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I am currently going over Nakahara'sGeometry, Topology, and Physicsand even though I have bumped into some typos/mistakes, there's something that I am sure is not a mistake but rather a misunderstanding I have of the basic concepts.

Namely, in page 181, he describes the notion ofhomogeneous space:

Thus far, the notion of such space makes total sense to me... however that last statement of homeomorphism is not clear at all... If somebody can provide proofs or some related theorem, I would appreciate it. Let G be a Lie group and H any subgroup of G. The coset space G/H admits a differentiable structure and G/H becomes a manifold, called a homogeneous space. Note that dim G/H = dimG - dimH. let G be a Lie group which acts on a manifold M transitively and let H(p) be an isotropy group of p in M. [the term 'isotropy group' may be known to others by 'stabiliser'... just saying.] H(p) is a Lie subgroup and the coset space G/H(p) is a homogeneous space. In fact, if G, H(p) and M satisfy technical requirements (e.g. G/H(p) be compact) it can be shown that G/H(p) is homeomorphic to M. See example below...

Anyway, here comes the example that he gives, which even complicates more my understanding:

Okay, from this, it's clear that SO(3) acts on S^2 transitively and hence we have that SO(3)/SO(2) is isomorphic to S^2. I.e... G/H = S^2. (However, since SO(2) is not a normal subgroup of SO(3), S^2 does not admit a group structure.) Let G = SO(3) be a group acting onR^3 [So I suppose M =R^3...] and H = SO(2) be the isotropy group of x elementR^3.

That said, it is clear to me that G/H(p) is compact (as the requirement above)...butI don't see how S^2 is homeomorphic toR^3. Can anybody explain this?

I mean, I see how –for example– S^2 - {p} is homeomorphic toR^2... but S^2 toR^3??

Maybe it's late and the question is just super-dumb... but I better ask it here so that I can sleep with my mind in peace.

Thank you in advance,

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# On the properties of Homogeneous Spaces

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