< ^ From:

< ^ Subject:

Dear GAP Forum

Cinzia Casagrande wrote:

> I have the following problem: I have a semigroup H inside a free group G.

> G is of finite rank but clearly infinite. H is given by some generators,

> but they could be redundant or have some relations. I would like to know

> the relations between these generators in the semigroup H, or at least to

> know which generators are necessary to get H. Is this possible in some

> way?

I would like to add that what you need is a SAGBI-basis (subalgebra analog of

Groebner basis for subalgebras) of more exactly, Factor- SAGBI basis, because

Free group is not free as a semigroup. The algorithm exists, but I do not know

available implementations in noncommutative case (though we also plan to have

it) - there are too many complications in the non-commutative case.

With best regards

Victor Ufnarovski

> < [top]