Constraints on axionlike particles with H.E.S.S. from the irregularity of the PKS 2155-304 energy spectrum

Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model of particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, the existence of ALPs can modify the energy spectrum of the gamma rays for a sufficiently large coupling between ALPs and photons. This modification would take the form of an irregular behavior of the energy spectrum in a limited energy range. Data from the H.E.S.S. observations of the distant BL Lac object PKS 2155-304 (z=0.116) are used to derive upper limits at the 95% C.L. on the strength of the ALP coupling to photons, ggammaa<2.1×10-11GeV-1 for an ALP mass between 15 and 60 neV. The results depend on assumptions on the magnetic field around the source, which are chosen conservatively. The derived constraints apply to both light pseudoscalar and scalar bosons that couple to the electromagnetic fieldFil: Medina, Maria Clementina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto Argentino de Radioastronomia (i); ArgentinaFil: H.E.S. S. collaboration

The pericope adultrae: Theories of insertion & omission

Contains fulltext : 76519.pdf (author's version ) (Open Access)RU Radboud Universiteit Nijmegen, 19 april 2010Promotor : Watt, J.G. van der417 p

A Puzzle to Challenge Genetic Programming

This report represents an initial investigation into the use of genetic programming to solve the N-prisoners puzzle. The puzzle has generated a certain level of interest among the mathematical community. We believ

First you have to get outside:reflections on the ecological location of qualitative fieldwork

Most methodology books do not explain how nature—or in the author’s case, heavy wet snow and swampy muskeg—can be an intrinsic part of a qualitative research design. Yet the author’s inability to make sense of the subarctic not only limited her preliminary qualitative analysis, but this lack of skill also nearly killed her. This article describes the author’s emergent belief that first-hand situated knowledge of the local ecology is an essential requirement of effective qualitative inquiry in social—ecological contexts. The author uses data from two ethnographic studies that were published in the Academy of Management Journal (2000) and Organization & Environment (2004) to illustrate this point. She discusses how the local ecology affected her qualitative research design in terms of access, type of data collected, and interpretation of local management practices. The author closes by calling for a renaturing of qualitative inquiry especially as it relates to research on sustainability