[Alta-Logic] peripatetic seminar talk: Real rank versus nonnegative rank

[Robin Cockett]

Title:  Real rank versus nonnegative rank

Time: 11:00am Wednesday, 23rd Nov., 2011

Place: ICT 616

Speaker: Pavel Hrubes

For a nonnegative real matrix M, its nonnegative rank is the smallest k 
such that M is a sum of k nonnegative
rank one matrices.   While it is easy to construct examples of matrices 
whose nonnegative rank is strictly greater
than the real rank, it is an open problem to determine how large  the 
gap between rank and nonnegative rank
can be.

I will discuss this problem and its connection to questions in 
computational complexity.