#### Sept 26, 14:15 in A315

#### Samuel Flender (Helsinki)

#### Newtonian versus relativistic cosmology

We show how the relativistic matter and velocity power spectra behave in
different gauges. We construct a new gauge where both spectra coincide
with Newtonian theory on all scales. However, in this gauge there are
geometric quantities present which do not exist in Newtonian theory, for
example the local variation of the Hubble parameter. Comparing this
quantity to second order Newtonian quantities, we find that Newtonian
theory is inaccurate on scales larger than 10 Mpc. This stresses the
importance of relativistic corrections to Newtonian cosmological N-body
simulations on these scales.