Alphabeta Math

Simplicial Subdivision and Simplicial Approximation

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1 · Prerequisites
2 · Logical flowchart

3 · Items

Definition

Face poset and order complex

Definition

Barycentric subdivision of an abstract simplicial complex

Definition

Canonical barycentric realization map

Lemma

Finite simplicial weak topology agrees with euclidean topology

Lemma

Barycentric face chains triangulate a geometric simplex

Theorem

Barycentric subdivision realizes homeomorphically

Definition

Open and closed stars in a subdivision

Lemma

Compact subsets of an arbitrary simplicial realization meet finitely many open simplices

Lemma

An augmented simplicial cone has an explicit chain contraction

Lemma

Simplicial chain maps carried by specified cones are chain homotopic

Definition

Oriented simplicial subdivision operator

Lemma

Oriented simplicial subdivision commutes with boundary

Lemma

Last vertex map is carried by original simplices

Theorem

Simplicial subdivision is a chain map and homology isomorphism

Lemma

Mesh of iterated simplicial barycentric subdivision tends to zero

Lemma

The open star criterion produces a simplicial map

Theorem

Finite simplicial approximation for maps of pairs

Definition

Relative derived subdivision of a finite simplicial pair

Lemma

Relative derived subdivision makes the fixed subcomplex full

Lemma

Relative subdivision neighbourhood adjustment

Theorem

Relative simplicial approximation after subdivision

Definition

Finite convex cell complex and linear subdivision

Lemma

Intersections of finite linear complexes form a convex cell complex

Lemma

Finite convex cell complexes admit compatible triangulations

Lemma

Two finite linear subdivisions have a common simplicial refinement

Sources