Using modified Gaussian distribution to study the physical properties of one and two-component ultracold atoms

Gaussian distribution is commonly used as a good approximation to study the trapped one-component Bose-condensed atoms with relatively small nonlinear effect. It is not adequate in dealing with the one-component system of large nonlinear effect, nor the two-component system where phase separation exists. We propose a modified Gaussian distribution which is more effective when dealing with the one-component system with relatively large nonlinear terms as well as the two-component system. The modified Gaussian is also used to study the breathing modes of the two-component system, which shows a drastic change in the mode dispersion at the occurrence of the phase separation. The results obtained are in agreement with other numerical results.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.

Oscillations of Bose condensates in a one-dimensional optical superlattice

Oscillations of atomic Bose-Einstein condensates in a 1D optical lattice with a two-point basis is investigated. In the low-frequency regime, four branches of modes are resolved, that correspond to the transverse in-phase and out-of-phase breathing modes, and the longitudinal acoustic and optical phonon modes of the condensates. Dispersions of these modes depend intimately on the values of two intersite Josephson tunneling strengths, $J_1$ and $J_2$, and the on-site repulsion $U$ between the atoms. Observation of these mode dispersions is thus a direct way to access them.Comment: 5 pages,2 figure

Center motions of nonoverlapping condensates coupled by long-range dipolar interaction in bilayer and multilayer stacks

We investigate the effect of anisotropic and long-range dipole-dipole interaction (DDI) on the center motions of nonoverlapping Bose-Einstein condensates (BEC) in bilayer and multilayer stacks. In the bilayer, it is shown analytically that while DDI plays no role in the in-phase modes of center motions of condensates, out-of-phase mode frequency ($\omega_o$) depends crucially on the strength of DDI ($a_d$). At the small-$a_d$ limit, $\omega_o^2(a_d)-\omega_o^2(0)\propto a_d$. In the multilayer stack, transverse modes associated with center motions of coupled condensates are found to be optical phonon like. At the long-wavelength limit, phonon velocity is proportional to $\sqrt a_d$.Comment: 7 pages, 5 figure

Energy recovery from solid waste. Volume 2: Technical report

A systems analysis of energy recovery from solid waste demonstrates the feasibility of several current processes for converting solid waste to an energy form. The social, legal, environmental, and political factors are considered in depth with recommendations made in regard to new legislation and policy. Biodegradation and thermal decomposition are the two areas of disposal that are considered with emphasis on thermal decomposition. A technical and economic evaluation of a number of available and developing energy-recovery processes is given. Based on present technical capabilities, use of prepared solid waste as a fuel supplemental to coal seems to be the most economic process by which to recover energy from solid waste. Markets are considered in detail with suggestions given for improving market conditions and for developing market stability. A decision procedure is given to aid a community in deciding on its options in dealing with solid waste, and a new pyrolysis process is suggested. An application of the methods of this study are applied to Houston, Texas