New tools for Loop Quantum Gravity with applications to a simple model

Loop Quantum Gravity is now a well established approach to quantum gravity. One of the main challenges still faced by the theory is constructing a consistent dynamics which would lead back to the standard dynamics of the gravitational field at large scales. Here we will review the recent U(N) framework for Loop Quantum Gravity and the new spinor representation (that provides a classical setting for the U(N) framework). Then, we will apply these techniques to a simple model in order to propose a dynamics for a symmetry reduced sector of the theory. Furthermore, we will explore certain analogies of this model with Loop Quantum Cosmology.Comment: 4 pages, to appear in Proceedings of Spanish Relativity Meeting 2011 (ERE 2011) held in Madrid, Spai

Global bifurcation of homoclinic trajectories of discrete dynamical systems

We prove the existence of an unbounded connected branch of nontrivial homoclinic trajectories of a family of discrete nonautonomous asymptotically hyperbolic systems parametrized by a circle under assumptions involving the topological properties of the asymptotic stable bundles

The impact of government debt on economic growth: an overview for Latin America

This paper investigates the impact of government debt on GDP in 16 Latin American economies, namely Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Dominican Republic, Honduras, Mexico,Nicaragua, Panama, Paraguay, Peru, Uruguay and Venezuela over a period of about fifty years (1960-2015). The short-run impact of debt on GDP growth is positive, but decreases to close to zero beyond public debt-to-GDP ratios between 64 and 71% (i.e. up to this threshold, additional debt has a stimulating impact on growth). The institutional variable selected shows the expected sign suggesting that countries with democratic governments exhibit higher growth rates.http://www.econ.unipg.it/files/generale/wp_2017/wp_28_2017_jacobo_jalile.pdfpublishedVersionFil: Jacobo, Alejandro D. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Fil: Jalile, Ileana R. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Economía, Econometrí

Analyzing trade policies: The case of contemporary protectionism in MERCOSUR

This paper explores the macro and microeconomic determinants of tariff and anti dumping (AD) initiations for the four founding members of MERCOSUR using pre and post-2008 crisis trade and protection data. Among other findings, the study reveals that Intra-industry trade is a source of revenues for governments and that crisis did not increase protectionism in countries where powerful exporters demand cheap imported inputs, but it did where this lobby is not powerful enough to overcome the need to raise public revenues. Concerning non-tariff barriers, the countries in the sample show a positive relationship between AD initiations and the tariff level. This could indicate that tariff and non-tariff instruments are both complementary. Finally, an appreciation of the currency makes an AD initiation more likely to occur in some countries of the sample. However, the crisis has not reinforced the relationship between an appreciation/depreciation on the probability of an initiation of an AD procedure.http://www.asepelt.org/modules.php?name=Content&pa=showpage&pid=63Fil: Jacobo, Alejandro D. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Fil: Jalile, Ileana R. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Economía, Econometrí

Ionic conductivity of nanocrystalline yttria-stabilized zirconia: Grain boundary and size effects

9 páginas, 6 figuras, 3 tablas.-- PACS number(s): 66.30.H-.-- et al.We report on the effect of grain size on the ionic conductivity of yttria-stabilized zirconia samples synthesized by ball milling. Complex impedance measurements, as a function of temperature and frequency are performed on 10 mol % yttria-stabilized zirconia nanocrystalline samples with grain sizes ranging from 900 to 17 nm. Bulk ionic conductivity decreases dramatically for grain sizes below 100 nm, although its activation energy is essentially independent of grain size. The results are interpreted in terms of a space-charge layer resulting from segregation of mobile oxygen vacancies to the grain-boundary core. The thickness of this space-charge layer formed at the grain boundaries is on the order of 1 nm for large micron-sized grains but extends up to 7 nm when decreasing the grain size down to 17 nm. This gives rise to oxygen vacancies depletion over a large volume fraction of the grain and consequently to a significant decrease in oxide-ion conductivity.We acknowledge financial support by Junta de Comunidades de Castilla-La Mancha through Project No. PAI-05-013, by CAM under Grant No. S2009/MAT-1756 (Phama), by Spanish MICINN through Grants No. MAT2008-06517-C02, No. MAT2008-06542-C04, and No. FIS2009-12964- C05-04, and Consolider Ingenio 2010 under Grant No. CSD2009-00013 (Imagine).Peer reviewe

On the time decay for the MGT-type porosity problems

In this work we study three different dissipation mechanisms arising in the so-called Moore-Gibson-Thompson porosity. The three cases correspond to the MGT-porous hyperviscosity (fourth-order term), the MGT-porous viscosity (second-order term) and the MGT-porous weak viscosity (zerothorder term). For all the cases, we prove that there exists a unique solution to the problem and we analyze the resulting point spectrum. We also show that there is an exponential energy decay for the first case, meanwhile for the second and third case only a polynomial decay is found. Finally, we present some one-dimensional numerical simulations to illustrate the behaviour of the discrete energy for each caseThis paper is part of the projects PGC2018-096696-B-I00 and PID2019-105118GB-I00, funded by the Spanish Ministry of Science, Innovation and Universities and FEDER "A way to make Europe".Peer ReviewedPostprint (author's final draft

Time decay for porosity problems

In this paper, we numerically study porosity problems with three different dissipa- tion mechanisms. The root behavior is analyzed for each case. Then, by using the finite element method and the Newmark- scheme, fully discrete approximations are introduced and some numerical results are described to show the energy evolution depending on the viscosity coefficient.Peer ReviewedPostprint (published version

Chaos-Based Optical Communications: Encryption Versus Nonlinear Filtering

7 pages, 8 figures.Several chaos encoding schemes codify the message in such a way that the mean value of the transmitted signal (carrier with the message) is different for bits “0” and “1”. We present a nonlinear filtering method that is able to detect very small changes in the mean value of a signal and therefore recover this kind of messages if its amplitude is larger than the chaotic fluctuations in the mean over the length of a bit.We also introduce a new codification method in which the mean value of the transmitted signal, over the length of each bit, is preserved and we show how it is able to beat the decryption scheme.This work was supported by MEC (Spain) and Feder under Projects TEC2006-1009/MIC (PhoDECC), TEC-2006-28105-E, and FIS2007-60327 (FISICOS); from EC Project PICASSO Grant IST-2005- 34551. The work of M. C. Soriano was supported by the MEC under a “Juan de la Cierva” contract.Peer reviewe

Review of Top Quark Physics

We present an overview of Top Quark Physics - from what has been learned so far at the Tevatron, to the searches that lie ahead at present and future colliders. We summarize the richness of the measurements and discuss their possible impact on our understanding of the Standard Model by pointing out their key elements and limitations. When possible, we discuss how the top quark may provide a connection to new or unexpected physics.Comment: 84 pp. With permission from the Annual Review of Nuclear & Particle Science. Final version of this material is scheduled to appear in the Annual Review of Nuclear & Particle Science Vol. 53, to be published in December 2003 by Annual Reviews (http://www.annualreviews.org