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Sep 10, 2020 at 14:17 comment added LSpice I am amused that a later question tried to clear up the "notoriously slippery concept" of torsion by asking about the Rolling without slipping interpretation of torsion.
S Mar 26, 2018 at 17:52 history suggested CommunityBot CC BY-SA 3.0
changed 'integrality' to 'integrability' (probably what was meant)
Mar 26, 2018 at 17:13 review Suggested edits
S Mar 26, 2018 at 17:52
May 20, 2017 at 20:06 comment added R. van Dobben de Bruyn More generally, it seems to me that the sheaf of torsion free connections should be a (sheaf) torsor under $\rho_1P$. The intrinsic torsion vanishes if and only if this torsor is trivial, i.e. the sheaf has a global section.
Dec 16, 2012 at 1:36 comment added David Corwin Don't you mean GL_n(C) in GL_{2n}(R)?
Dec 16, 2012 at 0:27 history edited John Pardon CC BY-SA 3.0
fixed spelling of "their"
Aug 2, 2010 at 11:58 comment added Chris Schommer-Pries @ algori: P is the G-principal bundle coming from the G-structure (see the link I provided) and $\rho_i(P)$ are the associated bundles induced by the representations $\rho_i$, which come from the short exact sequence I mention. Sorry if that was confusing. It seemed clear enough from context, but perhaps it wasn't. Anyway, I don't have my copy of Milnor and Stasheff handy, but I'm fairly certain this torsion is the same. Most of what I say is explained in more detail in D. Joyce's book "Compact Manifolds with Special Holonomy". I suggest looking there for more details.
Aug 2, 2010 at 5:43 comment added algori Chris -- your answer is very interesting but a bit difficult to follow, in particular since you use some notation that you do not define ($P,\rho_1 P,\ldots$), so I'd like to ask: is this notion of torsion the same as in Sebastian's answer below (i.e. the same as the one given e.g. in Milnor-Stasheff, Characteristic classes, appendix C)? More precisely, we take a connection on the (co)tangent bundle compatible with a given $G$-structure on a manifold. In example 1 the answer is yes, so I was wondering about the other two.
Apr 9, 2010 at 10:24 vote accept Jan Weidner
Apr 7, 2010 at 7:29 comment added Jan Weidner This answer is just great, thank you very much!
Apr 6, 2010 at 14:25 history answered Chris Schommer-Pries CC BY-SA 2.5