Past exam of the mathematics course of the University of Cambridge 2024 iii Paper 119 2 b Solution Created 2026-09-24 Updated 2026-09-25
Let be connected and nonempty. The limit of the underlying diagram of commutative rings is the subringIf is nonzero in one component, it is nonzero in every component: field homomorphisms are injective, and connectedness propagates this fact along zigzags. Hence the componentwise inverses are defined and compatible. Thus is a field. Since the inclusion is full, the same cone is limiting in the category of fields.