This is an announcement for the paper "Comparison of matrix norms on bipartite spaces" by Christopher King and Nilufer Koldan. Abstract: Two non-commutative versions of the classical L^q(L^p) norm on the algebra of (mn)x(mn) matrices are compared. The first norm was defined recently by Carlen and Lieb, as a byproduct of their analysis of certain convex functions on matrix spaces. The second norm was defined by Pisier and others using results from the theory of operator spaces. It is shown that the second norm is upper bounded by a constant multiple of the first for all 1 <= p <= 2, q >= 1. In one case (2 = p < q) it is also shown that there is no such lower bound, and hence that the norms are inequivalent. It is conjectured that the norms are inequivalent in all cases. Archive classification: math.FA Remarks: 25 pages The source file(s), 2normsv17.tex: 44891 bytes, is(are) stored in gzipped form as 0904.1710.gz with size 13kb. The corresponding postcript file has gzipped size 109kb. Submitted from: king@neu.edu The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/0904.1710 or http://arXiv.org/abs/0904.1710 or by email in unzipped form by transmitting an empty message with subject line uget 0904.1710 or in gzipped form by using subject line get 0904.1710 to: math@arXiv.org.