Bulletin of the American Physical Society
2005 TSAPS/AAPT/SPS Joint Fall Meeting
Thursday–Saturday, October 20–22, 2005; Houston, TX
Session A3: Theory I |
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Room: Waldorf Astoria B 210B |
Friday, October 21, 2005 10:30AM - 10:42AM |
A3.00001: A study of time reversal violation in two mechanisms through spin dependent total cross section measurements Guanghua Xu |
Friday, October 21, 2005 10:42AM - 10:54AM |
A3.00002: Quantum transport in chains with noisy off-diagonal couplings Anderey Pereverzev, Eric Bittner We present a model for conductivity and energy diffusion in a linear chain described by a quadratic Hamiltonian with Gaussian noise. We show that when the correlation matrix is diagonal, the noise-averaged Liouville-von Neumann equation governing the time-evolution of the system reduces to the Lindblad equation with Hermitian Lindblad operators. We show that the noise-averaged density matrix for the system expectation values of the energy density and the number density satisfy discrete versions of the heat and diffusion equations. Transport coefficients are given in terms of model Hamiltonian parameters. We discuss conditions on the Hamiltonian under which the noise-averaged expectation value of the total energy remains constant. For chains placed between two heat reservoirs, the gradient of the energy density along the chain is linear. [Preview Abstract] |
Friday, October 21, 2005 10:54AM - 11:06AM |
A3.00003: Bohmian Interpretation of Quantum Mechanics and Ehrenfest's Theorem for Energy Donald Kobe The Bohmian causal interpretation of quantum mechanics uses the wave function in polar form in the Schroedinger equation to obtain a Hamilton-Jacobi equation with a quantum potential and an equation of continuity. From the Hamilton-Jacobi equation Newton's second law is obtained with a quantum force. Quantum trajectories are determined by the classical forces and quantum force. The energy of a system of charged particles in an electromagnetic field is the sum of kinetic energy, conservative potential energy, and the quantum potential. The time derivative of the energy for this nonconservative system is the power supplied by the nonconservative electric field and a quantum power. When this equation is averaged over the probability density, the average of the quantum power is shown to be zero. This average equation is equivalent to Ehrenfest's theorem for energy, which states that the time derivative of the expectation value of the energy operator is equal to the expectation value of the power operator. Therefore, for the energy the Bohmian interpretation is equivalent to standard quantum mechanics. [Preview Abstract] |
Friday, October 21, 2005 11:06AM - 11:18AM |
A3.00004: Physics of Quantum Cascade Raman lasers Feng Xie, Alexey Belyanin The new semiconductor injection Raman laser is reviewed in this paper. It employs resonant stimulated Raman scattering in a system of electronic subbands in n-doped semiconductor (InGaAs/AlInAs or GaAs/AlGaAs) coupled quantum wells, embedded within the Quantum Cascade (QC)laser structure. The QC laser serves as an internal optical pump for the Raman process. Resonance with intersubband transitions leads to a significantly enhanced Raman gain, high conversion efficiency and low threshold. The device is driven electrically; no external optical pumping is needed. Raman laser can operate within a broad range of wavelengths by varying the energy differences between electron states in a coupled quantum well. These advantages lead to a new class of compact mid and far-infrared laser sources. [Preview Abstract] |
Friday, October 21, 2005 11:18AM - 11:30AM |
A3.00005: Integrable Cousin of a One-Dimensional Gravitating System Kenneth Yawn, Bruce Miller The first gravitational simulations employed a one-dimensional system consisting of N parallel mass sheets. In common with the famous Fermi-Pasta-Ulam problem, this system resists coming to equilibrium. Consequently it became of seminal interest in the new field of nonlinear dynamics. Exchange symmetry in acceleration partitions the configuration space of an N particle one-dimensional gravitational system (OGS) into N! equivalent cells. We take advantage of the consequent small angular separation of the acceleration in neighboring cells to construct a related, integrable, version of the system which takes the form of a central force problem in N-1 dimensions. The properties of the latter, including the construction of trajectories and possible continuum limits, are explored. Dynamical simulation is employed to compare the two models. For some initial conditions, excellent agreement is observed, yielding insight into the source of instability in the original system. [Preview Abstract] |
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