Geodesic
“Quasiphoton” In active media
Zapiski Nauchnykh Seminarov POMI, Mathematical problems in the theory of wave propagation. Part 15, Tome 148 (1985), pp. 104-115 
Ya. V. Kurylev. “Quasiphoton” In active media. Zapiski Nauchnykh Seminarov POMI, Mathematical problems in the theory of wave propagation. Part 15, Tome 148 (1985), pp. 104-115. http://geodesic.mathdoc.fr/item/ZNSL_1985_148_a10/
@article{ZNSL_1985_148_a10,
     author = {Ya. V. Kurylev},
     title = {{\textquotedblleft}Quasiphoton{\textquotedblright} {In} active media},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {104--115},
     year = {1985},
     volume = {148},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1985_148_a10/}
}
TY  - JOUR
AU  - Ya. V. Kurylev
TI  - “Quasiphoton” In active media
JO  - Zapiski Nauchnykh Seminarov POMI
PY  - 1985
SP  - 104
EP  - 115
VL  - 148
UR  - http://geodesic.mathdoc.fr/item/ZNSL_1985_148_a10/
LA  - ru
ID  - ZNSL_1985_148_a10
ER  - 
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%A Ya. V. Kurylev
%T “Quasiphoton” In active media
%J Zapiski Nauchnykh Seminarov POMI
%D 1985
%P 104-115
%V 148
%U http://geodesic.mathdoc.fr/item/ZNSL_1985_148_a10/
%G ru
%F ZNSL_1985_148_a10

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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.