Labor Informality in Latin America and the Caribbean: Patterns and Trends from Household Survey Microdata

This paper documents the main patterns and trends of alternative definitions of labor informality in Latin America and the Caribbean, by exploiting a large database of more than 100 household surveys covering the period 1989-2005. The evidence suggests that there are no signs of a consistent pattern of reduction in labor informality in the region. Regardless of the definition used, labor informality remains a pervasive characteristic of labor markets in LAC. In several countries the increase in labor informality seems to have been associated more to a sizeable increase in the propensity to set informal arrangements within groups, than to changes in the national employment structure toward more informal sectors.Informality, employment,Latinamerican, Caribean,Labor Market

Obtaining a New Representation for the Golden Ratio by Solving a Biquadratic Equation

In the present work we show how different ways to solve biquadratic equations can lead us to different representations of its solutions. A particular equation which has the golden ratio and its reciprocal as solutions is shown as an example.Comment: To appear in J. Appl. Math. Phys., 4 pages. Recreational Mathematic

A locally supersymmetric SO(10,2)SO(10,2) invariant action for D=12D=12 supergravity

We present an action for $N=1$ supergravity in $10+2$ dimensions, containing the gauge fields of the $OSp(1|64)$ superalgebra, i.e. one-forms $B^{(n)}$ with $n$=1,2,5,6,9,10 antisymmetric D=12 Lorentz indices and a Majorana gravitino $\psi$. The vielbein and spin connection correspond to $B^{(1)}$ and $B^{(2)}$ respectively. The action is not gauge invariant under the full $OSp(1|64)$ superalgebra, but only under a subalgebra ${\tilde F}$ (containing the $F$ algebra $OSp(1|32)$), whose gauge fields are $B^{(2)}$, $B^{(6)}$, $B^{(10)}$ and the Weyl projected Majorana gravitino ${1 \over 2} (1+\Gamma_{13}) \psi$. Supersymmetry transformations are therefore generated by a Majorana-Weyl supercharge and, being part of a gauge superalgebra, close off-shell. The action is simply $\int STr ({\bf R}^6 {\bf \Gamma})$ where ${\bf R}$ is the $OSp(1|64)$ curvature supermatrix two-form, and ${\bf \Gamma}$ is a constant supermatrix involving $\Gamma_{13}$ and breaking $OSp(1|64)$ to its ${\tilde F}$ subalgebra. The action includes the usual Einstein-Hilbert term.Comment: LaTeX, 13 pages. Added a reference, a Table in Appendix A for the gamma commutations in d=12, and corrected eq. (4.14) for the Einstein-Hilbert term; v4: corrected formulas (A.3), (A.4) and (A.10), modified last paragraph of Section 5, added acknowledgement

Ballistic quantum state transfer in spin chains: general theory for quasi-free models and arbitrary initial states

Ballistic quantum-information transfer through spin chains is based on the idea of making the spin dynamics ruled by collective excitations with linear dispersion relation. Unlike perfect state transfer schemes, a ballistic transmission requires only a minimal engineering of the interactions; in fact, for most practical purposes, the optimization of the couplings to the ends of the chain is sufficient to obtain an almost perfect transmission. In this work we review different ballistic quantum-state transfer protocols based on the dynamics of quasi-free spin chains, and further generalize them both at zero and finite temperature. In particular, besides presenting novel analytical results for XX, XY, and Ising spin models, it is shown how, via a complete control on the first and last two qubits of the chain, destructive thermal effects can be cancelled, leading to a high-quality state transmission irrespective of the temperature.Comment: 18 pages, 5 figures. Extracted from PhD thesi