25,186 research outputs found
Superfluid Pairing in Neutrons and Cold Atoms
Ultracold atomic gases and low-density neutron matter are unique in that they
exhibit pairing gaps comparable to the Fermi energy which in this sense are the
largest in the laboratory and in nature, respectively. This strong pairing
regime, or the crossover between BCS and BEC regimes, requires non-perturbative
treatments. We describe Quantum Monte Carlo results useful to understand the
properties of these systems, including infinite homogeneous matter and trapped
inhomogeneous gases.Comment: 14 pages, 4 figures; chapter in "50 Years of Nuclear BCS", edited by
R. A. Broglia and V. Zelevinsk
Cold neutrons trapped in external fields
The properties of inhomogeneous neutron matter are crucial to the physics of
neutron-rich nuclei and the crust of neutron stars. Advances in computational
techniques now allow us to accurately determine the binding energies and
densities of many neutrons interacting via realistic microscopic interactions
and confined in external fields. We perform calculations for different external
fields and across several shells to place important constraints on
inhomogeneous neutron matter, and hence the large isospin limit of the nuclear
energy density functionals that are used to predict properties of heavy nuclei
and neutron star crusts. We find important differences between microscopic
calculations and current density functionals; in particular the isovector
gradient terms are significantly more repulsive than in traditional models, and
the spin-orbit and pairing forces are comparatively weaker.Comment: 5 pages, 4 figures, final version. Additional material reference
added in the published versio
Coparenting in Fragile Families
Nonmarital childbearing has increased dramatically in the U.S. since the early 1960s, rising from 6% of all births in 1960 to fully 40% in 2007 (Hamilton, Martin, & Ventura, 2009). Whereas similar trends have occurred in many developed nations, the U.S. stands out in the extent to which such births are associated with socioeconomic disadvantage and relationship instability. This has given rise to a new term ‘fragile families,’ which we define as unmarried couples who have a child together. The increase in fragile families reflects changes not only in the initial context of births but also in the fundamental nature and patterns of childrearing.Fragile families, childbearing, nonmarital childbearing
Electron densities and temperatures in the f-region from backscatter measurements at arecibo
Diurnal variation in electron densities and temperatures in F region from backscatter measurements over Puerto Ric
Wildfire and MAMS data from STORMFEST
Early in 1992, NASA participated in an inter-agency field program called STORMFEST. The STORM-Fronts Experiment Systems Test (STORMFEST) was designed to test various systems critical to the success of STORM 1 in a very focused experiment. The field effort focused on winter storms in order to investigate the structure and evolution of fronts and associated mesoscale phenomena in the central United States. This document describes the data collected from two instruments onboard a NASA ER2 aircraft which was deployed out of Ellington Field in Houston, Texas from February 13 through March 15, 1992, in support of this experiment. The two instruments were the Wildfire (a.k.a. the moderate resolution imaging spectrometer-nadir (MODIS-N) Airborne Simulation (MAS)) and the Multispectral Atmospheric Mapping Sensor (MAMS)
- …