higher-order corrections to ion acoustic waves in degenerate electron-positron-ion plasmas

the nonlinear propagation of ion acoustic waves in ideal plasmas consisting of degenerate electrons and positrons, and isothermal ions is investigated. the korteweg de vries (k-dv) equation that contains the lowest order nonlinearity and dispersion is derived from the lowest order of perturbation and a linear inhomogeneous (k-dv type) equation that accounts for the higher order nonlinearity and the dispersion relation is obtained. the stationary wave solution for these equations has been found using the renormalization method. also, the effects of electrons and positrons densities and ion temperature on the amplitude and width of solitary waves are investigated, numerically. it is seen that higher order corrections significantly change the properties of the k-dv solitons. also, it is found that both compressive and rarefactive solitary waves can be propagated in such plasma system.