http://theses.ncl.ac.uk/jspui/handle/10443/1951 2026-04-11T17:33:28Z http://theses.ncl.ac.uk/jspui/handle/10443/2210 Title: Particle detectors in curved space quantum field theory Authors: Hinton, Kerry Abstract: Ambiguities of the particle concept in non-Minkowski spaces are reviewed. To study this and other aspects of quantum field theory in curved spaces, an operationalist approach is adopted through the use of particle detector models. A precise definition of this general concept is given and shown to include many different types of detector models. Five particular models are studied in detail and their responses in Rindler and Schwarzschild spaced are evaluated. In the Rindler case it is explicitly shown that acceleration radiation is anisotropic and time independent. Direct comparison of detectors’ responses is seen to be unsuitable for determining whether two different detectors ‘perceive’ a given situation identically. A method for comparing different detectors is constructed and applied to the models previously introduced. This leads to the notion of equivalence of different detectors, thereby circumventing the problems of direct comparison of their responses. In addition several general results about quantum fields in non-Minkowski spaces are proven. By studying the details of how particle detectors work, the reasons fordifferent detectors being (in)equivalent are revealed. Model detectors of the charged scalar field and spinor fields are then introduced and several problems of “overly simplistic” models are discussed: in particular problems arising from the fact that these fields contain several species of particles. Particle detector equivalence is then applied to these models and used to construct an elementary symmetry between the charged scalar and spinor field many-particle states in the Minkowski Fock space. Finally, a general discussion of several philosophical and practical aspects of using particle detectors to study quantum fields in curved spaces is presented and some points of general confusion are clarified. The particle detector model is operationalist and as such is seen to be most productive when used with close adherence to the Copenhagen interpretation of quantum mechanics. Description: PhD Thesis submitted in 1984 but edited in 2014 so that all text and equations are now typeface 1984-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/1952 Title: Regional gravity modelling and geohistory of the Parnaiba Basin (N.E. Brazil) Authors: Sousa, Mauro Andrade de Abstract: The Parn8.1ba Basin is one of the three large Palaeozoic intracratonic basins found in Brazil, the others being the Amazon and Parana. Parnaiba is an ovalshaped basin situated in NE Brazil and its area is about 600.000 km2 • Gravity data have been collected mainly along accessible roads crossing the Parn81ba Basin and merged with existing data bases of several Brazilian Institutions. The collection of all available geological and geophysical data included several gravity profiles crossing the eastern half of the basin. These profiles are part of a much larger data set forming polygons over a large proportion of the Brazilian territory. The whole gravity network has been internally adjusted and referred to the International Gravity Standardization Net 71. The net has been found precise to ±0.041 mGal. Although the distribution of gravity stations is not ideal, Bouguer and free-Air anomaly maps have been produced, these being the first gravity maps for the whole basin. Contrary to the basin physiography, the Bouguer map unexpectedly shows elongated gravity lows with NE-SW and NNW -SSE directions. These are parallel to the 'l'ransbrasiliano Lineament and subparallel to the Araguaia Fold Belt, respectively. A first attempt at interpreting the gravity anomalies resulted in the proposal of an anomalous, denser zone at lower crustal depths. The tectonic subsidence in the basinal area was estimated through systematic backstripping using 22 boreholes which reached the metamorphic or sedimentary basement. A non-uniform lithospheric stretching model was used as a first approximation for the modelling of the tectonic regime. This procedure was suggested by the presence of several grabenlike structures, as confirmed by shallow seismic sections, exploratory boreholes and gravity maps. Assuming an elastic rheology for the lithosphere, a regional W-E tectonic subsidence profile could be reproduced employing an axisymmetric subsurface load and a flexural ridigity of 0.2 x 1024 N m. Results of the present study are consistent with the apparent bimodality of the flexural ridigity of the continental lithosphere. Description: PhD Thesis 1996-01-01T00:00:00Z