  We propose to consider nonlinear fluctuations in the theory of liquid
$^{4}$He deforming the commutation relations between the generalized
coordinates and momenta. Generalized coordinates are coefficients of density
fluctuations of Bose particles. The deformation parameter takes into account
the effects of three- and four-particle correlations in the behavior of a
system. This parameter is defined from the experimental values of the
elementary excitation spectrum and the structure factor extrapolated to $T=0$
K. The numerical estimation of the ground state energy and the Bose condensate
fraction is made. The elementary excitation spectrum and the potential of
interaction between the helium atoms are recovered.
