Thread Subject: Definite-ness of matrix products

I realize this is not a Matlab-specific question, but I did not quite
know where else to post it...
What can be said about the 'definite-ness' of the following (matrix)
product:

   B*A*B',

when A > 0 (or A >= 0) and B is some matrix (not square).
Or, more specifically, what is required of B for B*A*B' > 0 to hold when
A > 0 (or >= 0 in both expressions) - if possible?

Thomas Arildsen

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