Microcredit and poverty. An overview of the principal statistical methods used to measure the program net impacts

The purpose of this paper is to examine di¤erent econometric approaches aiming to evaluate the impact of microcredit on poverty. Starting with a brief description of microcredit and the most common kinds of statistical biases connected to these studies, I describe the principal characteristics of Non-Randomized and Randomized approaches, in order to highlight strengths and weaknesses concerning the application of such methodologies.Microcredit, poverty, program impact, randomized approach, non-randomized approach.

Two-body problem in periodic potentials

We investigate the problem of two atoms interacting via a short range s-wave potential in the presence of a deep optical lattice of arbitrary dimension $D$. Using a tight binding approach, we derive analytical results for the properties of the bound state and the scattering amplitude. We show that the tunneling through the barriers induces a dimensional crossover from a confined regime at high energy to an anisotropic three dimensional regime at low energy. The critical value of the scattering length needed to form a two-body bound state shows a logaritmic dependence on the tunneling rate for D=1 and a power law for $D>1$. For the special case D=1, we also compare our analytical predictions with exact numerics, finding remarkably good agreement

Fermionic trimers in spin-dependent optical lattices

We investigate the formation of three-body bound states (trimers) in two-component Fermi gases confined in one dimensional optical lattice with spin-dependent tunneling rates. The binding energy and the effective mass of the trimer are obtained from the solution of the Mattis integral equation generalized to the case of unequal Bloch masses. We show that this equation admits multiple solutions corresponding to excited bound states, which are only stable for large mass asymmetry.Comment: 8 pages, 5 figures, special few-body issue of the Journal of the French Academy of Sciences (CRAS

BCS-BEC crossover in a random external potential

We investigate the ground state properties of a disordered superfluid Fermi gas across the BCS-BEC (Bose Einstein condensate) crossover. We show that, for weak disorder, both the depletion of the condensate fraction of pairs and the normal fluid density exhibit a nonmonotonic behavior as a function of the interaction parameter $1/k_Fa$, reaching their minimum value near unitarity. We find that, moving away from the weak coupling BCS regime, Anderson's theorem ceases to apply and the superfluid order parameter is more and more affected by the random potential.Comment: Revised version, one reference added, Phys. Rev. Lett. in pres

Formal and informal sectors: Interactions between moneylenders and traditional banks in the rural Indian credit market

This paper describes, through a theoretical approach, the interactions between institutional lenders and local moneylenders, and how these affect the rural credit market. It evaluates the effects produced by the introduction of "spillovers" in a rural credit market with rationing in which banks and moneylenders interact simultaneously while working in distinct segments. Due to the strong and consolidated social ties, it is probable that the spread of knowledge concerning potential debtors comes about in targeted and rapid way with reduced costs for the lenders as well.

Anderson localization of pairs in bichromatic optical lattices

We investigate the formation of bound states made of two interacting atoms moving in a one dimensional (1D) quasi-periodic optical lattice. We derive the quantum phase diagram for Anderson localization of both attractively and repulsively bound pairs. We calculate the pair binding energy and show analytically that its behavior as a function of the interaction strength depends crucially on the nature -extended, multi-fractal, localized- of the single-particle atomic states. Experimental implications of our results are discussed.Comment: final revised version with more explanations, 4 pages, 3 figure