Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2005/iii/paper-22/1/c/iii/solution

The Yoneda lemma, applied to the representing Omega-spectrum spaces in each degree, makes the comparison more explicit. Put
The 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 description
Thus , with bonding maps coming from the same telescope. For an inverse tower with maps , is the kernel and is the cokernel of
The first comparison quotients by spectrum homotopy; the second quotients by hyperphantom maps. These are different identifications.

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