Analytic Estimation of the Non-Linear Tune Shift due to the Quadrupole Magnet Fringe Field

Analytic expressions for the amplitude-dependent tune shift driven by the quadrupole magnet fringe field have been obtained. The magnitude of the effect is compared with other sources of non-linearity such as chromatic sextupoles, octupole errors of the main quadrupole magnetic field and kinematic terms. A numerical example was the calculation on the lattice of the VEPP-4M e+e- collider.