Effective Field Theory of the Linear O(N)O(N) Sigma Model

The low energy structure of a theory containing light and heavy particle species which are separated by a mass gap can adequately be described by an effective theory which contains only the light particles. In this work we present a thorough analysis of the effective field theory of the linear $O(N)$ sigma model in the spontaneously broken phase. In particular, we present a detailed discussion of two techniques, a short-distance expansion and a method based on loop-integrals, which can be used to explicitly evaluate the functional relationships between the low energy constants of the effective theory and the parameters of the underlying theory. We furthermore provide a detailed analysis of the matching relation between the linear sigma model and its effective theory, in order to clarify some discrepancies which can be found in the literature.Comment: 42 pages, LaTeX, BUTP-94/12, HUTP-94/A012, to appear in Ann. Phy

Effective Field Theory for a Heavy Higgs: a Manifestly Gauge Invariant Approach

For large values of the Higgs boson mass the low energy structure of the gauged linear sigma model in the spontaneously broken phase can adequately be described by an effective field theory. In this work we present a manifestly gauge invariant technique to explicitly evaluate the corresponding effective Lagrangian from the underlying theory. In order to demonstrate the application of this functional method, the effective field theory of the abelian Higgs model is thoroughly analyzed. We stress that this technique does not rely on any particular property of the abelian case. The application to the non-abelian theory is outlined.Comment: 32 pages, LaTeX. A postscript file is available at ftp://ftp-itp.unibe.ch/pub/preprints/1995/BUTP-95_5.ps.g

Aspectos gerais da fotossensibilizacao hepatogena em bovinos.

A sensibilização da pele a luz devido, geralmente, a ação de certas doenças, plantas ou outras substancias, e denominada fotossensibilizacao (Stedman's Medical 1972). O primeiro registro sobre a ocorrência de fotossensibilizacao hepatogena em bovinos mantidos em pastagens de Brachiaria decumbens, na América do Sul, foi feito na Venezuela (Centro Internacional de Agricultura Tropical 1975), onde a doença ocasionou a morte de doze garrotes nos primeiros dias de pastejo. No Brasil, Hutton (s.d.lL) fez observações sobre casos desta doença no gado Nelore, em pastagens de B. decumbens, em Rio Verde de Goiás. O surto acometeu, principalmente, bezerros antes e depois da desmama. Alem desta primeira constatação, vários outros autores descreveram esta doença em bovinos em pastagem de B. decumbens.bitstream/item/138531/1/COT-19.pdfCNPG

(Un)anticipated Technological Change in an Endogenous Growth Model

This paper examines numerically the impact of a negative exogenous shock to marginal productivity (such as ecological government regulation that becomes effective at some point in time) in an endogenous finite-time growth model with sluggish reallocation of human capital. The policy can be anticipated or unanticipated by firms, and it can also be announced but not implemented. It turns out that these frictions have a very strong long-run effect on output, consumption and on the optimal allocation of capital and labor in particular. The qualitative properties relate to homogenous labor models with positive productivity shocks. The problem is thus to maximize a function of a continuous system, where the system is subject to frictions and stepwise changes; for such a problem the application of calculus of variations necessary conditions is problematic. A numerical optimization method, which has had much success on qualitatively similar problems in engineering, has been employed.two-sector endogenous growth model; unanticipated and anticipated technological change; frictions in reallocation of human capital; Runge-Kutta parallel shooting algorithm