English

Easton functions and supercompactness

Logic 2013-11-05 v1

Abstract

Suppose κ\kappa is λ\lambda-supercompact witnessed by an elementary embedding j:VMj:V\rightarrow M with critical point κ\kappa, and further suppose that FF is a function from the class of regular cardinals to the class of cardinals satisfying the requirements of Easton's theorem: (1) α\forall\alpha α<cf(F(α))\alpha<\textrm{cf}(F(\alpha)) and (2) α<β\alpha<\beta \Longrightarrow F(α)F(β)F(\alpha)\leq F(\beta). In this article we address the question: assuming GCH, what additional assumptions are necessary on jj and FF if one wants to be able to force the continuum function to agree with FF globally, while preserving the λ\lambda-supercompactness of κ\kappa? We show that, assuming GCH, if FF is any function as above, and in addition for some regular cardinal λ>κ\lambda>\kappa there is an elementary embedding j:VMj:V\rightarrow M with critical point κ\kappa such that κ\kappa is closed under FF, the model MM is closed under λ\lambda-sequences, H(F(λ))MH(F(\lambda))\subseteq M, and for each regular cardinal γλ\gamma\leq \lambda one has (j(F)(γ)=F(γ))V(|j(F)(\gamma)|=F(\gamma))^V, then there is a cardinal-preserving forcing extension in which 2δ=F(δ)2^\delta=F(\delta) for every regular cardinal δ\delta and κ\kappa remains λ\lambda-supercompact. This answers a question of B. Cody, M. Magidor, On supercompactness and the continuum function, Ann. Pure Appl. Logic, (2013).

Keywords

Cite

@article{arxiv.1311.0303,
  title  = {Easton functions and supercompactness},
  author = {Brent Cody and Sy-David Friedman and Radek Honzik},
  journal= {arXiv preprint arXiv:1311.0303},
  year   = {2013}
}
R2 v1 2026-06-22T01:59:27.398Z