Inhomogeneities as a bias and as a probe
Precision Cosmology requires us to take into account the small scale inhomogeneities in the Universe when discussing cosmology. After a general introduction, I will discuss the effect of small scale inhomogeneities on the luminosity distance - redshift relation within LCDM: 1) How inhomogeneities bias the Hubble parameter due to peculiar velocities. This bias ameliorates the tension between CMB and and Supernovae measurements of the Hubble parameter. 2) How inhomogeneities serve as a probe of the primordial power spectrum on small scales through the lensing dispersion of Type Ia Supernovae.