Correlation energy in a spin polarized two dimensional electron liquid in the high density limit

We have obtained an analytic expression for the ring diagrams contribution to the correlation energy of a two dimensional electron liquid as a function of the uniform fractional spin polarization. Our results can be used to improve on the interpolation formulas which represent the basic ingredient for the constructions of modern spin-density functionals in two dimensions.Comment: 3 pages, 1 figur

Two exact properties of the perturbative expansion for the two-dimensional electron liquid with Rashba or Dresselhaus spin-orbit coupling

We have identified two useful exact properties of the perturbative expansion for the case of a two-dimensional electron liquid with Rashba or Dresselhaus spin-orbit interaction and in the absence of magnetic field. The results allow us to draw interesting conclusions regarding the dependence of the exchange and correlation energy and of the quasiparticle properties on the strength of the spin-orbit coupling which are valid to all orders in the electron-electron interaction.Comment: 6 pages, 1 figur

Determinants of international migrations to Italian provinces

International migration flows constitute one of the most policy-relevant elements of modern economies. The Italian experience is a case of particular interest given the rapid growth of immigration flows, the large number of countries of origin involved, and regional economic heterogeneity. This paper analyses the bilateral stocks of migrants coming from 142 countries and living in 103 Italian provinces to ascertain what characteristics of home countries and destination provinces are associated with international migrations. The results of the estimation of a gravity model on the stock of migrants show that economic, demographic and institutional variables are correlated with migration patterns. In light of the recent Arab Spring, it is interesting to note that migrants come to Italy predominantly from geographically close, democratic and middle-income countries.International migrations, Italy, Gravity model

High density limit of the two-dimensional electron liquid with Rashba spin-orbit coupling

We discuss by analytic means the theory of the high-density limit of the unpolarized two-dimensional electron liquid in the presence of Rashba or Dresselhaus spin-orbit coupling. A generalization of the ring-diagram expansion is performed. We find that in this regime the spin-orbit coupling leads to small changes of the exchange and correlation energy contributions, while modifying also, via repopulation of the momentum states, the noninteracting energy. As a result, the leading corrections to the chirality and total energy of the system stem from the Hartree-Fock contributions. The final results are found to be vanishing to lowest order in the spin-orbit coupling, in agreement with a general property valid to every order in the electron-electron interaction. We also show that recent quantum Monte Carlo data in the presence of Rashba spin-orbit coupling are well understood by neglecting corrections to the exchange-correlation energy, even at low density values.Comment: 11 pages, 5 figure

On the RKKY range function of a one dimensional non interacting electron gas

We show that the pitfalls encountered in earlier calculations of the RKKY range function for a non interacting one dimensional electron gas at zero temperature can be unraveled and successfully dealt with through a proper handling of the impurity potential.Comment: to appear in Phys. Re

Exchange energy and generalized polarization in the presence of spin-orbit coupling in two dimensions

We discuss a general form of the exchange energy for a homogeneous system of interacting electrons in two spatial dimensions which is particularly suited in the presence of a generic spin-orbit interaction. The theory is best formulated in terms of a generalized fractional electronic polarization. Remarkably we find that a net generalized polarization does not necessarily translate into an increase in the magnitude of the exchange energy, a fact that in turn favors unpolarized states. Our results account qualitatively for the findings of recent experimental investigations