... FORMULA FOR THE AC-CONDUCTIVITY561Since the integral in (3.27) is a Bochner integral in the Banach spaceK1, whereT is a bounded linear functional, they can be interchanged, and hence, using[BoGKS, ... isresponsible for the factor oflog1νd+2 in (4.2). By improving some of the estimates in the proof (at the price of making them more cumbersome), the numerical constant 205 in (4.2) may be ... velocity operator in the xj-direction is˙Xj:= i [H,Xj],where Xjdenotes the operator of multiplication by the j-th coordinate xj .In the continuum˙Xω,jis the closure of the operator...