Compactified Realisations

Last Tuesday was a bit hectic for me as I tried to coordinate the last minute changes needed to put two papers on the arXiv servers for the next day. The two articles which are now available are numbered 1111.6919 and 1111.6940:

• Calculating Non-adiabatic Pressure Perturbations during Multi-field Inflation
  Ian Huston, Adam J. Christopherson
  Abstract: Isocurvature perturbations naturally occur in models of inflation consisting of more than one scalar field. In this paper we calculate the spectrum of isocurvature perturbations generated at the end of inflation for three different inflationary models consisting of two canonical scalar fields. The amount of non-adiabatic pressure present at the end of inflation can have observational consequences through the generation of vorticity and subsequently the sourcing of B-mode polarisation. We compare two different definitions of isocurvature perturbations and show how these quantities evolve in different ways during inflation. Our results are calculated using the open source Pyflation numerical package which is available to download.
• Quantifying the behaviour of curvature perturbations during inflation
  Ellie Nalson, Adam J. Christopherson, Ian Huston, Karim A. Malik
  Abstract: How much does the curvature perturbation change after it leaves the horizon, and when should one evaluate the power spectrum? To answer these questions we study single field inflation models numerically, and compare the evolution of different curvature perturbations from horizon crossing to the end of inflation. In particular we calculate the number of efolds it takes for the curvature perturbation at a given wavenumber to settle down to within a given fraction of their value at the end of inflation. We find that e.g. in chaotic inflation, the amplitude of the comoving and the curvature perturbation on uniform density hypersurfaces differ by up to 180 % at horizon crossing assuming the same amplitude at the end of inflation, and that it takes approximately 3 efolds for the curvature perturbation to be within 1 % of its value at the end of inflation.

As part of the work on the first of these papers, my Pyflation code has been updated to version 0.2 and now allows multiple fields systems to be used at first order.

There seemed to be a glut of papers released last Wednesday, with the post-Thanksgiving queue being worked through and people aiming to apply for jobs in December. Apologies to those irked by the overwhelming astro-ph listing that day for my part in it!