S. Sivasubramanian

Equivalent circuit and simulations for the Landau-Khalatnikov model of ferroelectric hysteresis

We present the circuit equivalent of the Landau-Khalatnikov dynamical ferroelectric model. The differential equation for hysteretic behavior is subject to numerical computer simulations. The size and shape of the simulated hysteretic loops depend strongly on the frequency and the amplitude of the driving electric field. In previous experiments, this dependence made extraction of the coercive field rather difficult. An alternative experimental method for the determination of the coercive field is here suggested. We also develop in detail the dynamics of bifurcation of a driven Landau-Khalatnikov ferroelectric.

Quantum dissipation induced noncommutative geometry

Abstract The quantum statistical dynamics of a position coordinate x coupled to a reservoir requires theoretically two copies of the position coordinate within the reduced density matrix description. One coordinate moves forward in time while the other coordinate moves backward in time. It is shown that quantum dissipation induces, in the plane of the forward and backward motions, a noncommutative geometry. The noncommutative geometric plane is a consequence of a quantum dissipation induced phase interference which is closely analogous to the Aharonov–Bohm effect.

Physical Kinetics of Ferroelectric Hysteresis

The physical kinetics of single domain ferroelectric materials are studied employing Landau-Khalatnikov equation. The resulting hysteretic curves are obtained numerically. The effective coercive electric field is found to be theoretically dependent on the driving amplitude and frequency as observed in the experimental hysteretic measurements of ferroelectric materials. The effects of thermal noise on the polarization switching time are analyzed using the Fokker-Planck kinetic equation. It is found that the effect of thermal noise is rather significant in a single domain of small volume. It is also shown that for low temperatures quantum effects dominate classical thermal effects in inducing polarization switching in a single ferroelectric domain.

Non-commutative geometry and measurements of polarized two photon coincidence counts

Abstract Employing Maxwell’s equations as the field theory of the photon, quantum mechanical operators for spin, chirality, helicity, velocity, momentum, energy, and position are derived. The photon “Zitterbewegung” along helical paths is explored. The resulting non-commutative geometry of photon position and the quantum version of the Pythagorean theorem is discussed. The distance between two photons in a polarized beam of given helicity is shown to have a discrete spectrum. Such a spectrum should become manifest in measurements of two photon coincidence counts. The proposed experiment is briefly described.

Gauge invariant formulations of Dicke–Preparata super-radiant models

In a gauge invariant formulation of the molecular electric dipole–photon interaction, the rigorous coupling is strictly linear in the photon creation and photon annihilation operators. The linear coupling allows for a super-radiant phase transition as in the Hepp–Lieb formulation. A previous notion of a quadratic-coupling “no-go theorem” for super-radiance is incorrect. Also, incorrect is a previous assertion that the dipole–photon coupling has absolutely no effect on the thermal equations of state. These assertions were based on incorrect canonical transformations which eliminated the electric field (and thereby eliminated the dipole–photon interaction) which is neither mathematically nor physically consistent. The correct form of the canonical transformations are given in this work which allows for the physical reality of super-radiant condensed matter phases.

Quantum limits on pixel resolution from non-commutative photon coordinates

Abstract Non-commutative geometry sets lower bounds on pixel resolution in photon detector technology.

Resonance damping in ferromagnets and ferroelectrics

The phenomenological equations of motion for the relaxation of ordered phases of magnetized and polarized crystal phases can be developed in close analogy with one another. For the case of magnetized systems, the driving magnetic field intensity toward relaxation was developed by Gilbert. For the case of polarized systems, the driving electric field intensity toward relaxation was developed by Khalatnikov. The transport times for relaxation into thermal equilibrium can be attributed to viscous sound wave damping via magnetostriction for the magnetic case and electrostriction for the polarization case.

Electronic Detection of Gravitational Disturbances and Collective Coulomb Interactions

The cross section for a gravitational wave antenna to absorb a graviton may be directly expressed in terms of the non-local viscous response function of the metallic crystal. Crystal viscosity is dominated by electronic processes which then also dominate the graviton absorption rate. To compute this rate from a microscopic Hamiltonian, one must include the full Coulomb interaction in the Maxwell electric field pressure and also allow for strongly non-adiabatic transitions in the electronic kinetic pressure. The view that the electrons and phonons constitute ideal gases with a weak electron phonon interaction is not sufficiently accurate for estimating the full strength of the electronic interaction with a gravitational wave.