Univalent Semigroud

A univalent semigroud is an Idempotent Semigroud where all elements are Bicommutative; EG:

Somewhat shockingly, this means that the relation a b = [ a , b , a ] = a 𝑎 𝑏 𝑎 𝑏 𝑎 𝑎 a\leq b=[a,b,a]=a is Reflexive and Antisymmetric, which means that a b b a 𝑎 𝑏 𝑏 𝑎 a\leq b\land b\leq a forms an Identity System!

The proof is quite elementary. Reflexivity follows directly from idempotency. Antisymmetry is a bit trickier. First, a lemma, for every a , b 𝑎 𝑏 a,b , if a b 𝑎 𝑏 a\leq b , then a = [ a , b , b ] 𝑎 𝑎 𝑏 𝑏 a=[a,b,b]

a𝑎\displaystyle a =[a,b,a]absent𝑎𝑏𝑎\displaystyle=[a,b,a] (ab)𝑎𝑏\displaystyle(a\leq b)
=[a,a,a,b,b,b,a]absent𝑎𝑎𝑎𝑏𝑏𝑏𝑎\displaystyle=[a,a,a,b,b,b,a] (idempotency)idempotency\displaystyle(\text{idempotency})
=[a,b,b,a,a,b,a]absent𝑎𝑏𝑏𝑎𝑎𝑏𝑎\displaystyle=[a,b,b,a,a,b,a] (bicommutativity)bicommutativity\displaystyle(\text{bicommutativity})
=[a,b,b,a,a]absent𝑎𝑏𝑏𝑎𝑎\displaystyle=[a,b,b,a,a] (ab)𝑎𝑏\displaystyle(a\leq b)
=[a,a,a,b,b]absent𝑎𝑎𝑎𝑏𝑏\displaystyle=[a,a,a,b,b] (bicommutativity)bicommutativity\displaystyle(\text{bicommutativity})
=[a,b,b]absent𝑎𝑏𝑏\displaystyle=[a,b,b] (idempotency)idempotency\displaystyle(\text{idempotency})

A similar line of reasoning lets us deduce that a b 𝑎 𝑏 a\leq b implies a = [ b , b , a ] 𝑎 𝑏 𝑏 𝑎 a=[b,b,a] .

Now, suppose that a b b a 𝑎 𝑏 𝑏 𝑎 a\leq b\land b\leq a . We get

a𝑎\displaystyle a =[a,b,b]absent𝑎𝑏𝑏\displaystyle=[a,b,b] (lemma)lemma\displaystyle(\text{lemma})
=[a,[a,a,b],b]absent𝑎𝑎𝑎𝑏𝑏\displaystyle=[a,[a,a,b],b] (lemma)lemma\displaystyle(\text{lemma})
=[[a,a,a],b,b]absent𝑎𝑎𝑎𝑏𝑏\displaystyle=[[a,a,a],b,b] (para-associativity)para-associativity\displaystyle(\text{para-associativity})
=[[a,b,b],a,a]absent𝑎𝑏𝑏𝑎𝑎\displaystyle=[[a,b,b],a,a] (bicommutativity)bicommutativity\displaystyle(\text{bicommutativity})
=[b,a,a]absent𝑏𝑎𝑎\displaystyle=[b,a,a] (lemma)lemma\displaystyle(\text{lemma})
=babsent𝑏\displaystyle=b (lemma)lemma\displaystyle(\text{lemma})