52 research outputs found
An Introduction to Inductive Statistical Inference: from Parameter Estimation to Decision-Making
These lecture notes aim at a post-Bachelor audience with a background at an
introductory level in Applied Mathematics and Applied Statistics. They discuss
the logic and methodology of the Bayes-Laplace approach to inductive
statistical inference that places common sense and the guiding lines of the
scientific method at the heart of systematic analyses of quantitative-empirical
data. Following an exposition of exactly solvable cases of single- and
two-parameter estimation problems, the main focus is laid on Markov Chain Monte
Carlo (MCMC) simulations on the basis of Hamiltonian Monte Carlo sampling of
posterior joint probability distributions for regression parameters occurring
in generalised linear models for a univariate outcome variable. The modelling
of fixed effects as well as of correlated varying effects via multi-level
models in non-centred parametrisation is considered. The simulation of
posterior predictive distributions is outlined. The assessment of a model's
relative out-of-sample posterior predictive accuracy with information
entropy-based criteria WAIC and LOOIC and model comparison with Bayes factors
are addressed. Concluding, a conceptual link to the behavioural subjective
expected utility representation of a single decision-maker's choice behaviour
in static one-shot decision problems is established. Vectorised codes for MCMC
simulations of multi-dimensional posterior joint probability distributions with
the Stan probabilistic programming language implemented in the statistical
software R are provided. The lecture notes are fully hyperlinked. They direct
the reader to original scientific research papers, online resources on
inductive statistical inference, and to pertinent biographical information.Comment: 161 pages, 22 *.eps figures, LaTeX2e, hyperlinked references. First
thorough revision, extended list of reference
Deviation of geodesics in FLRW spacetime geometries
The geodesic deviation equation (`GDE') provides an elegant tool to
investigate the timelike, null and spacelike structure of spacetime geometries.
Here we employ the GDE to review these structures within the
Friedmann--Lema\^{\i}tre--Robertson--Walker (`FLRW') models, where we assume
the sources to be given by a non-interacting mixture of incoherent matter and
radiation, and we also take a non-zero cosmological constant into account. For
each causal case we present examples of solutions to the GDE and we discuss the
interpretation of the related first integrals. The de Sitter spacetime geometry
is treated separately.Comment: 17 pages, LaTeX 2.09, 3 *.eps figures, Contribution to the
forthcoming Engelbert Sch\"{u}cking Festschrift (Springer Verlag
Decision-theoretic approaches to non-knowledge in economics
The aim of this contribution is to provide an overview of conceptual approaches to incorporating a decision maker’s non-knowledge into economic theory. We will focus here on the particular kind of non-knowledge which we consider to be one of the most important for economic discussions: non-knowledge of possible consequence-relevant uncertain events which a decision maker would have to take into account when selecting between different strategies
Partially locally rotationally symmetric perfect fluid cosmologies
We show that there are no new consistent cosmological perfect fluid solutions
when in an open neighbourhood of an event the fluid kinematical
variables and the electric and magnetic Weyl curvature are all assumed
rotationally symmetric about a common spatial axis, specialising the Weyl
curvature tensor to algebraic Petrov type D. The consistent solutions of this
kind are either locally rotationally symmetric, or are subcases of the Szekeres
dust models. Parts of our results require the assumption of a barotropic
equation of state. Additionally we demonstrate that local rotational symmetry
of perfect fluid cosmologies follows from rotational symmetry of the Riemann
curvature tensor and of its covariant derivatives only up to second order, thus
strengthening a previous result.Comment: 20 pages, LaTeX2.09 (10pt), no figures; shortened revised version,
new references; accepted for publication in Classical and Quantum Gravit
Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe
The thoughts expressed in this article are based on remarks made by J\"urgen
Ehlers at the Albert-Einstein-Institut, Golm, Germany in July 2007. The main
objective of this article is to demonstrate, in terms of plausible
order-of-magnitude estimates for geometrical scalars, the relevance of spatial
curvature in realistic models of the Universe that describe the dynamics of
structure formation since the epoch of matter-radiation decoupling. We
introduce these estimates with a commentary on the use of a quasi-Newtonian
metric form in this context.Comment: 11 pages. Fully hyperlinked. Dedicated to the memory of J\"urgen
Ehlers. To appear in the upcoming Special Issue of "General Relativity and
Gravitation
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