Alpha-vacuum Decay And Linear Equation Of State Cosmology

This work is divided into two parts. The first addresses formal aspects of field theory in de Sitter space which are relevant to inflation while the second is a phenomenological model of dark energy and matter relevant to the evolution of structure and expansion of the universe. In the first part we consider the decay of the inflaton into scalars paying particular attention to the vacuum structure that arises in de Sitter space. Before presenting the details of particle decay in de Sitter space we outline a general proof of the vacuum structure that exists in curved spaces that is absent in Minkowski in order to demonstrate that the issues are not limited to idealized de Sitter. We also consider a time ordering prescription that apparently eliminates the dependence of the decay rate on the vacuum choice. Finally we consider the implications of these results and ask whether they indicate a possible resolution of vacuum ambiguity. The second part considers an alternative to the concordance ΛCDM model cosmology. We replace the cosmological constant and some portion of the CDM component by a fluid that exhibits a linear equation of state (one that is in fact appropriate to liquids). We then fit this model to cosmological observations of the expansion, microwave background and matter power spectrum. We find that the model potentially unifies dark matter and energy and we even consider micro-physical Lagrangians that would give rise to this linear equation of state