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Feb 16, 2017 at 14:12 history edited Sebastian Goette CC BY-SA 3.0
The original space was not really a simplicial set.
Feb 15, 2017 at 21:20 vote accept user1272680
Feb 15, 2017 at 21:20 comment added user1272680 Many thanks for the counterexample, this is really helpful!
Feb 15, 2017 at 20:53 comment added Sebastian Goette I was just rewriting the answer when your comment showed up. Thanks.
Feb 15, 2017 at 20:53 comment added HJRW Oh, it looks like you already did this in the edit!
Feb 15, 2017 at 20:52 history edited Sebastian Goette CC BY-SA 3.0
Also works as simplicial complex.
Feb 15, 2017 at 20:50 comment added HJRW This is easy to realize as an ordinary simplicial complex. Take a simplicial circle, and two simplicial discs: one wrapped twice round the circle, one wrapped three times round the circle. As you observe, this is simply connected but non-contractible. Now the removal of any 2-simplex turns the corresponding disc into a homotopy annulus, which again makes the result non-simply connected.
Feb 15, 2017 at 20:16 history answered Sebastian Goette CC BY-SA 3.0