# Eilenberg-MacLane space

A space, denoted by , representing the functor , where is a non-negative number, is a group which is commutative for and is the -dimensional cohomology group of a cellular space with coefficients in . It exists for any such and .

The Eilenberg–MacLane space can also be characterized by the condition: for and for , where is the -th homotopy group. Thus, is uniquely defined up to a weak homotopy equivalence. An arbitrary topological space can, up to a weak homotopy equivalence, be decomposed into a twisted product of Eilenberg–MacLane spaces (see Postnikov system). The cohomology groups of coincide with those of . Eilenberg–MacLane spaces were introduced by S. Eilenberg and S. MacLane .

#### References

[1a] | S. Eilenberg, S. MacLane, "Relations between homology and homotopy groups of spaces" Ann. of Math. , 46 (1945) pp. 480–509 |

[1b] | S. Eilenberg, S. MacLane, "Relations between homology and homotopy groups of spaces. II" Ann. of Math. , 51 (1950) pp. 514–533 |

[2] | R.E. Mosher, M.C. Tangora, "Cohomology operations and applications in homotopy theory" , Harper & Row (1968) |

[4] | E.H. Spanier, "Algebraic topology" , McGraw-Hill (1966) |

**How to Cite This Entry:**

Eilenberg–MacLane space.

*Encyclopedia of Mathematics.*URL: http://www.encyclopediaofmath.org/index.php?title=Eilenberg%E2%80%93MacLane_space&oldid=22371