Absoluteness of cardinalhood in limit ranks
ID: absoluteness-of-cardinalhood-in-limit-ranks
For limit ordinals , the structures and agree on whether any shared set is a cardinal number. They agree on being an ordinal. If is not a cardinal number, a bijection from some onto has rank of a set at most , hence belongs to . Its defining properties are bounded formulas in set theory. Both structures therefore see the same failure witness. This full agreement is stronger than downward absoluteness of cardinalhood between arbitrary transitive models.
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