In this paper we study stability radii of positive polynomial matrices under affine perturbations of the coefficient matrices. It is shown that the real and complex stability radii coincide. Moreover, explicit formulas are derived for these stability radii and illustrated by some examples.

Logarithmic divergences in pion and proton charge radii associated with chiral loops are investigated to assess systematic uncertainties in current lattice determi-nations of charge radii. The chiral corrections ooer a possible solution to the long standing problem of why present lattice calculations yield proton and pion radii which are similar in size.

In this paper we study stability radii of positive polynomial matrices under a2ne perturbations of the coe2cient matrices. 9 It is shown that the real and complex stability radii coincide. Moreover, explicit formulas are derived for these stability radii and illustrated by some examples. 11 c © 2003 Published by Elsevier Science B.V.