A Gr\"uss type operator inequality
  In [P. Renaud, "A matrix formulation of Gr\"uss inequality", Linear Algebra Appl. 335 (2001), 95--100] it was proved an operator inequality involving the usual trace functional. In this article, we give a refinement of such result and we answer positively the Renaud's open problem. 
Tamara Bottazzi and Cristian Conde
math.FA