Algebraic group action
= Algebraic group action
{title2=$G\times V\to V$}
= Algebraic action
{synonym}
This is a group action whose action map $G\times V\to V$ is a morphism of varieties. Orbits are locally closed: constructibility gives a relatively open piece, and its translates cover the orbit. An orbit of an irreducible group is irreducible and open in its closure. These facts control degenerations of <quiver representations>.