Vorticity from isocurvature in the early universe
  Vorticity is ubiquitous in nature however, to date, studies of vorticity in
cosmology and the early universe have been quite rare. In this paper, based on
a talk in session CM1 of the 13th Marcel Grossmann Meeting, we consider
vorticity generation from scalar cosmological perturbations of a perfect fluid
system. We show that, at second order in perturbation theory, vorticity is
sourced by a coupling between energy density and entropy gradients, thus
extending a well-known feature of classical fluid dynamics to a relativistic
cosmological framework. This induced vorticity, sourced by isocurvature
perturbations, may prove useful in the future as an additional discriminator
between inflationary models.
