Observer dependent entanglement

Understanding the observer-dependent nature of quantum entanglement has been a central question in relativistic quantum information. In this paper we will review key results on relativistic entanglement in flat and curved spacetime and discuss recent work which shows that motion and gravity have observable effects on entanglement between localized systems.Comment: Ivette Fuentes previously published as Ivette Fuentes-Guridi and Ivette Fuentes-Schulle

Skill-biased Technology Adoption: Evidence for the Chilean manufacturing sector

We examine the evolution of the demand for skilled workers relative to unskilled workers in the Chilean manufacturing sector following Chile’s liberalization of trade in the late 1970’s. Following such trade reforms, the standard Heckscher-Olin model predicts that a low labor-cost country like Chile should experience an increased demand for low skilled workers relative to high skilled workers. Alternatively, if trade liberalization is associated with the adoption of new technologies, and technology is skill-biased, the relative demand for skilled workers may rise. Using a newly available plant-level data set that spans the sixteen year period 1979-1995, we find that the relative demand for skilled workers rose sharply during the 1979-1986 period and then stabilized. The sharp increase in demand for skilled workers coincided with an increased propensity to adopt new technologies as measured by patent usage. Plant-level analysis of labor demand confirms a significant relationship between the relative demand for skilled workers and technology adoption as measured by patent usage and other technology indicators. Our results suggest that skill-biased technological change is a significant determinant of labor demand and wage structures in developing economies.

Are constant loop widths an artifact of the background and the spatial resolution?

We study the effect of the coronal background in the determination of the diameter of EUV loops, and we analyze the suitability of the procedure followed in a previous paper (L\'opez Fuentes, Klimchuk & D\'emoulin 2006) for characterizing their expansion properties. For the analysis we create different synthetic loops and we place them on real backgrounds from data obtained with the Transition Region and Coronal Explorer (\textit{TRACE}). We apply to these loops the same procedure followed in our previous works, and we compare the results with real loop observations. We demonstrate that the procedure allows us to distinguish constant width loops from loops that expand appreciably with height, as predicted by simple force-free field models. This holds even for loops near the resolution limit. The procedure can easily determine when loops are below resolution limit and therefore not reliably measured. We find that small-scale variations in the measured loop width are likely due to imperfections in the background subtraction. The greatest errors occur in especially narrow loops and in places where the background is especially bright relative to the loop. We stress, however, that these effects do not impact the ability to measure large-scale variations. The result that observed loops do not expand systematically with height is robust.Comment: Accepted for publication in Ap

Tree-structure Expectation Propagation for Decoding LDPC codes over Binary Erasure Channels

Expectation Propagation is a generalization to Belief Propagation (BP) in two ways. First, it can be used with any exponential family distribution over the cliques in the graph. Second, it can impose additional constraints on the marginal distributions. We use this second property to impose pair-wise marginal distribution constraints in some check nodes of the LDPC Tanner graph. These additional constraints allow decoding the received codeword when the BP decoder gets stuck. In this paper, we first present the new decoding algorithm, whose complexity is identical to the BP decoder, and we then prove that it is able to decode codewords with a larger fraction of erasures, as the block size tends to infinity. The proposed algorithm can be also understood as a simplification of the Maxwell decoder, but without its computational complexity. We also illustrate that the new algorithm outperforms the BP decoder for finite block-siz