Italian Event Detection Goes Deep Learning

This paper reports on a set of experiments with different word embeddings to initialize a state-of-the-art Bi-LSTM-CRF network for event detection and classification in Italian, following the EVENTI evaluation exercise. The net- work obtains a new state-of-the-art result by improving the F1 score for detection of 1.3 points, and of 6.5 points for classification, by using a single step approach. The results also provide further evidence that embeddings have a major impact on the performance of such architectures.Comment: to appear at CLiC-it 201

Accounting for Cross-Country Income Differences

Why are some countries so much richer than others? Development Accounting is a first-pass attempt at organizing the answer around two proximate determinants: factors of production and efficiency. It answers the question "how much of the cross-country income variance can be attributed to differences in (physical and human) capital, and how much to differences in the efficiency with which capital is used?" Hence, it does for the cross-section what growth accounting does in the time series. The current consensus is that efficiency is at least as important as capital in explaining income differences. I survey the data and the basic methods that lead to this consensus, and explore several extensions. I argue that some of these extensions may lead to a reconsideration of the evidence.

Peak algebras, paths in the Bruhat graph and Kazhdan-Lusztig polynomials

We give a new characterization of the peak subalgebra of the algebra of quasisymmetric functions and use this to construct a new basis for this subalgebra. As an application of these results we obtain a combinatorial formula for the Kazhdan-Lusztig polynomials which holds in complete generality and is simpler and more explicit than any existing one. We then show that, in a certain sense, this formula cannot be simplified.Comment: 31 page

Gelfand models and Robinson-Schensted correspondence

In [F. Caselli, Involutory reflection groups and their models, J. Algebra 24 (2010), 370--393] there is constructed a uniform Gelfand model for all non-exceptional irreducible complex reflection groups which are involutory. Such model can be naturally decomposed into the direct sum of submodules indexed by $S_n$-conjugacy classes, and we present here a general result that relates the irreducible decomposition of these submodules with the projective Robinson-Schensted correspondence. This description also reflects in a very explicit way the existence of split representations for these groups.Comment: 23 page

Special matchings in Coxeter groups

Special matchings are purely combinatorial objects associated with a partially ordered set, which have applications in Coxeter group theory. We provide an explicit characterization and a complete classification of all special matchings of any lower Bruhat interval. The results hold in any arbitrary Coxeter group and have also applications in the study of the corresponding parabolic Kazhdan--Lusztig polynomials.Comment: 19 page

A simple characterization of special matchings in lower Bruhat intervals

We give a simple characterization of special matchings in lower Bruhat intervals (that is, intervals starting from the identity element) of a Coxeter group. As a byproduct, we obtain some results on the action of special matchings.Comment: accepted for publication on Discrete Mathematic

Compressible streaming instabilities in rotating thermal viscous objects

We study electromagnetic streaming instabilities in thermal viscous regions of rotating astrophysical objects, such as, protostellar and protoplanetary magnetized accretion disks, molecular clouds, their cores, and elephant trunks. The obtained results can also be applied to any regions of interstellar medium, where different equilibrium velocities between charged species can arise. We consider a weakly and highly ionized three-component plasma consisting of neutrals and magnetized electrons and ions. The vertical perturbations along the background magnetic field are investigated. The effect of perturbation of collisional frequencies due to density perturbations of species is taken into account. The growth rates of perturbations are found in a wide region of wave number spectrum for media, where the thermal pressure is larger than the magnetic pressure. It is shown that in cases of strong collisional coupling of neutrals with ions the contribution of the viscosity is negligible.Comment: Accepted for publication in "Astrophysical Journal