Notation question: like a direct product

**pellman** · Jun28-09, 02:17 PM

I am coming across a notation in a math text whose form and context suggest it is something like a direct product. The symbol is a multiplication X with a vertical line connecting the two left side ends. Can someone identify this symbol please?

The context can be seen here http://books.google.com/books?id=3JX...esult&resnum=1 2/3rds the way down on the page. This is an online preview of the text I am reading.

**Hurkyl** · Jun28-09, 02:29 PM

Maybe a semidirect product?

**pellman** · Jun29-09, 06:44 AM

Hurkyl to the rescue again. That is it.

And look. The article lists the LaTex commands. $LaTeX Code: <BR>G = R^4 \\ltimes SL(2,C)<BR>$