• Ramakrishna Ramaswamy

      Articles written in Pramana – Journal of Physics

    • Continuous quantization procedure in quasiclassical scattering: Application to atom-Morse oscillator collisions

      Ramakrishna Ramaswamy

      More Details Abstract Fulltext PDF

      The recently developed method of continuous quantization is applied to the atom-Morse oscillator collinear collision problem. This geometrical formulation of the classical scattering process allows for the extraction of transition probabilities for classically forbidden processes with reasonable accuracy. The accuracy of this method over the simple (histogram) quasi-classical procedure is demonstrated for two-model systems.

    • Symmetry breaking in quantum chaotic systems

      Akhilesh Pandey Ramakrishna Ramaswamy Pragya Shukla

      More Details Abstract Fulltext PDF

      We show, using semiclassical methods, that as a symmetry is broken, the transition between universality classes for the spectral correlations of quantum chaotic systems is governed by the same parametrization as in the theory of random matrices. The theory is quantitatively verified for the kicked rotor quantum map. We also provide an explicit substantiation of the random matrix hypothesis, namely that in the symmetry-adapted basis the symmetry-violating operator is random.

    • Preface

      Ramakrishna Ramaswamy Katepalli R Sreenivasan

      More Details Fulltext PDF
    • Resonances and chaos in the collinear collision system (He, H2+) and its isotopic variants

      Susanta Mahapatra N Sathyamurthy Ramakrishna Ramaswamy

      More Details Abstract Fulltext PDF

      The collinear atom-diatom collision system provides one of the simplest instances of chaotic or irregular scattering. Classically, irregular scattering is manifest in the sensitive dependence of post-collision variables on initial conditions, and quantally, in the appearance of a dense spectrum of dynamical resonances. We examine the influence of kinematic factors on such dynamical resonances in collinear (He, H2+) collisions by computing the transition state spectra for collinear (He, HD+) and (He, DH+) collisions using the time-dependent quantum mechanical approach. The nearest neighbor spacing distributionP(s) and the spectral rigidity Δ3(L) for these resonances suggest that the dynamics is predominantlyirregular for collinear (He, HD+) and predominantlyregular for collinear (He, DH+). These findings are reinforced by a significantly larger “correlation hole” in ensemble averaged survival probability ≪P(t)≫ values for collinear (He, HD+) than for collinear (He,DH+). In addition we have also examined measures of classical chaos through the dependence of the final vibrational action,nf, on the initial vibrational phaseφi of the diatom, and Poincaré surfaces-of-section. They show that (He, HD+) collisions are partly chaotic over the entire energy range (0–2.78 eV) while (He, DH+) collisions, in contrast, are highly regular at collision energies below the classical threshold for reaction. Above the threshold, the scattering remains regular for initial vibrational statesv=0 and 1 of DH+.

    • Dynamical signatures of ‘phase transitions’: Chaos in finite clusters

      Vishal Mehra Saroj K Nayak Ramakrishna Ramaswamy

      More Details Abstract Fulltext PDF

      Finite clusters of atoms or molecules, typically composed of about 50 particles (and often as few as 13 or even less) have proved to be useful prototypes of systems undergoing phase transitions. Analogues of the solid-liquid melting transition, surface melting, structural phase transitions and the glass transition have been observed in cluster systems. The methods of nonlinear dynamics can be applied to systems of this size, and these have helped elucidate the nature of the microscopic dynamics, which, as a function of internal energy (or ‘temperature’) can be in a solidlike, liquidlike, or even gaseous state. The Lyapunov exponents show a characteristic behaviour as a function of energy, and provide a reliable signature of the solid-liquid melting phase transition. The behaviour of such indices at other phase transitions has only partially been explored. These and related applications are reviewed in the present article.

    • A plethora of strange nonchaotic attractors

      Surendra Singh Negi Ramakrishna Ramaswamy

      More Details Abstract Fulltext PDF

      We show that it is possible to devise a large class of skew-product dynamical systems which have strange nonchaotic attractors (SNAs): the dynamics is asymptotically on fractal attractors and the largest Lyapunov exponent is non-positive. Furthermore, we show that quasiperiodic forcing, which has been a hallmark of essentially all hitherto known examples of such dynamics is not necessary for the creation of SNAs.

    • Foreword

      Ramakrishna Ramaswamy Rajarshi Roy Neelima Gupte

      More Details Fulltext PDF
    • A perspective on nonlinear dynamics

      Neelima Gupte Ramakrishna Ramaswamy Rajarshi Roy

      More Details Abstract Fulltext PDF

      We present a brief report on the conference, a summary of the proceedings, and a discussion on the field of nonlinear science studies and its current frontiers.

    • Foreword

      Ramakrishna Ramaswamy Rajarshi Roy Neelima Gupte

      More Details Abstract Fulltext PDF
  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.