# Survey articles on homotopy groups of spheres

Are there general surveys or introductions to the homotopy groups of spheres? I'm interested especially in connections to low-dimensional geometry and topology.

• Retagged reference request in lieu of big list and soft-question. Seemed more specific, but feel free to undo. – Cam McLeman May 14 '10 at 16:13
• Cam, "reference-request" is a more precise tag. Thanks. – user2529 May 15 '10 at 4:26

Connections between homotopy groups of spheres and low-dimensional geometry and topology have traditionally been somewhat limited, with the Hopf bundle being the thing that comes most immediately to mind. A fairly recent connection is Soren Galatius' theorem that the homology groups of $Aut(F_n)$, the automorphism group of a free group, are isomorphic in a stable range of dimensions to the homology groups of "loop-infinity S-infinity", the space whose homotopy groups are the stable homotopy groups of spheres.