I need reference where they talk about to prove that spheres of dimension n≥2 don't admit ­­­­symmetric flat connections.



Does spheres of dimension n≥2 admit ­symmetric flat connections?
Manifolds which admit symmetric flat connections are known as affine manifolds. A standard result on these spaces is that the fundamental group of a compact affine manifold must be infinite.


For a reference, see Corollary 1.14 of the following lectures.
<https://arxiv.org/abs/1802.03624>


