2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/27297We suggest an effective field theory for disorderd conductors, which describes quantum kinetics of ballistically propagating electrons. This theory contains non-linear $σ$-model \cite{Efetov} as its long wave limit.RevTeX, 7 pages no figures (to be published in JETP Letters)Condensed Mattertext