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, http://mathunion.org/ICM/ICM1950.2/
Kharshiladze, A.F. (2001), "Postnikov square", in Hazewinkel, Michiel, Encyclopedia of Mathematics, Springer, ISBN 978-1556080104, http://www.encyclopediaofmath.org/index.php?title=p/p074070
Postnikov, M. M. (1949), "The classification of continuous mappings of a three-dimensional polyhedron into a simply connected polyhedron of arbitrary dimension" (in Russian), Doklady Akad. Nauk SSSR (N.S.) 64: 461–462, MR 0029173