SemiBase
← [6, 5660][6, 5662] →

[6, 5661] finitely based

not self-dualfamily proof

[6, 5661] is a semigroup with 3 idempotents and a zero, 1. It is finitely based: 28 identities define its variety, which no other semigroup of order six generates.

Cayley table

·123456
1111111
2111122
3111112
4111244
5123455
6123466

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, 5661)
Idempotents
1, 5, 6
Zero
1
Identity
none
Nilpotent
no
Commutative
no
Regular
no
Group
no
𝒥-classes
5
Rank
4, generated by {3, 4, 5, 6}
Self-dual
no: the class also stands for the opposite semigroup, with the transposed table

Identity basis

Shortest known basis: 28 identities reduced

  1. x³ ≈ x⁴
  2. x²y² ≈ xyxy
  3. x²y² ≈ xy²x
  4. x²yx ≈ x²yx²
  5. xyx² ≈ xyx³
  6. x²yzy ≈ x²zy²
  7. x²yzy ≈ xyxzy
  8. x²yzy ≈ xyzyx
  9. x²yz² ≈ xyzxz
  10. x²yz² ≈ xyz²x
  11. xyxz² ≈ xzyxz
  12. xyxz² ≈ xz²yx
  13. xyxzx ≈ xyxzx²
  14. x²yztz ≈ x²tzyz
  15. x²yztz ≈ xyzxtz
  16. x²yztz ≈ xyztzx
  17. xyxztz ≈ xyxtz²
  18. xyxztz ≈ xzyxtz
  19. xyxztz ≈ xztzyx
  20. xyxzt² ≈ xztyxt
  21. xyxzt² ≈ xzt²yx
  22. xyxztut ≈ xyxutzt
  23. xyxztut ≈ xztyxut
  24. xyxztut ≈ xztutyx
  25. x²yzytuvu ≈ x²tuvuyzy
  26. x²yztzuvwv ≈ x²uvwvyztz
  27. xyxzt²uvwv ≈ xyxuvwvzt²
  28. xyxztutvwsw ≈ xyxvwswztut

Reduced as far as the search went: some identity may still follow from the others. 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

The Lean theorem certifies a longer basis, of 64 identities; the shortest known basis above is equivalent to it.

Lean proof

Endpoint theorem: SemigroupBasis.CoRoots.Order6LeeZhangProposition20_7E4.S6_5661.representative_basis

BasisFor CoRoots.Order6LeeZhangProposition20_7E4.S6_5661.table.semigroup CoRoots.Order6LeeZhangProposition20_7E4.basis
Table
The theorem is about the semigroup with exactly this table.
Method
family proof. One basis is proved once to derive every identity of every semigroup of a family; on each table only the identities of the basis are checked, by computation.
Size
Checking this class alone compiles 27 Lean files with 17,606 lines: the endpoint theorem and everything it imports, the shared library included. Of these, 10,360 lines are used by the proof of this class and of no other.
Census
SemiBase.Census.S6_5661 checks that the theorem is about the table of this class and concludes Classified; SemiBase.Catalogue.Order6.S6_5661 is the table, with the elements numbered 0 to 5.

Variety

[6, 5661] generates the variety V[5661]; no other semigroup of order six generates it, and 6,804 semigroups of order six lie in it. [6, 5661] lies in 1 of the 505 varieties of the census, those whose basis it satisfies.

Directly above
none: a maximal variety of the census
Directly below
V[2771] V[3368] V[3554] V[3930] V[5613]

V[5661] in the inclusion graph, with the varieties above and below it.

Nearby tables

Semigroups whose Smallsemi table differs from this one in one or two entries (row, column), as the tables are listed, not up to renumbering.