A note on the Ostrowski–Schneider type inertia theorem in Euclidean Jordan algebras

Abstract

In a recent paper [7], Gowda et al. extended Ostrowski–Schneider type inertia results to certain linear transformations on Euclidean Jordan algebras. In particular, they showed that In ( a ) = In ( x ) whenever a ∘ x > 0 by the min–max theorem of Hirzebruch, where the inertia of an element x in a Euclidean Jordan algebra is defined by In ( x ) : = ( π ( x ) , ν ( x ) , δ ( x ) ) , with π ( x ) , ν ( x ) , and δ ( x ) denoting, respectively, the number of positive, negative, and zero eigenvalues, counting multiplicities. In this paper, we present a Peirce decomposition version of Wimmer’s result [13] and show that it is equivalent to the above result. In addition, we extend Higham and Cheng’s result ([8], Lemma 4.2) to the setting of Euclidean Jordan algebras.