
The elements [ f ′ ] ( f ′ : X ′ → Y ′ ) [f’](f’:X’ \to Y’) of the genus − G ( f ) - G(f) of a map f : X → Y f:X \to Y are equivalence classes of homotopy classes of maps f ′ f’ which satisfy: For every prime p p there exist homotopy equivalences h p : X p ′ → X p {h_p}:{X’_p} \to {X_p} and k p : Y p ′ → Y p {k_p}:{Y’_p} \to {Y_p} so that f p h p ∼ k p f p ′ {f_p}{h_p} \sim {k_p}{f’_p} . The genus of f f under X − G X ( f ) X - {G^X}(f) and the genus of f f over Y − G Y ( f ) Y - {G_Y}(f) are defined similarly. In this paper we prove that under certain conditions on f f , the sets G ( f ) G(f) , G X ( f ) {G^X}(f) and G Y ( f ) {G_Y}(f) are finite and admit an abelian group structure. We also compare the genus of f f to those of X X and Y Y , calculate it for some principal fibrations of the form K ( G , n − 1 ) → X → Y K(G,n - 1) \to X \to Y , and deal with the noncancellation phenomenon.
homotopy equivalences at a prime, Fiber spaces in algebraic topology, Localization and completion in homotopy theory, Homotopy groups, general; sets of homotopy classes, genus of a map, principal fibrations with an Eilenberg-MacLane space as fibre, Homotopy equivalences in algebraic topology, Loop spaces
homotopy equivalences at a prime, Fiber spaces in algebraic topology, Localization and completion in homotopy theory, Homotopy groups, general; sets of homotopy classes, genus of a map, principal fibrations with an Eilenberg-MacLane space as fibre, Homotopy equivalences in algebraic topology, Loop spaces
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