There are several artists called Lumen: 1) A Russian rock/alternative band from Ufa,
2) Formed in San Francisco, CA by several individuals who collectively despise post-rock.
3) A stoner/screamo band from the Czech Republic.
4) The duo Pinkie Maclure & John Wills. See also Pumajaw
5) An electronic/trance artist by the name of Chris Conklin who performs as Lumen.
6) A Portuguese group of folk/celtic/world music.

Read more about Lumen on Last.fm.