Positive definite matrices and differentiable reproducing kernel inequalities

AbstractLet I⊆R be a interval and k:I2→C be a reproducing kernel on I. By the Moore–Aronszajn theorem, every finite matrix k(xi,xj) is positive semidefinite. We show that, as a direct algebraic consequence, if k(x,y) is appropriately differentiable it satisfies a 2-parameter family of differential inequalities of which the classical diagonal dominance is the order 0 case. An application of these inequalities to kernels of positive integral operators yields optimal Sobolev norm bounds