SLIDE 22 Latin squares
A Latin square L of order n (L ∈ LS(n)) is a n × n array with elements chosen from [n] = {1, 2, ..., n}, such that each symbol
- ccurs precisely once in each row and each column.
Sn: Symmetric group on [n]. An isotopism of L is a triple Θ = (α, β, γ) ∈ S3
n, where α, β and γ
are respectively, permutations of rows, columns and symbols of L.
L = 1 2 3 4 2 3 4 1 3 4 1 2 4 1 2 3 Θ = ((1 2)(3 4), (2 3), Id) ⇒ LΘ = 2 4 3 1 1 3 2 4 4 2 1 3 3 1 4 2
An isotopism mapping L to itself is an autotopism. The stabilizer subgroup of L by the action of S3
n is its autotopism group:
A(L) = {Θ ∈ In : LΘ = L}.
Ra´ ul Falc´
u˜ nez An approach to the isotheory by means of extended pseudoisotopisms