  Non-adiabatic pressure perturbations naturally occur in models of inflation
consisting of more than one scalar field. The amount of non-adiabatic pressure
present at the end of inflation can have observational consequences through
changes in the curvature perturbation, the generation of vorticity and
subsequently the sourcing of B-mode polarisation. In this work, based on a
presentation at the 13th Marcel Grossmann Meeting, we give a very brief
overview of non-adiabatic pressure perturbations in multi-field inflationary
models and describe our recent calculation of the spectrum of isocurvature
perturbations generated at the end of inflation for different models which have
two scalar fields.
