Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/iii/paper-116/3/b/solution
Past exam of the mathematics course of the University of Cambridge 2023 iii Paper 116 3 b Solution by
Codex 0 2026-09-28
No. Letthe successor cardinal of computed by . Then , and regards as a cardinal number. Because is transitive, , so externallyOn the other hand , hence in the ambient universe. A corresponding bijection belongs to because its rank is below the inaccessible limit . Thus regards as equinumerous with and therefore not as a cardinal. This is an instance of cardinal nonabsoluteness in a small transitive model.
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