Proof Outlines as Proof Certificates: A System Description

We apply the foundational proof certificate (FPC) framework to the problem of designing high-level outlines of proofs. The FPC framework provides a means to formally define and check a wide range of proof evidence. A focused proof system is central to this framework and such a proof system provides an interesting approach to proof reconstruction during the process of proof checking (relying on an underlying logic programming implementation). Here, we illustrate how the FPC framework can be used to design proof outlines and then to exploit proof checkers as a means for expanding outlines into fully detailed proofs. In order to validate this approach to proof outlines, we have built the ACheck system that allows us to take a sequence of theorems and apply the proof outline "do the obvious induction and close the proof using previously proved lemmas".Comment: In Proceedings WoF'15, arXiv:1511.0252

Testing the Forecasting Performance of Ibex 35 Option-implied Risk-neutral Densities

Published also as: Documento de Trabajo Banco de España 0504/2005.risk-neutral densities, forecasting performance

Option-Implied Preferences Adjustments and Risk-Neutral Density Forecasts

The main objective of this paper is to analyse the value of information contained in prices of options on the IBEX 35 index at the Spanish Stock Exchange Market. The forward looking information is extracted using implied risk-neutral density functions estimated by a mixture of two-lognormals and three alternative risk-adjustments: the classic power and exponential utility functions and a habit-based specification that allows for a counter-cyclical variation of risk aversion. Our results show that at four-week horizon we can reject the hypothesis that between October 1996 and March 2000 the risk-neutral densities provide accurate predictions of the distributions of future realisations of the IBEX 35 index at a four-week horizon. When forecasting through risk-adjusted densities the performance of this period is statistically improved and we no longer reject that hypothesis. All risk-adjusted densities generate similar forecasting statistics. Then, at least for a horizon of four-weeks, the actual risk adjustment does not seem to be the issue. By contrast, at the one-week horizon risk-adjusted densities do not improve the forecasting ability of the risk-neutral counterparts.forecasting performance, risk adjustment, option implied densities

The last hero by Terry Pratchet: Deconstructing the epic archetype through humour

In his novels, Terry Pratchett has poked fun at almost everything, and through his sense of humour, has offered us his hilarious and critical view of human nature and the world around us. There is hardly a topic - philosophical, metaphysical or what have you, that his brilliant satire hasn't put under the microscope, but what is most astonishing is that his instrument of choice is the parody of epic imaginary worlds fiction. His critical analysis of reality through the distorted mirror that is fantasy fiction is perhaps, putting aside his sensational humour, Pratchett's trademark. With this in mind, instead of giving a general summary of his work, or his view of reality, this article will focus on his perception of literature, specifically, epic literature and the role of the hero. We will be looking at The Last Hero, from his extensive saga, DiscworldTerry Pratchett se ha reído en sus novelas de casi todo y, a través del humor, nos ha ofrecido su particular visión del mundo y de la naturaleza humana. Una visión desternillantemente crítica y lúcida. Difícilmente encontraremos un tema de actualidad o un problema filosófico o metafísico que su brillante sátira no haya puesto bajo el microscopio, pero lo más llamativo del asunto es que el instrumento elegido para ello haya sido la parodia de la narrativa de mundos épicos imaginarios. El análisis crítico de la realidad a través del espejo distorsionado de la literatura fantástica es quizás —dejando a un lado su excepcional sentido del humor— la seña de identidad más característica del genio creativo de Pratchett. Por ello, en este artículo no vamos a ocuparnos del sentido general de la obra del autor británico ni de su visión de la realidad; nos ocuparemos de su percepción de la literatura y, más concretamente la literatura épica a través de su figura principal: el héroe. Para ello, emplearemos como objeto de estudio su obra El último héroe, perteneciente a su extensa saga del Mundodisc

Las elecciones presidenciales filipinas de 2010: entre la inercia y la esperanza de cambio

Las elecciones generales de mayo de 2010 traerán un nuevo presidente después del largo mandato de Gloria Macapal-Arroyo. El futuro mandatario deberá hacer frente a los grandes desafíos en el bajo nivel de gobernanza y las deficiencias en el desarrollo. En mayo de 2010, tras casi una década de gobierno, terminará la era Macapagal-Arroyo. Los sondeos presidenciales dan el primer puesto al liberal “Noynoy” Aquino, beneficiado por la gran popularidad de sus padres, seguido del nacionalista Villar, continuando a mayor distancia el populista Estrada, condenado hace pocos años por cargos de corrupción, y el oficialista Gilberto Teodoro. El desarrollo de la campaña ha puesto en evidencia el poco peso de los partidos políticos frente a las personalidades que concurren en los comicios. A pesar de que las votaciones serán las primeras automatizadas en la historia, siguen persistiendo la violencia política y la amenaza de irregularidades. Los candidatos han centrado su discurso en la solución de la corrupción y la pobreza como principales lacras del país

Structural safety analysis of the aqueducts 'Coll de foix' and 'Capdevila' of the Canal of Aragon and Catalonia

The Canal of Aragon and Catalonia (CAC) is 134 km long and irrigates 105,000 ha (131 irrigation user communities) and it is owned by the River Ebro’s Water Agency. The aqueducts are located between km 67 and 71 of the canal and were designed by the civil engineer Félix de los Ríos Martín in 1907. The cross-section of both aqueducts, Coll de Foix and Capdevila, was extended within the framework of the project by Fernando Hué Herrero in 1962 in order to reach design flows of 26.1 m3/s and 25.7 m3/s, respectively. The structural performance of the aqueducts has been satisfactory; nevertheless, the hydraulic capacity has reduced over the years. As a result, the irrigation user communities have expressed the need to extend the cross-section of the aqueducts to meet the irrigation demands. Given the age of the structure and the different design considerations at the time, it is paramount to verify the structural reliability of the aqueducts in the new load configuration. Therefore, the objective of this contribution is to present the structural safety analysis conducted and to describe the new extended cross-section for both aqueducts (maintaining the original structural typology).Peer ReviewedPostprint (published version

The euro-area government securities markets. Recent developments and implications for market functioning

En este trabajo se analiza la evolucion reciente de los mercados de deuda publica del area del euro y se discuten las principales implicaciones para los bancos centrales y para el funcionamiento de los mercados. La evidencia sugiere que la introduccion del euro ha afecto significativamente a los precios relativos de las deudas soberanas. Tambien que la reduccion en la oferta relativa de bonos soberanos ha tenido, hasta ahora, un efecto limitado en el area del euro, lo que contrasta con lo que ha ocurrido en los mercados norteamericanos. (ad