Steenrod algebra
= Steenrod algebra
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{title2=$\mathcal A_p$}
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The Steenrod algebra organizes stable mod-$p$ <cohomology operations>. At $p=2$ it is generated by the <Steenrod squares>; at an odd prime it is generated by the <Steenrod reduced powers> and <Bockstein homomorphism>. Cohomology is a module over this algebra, and every continuous map induces a homomorphism preserving its action.