Sheaf Logic, Quantum Set Theory and the Interpretation of Quantum Mechanics

Based on the Sheaf Logic approach to set theoretic forcing, a hierarchy of Quantum Variable Sets is constructed which generalizes and simplifies the analogous construction developed by Takeuti on boolean valued models of set theory. Over this model two alternative proofs of Takeuti's correspondence, between self adjoint operators and the real numbers of the model, are given. This approach results to be more constructive showing a direct relation with the Gelfand representation theorem, revealing also the importance of these results with respect to the interpretation of Quantum Mechanics in close connection with the Deutsch-Everett multiversal interpretation. Finally, it is shown how in this context the notion of genericity and the corresponding generic model theorem can help to explain the emergence of classicality also in connection with the Deutsch- Everett perspective.Comment: 34 pages, 2 figure

Adaptive Response Modeling Using GIS, Blog 1

Student blog posts from the Great VCU Bike Race Book

Two new Lejeuneaceae records for the Colombian liverwort flora

Two epiphyllous Lejeuneaceae, Cololejeunea surinamensis and Drepanolejeunea polyrhiza, previously known from Amazonian Brazil, are recorded for the first time in Colombia. They were found as epiphylls on understory shrubs in the middle Caquetá area in Colombian Amazonia. Cololejeunea surinamensis was found in the Tierra Firme forests and D. polyrhiza was found in the floodplains of the Caquetá River.Dos especies de Lejeuneaceae epífilas, Cololejeunea surinamensis y Drepanolejeunea polyrhiza, previamente conocidas de los bosques amazónicos de Brasil son reportadas por primera vez para Colombia. Las especies fueron encontradas como epífilas sobre hojas de arbustos del sotobosque en el área del medio Caquetá en la amazonía Colombiana. Cololejeunea surinamensis fue encontrada en los bosques de tierra firme, mientras que D. polyrhiza fue encontrada en los planos inundables del Río Caquetá

Price volatility forecasts for agricultural commodities:an application of volatility models,option implieds and composite approaches forfutures prices of corn and wheat

There has been substantial research effort aimed to forecast futures price return volatilities of financial and commodity assets. Some part of this research focuses on the performance of time-series models (in particular ARCH models) versus option implied volatility models. A significant part of the literature related to this topic shows that volatility forecast accuracy is not easy to estimate regardless of the forecasting model applied. This paper examines the volatility accuracy of volatility forecast models for the case of corn and wheat futures price returns. The models applied here are a univariate GARCH, a multivariate ARCH (the BEKK model), an option implied and a composite forecast model. The composite model includes time-series (historical) and option implied volatility forecasts. The results show that the option implied model is superior to the historical models in terms of accuracy and that the composite forecast model was the most accurate one (compared to the alternative models) having the lowest mean-square-errors. Given these findings it is recommended to use a composite forecast model if both types of data are available i.e. the time-series (historical) and the option implied. In addition, the results of this paper are consistent to that part of the literature that emphasizes the difficulty on being accurate about forecasting asset price return volatility. This is because the explanatory power (coefficient of determination) calculated in the forecast regressions were relatively low.Agricultural commodities, BEKK model, multivariate GARCH, Samuelson hypothesis, theory of storage.

Can Reforms be Made Sustainable?: Analysis and Design Considerations for the Electricity Sector

This document discusses and proposes a new framework to improve the quality of programs supporting such reforms in Latin America. Firstly, it responds to the risk that the reforms in the region might be reversed, which might originate in the lack of public support for privatization and the succession of crises and events in the recent past (problems of supply in Chile and Brazil; price peaks in the spot market in El Salvador; the commercial unsustainability of the pool in Colombia; the ENRON/Andersen scandal, and the Argentine crisis among others), that have provided the enemies of reform with new political space. Secondly, it responds to evidence that the consolidation of sector reforms is not automatic, involving as it does the simultaneous creation of traditions of respect for the rights of investors and consumers. Finally, this paper partly builds upon the experience gathered from a project supporting the sustainability of electricity reform in Colombia, Guatemala and Honduras.Urban Development, Energy & Mining, electrcity sector, sustainable design, privatization, electricity reform

The Theory of Storage and Price Dynamics of Agricultural Commodity Futures: the Case of Corn and Wheat

Using a restricted version of the BEKK model it is tested an implication of the theory of storage that supply-and-demand fundamentals affect the price dynamics of agricultural commodities. The commodities under analysis are corn and wheat. An interest-storage-adjusted-spread was used as a proxy variable for supply-and-demand fundamentals to test the aforementioned implication for both commodities. It is also tested the Samuelson hypothesis that spot prices have higher volatility than futures prices. It is found that the interest-storage-adjusted-spread has had a statistically significant positive influence on the spot and futures returns for both commodities. Likewise, the results also show that spot price returns have higher volatility compared to futures price returns which is consistent with the Samuelson hypothesis. The results of the aforementioned tests are consistent with both theories and with the existing literature related to commodity futures.Agricultural commodities, BEKK model, multivariate GARCH, Samuelson hypothesis, theory of storage

Valuation relationships under growth

One of the most important topics onvaluation is the appropriate relationshipsbetween cash flows and rateof returns. I review those relationshipsunder the premise, by Myers(1974), of the cost of debt as the rightdiscount for the tax shield. Differenthypotheses have been advanced for the tax shield risk, each one producingdifferent valuation results, especiallywhen growth is present. Theconsequences of some common mistakeson valuation are explored. Onedifference between the results I obtainand results by others is the presenceof growth in the expressions forthe discount rates, which can be usedto asses the empirical validity of eachof the approaches.Cost of capital, return on equity, taxshield value, levered beta.