Hi-

The nearest relation, based on numerical red giant models with masses < 8 solar masses, was proposed by B. Paczynski (1970): the core-mass luminosity relation. The relation was explored further with improved models and found wanting by later investigators:

Article On the validity of the core-mass luminosity relation for TP-...

You will need familiarity with processes, like core dredge-ups of core material, thought to occur in the late stages of stellar evolution to understand the arguments.