2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55842A relativistically invariant scheme for the description of excited states in a one-kink sector is formulated. The normal oscillations of fluctuations against the background of a moving kink are determined. Zero mode of these oscillations is excluded automatically due to the properties of the integral equation describing normal oscillations. A Hamiltonian for elementary excitations is obtained reflecting the relativistic nature of the problem considered. (35 kb)11 pages, LaTex, corrected some typosHigh Energy Physics - Theorytext