3,284 research outputs found
Backaction-Driven Transport of Bloch Oscillating Atoms in Ring Cavities
We predict that an atomic Bose-Einstein condensate strongly coupled to an
intracavity optical lattice can undergo resonant tunneling and directed
transport when a constant and uniform bias force is applied. The bias force
induces Bloch oscillations, causing amplitude and phase modulation of the
lattice which resonantly modifies the site-to-site tunneling. For the right
choice of parameters a net atomic current is generated. The transport velocity
can be oriented oppositely to the bias force, with its amplitude and direction
controlled by the detuning between the pump laser and the cavity. The transport
can also be enhanced through imbalanced pumping of the two counter-propagating
running wave cavity modes. Our results add to the cold atoms quantum simulation
toolbox, with implications for quantum sensing and metrology.Comment: Published version: 5 pages, 4 figures; Supplementary Material
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Targeting Agricultural Drainage to Reduce Nitrogen Losses in a Minnesota Watershed
Agricultural nitrogen losses are the major contributor to nitrogen loads in the Mississippi River, and consequently, to the existence of a hypoxic, or dead, zone in the Gulf of Mexico. Focusing on two small agricultural watersheds in southeast Minnesota, simulation results from the Agricultural Drainage And Pesticide Management (ADAPT) model were combined with a linear-optimization model to evaluate the environmental and economic impact of alternative land-use policies for reducing nitrogen losses. Of particular importance was the studys explicit focus on agricultural subsurface (tile) drainage, which has been identified as the major pathway for agricultural nitrogen losses in the upper Midwest, and the use of drainage-focused abatement policies. Results indicate that tile-drained land plays a key role in nitrogen abatement, and that a combined policy of nutrient management on tile-drained land and retirement of non-drained land is a cost-effective means of achieving a 20- or 30-percent nitrogen-abatement goal. Results also indicate that although it is cost-effective to abate on tile-drained land, it is not cost-effective to undertake policies that plug or remove tile drains from the landscape, regardless of whether the land would be retired or kept in production. Therefore, results imply that although tile-drained land is a major source of nitrogen lost to waterways, it is not cost-effective to remove the land from production or to remove the drainage from the land. Because of its value to agricultural production, it is better to keep tile-drained land in production under nutrient management and focus retirement policies on relatively less-productive, non-drained acres.Environmental Economics and Policy, Land Economics/Use,
A WKB formalism for multicomponent fields and its application to gravitational and sound waves in perfect fluids
We review the WKB method for multicomponent fields obeying hyperbolic linear partial differential equations and derive a general necessary and sufficient condition for the formalism to provide transport equations. We apply the method to linearized perturbations of perfect fluid solutions to Einstein's equation and show that the gravitational and sound wave modes satisfy this condition, whereas a zero-frequency, non-propagating matter mode does not. We derive the transport equations for the wave amplitudes in leading order; they exhibit in particular the influence of background curvature on the propagation of gravitational waves
Leptogenesis from Spin-Gravity Coupling Following Inflation
The energy levels of the left and the right handed neutrinos is split in the
background of gravitational waves generated during inflation which in presence
of lepton number violating interactions gives rise to a net lepton asymmetry at
equilibrium. Lepton number violation is achieved by the same dimension five
operator which gives rise to neutrino masses after electro-weak symmetry
breaking. A net baryon asymmetry of the same magnitude can be generated from
this lepton asymmetry by electroweak sphaleron processes.Comment: Journal version (accepted for publication in Phys. Rev. Lett.
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