1. Curvature and isocurvature perturbations in two-field inflation Krzysztof Turzyński (University of Michigan) based on arXiv:0704.0212 with Z.Lalak, D.Langlois and S.Pokorski

2. Inflation  V solves the flatness problem solves the horizon problem dilutes any preexisting relics generates primordial density perturbations through quantum fluctuations of the coupled inflaton-gravity system small = slow-roll

3. Curvature perturbations gauge invariant variable describing perturbations 3-dim curvature of the comoving density hypersurfaces

4. Evolution of perturbations

5. Road map inflationradiation domination matter domination dark energy domination CMB hic sunt leones horizon length scale

7. Observations and inflation 10 –4 10 –3 10 –2 10 –1 10 –3 10 –2 Ellis, Lalak, Pokorski, kt, 2006

9. Motivation for multi-field scenarios V     inflation SUSY breaking

10. Curvature and isocurvature perturbations   Hubble crossing inflation ends fixed k curvature perturbation isocurvature perturbation

11. Equations

12. Examples double inflation roulette inflation

13. Examples roulette inflation

14. Examples

15. Conclusions good motivation to look for the implications of next-to-minimal models of inflation richer dynamics; possible generation of isocurvature perturbations (after reheating) message of caution: predictions may differ from the single-field case We have a tool (for studying the evolution of the multi-inflaton systems) and won’t hesitate to use it!