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I was hoping to get more intuition for homology, but can't exactly see what would a non-free homology group tell us about a space. The simplest example I know is the real projective plane, but that's still not simple enough to give me any insight. If there is no such space, I would be grateful for a hint towards why is this impossible.

Gambi
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This is a version of several questions which were asked and answered earlier:

  1. There are no 2-dimensional manifolds $M$ with torsion in $H_1$ embeddable in $R^3$ (see Mariano's answer here and Kevin's answer here).

  2. Also, there are no 3-dimensional manifolds with torsion in $H_1$ homeomorphic to open subsets in $R^3$, see Eric's answer here.

Moishe Kohan
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