Multipartite monogamy of the concurrence

Monogamy of entanglement is generally discussed using a bipartite entanglement measure as an upper bound. Here we discuss a new kind of monogamous relation where the upper bound is given by a multipartite measure of entanglement, the generalized concurrence. We show a new monogamous equality involving the multipartite concurrence, all the bipartite concurrences and the genuine tripartite entanglement for pure three qubits system. The result extends to mixed states in an inequality involving the generalized concurrence and all the bipartite concurrences. We provide a counter-example showing that the result cannot be extended for systems with more than three qubits.Comment: 4 page

A note on the use of quantile regression in beta convergence analysis

We discuss how to interpret conflicting results obtained by the use of quantile regression methods in growth regression tests of β-convergence hypothesis and the results obtained by nonparametric methods. We show that the assumption of linearity may cause the non-rejection of the β-convergence hypothesis by quantile regression. We also show that using a nonparametric form of quantile regression, we can reject the hypothesis of β-convergence and confirm the results of divergence and formation of convergence clubs. We illustrate the discussion by using the conflicting results on convergence found in the dataset of per-capita income of Brazilian municipalities between 1970 and 1996.

Bayesian Factor Selection in Dynamic Term Structure Models

This paper discusses Bayesian procedures for factor selection in dynamic term structure models through simulation methods based on Markov Chain Monte Carlo. The number of factors, besides influencing the fitting and prediction of observed yields, is also relevant to features such as the imposition of no-arbitrage conditions. We present a methodology for selecting the best specification in the Nelson-Siegel class of models using Reversible Jump MCMC.Term Structure Models, Model Selection, MCMC, Nelson-Siegel

Searching for merger debris in the Galactic halo: Chemodynamical evidence based on local blue HB stars

We report on the discovery of a group of local A-type blue horizontal-branch (HBA) stars moving in a prograde, comet-like orbit with very similar kinematics and abundances. This serendipitously discovered group contains 5 or 6 local HBA stars venturing very close to the Galactic centre; their [Fe/H] is around -1.7, and they seem to present minimum scatter in at least Mg, Si, Ti, Fe, Al, and Cr abundances. This ``Cometary Orbit Group'' (COG) was found while we were testing a new method to detect the debris associated with the merger of smaller, specific protogalactic entities into our galaxy. The method is primarily intended to identify field HBA stars with similar kinematics and detailed, multi-species abundance patterns as seen among members of a surviving remnant (e.g., omega Centauri). Quite possibly, the COG is the remnant, on a highly decayed orbit, of a merging event that took place in the relatively remote past (i.e., at least one revolution ago).Comment: 4 pages and 2 EPS figures, accepted for publication in Astronomy and Astrophysics Letter