Relative singular cohomology with local coefficients #
Let (X, A) be a topological pair and let L be a local coefficient system of R-modules on X.
Applying Hom(-, M) to the relative twisted chains of the pair gives its relative twisted cochain
complex, whose cohomology is the relative singular cohomology of (X, A) with coefficients in L
and values in M.
The twisted chains of A sit inside those of X as the summands indexed by the singular simplices
of A, so that inclusion is split in each degree. Applying Hom(-, M) to the short exact
sequence 0 ⟶ C(A; L) ⟶ C(X; L) ⟶ C(X, A; L) ⟶ 0 therefore again gives a short exact sequence
0 ⟶ C*(X, A; L) ⟶ C*(X; L) ⟶ C*(A; L) ⟶ 0,
and its long exact cohomology sequence is the long exact sequence of the pair with local
coefficients. This is the sequence in which the cap product with the orientation system expresses
Poincaré--Lefschetz duality, so the twisted theory, and not only the untwisted one of
TauCeti.AlgebraicTopology.Cohomology.Relative, is needed.
Main declarations #
TopPair.twistedCochainComplexandTopPair.twistedCohomology: the relative twisted cochain complex of a pair and its cohomology.TopPair.twistedCochainComplexCoefficientMapandTopPair.twistedCohomologyCoefficientMap: change of local coefficient system.TopPair.twistedCochainComplexMapandTopPair.twistedCohomologyMap: the maps induced by a map of topological pairs.TopPair.shortExact_twistedCochainComplexShortComplex: the twisted cochain sequence of a pair is short exact.TopPair.twistedCohomologyδ: the connecting morphismHⁿ(A; L) ⟶ Hᵐ(X, A; L)forn + 1 = m, with the exactness statementsTopPair.twistedCohomology_exact_relative,TopPair.twistedCohomology_exact_spaceandTopPair.twistedCohomology_exact_subspace, and its naturalityTopPair.twistedCohomologyδ_naturalityin maps of pairs andTopPair.twistedCohomologyδ_naturality_coefficientin morphisms of local coefficient systems.TopPair.twistedCohomologyConstantIso: for a constant system, relative twisted cohomology is ordinary relative singular cohomology.
References #
- A. Hatcher, Algebraic Topology, Sections 3.1 and 3.H.
- A. Dold, Lectures on Algebraic Topology, Springer, 1972, Chapters VII--VIII.
The relative singular cochain complex of a topological pair with coefficients in a local
coefficient system L on its ambient space and values in M: in degree n, the k-module of
morphisms from the relative twisted n-chains to M.
Equations
- P.twistedCochainComplex L k M = (P.twistedChainComplex L).linearYonedaObj k M
Instances For
The relative singular cohomology of a topological pair in degree n, with coefficients in a
local coefficient system on its ambient space and values in M.
Equations
- P.twistedCohomology L k M n = HomologicalComplex.homology (P.twistedCochainComplex L k M) n
Instances For
The cochain map on relative twisted cochains induced by a morphism of local coefficient systems.
Equations
Instances For
The degree-n component of the relative cochain map induced by a morphism of local
coefficient systems acts by precomposition.
The map on relative twisted cohomology induced by a morphism of local coefficient systems.
Equations
- P.twistedCohomologyCoefficientMap k M η n = HomologicalComplex.homologyMap (P.twistedCochainComplexCoefficientMap k M η) n
Instances For
The twisted cochain sequence C*(X, A; L) ⟶ C*(X; L) ⟶ C*(A; L) of a topological pair
(X, A): the image under Hom(-, M) of the twisted chain sequence of the pair.
Equations
Instances For
The first map of the twisted cochain sequence of a pair is the image under Hom(-, M) of the
quotient map from ambient to relative twisted chains.
The second map of the twisted cochain sequence of a pair is restriction from the ambient space to the subspace.
The twisted cochain sequence 0 ⟶ C*(X, A; L) ⟶ C*(X; L) ⟶ C*(A; L) ⟶ 0 of a topological
pair is short exact.
The map Hⁿ(X, A; L) ⟶ Hⁿ(X; L) from relative to absolute twisted cohomology.
Equations
- P.twistedCohomologyπ L k M n = HomologicalComplex.homologyMap (P.twistedCochainComplexShortComplex L k M).f n
Instances For
The connecting morphism Hⁿ(A; L) ⟶ Hᵐ(X, A; L) of the long exact sequence of a topological
pair, where n + 1 = m.
Equations
- P.twistedCohomologyδ L k M n m h = ⋯.δ n m ⋯
Instances For
Exactness at relative cohomology: Hⁿ(A; L) ⟶ Hᵐ(X, A; L) ⟶ Hᵐ(X; L) is exact for
n + 1 = m.
Exactness at ambient cohomology: Hⁿ(X, A; L) ⟶ Hⁿ(X; L) ⟶ Hⁿ(A; L) is exact.
Exactness at subspace cohomology: Hⁿ(X; L) ⟶ Hⁿ(A; L) ⟶ Hᵐ(X, A; L) is exact for
n + 1 = m.
The map from relative to absolute twisted cohomology is a monomorphism in degree zero.
The morphism between the twisted cochain sequences of a pair induced by a morphism of local coefficient systems.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The map from relative to absolute twisted cohomology commutes with a change of local coefficient system.
The map from relative to absolute twisted cohomology commutes with a change of local coefficient system.
The connecting morphism of the long exact sequence in relative twisted cohomology commutes with a change of local coefficient system.
The connecting morphism of the long exact sequence in relative twisted cohomology commutes with a change of local coefficient system.
The cochain map on relative twisted cochains induced by a map of topological pairs.
Equations
Instances For
The degree-n component of the relative cochain map induced by a map of pairs acts by
precomposition with the induced morphism of relative twisted chains.
The map on relative twisted cohomology induced by a map of topological pairs.
Equations
- TopPair.twistedCohomologyMap k M f L n = HomologicalComplex.homologyMap (TopPair.twistedCochainComplexMap k M f L) n
Instances For
The relative cochain map induced by a map of pairs commutes with a change of coefficients on the target pair.
The relative cochain map induced by a map of pairs commutes with a change of coefficients on the target pair.
The cohomology form of TopPair.twistedCochainComplexMap_naturality.
The cohomology form of TopPair.twistedCochainComplexMap_naturality.
The identity map of a pair induces on relative twisted cochains the coefficient-change map coming from the canonical identification of a system with its pullback along the identity.
The cohomology form of TopPair.twistedCochainComplexMap_id.
Maps of relative twisted cochain complexes respect composition of maps of pairs, after the canonical comparison between pullback along a composite and iterated pullback.
Maps of relative twisted cochain complexes respect composition of maps of pairs, after the canonical comparison between pullback along a composite and iterated pullback.
The cohomology form of TopPair.twistedCochainComplexMap_comp.
The cohomology form of TopPair.twistedCochainComplexMap_comp.
The cochain map on subspace twisted cochains induced by a map of pairs: restriction along the subspace component, after the canonical comparison of the pulled-back coefficient systems.
Equations
Instances For
The morphism between the twisted cochain sequences of two pairs induced by a map of pairs.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The map from relative to absolute twisted cohomology is natural in the pair.
The map from relative to absolute twisted cohomology is natural in the pair.
The connecting morphism of the long exact sequence in relative twisted cohomology is natural in maps of topological pairs.
The connecting morphism of the long exact sequence in relative twisted cohomology is natural in maps of topological pairs.
For a constant local coefficient system, the relative twisted cochain complex of a pair is the ordinary relative singular cochain complex with the same coefficient module.
Equations
Instances For
For a constant local coefficient system, relative twisted cohomology is ordinary relative singular cohomology.
Equations
- P.twistedCohomologyConstantIso k M N n = (HomologicalComplex.homologyFunctor (ModuleCat k) (ComplexShape.up ℕ) n).mapIso (P.twistedCochainComplexConstantIso k M N)