Pomeranchuk's theorem, named after Soviet physicist Isaak Pomeranchuk, states that difference of cross sections of interactions of elementary particles κ κ 1 + κ κ 2 and κ κ 1 + κ κ 2 ¯ ¯ (i. e. particle κ κ 1 with particle κ κ 2 , and with its antiparticle κ κ 2 ¯ ¯ ) approach 0 when s → → ∞ ∞ , where s is the energy in center of mass system.