ... More
Variety of power sums and divisors in the moduli space of cubic fourfoldsSep 07 2013Sep 19 2013We show that a cubic fourfold F that is apolar to a Veronese surface has the property that its variety of power sums VSP(F,10) is singular along a K3 surface of genus 20. We prove that these cubics form a divisor in the moduli space of cubic fourfolds ... More
Enabling accurate first-principle calculations of electronic properties with a corrected k dot p schemeJul 05 2016A computationally inexpensive kp-based interpolation scheme is developed that can extend the eigenvalues and momentum matrix elements of a sparsely sampled k-point grid into a densely sampled one. Dense sampling, often required to accurately describe ... More
Coexistence of ac and pp spectrum for kicked quasi-periodic potentialsJan 14 2019We introduce a class of real analytic "peaky" potentials for which the corresponding quasi-periodic 1D Schr\"odinger operators exhibit, for quasiperiodic frequencies in a set of positive Lebesgue measure, both absolutely continuous and pure point spectrum. ... More
Structure and binding in crystals of cage-like molecules: hexamine and platonic hydrocarbonsOct 07 2010In this paper, we show that first-principle calculations using a van der Waals density functional (vdW-DF), [Phys. Rev. Lett. $\mathbf{92}$, 246401 (2004)] permits determination of molecular crystal structure. We study the crystal structures of hexamine ... More
A stochastic model of cascades in 2D turbulenceDec 30 2011The dual cascade of energy and enstrophy in 2D turbulence cannot easily be understood in terms of an analog to the Richardson-Kolmogorov scenario describing the energy cascade in 3D turbulence. The coherent up- and downscale fluxes points to non-locality ... More
BREN: Body Reflection Essence-Neuter Model for Separation of Reflection ComponentsAug 25 2015We propose a novel reflection color model consisting of body essence and (mixed) neuter, and present an effective method for separating dichromatic reflection components using a single image. Body essence is an entity invariant to interface reflection, ... More
Little Randall-Sundrum Model and a Multiply Warped SpacetimeApr 04 2008Apr 10 2008A recent work has investigated the possibility that the mass scale for the ultraviolet (UV) brane in the Randall-Sundrum (RS) model is of the order 10^3 TeV. In this so called ``Little Randall-Sundrum'' (LRS) model the bounds on the gauge sector are less ... More
Full Restoration of Visual Encrypted Color ImagesNov 18 2011While strictly black and white images have been the basis for visual cryptography, there has been a lack of an easily implemented format for colour images. This paper establishes a simple, yet secure way of implementing visual cryptography with colour, ... More
Domain Representable Spaces Defined by Strictly Positive InductionJun 29 2010Sep 02 2010Recursive domain equations have natural solutions. In particular there are domains defined by strictly positive induction. The class of countably based domains gives a computability theory for possibly non-countably based topological spaces. A $ qcb_{0} ... More
Geometry of the Lagrangian Grassmannian Sp(3)/U(3) with applications to Brill-Noether lociSep 13 2002Dec 17 2002The geometry of Sp(3)/U(3) as a subvariety of Gr(3,6) is explored to explain several examples given by Mukai of non-abelian Brill-Noether loci, and to give some new examples. These examples identify Brill-Noether loci of vector bundles on linear sections ... More
Sinogram constrained TV-minimization for metal artifact reduction in CTApr 26 2014A new method for reducing metal artifacts in X-ray computed tomography (CT) images is presented. It bases on the solution of a convex optimization problem with inequality constraints on the sinogram, and total variation regularization for the reconstructed ... More
Simulating Viscous Fingering with a Timespace Method and Anisotropic Mesh AdaptationAug 17 2015We report findings related to a two dimensional viscous fingering problem solved with a timespace method and anisotropic elements. Timespace methods have attracted interest for solution of time dependent partial differential equations due to the implications ... More
GCD sums and complete sets of square-free numbersFeb 02 2014Oct 12 2014It is proved that \[ \sum_{k,{\ell}=1}^N\frac{\gcd(n_k,n_{\ell})}{\sqrt{n_k n_{\ell}}} \ll N\exp\left(C\sqrt{\frac{\log N \log\log\log N}{\log\log N}}\right) \] holds for arbitrary integers $1\le n_1<\cdots < n_N$. This bound is essentially better than ... More
Projective geometry of Wachspress coordinatesApr 03 2019We show that there is a unique hypersurface of minimal degree passing through the non-faces of a polytope which is defined by a simple hyperplane arrangement. This generalizes the construction of the adjoint curve of a polygon by Wachspress in 1975. The ... More
Note on the resonance method for the Riemann zeta functionJan 18 2017We improve Montgomery's $\Omega$-results for $|\zeta(\sigma+it)|$ in the strip $1/2<\sigma<1$ and give in particular lower bounds for the maximum of $|\zeta(\sigma+it)|$ on $\sqrt{T}\le t \le T$ that are uniform in $\sigma$. We give similar lower bounds ... More
What classicality? Decoherence and Bohr's classical conceptsSep 21 2010Mar 12 2012Niels Bohr famously insisted on the indispensability of what he termed "classical concepts." In the context of the decoherence program, on the other hand, it has become fashionable to talk about the "dynamical emergence of classicality" from the quantum ... More
Classification of Stochastic Runge-Kutta Methods for the Weak Approximation of Stochastic Differential EquationsMar 19 2013In the present paper, a class of stochastic Runge-Kutta methods containing the second order stochastic Runge-Kutta scheme due to E. Platen for the weak approximation of It\^o stochastic differential equation systems with a multi-dimensional Wiener process ... More
Stochastic B-series analysis of iterated Taylor methodsMar 23 2010Jul 29 2010For stochastic implicit Taylor methods that use an iterative scheme to compute their numerical solution, stochastic B--series and corresponding growth functions are constructed. From these, convergence results based on the order of the underlying Taylor ... More
Composition of stochastic B-series with applications to implicit Taylor methodsMar 23 2010Sep 03 2010In this article, we construct a representation formula for stochastic B-series evaluated in a B-series. This formula is used to give for the first time the order conditions of implicit Taylor methods in terms of rooted trees. Finally, as an example we ... More
Rational Quartic SpectrahedraOct 26 2018Rational quartic spectrahedra in $3$-space are semialgebraic convex subsets in $\mathbb{R}^3$ of semidefinite, real symmetric $(4 \times 4)$-matrices, whose boundary admit a rational parameterization. They are identified by the rank-$2$-locus and the ... More
Protostellar accretion traced with chemistry: Comparing synthetic C18O maps of embedded protostars to real observationsDec 01 2015Dec 19 2015Context: Understanding how protostars accrete their mass is a central question of star formation. One aspect of this is trying to understand whether the time evolution of accretion rates in deeply embedded objects is best characterised by a smooth decline ... More
Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA viewNov 28 2012Measuring the water deuterium fractionation in the inner warm regions of low-mass protostars has so far been hampered by poor angular resolution obtainable with single-dish ground- and space-based telescopes. Observations of water isotopologues using ... More
Subarcsecond resolution observations of warm water towards three deeply embedded low-mass protostarsMar 22 2012Water is present during all stages of star formation: as ice in the cold outer parts of protostellar envelopes and dense inner regions of circumstellar disks, and as gas in the envelopes close to the protostars, in the upper layers of circumstellar disks ... More
Rotation numbers for quasiperiodically forced circle maps - Mode-locking vs strict monotonicityJul 24 2006We describe the relation between the dynamical properties of a quasiperiodically forced orientation-preserving circle homeomorphism and the behavior of the fibered rotation number with respect to strictly monotone perturbations. Despite the fact that ... More
Algebraic Degree of Polynomial OptimizationFeb 09 2008Consider the polynomial optimization problem whose objective and constraints are all described by multivariate polynomials. Under some genericity assumptions, %% on these polynomials, we prove that the optimality conditions always hold on optimizers, ... More
Decay rates for approximation numbers of composition operatorsFeb 17 2013Dec 03 2013A general method for estimating the approximation numbers of composition operators on $\Ht$, using finite-dimensional model subspaces, is studied and applied in the case when the symbol of the operator maps the unit disc to a domain whose boundary meets ... More
The abelian fibration on the Hilbert cube of a K3 surface of genus 9Jul 01 2005In this paper we construct an abelian fibration over ${\bf P}^3$ on the Hilbert cube of the primitive K3 surface of genus 9. After the abelian fibration constructed by Mukai on the Hilbert square on the primitive K3 surface S of genus 5, this is the second ... More
Integral means and boundary limits of Dirichlet seriesDec 04 2007We study the boundary behavior of functions in the Hardy spaces HD^p for ordinary Dirichlet series. Our main result, answering a question of H. Hedenmalm, shows that the classical F. Carlson theorem on integral means does not extend to the imaginary axis ... More
Addendum to "K3-surfaces of genus 8 and varieties of sums of powers of cubic fourfolds"Nov 17 2006In this note, which is an addendum to the e-print math.AG/9810121, we prove that the variety VSP(F,10) of presentations of a general cubic form F in 6 variables as a sum of 10 cubes is a smooth symplectic 4-fold, which is deformation equivalent to the ... More
The effect of finite population size on the evolutionary dynamics in multi-person Prisoner's DilemmaAug 07 2006We study the influence of stochastic effects due to finite population size in the evolutionary dynamics of populations interacting in the multi-person Prisoner's Dilemma game. This paper is an extension of the investigation presented in a recent paper ... More
String Theory and the Vacuum Structure of Confining Gauge TheoriesSep 25 2004We discuss recent progress in the understanding of the vacuum structure (effective superpotentials) of confining gauge theories with N=1 supersymmetry. Even for non-supersymmetric theories, appropriate perturbative calculations (e.g. using the background ... More
Creating massive entanglement of Bose condensed atomsApr 26 2001Apr 30 2001We propose a direct, coherent coupling scheme that can create massively entangled states of Bose-Einstein condensed atoms. Our idea is based on an effective interaction between two atoms from coherent Raman processes through a (two atom) molecular intermediate ... More
K3-surfaces of genus 8 and varieties of sums of powers of cubic fourfoldsOct 19 1998Nov 17 2006The main outcome of this paper is that the variety VSP(F,10) of presentations of a general cubic form F in 6 variables as a sum of 10 cubes is a smooth symplectic 4-fold obtained a deformation of the Hilbert square of a K3 surface of genus 8. After publishing ... More
Abelian surfaces with two plane cubic curve fibrations and Calabi-Yau threefoldsOct 19 1998(1,d)-polarized abelian surfaces in P^(d-1) with two plane cubic curve fibrations lie in two elliptic P^2-scrolls. The union of these scrolls form a reducible Calabi-Yau 3-fold. In this paper we show that this occurs when d<10 and analyse the family of ... More
A Geometrical Construction of Rational Boundary States in Linear Sigma ModelsMar 28 2002Dec 12 2002Starting from the geometrical construction of special Lagrangian submanifolds of a toric variety, we identify a certain subclass of A-type D-branes in the linear sigma model for a Calabi-Yau manifold and its mirror with the A- and B-type Recknagel-Schomerus ... More
Conic bundles in projective fourspaceSep 27 1993P. Ellia and G.Sacchiero have shown that if $S$ is a smooth surface in $\Pn 4$ which is ruled in conics, then $S$ has degree 4 or 5. In this paper we give a proof of this result combining the ideas of Ellia and Sacchiero as they are used in the paper ... More
Relativistic Superfluids in Curved SpacetimeNov 07 2015Feb 11 2016Superfluids under an intense gravitational field are typically found in compact stellar cores. Most treatments of these superfluids, however, are done using a flat spacetime background. In this paper, the effect of spacetime curvature on relativistic ... More
Strong Regularities in Growth and Decline of Popularity of Social Media ServicesJun 25 2014We analyze general trends and pattern in time series that characterize the dynamics of collective attention to social media services and Web-based businesses. Our study is based on search frequency data available from Google Trends and considers 175 different ... More
Sommerfeld Enhancement from Multiple MediatorsMar 28 2012Mar 30 2013We study the Sommerfeld enhancement experienced by a scattering object that couples to a tower of mediators. This can occur in, e.g., models of secluded dark matter when the mediator scale is generated naturally by hidden-sector confinement. Specializing ... More
Observation of a Coulomb flux tubeSep 29 2017In Coulomb gauge there is a longitudinal color electric field associated with a static quark-antiquark pair. We have measured the spatial distribution of this field, and find that it falls off exponentially with transverse distance from a line joining ... More
Evaluating the Fabius functionSep 23 2016The Thue-Morse sequence (1, -1, -1, 1, -1, 1, 1, ...) can in a sense be naturally extended to a continuous function f called the Fabius function. It is shown how to determine the exact value of f(x) whenever x is the ratio between a positive integer and ... More
Enabling accurate first-principle calculations of electronic properties with a corrected k.p schemeJul 05 2016Mar 22 2017A computationally inexpensive k.p-based interpolation scheme is developed that can extend the eigenvalues and momentum matrix elements of a sparsely sampled k-point grid into a densely sampled one. Dense sampling, often required to accurately describe ... More
The Coulomb flux tube on the latticeApr 28 2017In Coulomb gauge a longitudinal electric field is generated instantaneously with the creation of a static quark-antiquark pair. The field due to the quarks is a sum of two contributions, one from the quark and one from the antiquark, and there is no obvious ... More
The minimum overlap problem revisitedSep 23 2016For a given partition of (1, 2, ..., 2n) into two disjoint subsets A and B with n elements in each, consider the maximum number of times any integer occurs as the difference between an element of A and an element of B. The minimum value of this maximum ... More
Niels Bohr as Philosopher of Experiment: Does Decoherence Theory Challenge Bohr's Doctrine of Classical Concepts?Feb 23 2015Niels Bohr's doctrine of the primacy of "classical concepts" is arguably his most criticized and misunderstood view. We present a new, careful historical analysis that makes clear that Bohr's doctrine was primarily an epistemological thesis, derived from ... More
Recovering Valuations on Demushkin FieldsJun 19 2015Let $K$ be a field with $G_K(2) \simeq G_{\mathbb{Q}_2}(2)$, where $G_F(2)$ denotes the maximal pro-2 quotient of the absolute Galois group of a field $F$. We prove that then $K$ admits a (non-trivial) valuation $v$ which is 2-henselian and has residue ... More
The Convex Hull of a VarietyApr 18 2010Jul 01 2010We present a characterization, in terms of projective biduality, for the hypersurfaces appearing in the boundary of the convex hull of a compact real algebraic variety.
$L^\infty$ to $L^p$ constants for Riesz projectionsMay 11 2010The norm of the Riesz projection from $L^\infty(\T^n)$ to $L^p(\T^n)$ is considered. It is shown that for $n=1$, the norm equals $1$ if and only if $p\le 4$ and that the norm behaves asymptotically as $p/(\pi e)$ when $p\to \infty$. The critical exponent ... More
Families of efficient second order Runge-Kutta methods for the weak approximation of Itô stochastic differential equationsMar 20 2013Recently, a new class of second order Runge-Kutta methods for It\^o stochastic differential equations with a multidimensional Wiener process was introduced by R\"o{\ss}ler. In contrast to second order methods earlier proposed by other authors, this class ... More
Continuous Weak Approximation for Stochastic Differential EquationsMar 18 2013A convergence theorem for the continuous weak approximation of the solution of stochastic differential equations by general one step methods is proved, which is an extension of a theorem due to Milstein. As an application, uniform second order conditions ... More
A micro/macro algorithm to accelerate Monte Carlo simulation of stochastic differential equationsSep 20 2010Nov 05 2011We present and analyze a micro/macro acceleration technique for the Monte Carlo simulation of stochastic differential equations (SDEs) in which there is a separation between the (fast) time-scale on which individual trajectories of the SDE need to be ... More
A statistical framework for fair predictive algorithmsOct 25 2016Predictive modeling is increasingly being employed to assist human decision-makers. One purported advantage of replacing human judgment with computer models in high stakes settings-- such as sentencing, hiring, policing, college admissions, and parole ... More
Approximation numbers of composition operators on the $H^2$ space of Dirichlet seriesFeb 17 2013Dec 09 2014By a theorem of Gordon and Hedenmalm, $\varphi$ generates a bounded composition operator on the Hilbert space $\mathscr{H}^2$ of Dirichlet series $\sum_n b_n n^{-s}$ with square-summable coefficients $b_n$ if and only if $\varphi(s)=c_0 s+\psi(s)$, where ... More
Sensitivity to temperature perturbations of the ageing states in a re-entrant ferromagnetSep 03 1998Dynamic magnetic properties and ageing phenomena of the re-entrant ferromagnet (Fe0.20Ni0.80)75P16B6Al3 are investigated by time dependent zero field cooled magnetic relaxation, m (t), measurements. The influence of a temperature cycling (perturbation), ... More
Variety of power sums and divisors in the moduli space of cubic fourfoldsSep 07 2013Feb 11 2017We show that a cubic fourfold F that is apolar to a Veronese surface has the property that its variety of power sums VSP(F,10) is singular along a K3 surface of genus 20. We prove that these cubics form a divisor in the moduli space of cubic fourfolds ... More
An optimal transport approach for solving dynamic inverse problems in spaces of measuresJan 29 2019In this paper we propose and study a novel optimal transport based regularization of linear dynamic inverse problems. The considered inverse problems aim at recovering a measure valued curve and are dynamic in the sense that (i) the measured data takes ... More
Convergence of Runge-Kutta Methods Applied to Linear Partial Differential-Algebraic EquationsMar 17 2013We apply Runge-Kutta methods to linear partial differential-algebraic equations of the form $Au_t(t,x) + B(u_{xx}(t,x)+ru_x(t,x))+Cu(t,x) = f(t,x)$, where $A,B,C\in\R^{n,n}$ and the matrix $A$ is singular. We prove that under certain conditions the temporal ... More
Large GCD sums and extreme values of the Riemann zeta functionJul 21 2015Nov 23 2016It is shown that the maximum of $|\zeta(1/2+it)|$ on the interval $T^{1/2}\le t \le T$ is at least $\exp\left((1/\sqrt{2}+o(1)) \sqrt{\log T \log\log\log T/\log\log T}\right)$. Our proof uses Soundararajan's resonance method and a certain large GCD sum. ... More
Structural Bifurcation Analysis in Chemical Reaction NetworksNov 01 2017Nov 06 2017In living cells, chemical reactions form a complex network. Complicated dynamics arising from such networks are the origins of biological functions. We propose a novel mathematical method to analyze bifurcation behaviors of a reaction system from the ... More
Solar-System Constraints on f(R) Chameleon GravityAug 08 2011We investigate the solar-system constraint on the f(R) theory of modified gravity with chameleon mechanism, where f(R) represents the deviation from general relativity in the gravity action. We obtain a stringent bound to a general, non-constant deviation ... More
Comparative analysis of rigidity across protein familiesMay 26 2009Jun 03 2009Rigidity analysis using the "pebble game" has been applied to protein crystal structures to obtain information on protein folding, assembly and t he structure-function relationship. However, previous work using this technique has not made clear how the ... More
Curvature dependence of propagating velocity for a simplified calcium modelFeb 19 2014It is known that curvature relation plays a key role in the propagation of two-dimensional waves in an excitable model. Such a relation is believed to obey the eikonal equation for typical excitable models (e.g., the FitzHugh-Nagumo (FHN) model), which ... More
Random fixed point theorems for Hardy-Rogers self-random operators with applications to random integral equationsJun 06 2017In this paper, we prove some random fixed point theorems for Hardy-Rogers self-random operators in separable Banach spaces and, as some applications, we show the existence of a solution for random nonlinear integral equations in Banach spaces. Some stochastic ... More
The rotational temperature of polar molecular ions in Coulomb crystalsApr 19 2005Jun 17 2005With MgH^+ ions as a test case, we investigate to what extent the rotational motion of smaller polar molecular ions sympathetically cooled into Coulomb crystals in linear Paul traps couples to the translational motions of the ion ensemble. By comparing ... More
A fast and memory-efficient spectral Galerkin scheme for distributed elliptic optimal control problemsDec 21 2017Many scientific and engineering challenges can be formulated as optimization problems which are constrained by partial differential equations (PDEs). These include inverse problems, control problems, and design problems. As a major challenge, the associated ... More
How little data is enough? Phase-diagram analysis of sparsity-regularized X-ray CTDec 21 2014We introduce phase-diagram analysis, a standard tool in compressed sensing, to the X-ray CT community as a systematic method for determining how few projections suffice for accurate sparsity-regularized reconstruction. In compressed sensing a phase diagram ... More
A two-stage estimation procedure for non-linear structural equation modelsMar 17 2018Oct 09 2018Applications of structural equation models (SEMs) are often restricted to linear associations between variables. Maximum likelihood (ML) estimation in non-linear models may be complex and require numerical integration. Furthermore, ML inference is sensitive ... More
Signature of deconfinement with spin down compression in cooling hybrid starsJan 02 2008Apr 05 2009The thermal evolution of neutron stars is coupled to their spin down and the resulting changes in structure and chemical composition. This coupling correlates stellar surface temperatures with rotational state as well as time. We report an extensive investigation ... More
Piece of CAKE: A Comprehensive Queue Management Solution for Home GatewaysApr 20 2018May 25 2018The last several years has seen a renewed interest in smart queue management to curb excessive network queueing delay, as people have realised the prevalence of bufferbloat in real networks. However, for an effective deployment at today's last mile connections, ... More
Finite First Hitting Time versus Stochastic Convergence in Particle Swarm OptimisationMay 27 2011We reconsider stochastic convergence analyses of particle swarm optimisation, and point out that previously obtained parameter conditions are not always sufficient to guarantee mean square convergence to a local optimum. We show that stagnation can in ... More
Low Temperature Ageing Behaviour of U-Nb $γ^{o}$ Phase AlloysMar 15 2018Ageing mechanisms of the U-7\%wtNb alloy have been investigated on samples exposed to temperatures of 150$^{o}$C for up to 5000\,hours. A variety of surface and bulk analytic techniques have been used to investigate microstructural, chemical and crystallographic ... More