Effective Action and Hawking Flux from Covariant Perturbation Theory

The computation of the radiation flux related to the Hawking temperature of a Schwarzschild Black Hole or another geometric background is still well-known to be fraught with a number of delicate problems. In spherical reduction, as shown by one of the present authors (W. K.) with D.V. Vassilevich, the correct black body radiation follows when two ``basic components'' (conformal anomaly and a ``dilaton'' anomaly) are used as input in the integrated energy-momentum conservation equation. The main new element in the present work is the use of a quite different method, the covariant perturbation theory of Barvinsky and Vilkovisky, to establish directly the full effective action which determines these basic components. In the derivation of W. K. and D.V. Vassilevich the computation of the dilaton anomaly implied one potentially doubtful intermediate step which can be avoided here. Moreover, the present approach also is sensitive to IR (renormalisation) effects. We realize that the effective action naturally leads to expectation values in the Boulware vacuum which, making use of the conservation equation, suffice for the computation of the Hawking flux in other quantum states, in particular for the relevant Unruh state. Thus, a rather comprehensive discussion of the effects of (UV and IR) renormalisation upon radiation flux and energy density is possible.Comment: 26 page

High-gain self-steering microwave repeater, volume 1 Final engineering report, Jan. 1966 - Apr. 1969

Engineering model of high gain self steering microwave transponder and application to satellite communication link

The Dimensional-Reduction Anomaly in Spherically Symmetric Spacetimes

In D-dimensional spacetimes which can be foliated by n-dimensional homogeneous subspaces, a quantum field can be decomposed in terms of modes on the subspaces, reducing the system to a collection of (D-n)-dimensional fields. This allows one to write bare D-dimensional field quantities like the Green function and the effective action as sums of their (D-n)-dimensional counterparts in the dimensionally reduced theory. It has been shown, however, that renormalization breaks this relationship between the original and dimensionally reduced theories, an effect called the dimensional-reduction anomaly. We examine the dimensional-reduction anomaly for the important case of spherically symmetric spaces.Comment: LaTeX, 19 pages, 2 figures. v2: calculations simplified, references adde

Conditions for Optimality and Strong Stability in Nonlinear Programs without assuming Twice Differentiability of Data

The present paper is concerned with optimization problems in which the data are differentiable functions having a continuous or locally Lipschitzian gradient mapping. Its main purpose is to develop second-order sufficient conditions for a stationary solution to a program with C^{1,1} data to be a strict local minimizer or to be a local minimizer which is even strongly stable with respect to certain perturbations of the data. It turns out that some concept of a set-valued directional derivative of a Lipschitzian mapping is a suitable tool to extend well-known results in the case of programs with twice differentiable data to more general situations. The local minimizers being under consideration have to satisfy the Mangasarian-Fromovitz CQ. An application to iterated local minimization is sketched

Comment on: ``Trace anomaly of dilaton coupled scalars in two dimensions''

The trace anomaly for nonminimally coupled scalars in spherically reduced gravity obtained by Bousso and Hawking (hep-th/9705236) is incorrect. We explain the reasons for the deviations from our correct (published) result which is supported by several other recent papers.Comment: 2 page

Bäuerliche Experimente in Österreich – Beurteilung von Video als möglicher Auslöser der Experimentiertätigkeit von Biobäuerinnen und Biobauern

Farmers’ experiments are an integral element of agricultural practice, contribute to the development of local knowledge and form the precondition for local innovations. This study addresses organic farmers’ experiments in Austria, and specifically video as tool for capturing and sharing lessons learned from farmers’ experimentation, as well as the potential of video to trigger farmers’ experiments. For 85 % of the surveyed organic farmers (n=34) farmers’ experiments were considered to have high relevance in the course of their farming activities. The elaborated videos stimulated 71 % of the farmers to conduct experiments. The videos were successfully applicable in adult and student agricultural education. After watching them, 12 of 16 students (75 %) came up with ideas for experiments they would like to try at their parents’ farms