f(R) theories

Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity - such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in Relativity, Published version, Comments are welcom

Teachers' meanings regarding educational practice

Item does not contain fulltextIn this article, a number of scientific schools of thought and research results are reviewed and found to show the importance of identifying the existential attributions of teachers. Important points of anchor are existential phenomenology and symbolic interactionism, the approach to organizations as emotional arenas, social-psychological theories, concerns theory, and, finally, a number of different perspectives on the professional identities of teachers. Next, those policy developments responsible for the emergence of specific existential attributions are considered. At the same time, the results of some recent studies attempting to explain the emergence of certain existential attributions are discussed: studies of the professional development of teachers, analyses of the feelings of uncertainty and concerns that occur among teachers during innovations, and research on tolerance of uncertainty among teachers during the current intensification of their jobs. Finally, redesigning the innovation process is discussed with an eye to just how the existential attributions of teachers can best be handled