“Quasiphoton” In active media

She paper concerns concentrated packets of waves moving along space-time rays in the case of the speed depending on the frequency $\omega$: $c=c_0(x,t)+\delta c_1(x,t,\varepsilon\omega)$, $\varepsilon\ll\delta\ll1$. Formal asymptotic solutions are constructed by means of comlex ray method. It is shown that these packets propagate on the prescripted frequencies determined by the properties of media.