Large-Scale Simulations of Reionization
  We use cosmological simulations to explore the large-scale effects of reionization. Since reionization is a process that involves a large dynamic range - from galaxies to rare bright quasars - we need to be able to cover a significant volume of the universe in our simulation without losing hte important small scale effects from galaxies. Here we have taken an approach that uses clumping factors derived from small scale simulations to approximate the radiative transfer on the sub-cell scales. Using this technique, we can cover a simulation size up to $1280 h^{-1} Mpc$ with $10 h^{-1} Mpc$ cells. This allows us to construct synthetic spectra of quasars similar to observed spectra of SDSS quasars at high reshifts and compare them to the observational data. These spectra can then be analyzed for HII region sizes, the presence of the Gunn-Peterson trough and the Lyman-$\alpha$ forest. 
Katharina Kohler, Nickolay Y. Gnedin, & Andrew J.S. Hamilton