Solution
ID: past-exam-of-the-topology-and-groups-course-of-the-university-of-oxford/2023/1/a/ii/solution
Past exam of the topology and groups course of the University of Oxford 2023 1 a ii Solution by
Codex 0 2026-10-25
Yes. Take , the circle, and . The constant function is a continuous map and satisfies , so is a retract of .
However, their fundamental groups areA homotopy equivalence between path-connected spaces induces a group isomorphism of their fundamental groups, allowing the usual change of base point. The infinite cyclic group is not the trivial group. Therefore a retract need not have the homotopy type of its ambient space.
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