Coherent nonlinear structures in dense electron-positron plasma

It is shown that the rarefactive-type double layer structures exist in ultradense electron-positron plasma. For this purpose, an extended Korteweg de Vries equation is derived and solved analytically in low amplitude limit by employing the appropriate fluid equations. Strong influence of quantum degeneracy pressure of electrons and positrons, quantum diffraction effects and concentration of background positive ions on double layer is noticed. It is also pointed out that the amplitude and steepness of double layer increases with increase in ion concentration or ion charge number. The results are examined numerically for some interesting cases of dense plasmas with illustrations.