FULL SPECTRUM OF TURBULENCE CONVECTIVE MIXING - I - THEORETICAL MAIN SEQUENCES AND TURN-OFF FOR 0.6-DIVIDED-BY-15 M-CIRCLE-DOT

We present the results of extensive evolutionary computations from the Zero Age Main Sequence to the Red Giants, for stars in the range 0.6 divided by 15 M. and with chemistry (Y, Z) = (0.274, 0.017). The novel ty of these computations is in the general treatment of convection, na mely: 1. convection as a whole is addressed in the Full Spectrum of Tu rbulence model (billions of eddy scales are considered) with the appro priate convective fluxes distribution, as opposed to the one-eddy Mixi ng Length Theory; 2. local chemical evolution also in the presence of convection is separately evaluated for each element, as a result of a process in which nuclear evolution and turbulent transport are fully c oupled by means of a diffusive scheme (coupled-diffusion); 3. convecti ve overshooting (when considered) is also addressed in the above coupl ed-diffusive scheme, assuming that the turbulent velocity exponentiall y vanishes outside the formally convective region according to an e-fo lding free parameter zeta, tuned to fit observations. After some tests on the small solar convective core in early main sequence, we discuss the effects of coupled-diffusion in the cores of larger mass stars, w here the nuclear lifetimes of some (pp and) CNO elements can be compar able to the mixing times. We also compute a full grid of tracks with a small amount of overshooting, finding that a unique free parameter ca n be suitable for the whole range of mass considered (solar and below solar included). Theoretical tracks are discus sed, and isochrones are compared to the observational HR diagram for the Pleiades, finding an age greater than or similar to 120 Myr, consistent with that obtained from the candidate brown dwarf PPL 15. An age is also derived for the young cluster alpha Persei, for which a datation from the detection o f lithium in brown dwarf candidates should be soon available. For comp leteness, and to facilitate comparisons with results by other authors, we also describe in details the ATON 2.0 code used for the present co mputations.