Geodesic defect anchoring on nematic shells

Nematic shells are colloidal particles coated with nematic liquid crystal molecules, which may freely glide and rotate on the colloid's surface while keeping their long axis on the local tangent plane. Molecular dynamics simulations on a nanoscopic spherical shell indicate that under appropriate adhesion conditions for the molecules on the equator, the equilibrium nematic texture exhibits at each pole a pair of +1/2 defects so close to one another to be treated as one +1 defect. Spirals connect the polar defects, though the continuum limit of the interaction potential would not feature any elastic anisotropy. A molecular averaging justifies an anchoring defect energy that feels the geodesics emanating from the defect. All our observations are explained by such a geodesic anchoring, which vanishes on flat manifolds

B decays in the upsilon expansion

Theoretical predictions for B decay rates are rewritten in terms of the Upsilon(1S) meson mass instead of the b quark mass, using a modified perturbation expansion. The theoretical consistency of this expansion is shown both at low and high orders. Our method improves the behavior of the perturbation series for semileptonic and nonleptonic inclusive decay modes, as well as for exclusive decay form factors. The results are applied to the determination of the semileptonic B branching ratio, charm counting, the ratio of B -> X tau nu and B -> X e nu decay rates, and form factor ratios in B -> D* e nu decay. We also comment on why it is not possible to separate perturbative and nonperturbative effects in QCD.Comment: 21 page

Institutions: Key variable for economic development in Latin America

This article examines economic development from 1996 to 2015 for 192 countries and specifically Latin America. Evidence shows that each 0.1-point increase in institutions impacts a 3.9% improvement in Latin American per capita output versus a 2.6% effect on world development. This new evidence from Latin America shows a missing opportunity to develop at higher annual pace than the 2.14% average, mainly due to the deterioration in rule of law. We conjecture the efficiency of monetary/fiscal policies will improve if policymakers emphasize projects that foster improvements to institutional quality, such as transparency, public spending quality and fiscal responsibility

Government size and openness: Evidence from the commodity boom in Latin America

Does government size increase to compensate for the volatility that arises from openness? We evaluate this compensation hypothesis by focusing on Latin America, whose economic growth in the 2000s has been often attributed to the commodity boom. Panel data regressions show that during the 2003-2010 commodity boom terms of trade volatility has positive effects on government size compared to the earlier 1990-2002 period. This key finding supports the compensation hypothesis, a result robust to dynamic panels allowing for reverse causation from government size to the real economy. Policy implications include diversification of the production structure and strengthening of regulatory framework