Automated Reasoning over Deontic Action Logics with Finite Vocabularies

In this paper we investigate further the tableaux system for a deontic action logic we presented in previous work. This tableaux system uses atoms (of a given boolean algebra of action terms) as labels of formulae, this allows us to embrace parallel execution of actions and action complement, two action operators that may present difficulties in their treatment. One of the restrictions of this logic is that it uses vocabularies with a finite number of actions. In this article we prove that this restriction does not affect the coherence of the deduction system; in other words, we prove that the system is complete with respect to language extension. We also study the computational complexity of this extended deductive framework and we prove that the complexity of this system is in PSPACE, which is an improvement with respect to related systems.Comment: In Proceedings LAFM 2013, arXiv:1401.056

Fixed Points of the Dissipative Hofstadter Model

The phase diagram of a dissipative particle in a periodic potential and a magnetic field is studied in the weak barrier limit and in the tight-biding regime. For the case of half flux per plaquette, and for a wide range of values of the dissipation, the physics of the model is determined by a non trivial fixed point. A combination of exact and variational results is used to characterize this fixed point. Finally, it is also argued that there is an intermediate energy scale that separates the weak coupling physics from the tight-binding solution.Comment: 4 pages 3 figure

Copper and Barium Abundances in the Ursa Major Moving Group

We present Cu and Ba abundances for 7 G-K dwarf stars, members of the solar-metallicity, 0.3 Gyr old Ursa Major Moving Group. All analyzed member stars show [Ba/Fe] excesses of +0.3-plus, associated with [Cu/Fe] deficiencies of up to -0.23 dex. The present results suggest that there is an anti-correlation between the abundances of Cu and the heavy elements produced by the main component of the neutron capture s-process. Other possible anomalies are Na and C deficiencies with respect to normal solar-metallicity stars. The new data do not confirm the recent claim that the group member HR6094 is a Ba dwarf star.Comment: 8 pages, 6 figures, accepted to MNRA

Electronic compressibility of a graphene bilayer

We calculate the electronic compressibility arising from electron-electron interactions for a graphene bilayer within the Hartree-Fock approximation. We show that, due to the chiral nature of the particles in this system, the compressibility is rather different from those of either the two-dimensional electron gas or ordinary semiconductors. We find that an inherent competition between the contributions coming from intra-band exchange interactions (dominant at low densities) and inter-band interactions (dominant at moderate densities) leads to a non-monotonic behavior of the compressibility as a function of carrier density.Comment: 4 pages, 4 figures. Final versio

Climate Change Threats to Semi-Arid Transhumance Grazing Systems: Proposals for Adaptation in Cabo Verde

Global warming has changed the rainfall regime in the Sahelian region, endangering and widespread poverty and chronic famines in Cape Verde, where rural communities\u27 well-being and food security depend on rainy agriculture. Local responses to rainfall new patterns and scarcity have been livestock reduction with significant revenue losses. Together with dry mist occurrences, these environmental constraints demand to define priority actions to adapt and mitigate climate change\u27s direct impacts. According to fifty household inquiries, this work explains the transhumant grazing practices on a semi-arid plateau in Tarrafal (Santiago, Cabo Verde), prospecting adaptation alternatives for sustainability. We related grazing patterns and pastoral infrastructures to the household\u27s socioeconomics, analyzing the livestock system - composition and management - and their relationship to rangeland utilization. Livestock of male-headed households is different from female-headed ones, mainly cattle in the firsts and goats in the lasts. Herds decreased during the 2016-2018 drought, including equine that lost interest in supporting farmers that abandoned the most remote agriculture patches. Based on a carrying capacity zoning, the geographical analysis assessed existing water supply structures\u27 suitability and designated new ones to improve transhumance effectiveness. New watering points along principal depressions allow to establish forage species - Parkinsonia aculeata, Opuntia ficus-indica, Pannisetum pedicellatum, and Desmanthus virgathus – and reduce stormwater runoff. It also means to improve natural resources by biodiversity conservation and wildlife management. These and other proposals could sustain and adapt the Tarrafal transhumant grazing system to climate change, reduce the farmers\u27 income loss, and improve food security