High Energy Physics Seminar

I will introduce the "separate universe" approach to determining some aspects of nonlinear gravitational evolution: specifically the bias of tracers such as halos and voids and squeezed limit bispectra. I will motivate and define the separate universe, and then show how it can be generalized for cosmologies with multiple fluctuating components in the energy density -- either different fluids or adiabatic and isocurvature modes. Finally, I'll describe results using these techniques that explicitly demonstrate how small-scale observables depend on the growth-history of long-wavelength density fluctuations and new small-scale observables that can arise.