Diagonal Matrix Elements of the Effective Hamiltonian for   $K^{0}-\bar{K}^{0} $ System in One Pole Approximation
  We study the properties of time evolution of the $K^{0}-\bar{K}^{0} $ system in spectral formulation. Within the one--pole model we find the exact form of the diagonal matrix elements of the effective Hamiltonian for this system. It appears that, contrary to the Lee--Oehme--Yang (LOY) result, these exact diagonal matrix elements are different if the total system is CPT--invariant but CP--noninvariant. 
Justyna Jankiewicz