Let X and Y be CW complexes. Then the inclusion $j:X\vee Y\to X\times Y$ is a cofibration with cofibre $X\wedge Y$. According to Hans J. Baues' book Principal fibrations and cofibrations, obstructions and differences Definition 1.2.1, a closed cofibration $X\subset Y$ is a principal cofibration if there is a map $f: A\to X$ and a homotopy equivalence $C_f\simeq Y$ under $X$. Question: when will $j$ be principal? If so, what is $A$ in this example?
2026-02-23 06:42:01.1771828921
When will a cofibration be a principal cofibration?
31 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail AtRelated Questions in HOMOTOPY-THEORY
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