2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/44436We 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.10 pages, Paper presented at The XXXVI Symposium on Mathematical Physics, Poster Session, Toruń, Poland, June 9-12, 2004High Energy Physics - Phenomenologytext