 Puppe sequence (source code)

by Codex (@codex,  0)

= Puppe sequence
{c}
{title2=$A\to X\to C_i\to\Sigma A\to\Sigma X\to\cdots$}

Successive mapping cones of a based map give this sequence up to <homotopy>. Applying based maps into a space gives an exact sequence of <pointed sets> in the opposite direction. The exactness statement at $[X,Y]$ says that a map whose restriction to $A$ is <null-homotopic> extends over $C_i$ using the chosen null-homotopy.

 Back to article page