Body-Pin Rigidity

9.1. The correspondence table🔗

Each row gives the paper's locus, the result, the node of this blueprint that documents it, and a status. Mapped means the result has a Lean anchor on that node; deviation means it is mapped but proved or represented by a different route, and the register below has the entry; informal means the paper's statement is deliberately not formalized and nothing depends on it; gap means the paper cites the result and the formalization does not contain it; lean-only means the Lean development contains the material and the paper does not. Six rows carry no node: three are the paper's worked examples and closing remark, which are covered in their chapters' prose, one is a one-declaration reduction recorded with the root theorem, and one is the trust boundary of Appendix A.2, quoted verbatim in its own section below rather than wrapped in a formal environment the paper does not have. The last is an optional compatibility export that no root theorem uses. The table is kept in machine-readable form in the repository file correspondence.toml, and the build checks each row here against it, so a row cannot drift from the entry it copies.

Section 1 states the theorem, and Appendix A gives the formal statement and the scope of the verification:

Paper

Result

Node

Status

§1

Loopless body–pin multigraph H

bodypin_incidence

mapped

§1

Expanded graph G_H as a union of body cliques

bodypin_expansion

mapped

(1.1)

Capacity \ell_H \in \{0, 3, 5, 6\}

pin_capacity

mapped

(1.2)/(A.2)

Partition condition \sum \ell_H(P_i, P_j) \ge 6(t-1)

partition_condition

mapped

(1.4)

Rigidity matrix D_F(a)

rigidity_matrix

mapped

§1

Generic rigidity as attained maximum rank

generic_rigidity_max_rank

mapped

Thm 1.1

Body–pin partition characterization, informal form

bodypin_partition_characterization

deviation

Thm A.1

Formally verified body–pin theorem, the root theorem

formal_statement

mapped

§1

Asimow–Roth: maximum rank implies generic rigidity

asimow_roth

informal

—

Euclidean equivalence, congruence and local rigidity

lean_local_rigidity

lean-only

§1

The regular and generic placements are open and dense

regular_placements

deviation

§1

Maximum rank and Euclidean local rigidity

euclidean_local_rigidity

deviation

—

Rigidity against continuous motions

lean_continuous_rigidity

lean-only

—

Equivalence reduces to the sufficiency direction

none

lean-only

—

Mathlib Graph compatibility export

none

lean-only

A.2

Trust boundary and axiom closure

none

informal

Section 2 develops the sparsity class and the deletion step:

Paper

Result

Node

Status

(1.3)

(2,2)-sparse and tight sets

sparse22

mapped

§2.1

Uncrossing of intersecting tight sets

uncrossing

mapped

§2.1

Addable-edge criterion

addable_edge_criterion

deviation

Lem 2.1

Addable edge among three vertices

addable_edge_triple

mapped

§2.2

Direction rows and the self-stress space over a coefficient field

rigidity_row

mapped

§2.2

Retained coordinate field L and the extension degree \delta_v

retained_coordinate_field

mapped

(2.1)-(2.3)

Block form and the self-stress exact sequence

stress_exact_sequence

mapped

(2.4)-(2.6)

The (s, t, u, \delta) ledger and the defect \Delta

deletion_ledger

deviation

§2.2, Ex 2.2

Certified response edge; the collinear two-edge path

certified_response_edge

mapped

Lem 2.3

Low-degree local classification

low_degree_classification

mapped

Lem 2.4

Descent of affine coefficients

affine_coefficient_descent

mapped

Lem 2.5

Rigidity rows among the three neighbours

neighbour_rigidity_rows

mapped

Section 3 proves the stress–codimension inequality, and Theorem 1.2 is its flag-free case:

Paper

Result

Node

Status

Def 3.1

Collinearity flag d_\gamma \subsetneq T_\gamma \subsetneq Q_\gamma

collinearity_flag

deviation

Def 3.2

Sparse collinearity-flag system

flag_system

deviation

Prop 3.3

Incidence forest; \codim X_{\mathcal{T}} = 2|\Gamma|

flag_incidence_forest

deviation

§3.2

Support multiplicity and the O, P, S split

support_multiplicity

mapped

Lem 3.4

Flag selection lemma

flag_selection

mapped

Lem 3.5

Completion-preserving pivot

missing_edge_pivot

mapped

Lem 3.6

Local classification at a private support vertex

private_local_classification

mapped

Lem 3.7

Addable edge or complete triangle outside the flags

outside_augmentation

mapped

Lem 3.8

Certified response edge, private-support case

private_augmentation

mapped

Thm 3.9

Stress–codimension inequality for collinearity flags

stress_codim_flags

mapped

Thm 1.2

Stress–codimension inequality (\Gamma = \emptyset)

stress_codim

deviation

Section 4 recasts the inequality geometrically, and only its grounded model enters the formal argument:

Paper

Result

Node

Status

§4, (4.7)

Grounded model and the grounded inequality

grounded_model

mapped

(4.2)-(4.3)

Direction complex; \Sigma_s(F) as determinantal loci

direction_complex

informal

Ex 4.1

The collinear triangle

none

informal

Thm 4.2

\codim \Sigma_s \ge s; N_F a local complete intersection, Cohen–Macaulay, pure

stress_strata_codimension

informal

Rem 4.3

Flag conditions against exact stress strata

none

informal

Section 5 converts the inequality into a height theorem, stated in Section 1 as Theorem 1.3:

Paper

Result

Node

Status

(5.1)

Split–Klein quadratic form and twists

split_klein_form

mapped

(5.2)

The ideal I_F and the distinct locus

isotropic_difference_ideal

deviation

Lem 5.1

Componentwise Witt shear

witt_shear_componentwise

mapped

Ex 5.2

A shear separating coincident coordinates

none

informal

Lem 5.3

\operatorname{ht} P + \trdeg = N for a polynomial ring

polynomial_dimension_formula

mapped

Thm 1.3

Height of the distinct isotropic-difference ideal

isotropic_ideal_height

deviation

Cor 5.4

The ungrounded isotropic-difference variety

ungrounded_variety

deviation

Section 6 returns to body–pin graphs and assembles both directions of the theorem:

Paper

Result

Node

Status

§6.1

Rigid-body twists and the pin compatibility equation

twist_system

mapped

Lem 6.1

Twist description of motions within a body

twist_description

mapped

Lem 6.2

The fibre of a pin; three pins imply collinear points

pin_fibre

mapped

§6.1

The twist-equality partition

twist_equality_partition

mapped

Lem 6.3

Selecting a (2,2)-sparse subgraph via matroid union

sparse_subgraph_selection

deviation

Lem 6.4

Dimension drop along free \mathbb{G}_m orbits

orbit_dimension_drop

deviation

Prop 6.5

Exceptional parameter image is a proper closed subset

exceptional_pin_parameters

mapped

§6.4

Necessity

necessity

mapped

§6.4

Sufficiency and final assembly

sufficiency_assembly

deviation

The remaining eight rows have no paper locus at all: they are the Lean-only infrastructure clusters, named after the proof step each serves.

Paper

Result

Node

Status

—

Construction theorem for (2,2)-tight graphs

lean_nixon_owen_reduction

lean-only

—

Transport of sparsity along an injective vertex map

lean_sparsity_transport

lean-only

—

Provenance weight and initial-ideal apparatus

lean_weight_apparatus

lean-only

—

Universal and provenance chart layer

lean_chart_layer

lean-only

—

Flag state transitions and budget ledger

lean_flag_moves

lean-only

—

Base-change and field-tower plumbing

lean_base_change

lean-only

—

Grouped cross-block bundle operator

lean_block_bundle_operator

lean-only

—

Genericity machinery for the necessity direction

lean_genericity

lean-only