Does migration reshape expenditures in rural households? Evidence from Mexico

Migration reshapes rural economies in ways that may go beyond the contribution of migrant remittances to household income. Consumption and investment expenditures by migrant-sending households may transmit some of the impacts of migration to others inside and outside the rural economy, and they also may shape the potential effects of migration within the source household. Numerous studies have attempted to quantify the impact of migrant remittances on expenditures in migrant-sending households following one of two approaches. The first asks how migrant remittances are spent. It has the advantage of being simple but the significant disadvantage of ignoring the fungibility of income from migrant and nonmigrant sources. Remittances almost certainly have indirect effects on expenditures by way of their contribution to households'total budgets. The second uses a regression approach that considers remittances as an explanatory variable, in addition to total income and other controls, in a household expenditure demand system. It has the advantage of enabling one to test whether remittances affect expenditures in ways that are independent of their contribution to total income. But it does not take into account other ways, besides remittances, in which migration may influence expenditure patterns in households with migrants. It also may suffer from econometric bias resulting from the endogeneity of migration and remittance receipts. The same variables may simultaneously affect both remittances and household expenditures, and unless one controls for this, biased estimates may result.Investment and Investment Climate,Economic Theory&Research,Housing&Human Habitats,Remittances,Consumption

Non-equilibrium ionization around clouds evaporating in the interstellar medium

It is of prime importance for global models of the interstellar medium to know whether dense clouds do or do not evaporate in the hot coronal gas. The rate of mass exchanges between phases depends very much on that. McKee and Ostriker's model, for instance, assumes that evaporation is important enough to control the expansion of supernova remnants, and that mass loss obeys the law derived by Cowie and McKee. In fact, the geometry of the magnetic field is nearly unknown, and it might totally inhibit evaporation, if the clouds are not regularly connected to the hot gas. Up to now, the only test of the theory is the U.V. observation (by the Copernicus and IUE satellites) of absorption lines of ions such as OVI or NV, that exist at temperatures of a few 100,000 K typical of transition layers around evaporating clouds. Other means of testing the theory are discussed

On-chip quantum tomography of mechanical nano-scale oscillators with guided Rydberg atoms

Nano-mechanical oscillators as well as Rydberg-atomic waveguides hosted on micro-fabricated chip surfaces hold promise to become pillars of future quantum technologies. In a hybrid platform with both, we show that beams of Rydberg atoms in waveguides can quantum-coherently interrogate and manipulate nanomechanical elements, allowing full quantum state tomography. Central to the tomography are quantum non-demolition measurements using the Rydberg atoms as probes. Quantum coherent displacement of the oscillator is also made possible, by driving the atoms with external fields while they interact with the oscillator. We numerically demonstrate the feasibility of this fully integrated on-chip control and read-out suite for quantum nano-mechanics, taking into account noise and error sources.Comment: 11 pages, 5 figures, 1 tabl

Ground state of a tightly bound composite dimer immersed in a Fermi Sea

In this paper we present a theoretical investigation for the ground state of an impurity immersed in a Fermi sea. The molecular regime is considered where a two-body bound state between the impurity and one of the fermions is formed. Both interaction and exchange of the bound fermion take place between the dimer and the Fermi sea. We develop a formalism based on a two channel model allowing us to expand systematically the ground state energy of this immersed dimer with the scattering length $a$. Working up to order $a^3$, associated to the creation of two particle-hole pairs, reveals the first signature of the composite nature of the bosonic dimer. Finally, a complementary variational study provides an accurate estimate of the dimer energy even at large scattering length.Comment: 11 pages; 3 figure