  We consider photoemission from cuprate high-temperature superconductors
taking into account joint relaxation of strongly coupled fields: a field of
correlated electrons and phonon field. Such relaxation occurs in systems with
predominantly long-range electron-phonon interaction at sufficiently high
carrier concentration due to coexistence of autolocalized and delocalized
carriers. A simple method to calculate analytically a high-energy part of the
ARPES spectrum arising is proposed. The approach suggested yields all the
high-energy spectral features like broad bands of Gaussian shape and vertical
dispersion patterns being in good quantitative agreement with the experiments
at any doping with both types of carriers. Demonstrated coexistence of
autolocalized and delocalized carriers in cuprate superconductors is important
for understanding their transport and magnetic properties. Presence of
large-radius autolocalized carriers shown may be helpful in explanation of
charge ordering in doped cuprates.
