Mumford–Tate group
In algebraic geometry, the Mumford–Tate group (or Hodge group) MT(F) constructed from a Hodge structure F is a certain algebraic group G. When F is given by a rational representation of an algebraic torus, the definition of G is as the Zariski closure of the image in the representation of the circle group, over the rational numbers. Mumford (1966) introduced Mumford–Tate groups over the complex numbers under the name of Hodge groups.