Smashing with a cw-complex preserves weak equivalences between well-pointed spaces - MathOverflow most recent 30 from http://mathoverflow.net 2013-06-19T23:08:31Z http://mathoverflow.net/feeds/question/108930 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/108930/smashing-with-a-cw-complex-preserves-weak-equivalences-between-well-pointed-space Smashing with a cw-complex preserves weak equivalences between well-pointed spaces Christian Wimmer 2012-10-05T16:23:43Z 2012-10-06T14:10:59Z <p>By well-pointed i mean that the inclusion of the base point is a h-cofibration, weak equivalences are the usual weak homotopy equivalences between spaces. this is claimed as part of theorem 6.9 (i) in <a href="http://www.math.uni-bonn.de/people/schwede/MMSS.pdf" rel="nofollow">model categories of diagram spectra</a> but as far as i can see without reference. can anyone point me to some place in the literature or indicate where this statement comes from ?</p> http://mathoverflow.net/questions/108930/smashing-with-a-cw-complex-preserves-weak-equivalences-between-well-pointed-space/108944#108944 Answer by Peter May for Smashing with a cw-complex preserves weak equivalences between well-pointed spaces Peter May 2012-10-05T18:46:30Z 2012-10-05T18:46:30Z <p>As usual, I apologize for excess concision. Let $A$ be a based CW complex, $X$ and $Y$ well-pointed spaces, $f\colon X\to Y$ a (weak) equivalence. The first claim in 6.9(i) is that $[X\wedge A,Z] \cong [X,F(A,Z)]$, and a proof is indicated. Since $f$ clearly induces a bijection on the right side, it must induce a bijection on the left side. By Yoneda (take $Z = X\wedge A$ to find an inverse to $f\wedge id$ in the homotopy category), that means that $f\wedge id\colon X\wedge A \to Y\wedge A$ is a weak equivalence. </p> http://mathoverflow.net/questions/108930/smashing-with-a-cw-complex-preserves-weak-equivalences-between-well-pointed-space/108996#108996 Answer by Peter May for Smashing with a cw-complex preserves weak equivalences between well-pointed spaces Peter May 2012-10-06T13:51:42Z 2012-10-06T14:10:59Z <p>I would like to just comment but don't see how. Christian, here's an answer to your last question. For based spaces, you can just do what you want by hand, as Fernando suggested, taking care to use disjoint basepoints to make your attaching maps of $A$ based. You are right to complain that the interplay of $h$ and $q$-model structures is not obvious. Based spaces are of course spaces over and under a point. In Parametrized homotopy theory'', Sigurdsson and I generalize to parametrized spaces, which are spaces over and under a give space, and then the combination of $h$, $q$, and related model structures is surprisingly delicate. In that book, the answer to your original question is axiomatized in a general model categorical context in 5.4.1 (see (v)) and the axioms are verified for parametrized spaces in 5.4.9. But that is like hitting a thumb tack with a sledge hammer. Maybe it will help to add that in the direct argument you do need to know that a wedge of weak equivalences is a weak equivalence, and that uses the well-pointed hypothesis.</p>