[6, 2580] finitely based
[6, 2580] is a commutative nilpotent semigroup: every product of 5 elements is equal to the zero. It is finitely based: 3 identities define its variety, which 6 other semigroups of order six also generate.
Cayley table
| · | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| 2 | 1 | 1 | 1 | 1 | 1 | 1 |
| 3 | 1 | 1 | 1 | 1 | 1 | 2 |
| 4 | 1 | 1 | 1 | 1 | 1 | 2 |
| 5 | 1 | 1 | 1 | 1 | 2 | 3 |
| 6 | 1 | 1 | 2 | 2 | 3 | 5 |
The product of the row element and the column element, numbered as in Smallsemi. Blue: idempotents on the diagonal; grey: the zero.
Structure
- Smallsemi
- SmallSemigroup(6, 2580)
- Idempotents
- 1
- Zero
- 1
- Identity
- none
- Nilpotent
- yes, of class 5
- Commutative
- yes
- Regular
- no
- Group
- no
- 𝒥-classes
- 6
- Rank
- 2, generated by {4, 6}
- Self-dual
- yes: anti-isomorphic to itself
Identity basis
Shortest known basis: 3 identities irredundant
- xy ≈ yx
- x²yz ≈ xy²z
- xyztu ≈ vxyztu
Irredundant: none of these identities follows from the others; for each, a semigroup satisfies the others but not it. Obtained from a basis certified in Lean by removing identities that follow from the others, with the prover Vampire; the equivalence rests on Vampire's proofs, not on Lean. Shortest known, not known to be minimal.
Basis certified in Lean: 3 identities
- xy ≈ yx
- x²yz ≈ xy²z
- xyztu ≈ vxyztu
Lean proof
Endpoint theorem: SemigroupBasis.Generated.Order6FinalL5TransferV3.S6_2580.representative_basis
BasisFor Generated.Order6FinalL5TransferV3.S6_2580.table.semigroup Generated.Order6FinalL5TransferV3.S6_2580.targetBasis
- Table
- The theorem is about the semigroup with exactly this table.
- Method
- transfer from order ≤ 5. A semigroup S with a certified basis lies in the variety of this one, as a subsemigroup; S has order at most five, and this semigroup satisfies the basis of S. Then every identity of this semigroup holds in S and follows from the basis, so the basis of S is a basis here too. This is the final sweep of such transfers.
- Size
- Checking this class alone compiles 27 Lean files with 18,557 lines: the endpoint theorem and everything it imports, the shared library included. Of these, 147 lines are used by the proof of this class and of no other.
- Census
- SemiBase.Census.S6_2580 checks that the theorem is about the table of this class and concludes Classified; SemiBase.Catalogue.Order6.S6_2580 is the table, with the elements numbered 0 to 5.
Variety
[6, 2580] generates the variety V[2578]; 6 other semigroups of order six generate it too, and 205 semigroups of order six lie in it. [6, 2580] lies in 7 of the 505 varieties of the census, those whose basis it satisfies.
- Directly above
- Directly below
V[2578] in the inclusion graph, with the varieties above and below it.