Strong downward Löwenheim–Skolem theorems for stationary logics, II: reflection down to the continuum.

Continuing (Fuchino et al. in Arch Math Log, 2020. https://doi.org/10.1007/s00153-020-00730-x), we study the Strong Downward Löwenheim–Skolem Theorems (SDLSs) of the stationary logic and their variations. In Fuchino et al. (2020) it has been shown that the SDLS for the ordinary stationary logic with weak second-order parameters SDLS (L stat ℵ 0 , < ℵ 2) down to < ℵ 2 is equivalent to the conjunction of CH and Cox's Diagonal Reflection Principle for internally clubness. We show that the SDLS for the stationary logic without weak second-order parameters SDLS - (L stat ℵ 0 , < 2 ℵ 0) down to < 2 ℵ 0 implies that the size of the continuum is ℵ 2 . In contrast, an internal interpretation of the stationary logic can satisfy the SDLS down to < 2 ℵ 0 under the continuum being of size > ℵ 2 . This SDLS is shown to be equivalent to an internal version of the Diagonal Reflection Principle down to an internally stationary set of size < 2 ℵ 0 . We also consider a version of the stationary logic and show that the SDLS for this logic in internal interpretation SDLS + int (L stat PKL , < 2 ℵ 0) for reflection down to < 2 ℵ 0 is consistent under the assumption of the consistency of ZFC + "the existence of a supercompact cardinal" and this SDLS implies that the continuum is (at least) weakly Mahlo. These three "axioms" in terms of SDLS are consequences of three instances of a strengthening of generic supercompactness which we call Laver-generic supercompactness. Existence of a Laver-generic supercompact cardinal in each of these three instances also fixes the cardinality of the continuum to be ℵ 1 or ℵ 2 or very large respectively. We also show that the existence of one of these generic large cardinals implies the " + + " version of the corresponding forcing axiom. [ABSTRACT FROM AUTHOR]

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