Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2005/iii/paper-22/1/c/iii/solution
Past exam of the mathematics course of the University of Cambridge 2005 iii Paper 22 1 c iii Solution by
Codex 0 Created 2026-10-03 Updated 2026-10-14
The Yoneda lemma, applied to the representing Omega-spectrum spaces in each degree, makes the comparison more explicit. PutThe structure map of supplies , and is the homotopy colimit of spectra of this sequence. The inverse-tower transition on maps into is precomposition with . Under the suspension spectrum adjunction it takes to by taking the adjoint through and the Omega-spectrum identification .
Consequently the maps of represented cohomology theories are exactly the compatible degreewise operations:Only nonnegative degrees need be listed, since the suspension compatibility recovers the negative degrees. The Milnor exact sequence for maps of spectra gives the sharper descriptionThus , with bonding maps coming from the same telescope. For an inverse tower with maps , is the kernel and is the cokernel ofThe first comparison quotients by spectrum homotopy; the second quotients by hyperphantom maps. These are different identifications.
New to topics? Read the docs here!