New self-gravito-acoustic mode in degenerate quantum plasmas

The existence of a new perturbation mode [`self-gravito-acoustic mode' (SGAM)] in cold self-gravitating degenerate quantum plasmas (SGDQPs) is theoretically predicted. This new SGAM is developed in the perturbed SGDQPs, in which the compression is mainly provided by the self-gravitational pressure of the heavy particle species, and the rarefaction is mainly provided by the degenerate pressure of the light particle species. The SGAM is a new perturbation mode since it completely disappears if the degenerate pressure of the light particle species is neglected. The prediction of this new SGAM is applied in a white dwarf SGDQP.Comment: Submitted to `Nature Physics

Self-gravito-acoustic shock signals in astrophysical compact objects

The existence of self-gravito-acoustic (SGA) shock signals (SSs) associated with negative self-gravitational potential in the perturbed state of the astrophysical compact objects (ACOs) (viz. white dwarfs, neutron stars, black holes, etc.) is predicted for the first time. A modified Burgers equation (MB), which is valid for both planar and non-planar spherical geometries, by the reductive perturbation method. It is shown that the longitudinal viscous force acting in the medium of any ACO is the source of dissipation, and is responsible for the formation of these SGA SSs. The time evolution of these SGA SSs is also shown for different values (viz. $0.5$, $1$, and $2$ ) of the ratio of nonlinear coefficient to dissipative coefficient in the MB equation. The theory presented here is so general that it can be applied in any ACO of planar or non-planar spherical shape.Comment: Submitted to `Physical Review Letters

New electro-acoustic waves in a degenerate quantum plasma system

The existence of new electro-acoustic (EA) waves [named here `degenerate pressure driven EA' (DPDEA) waves] propagating in a degenerate quantum plasma (DQP) system [containing non-inertial, cold, non-relativistically (NR)/ultra-relativistically (UR) degenerate electron species (DES), and inertial, cold, NR degenerate positive particle species (PPS)] is predicted for the first time. The DPDEA waves, in which the inertia is mainly provided by the mass density of the inertial PPS, and the restoring force is mainly provided by the non-inertial, NR/UR DES, are new since they are completely disappeared if the degenerate pressure of the plasma particle species is neglected. The dispersion relation (derived here for the first time) is applied in a white dwarf DQP system to show the dispersion properties of the new DPDEA waves

Self-gravitational solitary waves in astrophysical compact objects

The condition for the existence of self-gravitational solitary waves (SGSWs), and their polarity in any astrophysical compact object are theoretically found for the first time. The pseudo-potential approach, which is valid for arbitrary amplitude SGSWs, is emplyed. The general analytical results are applied in white dwarfs and neutron stars to identify the basic features (polarity, amplitude, and width) of the SGSWs formed in them. It found for the first time that the SGSWs exist with negative self-gravitational potential in perturbed states of white dwarfs and neutron stars. It is also estimated that for their typical degenerate plasma parmeters, the amplitude and the width of the SGSWs (moving with the speed 2 cm/s) in white dwarfs are $\sim -1.5$ ergs/gm and $\sim 50$ cm, respectively, and those of the SGSWs (moving with the speed $\sim 27$ m/s) in neutron stars are $\sim -7.76\times 10^4$ Joules/kg, and $5.5$ km, respectively.Comment: To be submitted in Physical Review E (section: Rapid communication

Electron-acoustic solitary pulses and double layers in multi-component plasmas

We consider the nonlinear propagation of finite amplitude electron-acoustic waves (EAWs) in multi-component plasmas composed of two distinct groups of electrons (cold and hot components), and non-isothermal ions. We use the continuity and momentum equations for cold inertial electrons, Boltzmann law for inertialess hot electrons, non-isothermal density distribution for hot ions, and Poisson's equation to derive an energy integral with a modified Sagdeev potential (MSP) for nonlinear EAWs. The MSP is analyzed to demonstrate the existence of arbitrary amplitude EA solitary pulses (EASPs) and EA double layers (EA-DLs). Small amplitude limits have also been considered and analytical results for EASPs and EA-DLs are presented. The implication of our results to space and laboratory plasmas is briely discussed

Pairing properties from random distributions of single-particle energy levels

Exploiting the similarity between the bunched single-particle energy levels of nuclei and of random distributions around the Fermi surface, pairing properties of the latter are calculated to establish statistically-based bounds on the basic characteristics of the pairing phenomenon. When the most probable values for the pairing gaps germane to the BCS formalism are used to calculate thermodynamic quantities, we find that while the ratio of the critical temperature Tc to the zero-temperature pairing gap is close to its BCS Fermi gas value, the ratio of the superfluid to the normal phase specific heats at Tc differs significantly from its Fermi gas counterpart. The largest deviations occur when a few levels lie closely on either side of the Fermi energy but other levels are far away from it. The influence of thermal fluctuations, expected to be large for systems of finite number of particles, were also investigated using a semiclassical treatment of fluctuations. When the average pairing gaps along with those differing by one standard deviations are used, the characteristic discontinuity of the specific heat at Tc in the BCS formalism was transformed to a shoulder-like structure indicating the suppression of a second order phase transition as experimentally observed in nano-particles and several nuclei. Contrasting semiclassical and quantum treatments of fluctuations for the random spacing model is currently underway.Comment: 8 pages and 12 figures added in new section

Dust-acoustic rogue waves in an opposite polarity dusty plasma featuring non-extensive statistics

Modulational instability (MI) of dust acoustic waves (DAWs), which propagates in an opposite polarity dusty plasma system, containing inertial warm negatively and positively charged dust particles as well as non-extensive q-distributed elec- trons and ions, has been theoretically investigated. The nonlinear Schrodinger (NLS) equation is derived by employing the reductive perturbation method. The NLS equation leads to the MI of DAWs as well as to the formation of DAW rogue waves (DARWs), which are formed due to the effects of nonlinearity in the propagation of DAWs. Both stable and unstable regions are revealed from the analysis of the NLS equation. It is observed that the basic features of the DAWs (viz. stability of the wave profile, MI growth rate, amplitude, and width of DARWs) are significantly modified by the various plasma parameters such as non-extensive parameter, electron number density, and electron temperature. The existence of the non-extensive electron/ion distribution creates an influence on the MI of the waves. It is observed that non-extensive distributed ions have more effect on the MI of the DAWs than electrons.Comment: 13 pages; 8 figure

Dust-acoustic envelope solitons in super-thermal plasmas

The modulational instability (MI) of the dust-acoustic waves (DAWs) in an electron-positron-ion-dust plasma (containing super-thermal electrons, positrons and ions along with negatively charged adiabatic dust grains) is investigated by the analysis of the nonlinear Schr\"{o}dinger equation (NLSE). To derive the NLSE, the reductive perturbation method has been employed. Two different parametric regions for stable and unstable DAWs are observed. The presence of super-thermal electrons, positrons and ions significantly modifies both the stable and unstable regions. The critical wave number $k_c$ (at which modulational instability sets in) depends on the super-thermal electron, positron, and ion, and adiabatic dust concentrations.Comment: 11 pages; 8 figure

Rogue waves in multi-pair plasma medium

The nonlinear propagation of ion-acoustic (IA) waves (IAWs), which are governed by the nonlinear Schr\"{o}dinger equation (NLSE), in multi-pair plasmas (MPPs) containing adiabatic positive and negative ion fluids as well as non-extensive ($q$-distributed) electrons and positrons, is theoretically investigated. It is observed that the MPP under consideration supports two types of modes (namely, fast and slow IA modes), and the modulationally stable and unstable parametric regimes for the fast and slow IA modes are determined by the sign of the ratio of the dispersive coefficient to the nonlinear one. It is also found that the modulationally unstable regime generates highly energetic IA rogue waves (IARWs), and the amplitude as well as the width of the IARWs decrease with increase in the value of $q$ (for both $q>0$ and $q<0$ limits). These new striking features of the IARWs are found to be applicable in the space [viz. D-region ($\rm H^+, O_2^-$) and F-region ($\rm H^+, H^-$) of the Earth's ionosphere] and laboratory MPPs [viz. fullerene ($\rm C^+, C^-$)].Comment: 8 figures, 5 page

Electrostatic rogue waves in double pair plasmas

A nonlinear Schr\"{o}dinger equation is derived to investigate the modulational instability (MI) of ion-acoustic (IA) waves (IAWs) in a double pair plasma system containing adiabatic positive and negative ion fluids along with super-thermal electrons and positrons. The analytical analysis predicts two types of modes, viz. fast ($\omega_f$) and slow ($\omega_s$) IA modes. The possible stable and unstable parametric regions for the IAWs in presence of external perturbation can be observed for both $\omega_f$ and $\omega_s$. The number density of the negative ions and positrons play a vital role in generating the IA rogue waves (IARWs) in the modulationally unstable region. The applications of our present work in astrophysical environments [viz. D-region ($\rm H^+, O_2^-$) and F-region ($\rm H^+, H^-$) of the Earth's ionosphere] as well as in laboratory plasmas [viz. pair-ion Fullerene ($\rm C^+, C^-$)] are pinpointed.Comment: 5 pages; 6 figure