2,330 research outputs found
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. , , and ) 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 ergs/gm and
cm, respectively, and those of the SGSWs (moving with the speed m/s) in neutron stars are Joules/kg, and 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 (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 (-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 (for both and
limits). These new striking features of the IARWs are found to be applicable in
the space [viz. D-region () and F-region () of
the Earth's ionosphere] and laboratory MPPs [viz. fullerene ()].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 () and slow () IA modes. The
possible stable and unstable parametric regions for the IAWs in presence of
external perturbation can be observed for both and . 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 () and F-region () of the Earth's
ionosphere] as well as in laboratory plasmas [viz. pair-ion Fullerene ()] are pinpointed.Comment: 5 pages; 6 figure
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