The theoretical investigations have been made for the propagation of positron acoustic solitary waves (PASWs) in a weakly inhomogeneous plasma composing immobile positive ions, mobile cold positrons, and superthermal hot positrons and electrons. The Korteweg-de Varies (KdV) and modified KdV (mKdV) equations with variable coefficients are derived using the appropriate coordinate transformation and the reductive perturbation method (RPM). The effects of positron concentration, temperature ratios for hot positrons and electrons, hot to cold positrons density ratio, electron to cold positron density ratio, ion to cold positron density and population of hot electrons as well as positrons superthermality on the nonlinear propagation of PASWs are examined to understand the local electrostatic disturbances. It is also found that the presence of superthermal (kappa distributed) hot positrons and hot electrons significantly modify the basic features of PASWs. The critical values for hot positrons and cold positrons also play a vital role in the formation of only compressive PASWs in the plasmas.
