Biomedical subjects

Srihari Keshavamurthy

Publications and source records attributed to Srihari Keshavamurthy.

4 recordsLinked to original sources

PubMed2006

Intramolecular vibrational energy redistribution as state space diffusion: classical-quantum correspondence.

We study the intramolecular vibrational energy redistribution (IVR) dynamics of an effective spectroscopic Hamiltonian describing the four coupled high frequency modes of CDBrClF. The IVR dynamics ensuing from nearly isoenergetic zeroth-order states, an edge (overtone) and an interior (combination) state, is studied from a state space diffusion perspective. A wavelet based time-frequency analysis reveals an inhomogeneous phase space due to the trapping of classical trajectories. Consequently the interior state has a smaller effective IVR dimension as compared to the edge state.

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PubMed2005

Resonance-assisted tunneling in three degrees of freedom without discrete symmetry.

We study dynamical tunneling in a near-integrable Hamiltonian with three degrees of freedom. Despite the absence of discrete symmetry we show that the mixing of near-degenerate quantum states is due to dynamical tunneling mediated by the nonlinear resonances in the classical phase space. Identifying the key resonances allows us to selectively suppress the dynamical tunneling by adding weak counter-resonant terms.

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PubMed2005

On dynamical tunneling and classical resonances.

This work establishes a firm relationship between classical nonlinear resonances and the phenomenon of dynamical tunneling. It is shown that the classical phase space with its hierarchy of resonance islands completely characterizes dynamical tunneling and explicit forms of the dynamical barriers can be obtained only by identifying the key resonances. Relationship between the phase space viewpoint and the quantum mechanical superexchange approach is discussed in near-integrable and mixed regular-chaotic situations. For near-integrable systems with sufficient anharmonicity the effect of multiple resonances, i.e., resonance-assisted tunneling, can be incorporated approximately. It is also argued that the presumed relation of avoided crossings to nonlinear resonances does not have to be invoked in order to understand dynamical tunneling. For molecules with low density of states the resonance-assisted mechanism is expected to be dominant.

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PubMed2003

Exploring classical phase space structures of nearly integrable and mixed quantum systems via parametric variation.

The correlation between overlap intensities and level velocities has been introduced as a sensitive measure capable of revealing phase space localization. Previously applied to chaotic quantum systems, here we extend the theory to near-integrable and mixed quantum systems. This measure is useful in the latter cases because it has the ability to highlight certain phase space structures depending upon the perturbation used to parametrically vary the Hamiltonian. A detailed semiclassical theory is presented relating the correlation coefficient to the phase space weighted derivatives of the classical action. In the process, we confront the question of whether the Hannay-Ozorio de Almeida sum rules are simply extendable to mixed phase space systems. In addition, the variant Planck's over 2pi scalings of the correlation coefficient and relevant quantities are derived for nearly integrable systems. Excellent agreement is found between the theory and the results for integrable billiards as well as for the standard map.

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