  We study analytically and numerically the generation of shock waves in a
quasi one-dimensional Bose-Einstein condensate (BEC) made of dilute and
ultracold alkali-metal atoms. For the BEC we use an equation of state based on
a 1D nonpolynomial Schrodinger equation (1D NPSE), which takes into account
density modulations in the transverse direction and generalizes the familiar 1D
Gross-Pitaevskii equation (1D GPE). Comparing 1D NPSE with 1D GPE we find
quantitative differences in the dynamics of shock waves regarding the velocity
of propagation, the time of formation of the shock, and the wavelength of
after-shock dispersive ripples.
