Quantum Dynamics Using Lie Algebras, with Explorations in the Chaotic Behavior of Oscillators

• Main Author: Sayer, Ryan Thomas
• Format: Others
• Published: BYU ScholarsArchive 2012
• Subjects: quantum dynamics; oscillator; driving force; dynamical chaos; Lie algebra; mean field; anharmonicity; Lyapunov exponent; transition probability; Astrophysics and Astronomy; Physics
• Online Access: https://scholarsarchive.byu.edu/etd/3285; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4284&context=etd

We study the time evolution of driven quantum systems using analytic, algebraic, and numerical methods. First, we obtain analytic solutions for driven free and oscillator systems by shifting the coordinate and phase of the undriven wave function. We also factorize the quantum evolution operator using the generators of the Lie algebra comprising the Hamiltonian. We obtain coupled ODE's for the time evolution of the Lie algebra parameters. These parameters allow us to find physical properties of oscillator dynamics. In particular we find phase-space trajectories and transition probabilities. We then search for chaotic behavior in the Lie algebra parameters as a signature for dynamical chaos in the quantum system. We plot the trajectories, transition probabilities, and Lyapunov exponents for a wide range of the following physical parameters: strength and duration of the driving force, frequency difference, and anharmonicity of the oscillator. We identify conditions for the appearance of chaos in the system.