الفهرس 
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Abstract
The research work addressed in this thesis is related to the theoretical study of polarization and self-gravitational forces that affect the wave dynamics of nonlinear structures in a complex plasma. Since Maxwellian distribution is inadequate to describe various plasma environments, so we have considered, non-Maxwellian (q nonextensive distribution) and polytropic for present research work. We have used reductive perturbation technique and Sagdeev pseudopotential method to derive nonlinear evolution equations. The thesis highlights the existence of different kinds of solitary waves, shock waves, double layers and cnoidal waves in a variety of plasmas.
In the second chapter, we have studied both linear and nonlinear properties of gravito-electrostatic plasma model. An inertial opposite polarity charged dust grains are considered as well as inertialess non-extensively distributed ions and electrons. The general dispersion relation is obtained. It is found that the polarization force and the non-extensively distributed ions effects play a direct destabilizing role in Jeans instability. A new pair of gravito-electrostatically coupled energy integral equation has been obtained by applying the Sagdeev pseudo-potential technique. Self-gravitational rarefactive soliton pulses and electrostatic compressive soliton-like patterns are seen to occur.
In the third chapter, we have derived the Zakharov-Kuznetsov (ZK) equation in a magnetized complex plasma by using the reductive perturbation technique. The nonlinear characteristics of the dust acoustic cnoidal (periodic) and solitary waves are investigated using the bifurcation theory. It is noticed that the dust acoustic wave properties depend strongly on the self-gravitational and the polarization parameters as well as the non-extensive indexes for electrons and ions.
In the fourth chapter, Employing the reductive perturbation technique, a Korteweg-de Vries-Burgers (KdVB) equation is derived in an unmagnetized complex plasma containing adiabatic electrons and ions, and negatively charged dust grains (including the effects of modified polarization force). Moreover, the bifurcation and phase portrait analyses are presented to recognize different types of possible solutions. The dependence of the properties of nonlinear DA waves on the system parameters is investigated.
Key Words : Self-gravitational force –Polaization force – Dust acoustic wave- Solitary wave- cnoidal wave- shock wave- nonextensive distribution -ZK Eq.- KdV- Burgers Eq. – KdV Eq.