Speaker: Michael Orlitzky
A real symmetric n-by-n matrix A is copositive if <Ax,x> is nonnegative for all x in the nonnegative orthant. Copositive programming has attracted much attention since Burer showed that nonconvex quadratic programming problems can be formulated as completely-positive programs. Alas, the power of copositive programming is offset by its difficulty: simple questions like "is this matrix copositive?" have difficult answers. In 1958, Jerry Gaddum proposed a recursive procedure to check if a given matrix is copositive by solving a series of matrix games. It is easy to implement and conceptually simple.