15532720
Effective field theory: A Complete relativistic nuclear model
We analyzed the results for finite nuclei and infinite nuclear and neutron matter using the standard $\sigma-\omega$ model and with the effective field theory. For the first time, we have shown here quantitatively that the inclusion of self-interaction of the vector mesons and the cross-interaction of all the mesons taken in the theory explain naturally the experimentally observed softness of equation of state without loosing the advantages of standard $\sigma-\omega$ model for finite nuclei. Recent experimental observations support our findings and allow us to conclude that without self- and cross-interactions the relativistic mean field theory is incomplete.
122441975
Nuclear symmetry energy effects in finite nuclei and neutron star
Abstract Within a relativistic mean-field model with nonlinear isoscalar–isovector coupling, we explore the possibility of constraining the density dependence of nuclear symmetry energy from a systematic study of the neutron skin thickness of finite nuclei and neutron star properties. We find the present skin data supports a rather stiff symmetry energy at subsaturation densities that corresponds to a soft symmetry energy at supranormal densities. Correlation between the skin of 208Pb and the neutron star masses and radii with kaon condensation has been studied. We find that 208Pb skin estimate suggest star radii that reveals considerable model dependence. Thus precise measurements of neutron star radii in conjunction with skin thickness of heavy nuclei could provide significant constraint on the density dependence of symmetry energy.
119263744
Axially-symmetric Neutron stars: Implication of rapid rotation
Models of relativistic rotating neutron star composed of hyperon rich matter is constructed in the framework of an effective field theory in the mean-field approach. The gross properties of compact star is calculated at both static and the mass-shedding limit in the axially symmetric basis. The effect of appearance and abundance of hyperons on equation of state of dense matter and stellar properties is lineated with particular emphasis on the underlying nuclear interactions. We find that the models can explain fast rotations, which supports the existence of millisecond pulsars. An important offshoot of the present investigation is that, irrespective of the model parameters and interaction taken, the star seems to sustain faster rotations (an increase in rotational frequency up to $\approx$ 50%) without any further deformation.
121406020
Exotic clustering in heavy and superheavy nuclei within the relativistic and non-relativistic mean field formalisms
The clustering phenomenon in heavy and superheavy nuclei is studied within the relativistic mean field (RMF) approach using axially deformed basis and the non-relativistic Skyrme?Hartree?Fock (SHF) formalism. The calculated ground and intrinsic excited state properties, and the total matter densities as well as the neutron?proton asymmetry distributions are analysed to look for the cluster configurations and/or exotic clusters in the known cluster emitting 222Ra, 232U, 236Pu and 242Cm nuclei, and the superheavy nuclei with Z = 114, N = 172?184. Both the theories predict N ? Z, ?-like matter or clustering in the ground states, and both N ? Z matter and N ? Z clustering in the excited intrinsic states of radioactive actinides, though this result is more apparent and universal for the RMF approach. For superheavy nuclei, the detailed analysis shows a non-clustering, 'bubble'-like structure for Z = 114, N = 184 nucleus in the RMF method and Z = 114, N = 176 or 180 nucleus in the SHF method, as the signatures of doubly closed shell nuclei. Our earlier similar calculations for Z = 120 nuclei predicted the same for Z = 120, N = 172 nucleus in the RMF model. Also, in contrast to radioactive actinides, in superheavy nuclei the two fragments, N ? Z cluster configurations at the centre of ground superdeformed states in the RMF approach, and the same for at least some of the excited superdeformed states in the SHF method, are some of the interesting results obtained. Thus, new possibilities of exotic clusters at the centre of superheavy nuclei are indicated as ground or excited intrinsic superdeformed state configurations, more so as ground superdeformed states in the RMF theory. The N/Z ratios of the clusters are also calculated on the basis of the (average value of) colour code of the contours, which give a reasonable correspondence with the experimental data on cluster decay of radioactive nuclei.
119341992
Phase transition and properties of a compact star
We investigate the phase transition to a deconfined phase and the consequences in the formation of neutron stars. We use the recently proposed effective-field-theory-motivated relativistic mean-field theory for the hadrons and the MIT bag model and color-flavor locked (CFL) phase for the quark matter to get the appropriate equation of state. The properties of the stars are then calculated. The differences between unpaired and CFL quark matter are discussed.
119276868
Nuclear symmetry energy effects on liquid-gas phase transition in hot asymmetric nuclear matter
The liquid-gas phase transition in hot asymmetric nuclear matter is investigated within the relativistic mean-field model using the density dependence of nuclear symmetry energy constrained from the measured neutron skin thickness of finite nuclei. We find symmetry energy has a significant influence on several features of liquid-gas phase transition: the boundary and area of the liquid-gas coexistence region, the maximal isospin asymmetry, and the critical values of pressure and isospin asymmetry, all of which systematically increase with increasing softness in the density dependence of symmetry energy. The critical temperature below which the liquid-gas mixed phase exists is found higher for a softer symmetry energy.
118316994
Irregularly Shaped Satellites-Phobos & Deimos- moons of Mars, and their evolutionary history
Phobos, a moon of Mars, is below the Clarke synchronous orbit and due to tidal interaction is losing altitude. With this altitude loss it is doomed to the fate of total destruction by direct collision with Mars. On the other hand Deimos, the second moon of Mars is in extra-synchronous orbit and almost stay put in the present orbit. The reported altitude loss of Phobos is two meter per century by wikipedia and sixty ft per century according to ozgate url . The reported time in which the destruction will take place is fiftyMy and fortyMy respectively. The authors had proposed a planetary-satellite dynamics based on detailed study of Earth-Moon. Based on this planetary satellite dynamics, two meter/century approach velocity leads to the age of Phobos to be twenty three Gyrs which is physically untenable since our Solar System age is four and a half Gyrs. Hence the present altitude loss is assumed to be twenty meter per century. This leads to the age of Phobos to be two decimal three Gyrs and age of Deimos to be two decimal two six Gyrs which is an acceptable result and from this analysis it is predicted that the travel time from the present orbital radius of nine thousand three hundred and eighty km to the Martian surface at three thousand, three hundred and ninety seven km is ten decimal and four Myrs. Hence doomsday of Phobos is at ten decimal and fourMyrs from now. Mars Express studies have confirmed that Phobos is indeed trapped in a death spiral.
119189441
Basic Mechanics of Planet-Satellite Interaction with special reference to Earth-Moon System
In1879 George Howard Darwin theoretically analyzed the outward spiraling orbit of Moon and the subsequent lengthening of the Mean Solar Day. The author redid the same analysis based on the fact that Moon was receding at the rate of 3.8 cm per annum. Basic Mechanics of Earth-Moon is worked out and various system parameters are optimized to fit the given boundary condition obtained by Apollo Mission and other modern means of observations. Based on this theoretical formulation the theoretical graph of the lengthening of the Mean Solar Day with respect to time is drawn and is compared with the observational graph of the same based on pale ontological data, paleo tidal data and iron-banded formation. The observational data on Mean Solar Day is found to follow the theoretical smooth curve in post-Cambrian Era but is found to deviate in the remote past. This deviation is corrected by taking the evolving form of Moment of Inertia of Earth. The deviation of the observed data prompts the Author to suggest that the lengthening of the Mean Solar Day curve could possibly be used as an analytical seismograph for the impending earthquakes and sudden volcanic eruptions. The Basic Mechanics of E-M system is generalized to lay the foundation of simulation software for any Planet-Satellite pair in our Solar System.