Pomeranchuk's theorem, named after Soviet physicist Isaak Pomeranchuk, states that difference of cross sections of interactions of elementary particles ${\displaystyle \kappa _{1}+\kappa _{2}}$ and ${\displaystyle \kappa _{1}+{\bar {\kappa _{2}}}}$ (i. e. particle ${\displaystyle {\kappa _{1}}}$ with particle ${\displaystyle \kappa _{2}}$, and with its antiparticle ${\displaystyle {\bar {\kappa _{2}}}}$) approach 0 when ${\displaystyle s\to \infty }$, where ${\displaystyle s}$ is the energy in center of mass system.