Subdiscriminant of symmetric matrices are sums of squares.

Marie-Françoise Roy Subdiscriminant of symmetric matrices are sums of squares. 2005 conf/dagstuhl/2005P5021 Mathematics, Algorithms, Proofs http://drops.dagstuhl.de/opus/volltexte/2006/347 db/conf/dagstuhl/P5021.html#Roy05