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Finite semimodular lattices. Presentation by pictures November 2012. Introduction. We present here some new structure theorems for finite semimodular lattices which is a geometric approach. We introduce some new constructions: --- a special gluing, the patchwork , --- the nesting,
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Finite semimodular lattices Presentation by pictures November 2012
Introduction • We present here some new structure theorems for finite semimodular lattices which is a geometric approach. • We introduce some new constructions: --- a special gluing, the patchwork, --- the nesting, and spacial lattices: --- source lattices, --- pigeonhole lattices
Planar distributive lattices How does it look like a finite planar distributive lattice ? On the following picture we have a typical example:
The smallest “building stones” of planar distributive latticesare the following three lattices, the planar distributive pigeonholes.We can get all planar distributive lattice using a special gluing: the patchwork.
Here is a special case of the Hall-Dilworth gluig: patching of two squares along the edges
Dimension • Dim(L) the Kuros-Ore dimension is is the minimal number of join-irreducibles to span the unit element of L, • dim(L) is the width of J(L).
The same lattice with colored covering squeres, this is a patchwork
Patchwork irreducible planar lattices and pigeonholes,antislimming • Mn
Planar semimodular lattices • A planar semimodular lattices L is called slim if no three join-irreducible elements form an antichain. This is equvivalent to: L does not contain M3 (it is diamond-free).
The beretD of a lattice L is the set of all dual atoms and 1. This is a cover-preserving join-congruence where the beret is the only one non-trivial congruence class. We get S7 from C3 x C3 : C3 x C3 / D
Slim semimodular lattices • Theorem. (Czédli-Schmidt) Every slim semimodular lattice is the patchwork of pigeonholes. • Corollary. Every planar semimodular lattice is the antislimming of a patchwork of pigeonholes.
Higher dimension • Rectanular lattice: J(L) is the disjoint sum of chains.