Volume 36, Issue 5
May 1991, pages 445-579
pp 445-488 May 1991 Review
Role of general relativity in accretion disk dynamics
In this we briefly review the discussions on accretion dynamics, the standard scenario and the ones including the effects of electromagnetic fields. The emphasis throughout is to show the relevance of general relativistic formalism in discussing the dynamics of magnetofluid around compact objects.
pp 489-496 May 1991 Research Articles
Finite discontinuities in the energy eigenvalue spectra of anharmonic oscillators
The existence of finite discontinuities in the energy eigenvalue spectra of certain multiterm potentials when their coupling parameters attain suitably chosen limiting values has been reported in the literature. We show that such discontinuities are also characteristic of such well-known systems as generalized anharmonic oscillators and the doubly anharmonic oscillator in one dimension. The present study strengthens the general conjecture that eigenvalue spectra are likely to display discontinuities in situations where a potential undergoes an abrupt change in shape with smooth variation of its coupling parameters.
pp 497-510 May 1991 Research Articles
Separability, gauge invariance and nonsuperluminality in direct interaction dynamics
We discuss the classical mechanics of relativistic systems with direct interaction. We show that various desiderata can all be accommodated in the single time approach by restricting the observables to the gauge invariant variables. We show how such observables can be constructed in general. We explicitly construct position observables in a general system and show that they lead to separable, invariant world lines. Nonsuperluminality is explicitly demonstrated for two body systems interacting via central forces of semibounded magnitude provided they ensure timelike canonical momenta. For two particles, our results reproduce the usual solution in covariant equal-time gauge.
pp 511-518 May 1991 Research Articles
Higher-dimensional white holes
White holes (relativistic anticollapsing objects) are considered both in the five-dimensional Kaluza-Klein theory and in the many-dimensional representation of extended space-time manifolds with horizons within the framework of general relativity. In the last model white holes (e.g. Kerr-Newman) appear as anticollapsing from extra (additional) dimensions. These dimensions are connected with the global structure of space-time manifolds.
pp 519-530 May 1991 Research Articles
Dirac equation in time dependent electric field and Robertson-Walker space-time
We show that the motion of a Dirac electron in a time dependent electromagnetic field can be considered as a motion in a dielectric medium with time dependent dielectric function. We find that this electromagnetic case is analogous to the description in Robertson-Walker (RW) space-time. We solve the Dirac equation is such a simulated space-time.
pp 531-536 May 1991 Research Articles
Distribution of degeneracies in simple quantum systems
Mustansir Barma V Subrahmanyam
In some simple quantum mechanical systems, the degeneracy of typical energy levels grows as a power of the energy or size. We ask whether, after dividing out this average growth, there is a well defined probability distribution of scaled degeneracies in the limit of large size or energy. The answer is yes, for a free particle in a sphere or cube. For the sphere, the distribution of scaled degeneracies is shown to follow a circular law. For the cube, a numerical study shows that the distribution rises linearly for low values of the scaled degeneracy and decays exponentially for large values.
pp 537-555 May 1991 Research Articles
Algebra for fermions with a new exclusion principle
We construct the algebra of the creation and destruction operators for spin 1/2 particles obeying a new exclusion principle which is “more exclusive” than Pauli’s exclusion principle: an orbital state shall not contain more than one particle, whether spin up or spin down. The consequences of this algebra are studied and applications to the Hubbard model in condensed matter physics are indicated.
pp 557-563 May 1991 Research Articles
Singlet N-N scattering with exchange of confined gluons among relativistic quark clusters
Confined-gluon-exchange among relativistically confined quark clusters is used to obtain singlet S and P wave N-N scattering phase-shifts. A good agreement is obtained with the experimental results.
pp 565-579 May 1991 Research Articles
Three-body formalism for deuteron stripping reactions
V S Mathur Priyadarshini Padhy
A three-body formalism for deuteron stripping reactions has been developed. The equations of Altet al (1967) (AGS) for the three particle system (target A, n, p) are reduced to a set of coupled one-dimensional integral equations with the use of (i) angular momentum basis for representation and (ii) separable approximation for the two bodyt-matrices (which delineate the interactions between the particle pairs). The on-shell solutions of this set of integral equations are then related to the cross sections of the rearrangement processes. The inputs in this calculation, viz., the separable interactions between the particle pairs in the respective channels are simply constructed from the respective two body bound state in accordance with the bound state approximation (BSA) conforming to the ‘unitarity’ requirement. Using this formalism preliminary calculations for the (d, p) and (d, n) reaction cross sections on^{16}O have been carried out and they seem to have considerable semblance with the observed cross sections.
Current Issue
Volume 93 | Issue 6
December 2019
Click here for Editorial Note on CAP Mode
© 2017-2019 Indian Academy of Sciences, Bengaluru.