Vacuum Energy Induced by an External Magnetic Field in a Curved Space
  The asymptotic expansion of the product of an operator raised to an arbitrary power and an exponential function of this operator is obtained. With the aid of this expansion, the density of vacuum energy induced by a static external magnetic field of an Abelian or non-Abelian nature is expressed in terms of the DeWitt-Seeley-Gilkey coefficients. 
Yu. A. Sitenko and D. G. Rakityansky