Solitary wave families of a generalized microstructure PDE

Wave propagation in a generalized microstructure PDE, under the Mindlin relations, is considered. Limited analytic results exist for the occurrence of one family of solitary wave solutions of these equations. Since solitary wave solutions often play a central role in the long-time evolution of an initial disturbance, we consider such solutions here (via normal form approach) within the framework of reversible systems theory. Besides confirming the existence of the known family of solitary waves, we find a continuum of delocalized solitary waves (or homoclinics to small-amplitude periodic orbits). On isolated curves in the relevant parameter region, the delocalized waves reduce to genuine embedded solitons. The new family of solutions occur in regions of parameter space distinct from the known solitary wave solutions and are thus entirely new. Directions for future work are also mentioned.     

On the Jacobi Last Multiplier, integrating factors and the Lagrangian formulation of differential equations of the Painlevé–Gambier classification

We use a formula derived almost seventy years ago by Madhav Rao connecting the Jacobi Last Multiplier of a second-order ordinary differential equation and its Lagrangian and determine the Lagrangians of the Painlevé equations. Indeed this method yields the Lagrangians of many of the equations of the Painlevé–Gambier classification. Using the standard Legendre transformation we deduce the corresponding Hamiltonian functions. While such Hamiltonians are generally of non-standard form, they are found to be constants of motion. On the other hand for second-order equations of the Liénard class we employ a novel transformation to deduce their corresponding Lagrangians. We illustrate some particular cases and determine the conserved quantity (first integral) resulting from the associated Noetherian symmetry. Finally we consider a few systems of second-order ordinary differential equations and deduce their Lagrangians by exploiting again the relation between the Jacobi Last Multiplier and the Lagrangian.     

Exponential type vector variational-like inequalities and vector optimization problems with exponential type invexities

A new class of exponential form of vector variational-like inequality problems is introduced, and then the equivalence among (weakly) efficient solutions, vector critical points of vector optimization problem and the solutions of vector variational-like inequalities under the framework of (p,r)-invexity is established. To the best our knowledge, the presented results are new and highly application oriented to other results based on generalized invexities to the context of optimization problems in the literature.     

Slope and curvature of Isgur-Wise function using variationally improved perturbation theory in a quantum chromodynamics inspired potential model

We used variationally improved perturbation theory (VIPT) in calculating the slope and curvature of Isgur-Wise (I-W) function with the Cornell potential −$ \frac{{4\alpha _s }} {{3r}} $ \frac{{4\alpha _s }} {{3r}} +br + c instead of the usual stationary state perturbation theory as done earlier. We used −(4α _s /3r), i.e. the Coulombic potential, as the parent and the linear one, i.e. br+c as the perturbed potential in the theory and calculated the slope and curvature of Isgur-Wise function including three states in the summation involved in the first-order correction to wave function in the method.     

Analytical design of photonic band-gap fibers and their dispersion characteristics

The paper essentially deals with the analysis of photonic band-gap fibers in analogy with the electron wave motion in periodic crystal lattice. As such, the analyses are based on Bloch formulation. The dispersion characteristics of such fibers are presented by considering some illustrative values of design parameters. The effect of design parameters on the dispersion characteristics is also presented in terms of the variation of widths of allowed and forbidden bands of band-gap fibers. It is found that the number of allowed bands increases with the increase in difference between refractive indices of different layers. Further, widths of the allowed and forbidden bands increase with the increase in layer thickness.     

Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

The magnetization of PrFeAsO0.60F0.12 superconductor

The magnetization of the PrFeAsO_0.60F_0.12 polycrystalline sample has been measured as functions of temperature and magnetic field (H). The observed total magnetization is the sum of a superconducting irreversible magnetization and a paramagnetic magnetization. Analysis of dc susceptibility χ(T) in the normal state shows that the paramagnetic component of magnetization comes from the Pr³⁺ magnetic moments. The intragrain critical current density (J_L) derived from the magnetization data is large. The J_L(H) curve displays a second peak which shifts towards the high-field region with decreasing temperature. In the low-field region, a plateau up to a field H^* followed by a power law H^?5/8 behavior of J_L(H) is the characteristic of the strong pinning. A vortex phase diagram for the present superconductor has been obtained from the magnetization and resistivity data.     

Direct calculation of time varying Aharonov-Bohm effect

The Aharonov-Bohm effect (ABE) for steady magnetic fields is a well known phenomenon. However, if the current in the infinite solenoid that creates the magnetic field is time-dependent, that is in the presence of both magnetic and electric fields, there is no agreement whether the effect would be present. In this note, we try to investigate time varying ABE by a direct calculation in a set-up with a weak time dependent magnetic field. We find that the electric field arising out of the time-varying magnetic field in the path of the electrons does not enter the action integral but only changes the path of the electron from the source to the slits and then on to the detector. We find a frequency dependent AB phase shift. At low frequencies the result smoothly approaches the one for a constant field as the frequency tends towards zero. On the other hand, for high frequencies such that the AB-phase induced in the path of the wave packet oscillates rapidly, the net effect will be very small which is borne out by our results.     

Some results on the stability and dynamics of finite difference approximations to nonlinear partial differential equations

A miscellany of results on the nonlinear instability and dynamics of finite difference discretizations of the Burgers and Kortweg de Vries equations is obtained using a variety of phase-plane, functional analytic, and regularity methods. For the semidiscrete (space-discrete, time-continuous) schemes, large-wave-numer instabilities occurring in special exact solutions are investigated, and parameter values for which the semidiscrete scheme is monotone are considered. For fully discrete schemes (space and time discrete), large-wave-number instabilities introduced by various time-stepping schemes such as forward Euler, leapfrog, and Runge–Kutta schemes are analyzed. Also, a time step restriction for the monotonicity of the forward-Euler time-stepping scheme, and regularity of a 4-stage monotone/conservative Runge–Kutta time stepping are investigated. The techniques used here may be employed, in conjunction with bifurcation-theoretic and weakly nonlinear analyses, to analyze the stability of numerical schemes for other nonlinear partial differential equations of both dissipative and dispersive varieties. © 1993 John Wiley & Sons, Inc.