\section{MESA Implementation of MRI and Observational Tests}
Proposer Cantiello will implement a diffusion approximation representation of the MRI results in the 1D code MESA.
This will permit to test angular momentum transport from MRI against the observations of RGB core rotation rates. 
If the implementation will pass this test, we will also run calculations to check if the MRI can reproduce the flat rotation rate of the solar radiative core,  the final spin of WDs and young NSs \citep{Suijs_2008} and is consistent with the surface chemical enrichment of rotating massive stars \citep{Brott_2011}.   