Control of Linear Systems and
the Real Schubert Calculus


Mathematics Colloquium
University of Wisconsin,
Parkside

Frank Sottile
University of Wisconsin &
University of Massachusetts
3 December 1999
 

In 1981, Brockett and Byrnes showed how the static feedback laws which control a given linear system are determined through the Schubert calculus of enumerative geometry. This elementary talk will describe that connection and discuss methods to solve the resulting systems of polynomial equations.

The related questions of finding real feedback laws and of trying to do Schubert's calculus over the real numbers are intertwined with a precise conjecture of Shapiro and Shapiro, which we discuss. We also describe a new result which shows it is possible to do Schubert's calculus over the real numbers and proves a version of this conjecture.