6,500 research outputs found
Probing the Kondo Lattice Model with Alkaline Earth Atoms
We study transport properties of alkaline-earth atoms governed by the Kondo
Lattice Hamiltonian plus a harmonic confining potential, and suggest simple
dynamical probes of several different regimes of the phase diagram that can be
implemented with current experimental techniques. In particular, we show how
Kondo physics at strong coupling, low density, and in the heavy fermion phase
is manifest in the dipole oscillations of the conduction band upon displacement
of the trap center.Comment: 5 pages, 4 figure
Phase diagram of the Bose Kondo-Hubbard model
We study a bosonic version of the Kondo lattice model with an on-site
repulsion in the conduction band, implemented with alkali atoms in two bands of
an optical lattice. Using both weak and strong-coupling perturbation theory, we
find that at unit filling of the conduction bosons the superfluid to Mott
insulator transition should be accompanied by a magnetic transition from a
ferromagnet (in the superfluid) to a paramagnet (in the Mott insulator).
Furthermore, an analytic treatment of Gutzwiller mean-field theory reveals that
quantum spin fluctuations induced by the Kondo exchange cause the otherwise
continuous superfluid to Mott-insulator phase transition to be first order. We
show that lattice separability imposes a serious constraint on proposals to
exploit excited bands for quantum simulations, and discuss a way to overcome
this constraint in the context of our model by using an experimentally realized
non-separable lattice. A method to probe the first-order nature of the
transition based on collapses and revivals of the matter-wave field is also
discussed.Comment: 10 pages, 5 figures, V2: extended discussion of effective
Hamiltonians and mean-field theory, added Fig.
Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign
We present an evaluation of sources, sinks and turbulent transport of nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary layer over French Guyana and Suriname during the October 2005 GABRIEL campaign by simulating observations with a single-column chemistry and climate model (SCM) along a zonal transect. Simulated concentrations of O3 and NO as well as NO2 photolysis rates over the forest agree well with observations when a small soil-biogenic NO emission flux was applied. This suggests that the photochemical conditions observed during GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a compensation point approach to simulate nocturnal deposition and daytime emissions of acetone and methanol and produces daytime boundary layer mixing ratios in reasonable agreement with observations. The area average isoprene emission flux, inferred from the observed isoprene mixing ratios and boundary layer height, is about half the flux simulated with commonly applied emission algorithms. The SCM nevertheless simulates too high isoprene mixing ratios, whereas hydroxyl concentrations are strongly underestimated compared to observations, which can at least partly explain the discrepancy. Furthermore, the model substantially overestimates the isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein (MACR) partly due to a simulated nocturnal increase due to isoprene oxidation. This increase is most prominent in the residual layer whereas in the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing ratios, assuming efficient removal of MVK and MACR. Entrainment of residual layer air masses, which are enhanced in MVK and MACR and other isoprene oxidation products, into the growing boundary layer poses an additional sink for OH which is thus not available for isoprene oxidation. Based on these findings, we suggest pursuing measurements of the tropical residual layer chemistry with a focus on the nocturnal depletion of isoprene and its oxidation products
The Architecture of Confinement: An Exploration of Spatial Boundaries in Wright, Poe, and Foucault
Senior Project submitted to The Division of Languages and Literature of Bard College
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