| Description: Define the block lift
map. Given a relation 𝑅 and a carrier/set
𝐴, we form the block relation (𝑅 ⋉
◡ E ) (i.e., "follow
both 𝑅 and element"), restricted to
𝐴
(or, equivalently, "follow
both 𝑅 and elements-of-A", cf. xrnres2 38677). Then map each domain
element 𝑚 to its coset [𝑚] under that restricted
block relation.
For 𝑚 in the domain, which requires
(𝑚
∈ 𝐴 ∧ 𝑚 ≠ ∅ ∧ [𝑚]𝑅 ≠ ∅) (cf. eldmxrncnvepres 38685),
the fiber has the product form
[𝑚](𝑅 ⋉ ◡ E ) = ([𝑚]𝑅 × 𝑚), so the block relation
lifts a block 𝑚 to the rectangular grid
"external labels ×
internal members", see dfblockliftmap2 38712. Contrast: while the adjoined
lift, via (𝑅 ∪ ◡ E ), attaches neighbors and members
in a single
relation (see dfadjliftmap2 38708), the block lift labels each
internal
member by each external neighbor.
For the general case and a two-stage construction (first block lift, then
adjoin membership), see the comments to df-adjliftmap 38706. For the
equilibrium condition, see df-blockliftfix 38732. (Contributed by Peter
Mazsa, 24-Jan-2026.) (Revised by Peter Mazsa,
22-Feb-2026.) |