Results for "Kristoffer H. Madsen"

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Ergodicity-breaking reveals time optimal economic behavior in humansJun 11 2019Jun 19 2019Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theory reveals how individuals should tolerate risk in different environments. To optimise wealth over time, agents ... More
Postprocessing seasonal weather forecastsJul 23 2019Seasonal weather forecasts are crucial for long-term planning in many practical situations and skillful forecasts may have substantial economic and humanitarian implications. Current seasonal forecasting models require statistical postprocessing of the ... More
An explicit formula for optimal portfolios in complete Wiener driven markets: a functional Itô calculus approachOct 17 2016Dec 29 2017We consider a standard optimal investment problem in a complete financial market driven by a Wiener process and derive an explicit formula for the optimal portfolio process in terms of the vertical derivative from functional It^o calculus. An advantage ... More
Global bifurcation of waves with multiple critical layersJul 12 2019Analytic global bifurcation theory is used to construct a large variety of families of steady periodic two-dimensional gravity water waves with real-analytic vorticity distributions, propagating in an incompressible fluid. The waves that are constructed ... More
Deep Convolutional Neural Networks for Interpretable Analysis of EEG Sleep Stage ScoringOct 02 2017Sleep studies are important for diagnosing sleep disorders such as insomnia, narcolepsy or sleep apnea. They rely on manual scoring of sleep stages from raw polisomnography signals, which is a tedious visual task requiring the workload of highly trained ... More
Optimized Orthogonal Basis Tight Binding. Application to IronApr 18 2011The formal link between the linear combination of atomic orbitals approach to density functional theory and two-center Slater-Koster tight-binding models is used to derive an orthogonal $d$-band tight-binding model for iron with only two fitting parameters. ... More
h: A Plank for Higher-order Attribute Contraction SchemesNov 09 2017We present and formalize h, a core (or "plank") calculus that can serve as the foundation for several compiler specification languages, notably CRSX (Combinatory Reductions Systems with eXtensions), HACS (Higher-order Attribute Contraction Schemes), and ... More
Three-dimensional turbulent relative dispersion by the Gledzer-Ohkitani-Yamada shell modelFeb 03 2010We study pair dispersion in a three-dimensional incompressible high Reynolds number turbulent flow generated by Fourier transforming the dynamics of the Gledzer-Ohkitani-Yamada (GOY) shell model into real space. We show that GOY shell model can successfully ... More
Short Selling with Margin Risk and Recall RiskMar 28 2019Short sales are regarded as negative purchases in textbook asset pricing theory. In reality, however, the symmetry between purchases and short sales is broken by a variety of costs and risks peculiar to the latter. We formulate an optimal stopping model ... More
Traveling gravity water waves with critical layersAug 19 2015Dec 09 2016We establish the existence of small-amplitude uni- and bimodal steady periodic gravity waves with an affine vorticity distribution, using a bifurcation argument that differs slightly from earlier theory. The solutions describe waves with critical layers ... More
On time-inconsistent stopping problems and mixed strategy stopping timesApr 19 2018May 07 2018A game-theoretic framework for time-inconsistent stopping problems where the time-inconsistency is due to the consideration of a non-linear function of an expected reward is developed. A class of mixed strategy stopping times that allows the agents in ... More
On Finding Equilibrium Stopping Times for Time-Inconsistent Markovian ProblemsSep 15 2017Dec 04 2018Standard Markovian optimal stopping problems are consistent in the sense that the first entrance time into the stopping set is optimal for each initial state of the process. Clearly, the usual concept of optimality cannot in a straightforward way be applied ... More
Nonparametric Modeling of Dynamic Functional Connectivity in fMRI DataJan 04 2016Jun 08 2016Dynamic functional connectivity (FC) has in recent years become a topic of interest in the neuroimaging community. Several models and methods exist for both functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), and the results ... More
Equations of Rees algebras of ideals in two variablesNov 12 2015Let I be an ideal of height two in R=k[x_0,x_1] generated by forms of the same degree, and let K be the ideal of defining equations of the Rees algebra of I. Suppose that the second largest column degree in the syzygy matrix of I is e. We give an algorithm ... More
A Spatially Resolved Study of the Synchrotron Emission and Titanium in Tycho's Supernova Remnant with NuSTARApr 27 2015Oct 28 2015We report results from deep observations (~750 ks) of Tycho's supernova remnant (SNR) with NuSTAR. Using these data, we produce narrow-band images over several energy bands to identify the regions producing the hardest X-rays and to search for radioactive ... More
Probabilistic PARAFAC2Jun 21 2018The PARAFAC2 is a multimodal factor analysis model suitable for analyzing multi-way data when one of the modes has incomparable observation units, for example because of differences in signal sampling or batch sizes. A fully probabilistic treatment of ... More
Materials Screening for the Discovery of New Half-Heuslers: Machine Learning versus Ab Initio MethodsJun 01 2017Machine learning (ML) is increasingly becoming a helpful tool in the search for novel functional compounds. Here we use classification via random forests to predict the stability of half-Heusler (HH) compounds, using only experimentally reported compounds ... More
Exceptionally strong phonon scattering by B substitution in cubic SiCMar 15 2017We use ab-initio calculations to predict the thermal conductivity of cubic SiC with different types of defects. An excellent quantitative agreement with previous experimental measurements is found. The results unveil that B$_\mathrm{C}$ substitution has ... More
Higher-order Rewriting for Executable Compiler SpecificationsFeb 18 2011In this paper we outline how a simple compiler can be completely specified using higher order rewriting in all stages: parsing, analysis/optimization, and code emission, specifically using the crsx.sf.net system for a small declarative language called ... More
Tracking the Consumption Junction: Temporal Dependencies between Articles and Advertisements in Dutch NewspapersMar 27 2019Historians have regularly debated whether advertisements can be used as a viable source to study the past. Their main concern centered on the question of agency. Were advertisements a reflection of historical events and societal debates, or were ad makers ... More
Lie-Butcher series, Geometry, Algebra and ComputationJan 13 2017Oct 27 2017Lie-Butcher (LB) series are formal power series expressed in terms of trees and forests. On the geometric side LB-series generalizes classical B-series from Euclidean spaces to Lie groups and homogeneous manifolds. On the algebraic side, B-series are ... More
Towards end-to-end optimisation of functional image analysis pipelinesOct 13 2016The study of neurocognitive tasks requiring accurate localisation of activity often rely on functional Magnetic Resonance Imaging, a widely adopted technique that makes use of a pipeline of data processing modules, each involving a variety of parameters. ... More
Adaptive Smoothing in fMRI Data Processing Neural NetworksOct 02 2017Functional Magnetic Resonance Imaging (fMRI) relies on multi-step data processing pipelines to accurately determine brain activity; among them, the crucial step of spatial smoothing. These pipelines are commonly suboptimal, given the local optimisation ... More
Multiwavelength WHAM Observations of Extra-planar Warm Ionized Gas in the GalaxySep 20 2004We report on observations of several optical emission lines toward a variety of newly revealed faint, large-scale H-alpha-emitting structures in the warm ionized medium (WIM) of the Galaxy. The lines include [N II] 6583, [N II] 5755, [S II] 6716, [O III] ... More
A Pair of Planets Likely in Mean-motion Resonance From Gravitational MicrolensingJan 14 2019Jun 14 2019We combine statistical arguments and dynamical analysis to study the orbital configuration of the microlensing planetary system OGLE-2012-BLG-0026L. This system is known to host two massive planets, with both projected close to the Einstein ring at the ... More
Ergodicity-breaking reveals time optimal economic behavior in humansJun 11 2019Jun 12 2019Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theory reveals how individuals should tolerate risk in different environments. To optimise wealth over time, agents ... More
Ergodicity-breaking reveals time optimal economic behavior in humansJun 11 2019Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theory reveals how individuals should tolerate risk in different environments. To optimise wealth over time, agents ... More
Scalable Group Level Probabilistic Sparse Factor AnalysisDec 14 2016Many data-driven approaches exist to extract neural representations of functional magnetic resonance imaging (fMRI) data, but most of them lack a proper probabilistic formulation. We propose a group level scalable probabilistic sparse factor analysis ... More
Rational homotopy theory of automorphisms of manifoldsJan 16 2014Mar 10 2017We study the rational homotopy types of classifying spaces of automorphism groups of smooth simply connected manifolds of dimension at least five. We give dg Lie algebra models for the homotopy automorphisms and the block diffeomorphisms of such manifolds. ... More
An abstract analysis of optimal goal-oriented adaptivityMay 18 2015We provide an abstract framework for optimal goal-oriented adaptivity for finite element methods and boundary element methods in the spirit of [Carstensen et al., Comput. Math. Appl. 67 (2014)]. We prove that this framework covers standard discretizations ... More
Eliminating Gibbs Phenomena: A Non-linear Petrov-Galerkin Method for the Convection-Diffusion-Reaction EquationAug 02 2019In this article we consider the numerical approximation of the convection-diffusion-reaction equation. One of the main challenges of designing a numerical method for this problem is that boundary layers occurring in the convection-dominated case can lead ... More
Emergence of multiplicity of time scales in the modeling of climate, matter, life, and economyJul 01 2019We address dfferences between characteristic times in climate change and show the universal emergence of multiple time scales in material sciences, biomedicine and economics.
Ionization of oriented carbonyl-sulfide molecules by intense circularly polarized laser pulsesJul 15 2010Mar 24 2011We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl-sulphide molecules by circularly-polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries ... More
Strategy Complexity of Concurrent Stochastic Games with Safety and Reachability ObjectivesJun 08 2015We consider finite-state concurrent stochastic games, played by k>=2 players for an infinite number of rounds, where in every round, each player simultaneously and independently of the other players chooses an action, whereafter the successor state is ... More
Towards Online Observability-Aware Trajectory Optimization for Landmark-based EstimatorsAug 10 2019As autonomous systems rely increasingly on onboard sensors for localization and perception, the parallel tasks of motion planning and uncertainty minimization become increasingly coupled. This coupling is well-captured by augmenting the planning objective ... More
The odd side of torsion geometryJul 12 2012Dec 10 2012We introduce and study a notion of `Sasaki with torsion structure' (ST) as an odd-dimensional analogue of K\"ahler with torsion geometry (KT). These are normal almost contact metric manifolds that admit a unique compatible connection with 3-form torsion. ... More
Atypicality for Heart Rate Variability Using a Pattern-Tree Weighting MethodOct 12 2017Heart rate variability (HRV) is a vital measure of the autonomic nervous system functionality and a key indicator of cardiovascular condition. This paper proposes a novel method, called pattern tree which is an extension of Willem's context tree to real-valued ... More
Harmonic structures and intrinsic torsionAug 19 2013Nov 19 2014We discuss the construction of Sp(2)Sp(1)-structures whose fundamental form is closed. In particular, we find 10 new examples of 8-dimensional nilmanifolds that admit an invariant closed 4-form with stabiliser Sp(2)Sp(1). Our constructions entail the ... More
Multispecies time-dependent restricted-active-space self-consistent-field theory for ultracold atomic and molecular gasesMay 03 2018We discuss the multispecies time-dependent restricted-active-space self-consistent-field theory, an \textit{ab initio} wavefunction-based theory for mixtures of ultracold atomic and molecular gases. We present the general theory, based on the time-dependent ... More
The stable moduli space of Riemann surfaces: Mumford's conjectureDec 23 2002Jul 14 2004The main result of this paper amounts to a complete evaluation of the integral cohomological structure of the stable mapping class group. In particular it verifies the conjecture of D.Mumford about the rational cohomology of the stable mapping class group. ... More
Multi-moment mapsDec 09 2010Mar 17 2011We introduce a notion of moment map adapted to actions of Lie groups that preserve a closed three-form. We show existence of our multi-moment maps in many circumstances, including mild topological assumptions on the underlying manifold. Such maps are ... More
Stability for closed surfaces in a background spaceFeb 12 2010In this paper we present a new proof of the homological stability of the moduli space of closed surfaces in a simply connected background space $K$, which we denote by $S_g (K)$. The homology stability of surfaces in $K$ with an arbitrary number of boundary ... More
Functional form of the generalized gradient approximation for exchange: The PBE$α$ functionalSep 15 2006Nov 14 2006A new functional form for the exchange enhancement in the generalized gradient approximation within density functional theory is given. The functional form satisfies the constraints used to construct the Perdew-Burke-Ernzerhof (PBE) functional but can ... More
Oxygen Ordering Superstructures and Structural Phase Diagram of YBa_2Cu_3O_{6+x} Studied by Hard X-ray DiffractionJun 16 1999High energy x-ray diffraction is used to investigate the bulk oxygen ordering properties of YBa_2Cu_3O_{6+x}. Superstructures of Cu-O chains aligned along the b axis and ordered with periodicity ma, along the a axis have been observed. For $x < 0.62$ ... More
An Investigation of Diffuse Interstellar Gas toward a Large, Low Extinction Window into the Inner GalaxyMay 24 2005Halpha and Hbeta spectroscopy with the Wisconsin H-Alpha Mapper (WHAM) reveals a strong concentration of high velocity emission in a ~ 5 by 5 deg area centered near (l.b) = (27,-3), known as the Scutum Cloud. The high velocities imply that we are detecting ... More
Differential Description Length for Hyperparameter Selection in Machine LearningFeb 13 2019May 22 2019This paper introduces a new method for model selection and more generally hyperparameter selection in machine learning. Minimum description length (MDL) is an established method for model selection, which is however not directly aimed at minimizing generalization ... More
A Rotating-Frame Perspective on High-Harmonic Generation of Circularly Polarized LightFeb 23 2016We employ a rotating frame of reference to elucidate high-harmonic generation of circularly polarized light by bicircular driving fields. In particular, we show how the experimentally observed circular components of the high-harmonic spectrum can be directly ... More
Non-Sequential Double Recombination High Harmonic Generation in Molecular-like SystemsDec 07 2016Dec 08 2016We present a study of non-sequential double recombination (NSDR) high harmonic generation (HHG) in a molecular-like system. Using a Coulomb-corrected three-step model we are able to classically describe the observed NSDR HHG cutoffs precisely for all ... More
Coloring $n$-String TanglesSep 21 2006This expository paper describes how the knot invariant Fox coloring can be applied to tangles.
Quaternionic geometry in dimension eightOct 16 2016We describe the 8-dimensional Wolf spaces as cohomogeneity one SU(3)-manifolds, and discover perturbations of the quaternion-kaehler metric on the simply-connected 8-manifold G_2/SO(4) that carry a closed fundamental 4-form but are not Einstein.
A note on dual modules and the transposeJun 05 2019It is a classical result in matrix algebra that any square matrix over a field can be conjugated to its transpose by a symmetric matrix. For $F$ a non-Archimedean local field, Tupan used this to give an elementary proof that transpose inverse takes each ... More
The Discrete-Dual Minimal-Residual Method (DDMRes) for Weak Advection-Reaction Problems in Banach spacesAug 14 2018We propose and analyse a minimal-residual method in discrete dual norms for approximating the solution of the advection-reaction equation in a weak Banach-space setting. The weak formulation allows for the direct approximation of solutions in the Lebesgue ... More
Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamicsOct 28 2012Dec 04 2012We present detuning-dependent spectral and decay-rate measurements to study the difference between spectral and dynamical properties of single quantum dots embedded in micropillar and photonic-crystal cavities. For the micropillar cavity, the dynamics ... More
Variability in the Near-Infrared Synchrotron Emission From Cassiopeia AJun 03 2016We present multi-epoch Ks band imaging of the supernova remnant Cassiopeia A (Cas A). The morphology of the emission in this band is generally diffuse and filamentary, consistent with synchrotron radiation observed at radio wavelengths. However, in one ... More
Fossil imprint of a powerful flare at the Galactic Centre along the Magellanic StreamSep 21 2013The Fermi satellite discovery of the gamma-ray emitting bubbles extending 50 deg (10 kpc) from the Galactic Centre has revitalized earlier claims that our Galaxy has undergone an explosive episode in the recent past. We now explore a new constraint on ... More
Best Practices for Administering Concept InventoriesApr 25 2014There are a plethora of concept inventories in physics available for faculty to use, but it is not always clear exactly why you would use these tests, or how you should administer them and interpret the results. These multiple-choice research-based tests ... More
The Integral Screened Configuration Interaction MethodSep 25 2016We present the formulation and implementation of the Integral-Screened Configuration-Interaction method (ISCI). The ISCI is a minimal-operational count integral-driven direct Configuration-Interaction (CI) method with a simple and rigorous integral screening ... More
Enhanced high-order harmonic generation in donor-doped band-gap materialsSep 17 2018Jan 29 2019We find that a donor-doped band-gap material can enhance the overall high-order harmonic generation (HHG) efficiency by several orders of magnitude, compared with undoped and acceptor-doped materials. This significant enhancement, predicted by time-dependent ... More
Nuclear-Motion Effects in Attosecond Transient Absorption Spectroscopy of MoleculesFeb 20 2015Apr 15 2015We investigate the characteristic effects of nuclear motion on attosecond transient absorption spectra in molecules by calculating the spectrum for different model systems. Two models of the hydrogen molecular ion are considered: one where the internuclear ... More
Classification of String-like Solutions in Dilaton GravityOct 22 2001Jan 18 2002The static string-like solutions of the Abelian Higgs model coupled to dilaton gravity are analyzed and compared to the non-dilatonic case. Except for a special coupling between the Higgs Lagrangian and the dilaton, the solutions are flux tubes that generate ... More
Intrinsic spectral blueshifts in rapidly rotating stars?Sep 12 2003Spectroscopic radial velocities for several nearby open clusters suggest that spectra of (especially earlier-type) rapidly rotating stars are systematically blueshifted by 3 km/s or more, relative to the spectra of slowly rotating ones. Comparisons with ... More
Time-inconsistent stochastic control: solving the extended HJB system is a necessary condition for regular equilibriaNov 09 2016Time-inconsistent stochastic control is a game-theoretic generalization of standard stochastic control, with well-known applications in economics and finance. One of the most important results of standard (time-consistent) stochastic control is the characterization ... More
X-ray photon correlation spectroscopy of protein dynamics at nearly diffraction limited storage ringsJun 21 2019This study explores the possibility to measure dynamics of proteins in solution using X-ray photon correlation spectroscopy (XPCS) at nearly diffraction limited storage rings (DLSR). We calculate the signal to noise ratio (SNR) of XPCS experiments from ... More
Constructive martingale representation using Functional Itô Calculus: a local martingale extensionNov 28 2016The constructive martingale representation theorem and the vertical derivative of Functional It\^o Calculus are extended, from the space of square integrable martingales, to a space of local martingales. The relevant filtration is the augmented filtration ... More
Optimal Stopping of a Brownian Bridge with an Uncertain Pinning TimeFeb 26 2019Jul 07 2019We consider the problem of optimally stopping a Brownian bridge with an uncertain pinning time so as to maximise the value of the process upon stopping. Adopting a Bayesian approach, we consider a general prior distribution of the pinning time and allow ... More
Solitary gravity-capillary water waves with point vorticesMar 20 2015Nov 02 2015We construct small-amplitude solitary traveling gravity-capillary water waves with a finite number of point vortices along a vertical line, on finite depth. This is done using a local bifurcation argument. The properties of the resulting waves are also ... More
A regular equilibrium solves the extended HJB systemNov 09 2016Mar 15 2019Control problems not admitting the dynamic programming principle are known as time-inconsistent. The game-theoretic approach is to interpret such problems as intrapersonal dynamic games and look for subgame perfect Nash equilibria. A fundamental result ... More
Optimally Stopping a Brownian Bridge with an Unknown Pinning Time: A Bayesian ApproachFeb 26 2019Jul 19 2019We consider the problem of optimally stopping a Brownian bridge with an unknown pinning time so as to maximise the value of the process upon stopping. Adopting a Bayesian approach, we allow the stopper to update their belief about the value of the pinning ... More
Compact Toroidal Ion Trap Design and OptimizationJul 14 2010We present the design of a new type of compact toroidal, or "halo", ion trap. Such traps may be useful for mass spectrometry, studying small Coulomb cluster rings, quantum information applications, or other quantum simulations where a ring topology is ... More
Timing and Flux Evolution of the Galactic Center Magnetar SGR J1745-2900Mar 21 2014We present the X-ray timing and spectral evolution of the Galactic Center magnetar SGR J1745-2900 for the first ~4 months post-discovery using data obtained with the Nuclear Spectroscopic Telescope Array (NuSTAR)} and Swift observatories. Our timing analysis ... More
The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTARMar 03 2016We present the first observations of quiescent active regions (ARs) using NuSTAR, a focusing hard X-ray telescope capable of studying faint solar emission from high temperature and non-thermal sources. We analyze the first directly imaged and spectrally ... More
A regular equilibrium solves the extended HJB systemNov 09 2016Dec 11 2018Control problems not admitting the dynamic programming principle are known as time-inconsistent. The game-theoretic approach is to interpret such problems as intrapersonal dynamic games and look for subgame perfect Nash equilibria. A fundamental result ... More
Constructive martingale representation in functional Itô calculus: a local martingale extensionNov 28 2016Dec 10 2018The constructive martingale representation theorem of functional It\^o calculus is extended, from the space of square integrable martingales, to the space of local martingales. The setting is that of an augmented filtration generated by a Wiener process. ... More
High-throughput exploration of alloying as design strategy for thermoelectricsAug 14 2015We explore a material design strategy to optimize the thermoelectric power factor. The approach is based on screening the band structure changes upon a controlled volume change. The methodology is applied to the binary silicides and germanides. We first ... More
Comparing the performance of LDA and GGA functionals in predicting the lattice thermal conductivity of semiconductor materials: the case of AlAsNov 15 2018In this contribution we assess the performance of two different exchange-correlation functionals in the first-principle prediction of the lattice thermal conductivity of bulk semiconductors, namely the local density approximation (LDA) and the Perdew-Burke-Ernzerhof ... More
BoltzTraP. A code for calculating band-structure dependent quantitiesFeb 08 2006A program for calculating the semi-classic transport coefficients is described. It is based on a smoothed Fourier interpolation of the bands. From this analytical representation we calculate the derivatives necessary for the transport distributions. The ... More
Ultrafast molecular orbital imaging of a pentacene thin film using a free electron laserJul 24 2019We use time-resolved molecular orbital mapping to explore fundamental processes of excited wave packets and charge transfer dynamics in organic films on femtosecond time scales. We investigate a bilayer pentacene film on Ag(110) by optical laser pump ... More
Asymmetries in core-collapse supernovae from maps of radioactive $^{44}$Ti in CassiopeiaAMar 19 2014Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive 44Ti, synthesized in an exploding star near the boundary between ... More
Optimal Stopping of a Brownian Bridge with an Uncertain Pinning TimeFeb 26 2019We consider the problem of optimally stopping a Brownian bridge with an uncertain pinning time so as to maximise the value of the process upon stopping. Adopting a Bayesian approach, we consider a general prior distribution of the pinning time and allow ... More
An explicit formula for optimal portfolios in complete Wiener driven markets: a functional Itô calculus approachOct 17 2016The optimal investment problem is one of the most important problems in mathematical finance. The main contribution of the present paper is an explicit formula for the optimal portfolio process. Our optimal investment problem is that of maximizing the ... More
Charge order in Magnetite. An LDA+$U$ studyDec 21 2004The electronic structure of the monoclinic structure of Fe$_3$O$_4$ is studied using both the local density approximation (LDA) and the LDA+$U$. The LDA gives only a small charge disproportionation, thus excluding that the structural distortion should ... More
Bayesian regional flood frequency analysis for large catchmentsFeb 26 2018Mar 02 2018Regional flood frequency analysis is commonly applied in situations where there exists insufficient data at a location for a reliable estimation of flood quantiles. We develop a Bayesian hierarchical modeling framework for a regional analysis of data ... More
Interface of the polarizable continuum model of solvation with semi-empirical methods in the GAMESS programMar 19 2013May 22 2013An interface between semi-empirical methods and the polarized continuum model (PCM) of solvation successfully implemented into GAMESS following the approach by Chudinov et al (Chem. Phys. 1992, 160, 41). The interface includes energy gradients and is ... More
Constraints on the Progenitor of Cassiopeia ANov 29 2005We compare a suite of 3D explosion calculations and stellar models incorporating advanced physics with observational constraints on the progenitor of Cassiopeia A. We consider binary and single stars from 16 to 40 solar masses with a range of explosion ... More
Ultrafast Structural Dynamics of Photo-Reactions Revealed by Model-Independent X-ray Cross-Correlation AnalysisNov 19 2018We applied angular X-ray Cross-Correlation analysis (XCCA) to scattering images from a femtosecond resolution LCLS X-ray free-electron laser (XFEL) pump-probe experiment with solvated PtPOP ([Pt$_2$(P$_2$O$_5$H$_2$)$_4$]$^{4-}$) metal complex molecules. ... More
A Chandrasekhar Mass Progenitor for the Type Ia Supernova Remnant 3C 397 from The Enhanced Abundances of Nickel and ManganeseFeb 14 2015Despite decades of intense efforts, many fundamental aspects of Type Ia supernova (SNe Ia) remain elusive. One of the major open questions is whether the mass of the exploding white dwarf (WD) is close to the Chandrasekhar limit. Here we report the detection ... More
Observation of Attractive and Repulsive Polarons in a Bose-Einstein CondensateApr 26 2016Aug 01 2016The problem of an impurity particle moving through a bosonic medium plays a fundamental role in physics. However, the canonical scenario of a mobile impurity immersed in a Bose-Einstein condensate (BEC) has not yet been realized. Here, we use radio frequency ... More
The First Cold AntihydrogenJan 29 2004Antihydrogen, the atomic bound state of an antiproton and a positron, was produced at low energy for the first time by the ATHENA experiment, marking an important first step for precision studies of atomic antimatter. This paper describes the first production ... More
Evidence For The Production Of Slow Antiprotonic Hydrogen In VacuumAug 28 2007We present evidence showing how antiprotonic hydrogen, the quasistable antiproton-proton (pbar-p) bound system, has been synthesized following the interaction of antiprotons with the hydrogen molecular ion (H2+) in a nested Penning trap environment. From ... More
Cold-Antimatter PhysicsMar 21 2005The CPT theorem and the Weak Equivalence Principle are foundational principles on which the standard description of the fundamental interactions is based. The validity of such basic principles should be tested using the largest possible sample of physical ... More
ATHENA -- First Production of Cold Antihydrogen and BeyondSep 21 2004Apr 19 2005Atomic systems of antiparticles are the laboratories of choice for tests of CPT symmetry with antimatter. The ATHENA experiment was the first to report the production of copious amounts of cold antihydrogen in 2002. This article reviews some of the insights ... More
Ab initio lattice thermal conductivity of bulk and thin-film $α$-Al$\mathrm{_2}$O$\mathrm{_3}$Jun 22 2018Aug 28 2018The thermal conductivities ($\kappa$) of bulk and thin-film $\alpha$-Al$_2$O$_3$ are calculated from first principles using both the local density approximation (LDA), and the generalized gradient approximation (GGA) to exchange and correlation. The room ... More
Comparison of the Green-Kubo and homogeneous non-equilibrium molecular dynamics methods for calculating thermal conductivityMar 16 2017Jun 01 2017Different molecular dynamics methods like the direct method, the Green-Kubo (GK) method and homogeneous non-equilibrium molecular dynamics (HNEMD) method have been widely used to calculate lattice thermal conductivity ($\kappa_\ell$). While the first ... More
Time series analysis in Astronomy: limits and potentialitiesOct 15 2004In this paper we consider the problem of the limits concerning the physical information that can be extracted from the analysis of one or more time series (light curves) typical of astrophysical objects. On the basis of theoretical considerations and ... More
A Quark-Antiquark Condensate in Three-Dimensional QCDMar 16 1998Jul 08 1998Three-dimensional lattice QCD is studied by Monte Carlo simulations within the quenched approximation. At zero temperature a quark-antiquark condensate is observed in the limit of vanishing quark masses. The condensate vanishes continuously at the finite-temperature ... More
New Measurements of the Motion of the Zodiacal DustMay 26 2004Using the Wisconsin H-Alpha Mapper (WHAM), we have measured at high spectral resolution and high signal-to-noise the profile of the scattered solar Mg I 5184 absorption line in the zodiacal light. The observations were carried out toward 49 directions ... More
Wavelength Shifts in Solar-Type SpectraSep 09 2004Spectral-line displacements away from the wavelengths naively expected from the Doppler shift caused by stellar radial motion may originate as convective shifts (correlated velocity and brightness patterns in the photosphere), as gravitational redshifts, ... More
Non-destructive profilometry of optical nanofibresJun 13 2016Oct 06 2016Single-mode optical nanofibres are a central component of a broad range of applications and emerging technologies. Their fabrication has been extensively studied over the past decade, but imaging of the final sub-micrometre products has been restricted ... More
Strong-field approximation for Coulomb explosion of H_2^+ by short intense laser pulsesApr 19 2007We present a simple quantum mechanical model to describe Coulomb explosion of H$_2^+$ by short, intense, infrared laser pulses. The model is based on the length gauge version of the molecular strong-field approximation and is valid for pulses shorter ... More
ExB mean flows in finite ion temperature plasmasApr 14 2016Apr 24 2017The impact of ion pressure dynamics on E x B mean flows is investigated. Using a simplified, two-dimensional, drift ordered fluid model in the thin-layer approximation, three stresses in addition to the Reynolds stress are shown to modify the E x B mean ... More