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Apr 20, 2013 at 20:25 answer added Anonymous timeline score: 0
Apr 15, 2013 at 15:42 comment added John Wiltshire-Gordon @Chris Schommer-Pries: Good point, but I'd like a combinatorial answer. In particular, if there are finitely many simplices before, I'd like finitely many after.
Apr 15, 2013 at 14:03 comment added Chris Schommer-Pries The singular simplicial set of the space $|X| \setminus |A|$ has the property you ask for, namely its geometric realization is homotopy equivalent to $|X| \setminus |A|$. Perhaps you want some additional constraints?
Apr 15, 2013 at 11:00 answer added Tim Porter timeline score: 1
Apr 15, 2013 at 1:34 history edited John Wiltshire-Gordon CC BY-SA 3.0
Clearer explanation
Apr 15, 2013 at 1:31 comment added John Wiltshire-Gordon Dear Professor May, I meant geometrically realizing A and X first and then performing subtraction in the category of spaces.
Apr 15, 2013 at 1:27 comment added Peter May John, what precisely do you mean by X\A and taking its `geometric realization'. It seems you mean the simplices of X not in A, which as you observe is not a simplicial set, so its geometric realization has no obvious meaning. You are desperately trying to avoid X/A. In your equivariant example, presumably G is a group acting simplicially and A is the subcomplex of simplices with nontrivial stabilizer. Then you might replace X\A by the maximal G-free subcomplex of X, which maybe makes sense.
Apr 14, 2013 at 23:07 history asked John Wiltshire-Gordon CC BY-SA 3.0