Results for "Haakon Bakka"

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Approximate Bayesian inference for spatial flood frequency analysisJul 10 2019Extreme floods cause casualties, widespread property damage, and damage to vital civil infrastructure. Predictions of extreme floods within gauged and ungauged catchments is crucial to mitigate these disasters. A Bayesian framework is proposed for predicting ... More
Joint models as latent Gaussian models - not reinventing the wheelJan 27 2019Joint models have received increasing attention during recent years with extensions into various directions; numerous hazard functions, different association structures, linear and non-linear longitudinal trajectories amongst others. Many of these resulted ... More
Accounting for physical barriers in species distribution modeling with non-stationary spatial random effectsAug 12 2016This paper is motivated by a study on the spatial distribution of fish larvae in reproduction habitats of three commercially important fish species in the Finnish archipelago. Species distribution modeling (SDM) requires realistic models that account ... More
INLA goes extreme: Bayesian tail regression for the estimation of high spatio-temporal quantilesFeb 04 2018This work has been motivated by the challenge of the 2017 conference on Extreme-Value Analysis (EVA2017), with the goal of predicting daily precipitation quantiles at the $99.8\%$ level for each month at observed and unobserved locations. We here develop ... More
Geostatistical modeling to capture seismic-shaking patterns from earthquake-induced landslidesJul 23 2018In this paper, we investigate earthquake-induced landslides using a geostatistical model that includes a latent spatial effect (LSE). The LSE represents the spatially structured residuals in the data, which are complementary to the information carried ... More
Calibration of the Mass-Temperature Relation for Clusters of Galaxies Using Weak Gravitational LensingMar 10 2006May 25 2007The main uncertainty in current determinations of the power spectrum normalization, sigma_8, from abundances of X-ray luminous galaxy clusters arises from the calibration of the mass-temperature relation. We use our weak lensing mass determinations of ... More
Spatial modelling with R-INLA: A reviewFeb 18 2018May 08 2018Coming up with Bayesian models for spatial data is easy, but performing inference with them can be challenging. Writing fast inference code for a complex spatial model with realistically-sized datasets from scratch is time-consuming, and if changes are ... More
Approximations and bounds for binary Markov random fieldsJan 29 2015May 22 2015Discrete Markov random fields form a natural class of models to represent images and spatial data sets. The use of such models is, however, hampered by a computationally intractable normalising constant. This makes parameter estimation and a fully Bayesian ... More
Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit couplingOct 09 2017Feb 27 2018We present a theoretical description and numerical simulations of the superconducting transition in hybrid structures including strong spin-orbit interactions. The spin-orbit coupling is taken to be of Rashba type for concreteness, and we allow for an ... More
The Density Profile of Cluster-scale Dark Matter HalosJun 26 2002Apr 04 2003We measure the average gravitational shear profile of 6 massive clusters (M_vir ~ 10^15 M_sun) at z=0.3 out to a radius ~2h^-1 Mpc. The measurements are fitted to a generalized NFW-like halo model \rho(r) with an arbitrary r -> 0 slope \alpha. The data ... More
Probing galaxy density profiles with future supernova surveysJun 15 2004Oct 12 2004In this paper we discuss the possibility to measure the Hubble parameter and the slope of galaxy density profiles using future supernova data. With future supernova surveys such as SNAP, large numbers of core collapse supernovae will be discovered, a ... More
Multilevel ensemble Kalman filtering for spatially extended modelsAug 30 2016This work embeds a multilevel Monte Carlo (MLMC) sampling strategy into the Monte Carlo step of the ensemble Kalman filter (EnKF), thereby yielding a multilevel ensemble Kalman filter (MLEnKF) which has provably superior asymptotic cost to a given accuracy ... More
Gravitational Wave Signals from 3D Neutrino Hydrodynamics Simulations of Core-Collapse SupernovaeJul 15 2016Apr 18 2017We present gravitational wave (GW) signal predictions from four 3D multi-group neutrino hydrodynamics simulations of core-collapse supernovae of progenitors with 11.2 Msun, 20 Msun, and 27 Msun. GW emission in the pre-explosion phase strongly depends ... More
Eco-Strategy: Towards a New Generation Managerial Model Based on Green IT and CSRMay 09 2016The sustainable development strategy in the management of information and communication technology (ICT) is an advanced research sector which provides a theoretical framework for integrating social and environmental responsibilities of business in the ... More
Probing the nature of dark matter with Cosmic X-rays: Constraints from "Dark blobs" and grating spectra of galaxy clustersOct 02 2006Gravitational lensing observations of galaxy clusters have identified dark matter ``blobs'' with remarkably low baryonic content. We use such a system to probe the particle nature of dark matter with X-ray observations. We also study high resolution X-ray ... More
Magnon-polarons in cubic collinear AntiferromagnetsDec 20 2018We present a theoretical study of excitations formed by hybridization between magnons and phonons - magnon-polarons - in antiferromagnets. We first outline a general approach to determining which magnon and phonon modes can and cannot hybridize in a system ... More
Gravitational Wave Signals from 3D Neutrino Hydrodynamics Simulations of Core-Collapse SupernovaeJul 15 2016We present gravitational wave (GW) signal predictions from four 3D multi-group neutrino hydrodynamics simulations of core-collapse supernovae of progenitors with 11.2 Msun, 20 Msun, and 27 Msun. GW emission in the pre-explosion phase strongly depends ... More
Magnetostriction in AntiferromagnetsAug 27 2018Oct 03 2018We consider magnetostriction in magnetic materials. Starting from a microscopic lattice model of the magneto-elastic coupling, we derive the continuum magnetostriction Hamiltonian in cubic ferromagnets and antiferromagnets. In ferromagnets, our results ... More
Magnon decay theory of Gilbert damping in metallic antiferromagnetsJul 01 2019Gilbert damping is a key property governing magnetization dynamics in ordered magnets. We present a theoretical study of intrinsic Gilbert damping induced by magnon decay in antiferromagnetic metals through $s$-$d$ exchange interaction. Our theory delineates ... More
Weak Gravitational Lensing by a Sample of X-Ray Luminous Clusters of Galaxies -- II. Comparison with Virial MassesJun 14 2002Aug 01 2002Dynamic velocity dispersion and mass estimates are given for a sample of five X-ray luminous rich clusters of galaxies at intermediate redshifts (z~0.3) drawn from a sample of 39 clusters for which we have obtained gravitational lens mass estimates. The ... More
Searching for decaying axion-like dark matter from clusters of galaxiesMar 13 2007We consider the possibility of constraining the lifetime of radiatively decaying dark matter particles in clusters of galaxies inspired from generic axions of the Kaluza-Klein type. Such axions have been invoked as a possible explanation for the coronal ... More
Galaxy-Galaxy Lensing in the Hubble Deep Field: The Halo Tully-Fisher Relation at Intermediate RedshiftNov 27 1997Mar 11 1998A tangential distortion of background source galaxies around foreground lens galaxies in the Hubble Deep Field is detected at the 99.3% confidence level. An important element of our analysis is the use of photometric redshifts to determine distances of ... More
Triaxiality and non-thermal gas pressure in Abell 1689Mar 01 2011Jun 05 2011Clusters of galaxies are uniquely important cosmological probes of the evolution of the large scale structure, whose diagnostic power depends quite significantly on the ability to reliably determine their masses. Clusters are typically modeled as spherical ... More
Resolving the discrepancy between lensing and X-ray mass estimates of the complex galaxy cluster Abell 1689Nov 18 2008There is a long-standing discrepancy between galaxy cluster masses determined from X-ray and gravitational lensing observations of which Abell 1689 is a well-studied example. In this work we take advantage of 180 ks of Chandra X-ray observations and a ... More
Combined strong and weak lensing analysis of 28 clusters from the Sloan Giant Arcs SurveySep 12 2011Nov 22 2011We study the mass distribution of a sample of 28 galaxy clusters using strong and weak lensing observations. The clusters are selected via their strong lensing properties as part of the Sloan Giant Arcs Survey (SGAS) from the Sloan Digital Sky Survey ... More
Masses of galaxy clusters from gravitational lensingMar 13 2013Despite consistent progress in numerical simulations, the observable properties of galaxy clusters are difficult to predict ab initio. It is therefore important to compare both theoretical and observational results to a direct measure of the cluster mass. ... More
Higher order multipoles in metamaterial homogenizationJan 06 2017Apr 19 2018The higher order multipoles above the electric quadrupole are commonly neglected in metamaterial homogenization. We show that they nevertheless can be significant when second order spatial dispersive effects, such as the magnetic response, are considered. ... More
Subaru Weak Lensing Measurements of Four Strong Lensing Clusters: Are Lensing Clusters Over-Concentrated?Jan 28 2009Apr 30 2009We derive radial mass profiles of four strong lensing selected clusters which show prominent giant arcs (Abell 1703, SDSS J1446+3032, SDSS J1531+3414, and SDSS J2111-0115), by combining detailed strong lens modeling with weak lensing shear measured from ... More
Optical Photometry of GRB 021004: The First MonthNov 05 2002Feb 12 2003We present U,B,V,R_C,and I_C photometry of the optical afterglow of the gamma-ray burst GRB 021004 taken at the Nordic Optical Telescope between approximately eight hours and 30 days after the burst. This data is combined with an analysis of the 87 ksec ... More
The Shear TEsting Programme 1: Weak lensing analysis of simulated ground-based observationsJun 06 2005Feb 10 2006The Shear TEsting Programme, STEP, is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wide-field surveys. In this first STEP paper we present the results of a blind ... More