# free hull

Let $A$ be an arbitrary set, let $A^{\ast}$ be the free monoid on $A$, and let $X$ be a subset of $A^{\ast}.$ It follows from the characterization of free submonoids that the intersection $M$ of all the free submonoids of $A^{\ast}$ that contain $X$ is a free submonoid of $A^{\ast}$. The minimal generating set $H$ of $M$ is called the free hull of $X$.

Title free hull FreeHull 2013-03-22 18:21:40 2013-03-22 18:21:40 Ziosilvio (18733) Ziosilvio (18733) 4 Ziosilvio (18733) Definition msc 20M05 msc 20M10