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LeanPool.NandakumarRamanaRao.NRR.PrimePolyhedron.FoxNeuwirth.EquivariantPrismGlobalCancellation

Global signed cancellation for the refined equivariant prism #

The compatible perturbation assigns one vector to every global sampled prism vertex. Hence the positive-ray index of a codimension-one face depends only on its ordered list of global vertices, not on the refined prism simplex in which that face is encountered.

This file turns the local affine boundary theorem into a single global finite cancellation identity. A facet occurrence is a pair consisting of a refined prism simplex and an omitted vertex. Its ordered global-vertex signature records the induced parametrized facet. Occurrences with the same signature have the same unsigned positive-ray index. After multiplying by the orbit-cycle, spatial-subdivision, staircase, prism-subdivision, and alternating face signs, the sum over all facet occurrences is zero.

The final section separates signatures in the lower horizontal layer, the upper horizontal layer, and the nonhorizontal part. The endpoint module proves vanishing of the nonhorizontal contribution and identifies the horizontal sums with the endpoint refined counts.

Positive-ray index of an oriented facet before multiplication by its alternating boundary sign.

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    Transport an omitted facet vertex to the face-index type used by the simplicial boundary.

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      If two oriented facets have the same ordered vertex values, their unsigned positive-ray indices agree.

      Relabel every output coordinate vector of a local affine simplex by a prime symmetry.

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        Prime relabelling preserves the unsigned positive-ray index. The open diagonal ray and the coordinate mean are invariant under coordinate permutation; the determinant changes by the sign of the selected prime permutation, whose image in ZMod p is one.

        If the ordered values of one facet are a simultaneous prime relabelling of another, their unsigned positive-ray indices agree.

        @[reducible, inline]

        One codimension-one occurrence in the fully refined prism triangulation.

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          Ordered global vertices of one induced prism facet. Equality of signatures means equality as an ordered sampled facet, which is the correct relation for oriented boundary cancellation.

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            @[instance_reducible]
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            Equal ordered facet signatures give equal ordered local vertex values.

            The unsigned index of a local occurrence depends only on its ordered global-vertex signature.

            A chosen unsigned index for an ordered global facet signature. If the signature is not realized by the triangulation, its value is zero.

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              On a realized signature, the chosen global weight is the unsigned index of every occurrence with that signature.

              Coefficient of one fully refined prism simplex. It combines the original orbit-cycle coefficient, the spatial barycentric-subdivision sign, the staircase sign, and the further prism subdivision sign.

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                Signed incidence coefficient of one facet occurrence in the global refined prism chain.

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                  Total signed boundary coefficient of one ordered global facet signature.

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                    Expanded global signed positive-ray boundary sum over all local facet occurrences.

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                      The expanded occurrence sum is the sum over geometric ordered facet signatures of boundary coefficient times the common unsigned positive-ray index.

                      The global occurrence sum can equally be grouped by refined prism simplices and written using the local signed facet indices.

                      Global signed prism-facet cancellation. Under local general position, every local affine boundary sum is zero, so the globally glued signed sum over all refined prism facets vanishes.

                      Public global signed prism-facet cancellation theorem. The sum ranges over every fully refined prism simplex and every oriented facet occurrence.

                      Global occurrence-level cancellation specialized to the compatible generic perturbation.

                      Cancellation specialized to the assignment produced by the generic perturbation theorem.

                      Horizontal and nonhorizontal decomposition #

                      Time coordinate of one vertex in an ordered global facet signature.

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                        A facet signature lies in the lower horizontal layer.

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                          A facet signature lies in the upper horizontal layer.

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                            @[instance_reducible]
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                            Lower horizontal contribution to the global signed facet sum.

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                              Upper horizontal contribution to the global signed facet sum.

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                                Contribution of every signature not wholly contained in either horizontal layer.

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                                  A signature cannot lie in both horizontal layers when the facet has a vertex.

                                  The signature sum splits into lower-horizontal, upper-horizontal, and nonhorizontal pieces.

                                  Once internal and spatial-side signatures have been shown to cancel, the two horizontal contributions are opposite. This is the exact algebraic endpoint consumed by the refined homotopy-invariance theorem.