Signatures of Bose-Einstein condensation in an optical lattice

We discuss typical experimental signatures for the Bose-Einstein condensation (BEC) of an ultracold Bose gas in an inhomogeneous optical lattice at finite temperature. Applying the Hartree-Fock-Bogoliubov-Popov formalism, we calculate quantities such as the momentum-space density distribution, visibility and peak width as the system is tuned through the superfluid to normal phase transition. Different from previous studies, we consider systems with fixed total particle number, which is of direct experimental relevance. We show that the onset of BEC is accompanied by sharp features in all these signatures, which can be probed via typical time-of-flight imaging techniques. In particular, we find a two-platform structure in the peak width across the phase transition. We show that the onset of condensation is related to the emergence of the higher platform, which can be used as an effective experimental signature.Comment: 5 pages, 3 figure

Inequality and Internal Migration in China: Evidence from Village Panel Data

This paper analyzes the impact of rural-to-urban migration on income inequality and gender wage gap in source regions using a newly constructed panel dataset for around 100 villages over a ten-year period from 1997 to 2006 in China. Since income inequality is time-persisting, we use a system GMM framework to control for the lagged income inequality, in which contemporary emigration is also validly instrumented. We found a Kuznets (inverse U-shaped) pattern between migration and income inequality in the sending communities. Specifically, contemporary emigration increases income inequality, while lagged emigration has strong income inequalityreducing effect in the sending villages. A 50-percent increase in the lagged emigration rate translates into one-sixth to one-seventh standard deviation reduction in inequality. These effects are robust to the different specifications and different measures of inequality. More interestingly, the estimated relationship between emigration and the gender wage gap also has an inverse Ushaped pattern. Emigration tends to increase the gender wage gap initially, and then tends to decrease it in the sending villages.Internal Migration; Inequality; System GMM