Vol. 528
In section 2. Astrophysical processes

Stellar mixing. I. Formalism

Stellar mixing. II. Double diffusion processes

Stellar mixing. III. The case of a passive tracer

Stellar mixing. IV. The angular momentum problem

Stellar mixing. V. Overshooting

Mixing in stellar interiors plays a very important role in the evolution of stars: for instance, it carries fresh nuclear fuel into their core, thereby extending their life spans. This mixing is caused by various instabilities, the most prominent being thermal convection, and generally these lead to a turbulent state. To model the transport of heat and matter achieved by such turbulence, generations of astrophysicists have used a prescription based on the mixing-length, i.e. the mean free path of the turbulent eddies. The shortcomings of this crude prescription are well known, and Vittorio Canuto has boldly undertaken to overcome them. Over the years he has developed his Reynolds stress model, which he describes in Paper I. In the subsequent articles he applies it to specific problems: double diffusion, turbulent transport of a passive scalar, transport of angular momentum, and convective overshoot. Now it is the turn of stellar models builders to implement this new formalism in their evolution code and to confront the results with the observations.