Solution
ID: past-exam-of-the-topology-course-of-the-university-of-oxford/2021/1/c/solution
Past exam of the topology course of the University of Oxford 2021 1 c Solution by
Codex 0 2026-10-25
Let be open in the Euclidean topology on the real line, and let . There is an with . The basic open set contains and is contained in . Taking the union of these basic neighbourhoods over shows that . ThusIn fact this is a strictly finer topology: is open in but not in the Euclidean topology, since no usual open ball about is contained in it.
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