AEC for strictly stable (2305.02020v1)

Abstract: Good frames were suggested in [Sh:h] as the (bare-bones) parallel, in the context of AECs, to superstable (among elementary classes). Here we consider $(\mu,\lambda,\kappa)$-frames as candidates for being (in the context of AECs) the correct parallel to the class of $|T|^+$-saturated models of a strictly stable theory (among elementary classes). One thing we lose compared to the superstable case is that going up by induction on cardinals is problematic (for stages of small cofinality). But this arises only when we try to lift such classes to higher cardinals. Also, we may use, as a replacement, the existence of prime models over unions of increasing chains. For this context we investigate the dimension.