Department of Mathematics Calendar
Rainer Sinn, Georgia Tech, “Pythagoras numbers of real projective varieties”
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The Pythagoras number of field F, studied in the theory of quadratic forms, is the smallest k such that every sum of squares in F is a sum of k squares. We will reinterpret this definition for coordinate rings of real projective varieties and discuss ways to give bounds on this invariant. A central concept for lower bounds is what we call quadratic persistence of a projective variety.