= Karol Borsuk
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<Karol Borsuk> was a <mathematician> whose work helped develop <topology>, particularly the study of <retracts> and the relationship between geometric and topological structure. His collaboration with <Stanisław Ulam> produced results about continuous mappings and topological invariants.https://mathshistory.st-andrews.ac.uk/Biographies/Borsuk/[Biography, dissertation on retracts and collaboration with Ulam]{ref} The <Borsuk-Ulam theorem> states that every <continuous map> from the sphere $S^n$ to $\mathbb R^n$ takes the same value at some pair of antipodal points. The equal-value pair is forced by global topology, even though the map may have no explicit symmetry. This provides a tool for existence proofs rather than a recipe for locating the pair.
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{title=Portrait of <Karol Borsuk>}
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