Documentation

TauCeti.AlgebraicTopology.Singular.MappingTorus.Basic

Singular chains of a mapping torus #

The fibre of the mapping torus of φ : F ≃ₜ F has a canonical inclusion at height zero. Traversing the cylinder from height zero to height one gives a homotopy from this inclusion after φ to the inclusion itself. This file transfers that homotopy to singular chains and homology, and constructs the resulting map from the mapping cone of id - φ_* to the singular chains of the mapping torus.

Thus the inclusion coequalizes the identity and monodromy maps, first up to chain homotopy and then on homology. Equivalently, its composite with id - φ_* is null-homotopic. The universal property of the mapping cone then gives the chain map which underlies the Wang sequence.

Main declarations #

The construction follows the mapping-torus derivation of the Wang sequence; see A. Hatcher, Algebraic Topology, Section 2.2. The chain homotopy itself is obtained from Mathlib's homotopy invariance of singular chains, TopCat.Homotopy.singularChainComplexFunctorObjMap.

The endomorphism of singular chains induced by the monodromy of a mapping torus.

Instances For

    The monodromy chain map is the singular-chain functor applied to the monodromy.

    The map on singular chains induced by inclusion of the fibre at height zero.

    Instances For

      The fibre-inclusion chain map is the singular-chain functor applied to the fibre inclusion.

      The singular-chain map induced by monodromy followed by fibre inclusion is chain-homotopic to the fibre-inclusion chain map.

      Instances For
        @[simp]

        The components of the singular-chain homotopy are those induced by the cylinder homotopy.

        The Wang endomorphism id - φ_* on the singular chains of the fibre.

        Instances For

          The fibre inclusion after id - φ_* is null-homotopic. The sign is chosen so that the endomorphism on the fibre is literally id - φ_*, rather than its negative.

          Instances For
            @[simp]

            The null-homotopy used in the Wang mapping-cone map is the negative of the canonical monodromy homotopy.

            @[reducible, inline]

            The chain-level mapping cone of id - φ_* used in the mapping-cone formulation of the Wang sequence.

            Instances For

              The canonical chain map from the mapping cone of id - φ_* to singular chains of the mapping torus. It is induced by fibre inclusion and the canonical monodromy homotopy.

              Instances For

                The map on singular chains induced by a map between the fibres of two mapping tori.

                Instances For

                  The fibre chain map is the singular-chain functor applied to the map of fibres.

                  The map on singular chains induced by a map of mapping tori.

                  Instances For

                    The mapping-torus chain map is the singular-chain functor applied to the map of mapping tori.

                    The commuting square between the Wang endomorphisms associated to a map intertwining monodromies.

                    Instances For

                      The map between Wang mapping cones induced by a map intertwining the monodromies.

                      Instances For