Order parameter of MgB_2: a fully gapped superconductor

We have measured the low-temperature specific heat C(T) for polycrystalline MgB_2 prepared by high pressure synthesis. C(T) below 10 K vanishes exponentially, which unambiguously indicates a fully opened superconducting energy gap. However, this gap is found to be too small to account for Tc of MgB_2. Together with the small specific heat jump DeltaC/gamma_nTc=1.13, scenarios like anisotropic s-wave or multi-component order parameter are called for. The magnetic field dependence of gamma(H) is neither linear for a fully gapped s-wave superconductor nor H^1/2 for nodal order parameter. It seems that this intriguing behavior of gamma(H) is associated with the intrinsic electronic properties other than flux pinning.Comment: 7 pages, 5 figures; revised text and figures; references updated, Phys. Rev. Lett., in pres

Happiness, Ideology and Crime in Argentine Cities

This paper uses self-reported data on victimization, subjective well being and ideology for a panel of individuals living in six Argentine cities. While no relationship is found between happiness and victimization experiences, a correlation is documented, however, between victimization experience and changes in ideological positions. Specifically, individuals who are the victims of crime are subsequently more likely than non-victims to state that inequality is high in Argentina and that the appropriate measure to reduce crime is to become less punitive (demanding lower penalties for the same crime)