In Section 5 [001F] we define opaque functors, exposing their relation with absolute extensions and exact squares, and we show their role for Deleanu-Frei-Hilton’s Categorical Shape Theory (cf. A. Frei (Frei, 1976)) and for Kan extensions of cohomological theories (cf. J.L. Mac Donald (MacDonald, 1976)).
Bibliography
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Frei, A. (1976). On categorical shape theory. Cahiers De Topologie Et Géométrie Différentielle Catégoriques, 17(3), 261–294.Details
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MacDonald, J. L. (1976). Natural factorizations and the Kan extension of cohomology theories. Cahiers De Topologie Et Géométrie Différentielle Catégoriques, 17(1), 69–93. http://eudml.org/doc/91162Details