Ion acoustic solitons and double layers in electron-positron-ion plasmas with dust particulates

Propagation of small but finite amplitude ion acoustic solitons and double layers are investigated in electron-positron-ion plasmas in presence of highly negatively charged impurities or dust. The presence of negatively charged dust particulates can result in existence of two critical concentrations of ion-electron density ratio alpha. One of them alpha(D) decides the existence of double layers, whereas the other one alpha(R) decides the nature of the solitons and double layers. The system supports both compressive and rarefactive solitons as well as double layers. The parameter regimes of transitions from compressive to rarefactive solitons and double layers are also specified.