The nonlinear propagation of ion-acoustic Gardner solitons (GSs) and double layers (DLs) in electron-positron-ion (EPI) plasma in the presence of an external static magnetic field has been examined. The Korteweg–de Vries (KdV), modified KdV (mKdV), and Gardner equations have been derived by the reductive perturbation technique. It is seen that the amplitude, polarity, speed, width of such solitons are significantly modified by the species densities and by the obliquity angle. Compressive or rarefactive KdV solitons are obtained, but only compressive solitons are obtained in the mKdV case, wherever Gardner positive and negative DLs exist. The results of our present investigation may be useful for understanding the nonlinear wave propagation in dense quantum plasmas such as those existing in white dwarfs, neutron stars and intense laser-solid matter interaction experiments as an example of laboratory plasmas.

研究了在存在外部静磁场的情况下，离子声Gardner孤子（GSs）和双层（DLs）在电子-正电子（EPI）等离子体中的非线性传播。Korteweg-de Vries（KdV），修正的KdV（mKdV）和Gardner方程是通过归纳摄动技术得出的。可以看出，这种孤子的振幅，极性，速度，宽度被物质密度和倾角显着改变。获得压缩或稀疏KdV孤子，但在存在Gardner正负DL的mKdV情况下，仅获得压缩孤子。我们目前的研究结果可能有助于理解稠密量子等离子体（例如存在于白矮星中的等离子体）中的非线性波传播，