Studies in Supersymmetry and Cosmology.
Abstract
The discussion of three studies in supersymmetry and one on the generation of a baryon asymmetry in the early universe are presented. Specifically, the following results are obtained:. (i) It is possible to confine a supersymmetric system of fields without breaking supersymmetry. This is done by introducing external sources coupled to the fields and selecting them in such a way as to respect the supersymmetric invariance of the action. The "perfect conductor" limit is seen to satisfy this requirement and it is shown in a particular example how this gives rise to an exact cancellation of the Casimir force, as expected from other considerations. (ii) In a simple nonlinear supersymmetric model, the classical solitonlike solutions are found to be pure gauge transformations of the ordinary bosonic solitons. The solutions are found under the assumption that the fields have to belong to a global Grassmann algebra consistent with supersymmetry. It is also found that it is possible to accommodate scattering solutions which are not purely gauge rotations and which give nilpotent contributions to the energy. It is argued that a reinterpretation of the anticommuting character of the parameters of a supersymmetry transformation is needed. (iii) In the study of the quantum corrections to the classical states of (ii) it is found that the Grassmann character of the classical fields imposes too many constraints which are incompatible with the quantization scheme. A new anticommuting algebra is proposed to substitute the Grassmann algebra, and the following proposed to substitute the Grassmann algebra, and the following features are obtained: (a) supersymmetric invariance is unaffected; (b) the quantum corrections are the usual ones that can be obtained if no supersymmetry was invoked; (c) the algebra is governed by a scalar parameter, l, which sets the scale of the quantum corrections (in this sense l can be viewed as also governing the quantum perturbation series); (d) a finite supersymmetry transformation becomes a series expansion in l which, to the lowest order, coincides with the expansion in powers of (H/2PI), thus shedding some light on the miraculous cancellations that occur in supersymmetry. (iv) In the context of the very early universe (GUT era), a very simple model for baryon production is discussed. It is shown that, under standard assumptions, it is unrealistic to view the early universe as in adiabatical expansion, close to equilibrium throughout the baryongeneration era.
 Publication:

Ph.D. Thesis
 Pub Date:
 November 1982
 Bibcode:
 1982PhDT........11Z
 Keywords:

 Physics: Elementary Particles and High Energy