P K Kaw
Articles written in Pramana – Journal of Physics
Volume 2 Issue 6 June 1974 pp 304-311 Solids
Kinetic theory of parametric excitation of acoustic waves in piezoelectric semiconductors
A K Sundaram P K Kaw S K Sharma
Using a kinetic description for electrons and the usual equation of motion for lattice displacement we have derived a general dispersion relation for acoustic waves in a piezoelectric semiconductor, in the presence of a strong high frequency electric field oscillating near the electron plasma frequency. Earlier hydrodynamic results valid for
Volume 35 Issue 3 September 1990 pp 287-301 Research Articles
Model equations from a chaotic time series
A K Agarwal D P Ahalpara P K Kaw H R Prabhakara A Sen
We present a method for obtaining a set of dynamical equations for a system that exhibits a chaotic time series. The time series data is first embedded in an appropriate phase space by using the improved time delay technique of Broomhead and King (1986). Next, assuming that the flow in this space is governed by a set of coupled first order nonlinear ordinary differential equations, a least squares fitting method is employed to derive values for the various unknown coefficients. The ability of the resulting model equations to reproduce global properties like the geometry of the attractor and Lyapunov exponents is demonstrated by treating the numerical solution of a single variable of the Lorenz and Rossler systems in the chaotic regime as the test time series. The equations are found to provide good short term prediction (a few cycle times) but display large errors over large prediction time. The source of this shortcoming and some possible improvements are discussed.
Volume 48 Issue 2 February 1997 pp 655-674 Applications
Collective thermalization in quark gluon plasma
S Sengupta J R Bhatt P K Kaw J C Parikh
A very important question in ultrarelativistic heavy ion collisions is that of thermalization of the high energy density quark gluon plasma forud in the central rapidity region. Different approaches have been adopted by various authors to study this thermalization problem. These include phenomenological string and capacitor plate models, perturbative QCD based parton cascade models and the classical non-perturbative approach. In this paper we briefly review the earlier studies and discuss our work which emphasizes the role of non-perturbative collective effects (classical chaos) in the thermalization of the plasma. In particular, using classical equations of motion of a coloured parton in self-consistent colour fields, we have carried out a 1+1 dimensional simulation of coloured partonic matter. We find that in certain parameter domains, the system exhibits chaotic behaviour in non-abelian plasma oscillations, which then leads to thermalization of the plasma.
Volume 48 Issue 2 February 1997 pp 675-692 Applications
Nonlinear propagation of relativistically intense electromagnetic waves in a collisionless plasma
We discuss the nonlinear propagation of relativistically intense electromagnetic waves into collisionless plasmas with special emphasis on one dimensional plane wave solutions of the propagating, standing and modulated types. These solutions exhibit a rich variety of phenomena associated with relativistic electron mass variation and coupling between transverse electromagnetic and longitudinal fields. They have important applications to problems of laser propagation, self-focusing in overdense plasmas, particle and photon acceleration and to electromagnetic radiation around pulsars.
Volume 49 Issue 1 July 1997 pp 129-129 Plasma Physics
Volume 55 Issue 5-6 November 2000 pp 727-732 Takamak Plasmas, Contributed Papers
Mirnov coil data analysis for tokamak ADITYA
D Raju R Jha P K Kaw S K Mattoo Y C Saxena Aditya Team
The spatial and temporal structures of magnetic signal in the tokamak ADITYA is analysed using recently developed singular value decomposition (SVD) technique. The analysis technique is first tested with simulated data and then applied to the ADITYA Mirnov coil data to determine the structure of current peturbation as the discharge progresses. It is observed that during the current rise phase, current perturbation undergoes transition from
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