Postnikov square

In algebraic topology, a Postnikov square is a certain cohomology operation from a first cohomology group H¹ to a third cohomology group H³, introduced by Postnikov (1949). Eilenberg (1952) described a generalization taking classes in H^t to H^2t+1.

References

• Eilenberg, Samuel (1952), "Homotopy groups and algebraic homology theories", Proceedings of the International Congress of Mathematicians, Cambridge, Mass., 1950, vol. 2, Providence, R.I.: Amer. Math. Soc., pp. 350–353, MR 0045388 
• Kharshiladze, A.F. (2001), "p/p074070", in Hazewinkel, Michiel, Encyclopedia of Mathematics, Springer, ISBN 978-1-55608-010-4 
• Postnikov, M. M. (1949), "The classification of continuous mappings of a three-dimensional polyhedron into a simply connected polyhedron of arbitrary dimension", Doklady Akad. Nauk SSSR (N.S.) (in Russian) 64: 461–462, MR 0029173