User talk:Artagas

Central product

 * Copy of my to 

No thank you! Your edit was good. It pointed out (1) that there is a stricter definition in common use, (2) the internal/external distinction, (3) the external distinction is tricky because the map really matters. It also motivated me to include a stub section on "applications", and took care of the lack of a second reference. Hopefully it will also motivate me to cover the specific case of two matrix groups over the same field, where the central subgroups are the scalar subgroups (this is subtly mentioned in CRLG-McK, but I think without example). JackSchmidt (talk) 01:02, 29 June 2009 (UTC)