The acquisition and alteration of food consumption patterns in preverbal and verbal children.
Supersymmetric string theories are the best candidates we have for a unification of all
the fundamental interactions known in physics. These theories still need to be confronted
with experiment. However, direct evidence for string effects only becomes important at
high energies. This means that, at present, one can only hope to constrain these theories
through their low energy limits. Of these, the most promising are supergravities where
the fields and their interactions are severely constrained by the superstring theory. In this
thesis we will consider some of the additional constraints imposed by cosmology on these
In the first part our attention will be focused on the problem of stabilising the dilaton
field. The vacuum expectation value (vev) of the dilaton is related to both gauge and gravitational
coupling constants. This means that for the theory to be realistic the dilaton
needs to acquire a finite vev. The most popular way of doing this is through the condensation
of gauginos. In this thesis we will propose a particular model where the dilaton is
stabilised at reasonable values with a vanishing cosmological constant. We will also show
a way of dynamically evolving the dilaton to this stable point in a cosmological setting.
In a second part we will address the "moduli problem". Moduli fields arise generically
in string-inspired theories, their vev being related to the compactification radius. The
expected mass and coupling of these fields would make them incompatible with the standard
nucleosynthesis scenario. Thermal inflation has been proposed as a mechanism that
would permit one to solve this problem. In this thesis we will examine in detail how this
mechanism can be implemented in a supergravity model and we will also consider the
possibility of defect production in this scenario.