Skip to main content
2 of 2
added 17 characters in body
Michael Albanese
  • 19.4k
  • 9
  • 87
  • 161

The previous answers gave analogues to the universal covering space and looked at the homotopy groups of these analogues.

However, the analogy to the $n=1$ case is not complete: While $\pi_1(X)$ classifies the automorphisms over $X$ of the universal covering space, the $\pi_n(X)$ don't classify the automorphisms over $X$ of these $n$-connected analogues. In fact, the higher $\pi_n(X)$ don't seem to classify anything else than homotopy classes of maps $S^n \to X$.

This is one of the motivations for using $n$-groupoids as invariants of spaces, see the discussion here, right before the references: http://ncatlab.org/nlab/show/fundamental+group+of+a+topos

or, starting on page 17 with a nice story on the invention of the higher homotopy groups, and the desire for a non-abelian homology: http://www.intlpress.com/hha/v1/n1/a1/

Peter Arndt
  • 12.3k
  • 3
  • 58
  • 94