Dear Colleagues,

We continue our Colloquium in the Math Department.

Charles Johnson, Department of Mathematics,

College of William and Mary, 

Williamsburg, Virginia.

Sums of Matrices and an Unexpected Result for an
Unnatural Problem

Tuesday, April 20, EMCS 422, 3:00 pm.

Abstract
A matrix is called totally positive (nonnegative) if ALL its minors
are positive (nonnegative), and a matrix with nonpositive off-diagonal entries 
is an M-matrix if its inverse exists and is nonnegative (entry-wise). We
consider two questions: which positive matrices occur as sums of totally positive
matrices and of inverse M-matrices. In each case there is an interesting
surprise. 



Lucas van der Merwe
Department of Mathematics
University of Tennessee at Chattanooga
Lucas van der Merwe
Department of Mathematics
(Wiskunde Departement)
University of Tennessee at Chattanooga