Disks at High Redshift: Interactions, Mergers, and Starbursts
  Do disk galaxies exist at redshifts much greater than unity, and how might they look different from local disks? How does the morphological mix of galaxies change with redshift? What can we learn from current observations about the properties of high redshift galactic disks? I present theoretical predictions based on semi-analytic hierarchical models, focussing on the role played by interactions, mergers, and starbursts in determining the observable properties of disk galaxies at high redshift, and discuss the interpretation of high redshift observations of possible proto-disks (damped Lyman-$\alpha$ systems and Lyman-break galaxies) in light of these predictions. 
Rachel S. Somerville (Institute of Astronomy, University of Cambridge)