Representing Default Logic in Modal Logic

The nonmonotonic logic called Default Logic is shown to be representable in a monotonic Modal Quantificational Logic whose modal laws are stronger than S5. Specifically, it is proven that a set of sentences of First Order Logic is a fixed-point of the fixed-point equation of Default Logic with an initial set of axioms and defaults if and only if the meaning or rather disquotation of that set of sentences is logically equivalent to a particular modal functor of the meanings of that initial set of sentences and of the sentences in those defaults. This result is important because the modal representation allows the use of powerful automatic deduction systems for Modal Logic and because unlike the original Default Logic, it is easily generalized to the case where quantified variables may be shared across the scope of the components of the defaults thus allowing such defaults to produce quantified consequences. Furthermore, this generalization properly treats such quantifiers since both the Barcan Formula and its converse hold.

On the Relationship between Quantified Reflective Logic and Quantified Default Logic

Reflective Logic and Default Logic are both generalized so as to allow universally quantified variables to cross modal scopes whereby the Barcan formula and its converse hold. This is done by representing both the fixed-point equation for Reflective Logic and the fixed-point equation for Default both as necessary equivalences in the Modal Quantificational Logic Z. and then inserting universal quantifiers before the defaults. The two resulting systems, called Quantified Reflective Logic and Quantified Default Logic, are then compared by deriving metatheorems of Z that express their relationships. The main result is to show that every solution to the equivalence for Quantified Default Logic is a strongly grounded solution to the equivalence for Quantified Reflective Logic. It is further shown that Quantified Reflective Logic and Quantified Default Logic have exactly the same solutions when no default has an entailment condition.

Dividend increases and initiations and default risk in equity returns

This study extends the Grullon, Michaely, and Swaminathan (2002) analysis by incorporating default risk. Using data for firms that either increased or initiated cash dividend payments during the 23-year period 1986-2008, we find reduction in default risk. This reduction is shown to be a priced risk factor beyond the Fama and French (1993) risk measures, and it explains the dividend payment decision and the positive market reaction around dividend increases and initiations. Further analysis reveals that the reduction in default risk is a significant factor in explaining the 3-year excess returns following dividend increases and initiations. © Copyright Michael G. Foster School of Business, University of Washington 2011.

'Digital by Default' and the 'hard to reach' : exploring solutions to digital exclusion in remote rural areas

The research reported here is supported by the award made by the RCUK Digital Economy programme to the dot.rural Digital Economy Hub [award reference: EP/G066051/1].

Explanation, Dialogue and Default Logic

La distinción entre argumentación y explicación es una tarea complicada pero necesaria por diversas razones. Una de ellas es la necesidad de incorporar la explicación en un movimiento del diálogo como resultado de una obligación dialéctica. Se propusieron distintos sistemas de diálogo que exploran la distinción enfatizando aspectos pragmáticos. En el presente trabajo me ocupo de aspectos estructurales de la explicación analizados en el marco de la lógica por defecto que permite caracterizar ciertas objeciones en el diálogo. Asimismo, considero que la versión operacional de la lógica por defecto constituye una aproximaciónadecuada en la construcción de la explicación y en la representación de la instancia de diálogo en el intercambio dialéctico

Default Invariance: Naïve Category of Law and Finance

Default invariance is the idea that default does not change at any scale of law and finance. Default is a conserved quantity in a universe where fundamental principles of law and finance operate. It exists at the micro-level as part of the fundamental structure of every financial transaction, and at the macro- level, as a fixed critical point within the relatively stable phases of the law and finance cycle. A key point is that default is equivalent to maximizing uncertainty at the micro-level and at the macro-level, is equivalent to the phase transition where unbearable fluctuations occur in all forms of risk transformation, including maturity, liquidity and credit. As such, default invariance is the glue that links the micro and macro structures of law and finance. In this essay, we apply naïve category theory (NCT), a type of mapping logic, to these types of phenomena. The purpose of using NCT is to introduce a rigorous (but simple) mathematical methodology to law and finance discourse and to show that these types of structural considerations are of prime practical importance and significance to law and finance practitioners. These mappings imply a number of novel areas of investigation. From the micro- structure, three macro-approximations are implied. These approximations form the core analytical framework which we will use to examine the phenomena and hypothesize rules governing law and finance. Our observations from these approximations are grouped into five findings. While the entirety of the five findings can be encapsulated by the three approximations, since the intended audience of this paper is the non-specialist in law, finance and category theory, for ease of access we will illustrate the use of the mappings with relatively common concepts drawn from law and finance, focusing especially on financial contracts, derivatives, Shadow Banking, credit rating agencies and credit crises.

Estimating dynamic models with aggregate shocks and an application to mortgage default in Colombia

We estimate a dynamic model of mortgage default for a cohort of Colombian debtors between 1997 and 2004. We use the estimated model to study the effects on default of a class of policies that affected the evolution of mortgage balances in Colombia during the 1990's. We propose a framework for estimating dynamic behavioral models accounting for the presence of unobserved state variables that are correlated across individuals and across time periods. We extend the standard literature on the structural estimation of dynamic models by incorporating an unobserved common correlated shock that affects all individuals' static payoffs and the dynamic continuation payoffs associated with different decisions. Given a standard parametric specification the dynamic problem, we show that the aggregate shocks are identified from the variation in the observed aggregate behavior. The shocks and their transition are separately identified, provided there is enough cross-sectionavl ariation of the observeds tates.

Trends in vertical movement of hexazinone herbicide considering typic eutrorthox soil of Espraiado´s stream cultivated with sugar-cane crop - local and default data scenarios.

2009

Explanation, Dialogue and Default Logic

La distinción entre argumentación y explicación es una tarea complicada pero necesaria por diversas razones. Una de ellas es la necesidad de incorporar la explicación en un movimiento del diálogo como resultado de una obligación dialéctica. Se propusieron distintos sistemas de diálogo que exploran la distinción enfatizando aspectos pragmáticos. En el presente trabajo me ocupo de aspectos estructurales de la explicación analizados en el marco de la lógica por defecto que permite caracterizar ciertas objeciones en el diálogo. Asimismo, considero que la versión operacional de la lógica por defecto constituye una aproximaciónadecuada en la construcción de la explicación y en la representación de la instancia de diálogo en el intercambio dialéctico

Explanation, Dialogue and Default Logic

La distinción entre argumentación y explicación es una tarea complicada pero necesaria por diversas razones. Una de ellas es la necesidad de incorporar la explicación en un movimiento del diálogo como resultado de una obligación dialéctica. Se propusieron distintos sistemas de diálogo que exploran la distinción enfatizando aspectos pragmáticos. En el presente trabajo me ocupo de aspectos estructurales de la explicación analizados en el marco de la lógica por defecto que permite caracterizar ciertas objeciones en el diálogo. Asimismo, considero que la versión operacional de la lógica por defecto constituye una aproximaciónadecuada en la construcción de la explicación y en la representación de la instancia de diálogo en el intercambio dialéctico

The EU ban on uncovered sovereign credit default swaps: assessing impacts on liquidity, volatility and price discovery

This article addresses the effects of the prohibition against naked CDS buying implemented by the European Union in November 2012. Three aspects of market quality are analyzed: liquidity, volatility, and price informativeness. Overall, our results suggest that the ban produced negative effects on liquidity and price informativeness. First, we find that in territories within the scope of the EU regulation, the bid–ask spreads on sovereign CDS contracts rose after the ban, but fell for countries outside its bounds. Open interest declined for both groups of CDS reference entities in our sample, but significantly more in the constraint group. Price delay increased more prominently for countries affected by the ban, whereas price precision decreased for these countries while increasing for CDSs written on other sovereign reference entities. Most notably, our findings indicate that hese negative effects were more pronounced amid reference entities exhibiting lower credit risk. With respect to volatility, the evidence suggests that the ban was successful in stabilizing the CDS market in that volatility decreased, particularly for contracts written on riskier CDS entities.

Determination of preventive maintenance lead time using hybrid analysis

The time for conducting Preventive Maintenance (PM) on an asset is often determined using a predefined alarm limit based on trends of a hazard function. In this paper, the authors propose using both hazard and reliability functions to improve the accuracy of the prediction particularly when the failure characteristic of the asset whole life is modelled using different failure distributions for the different stages of the life of the asset. The proposed method is validated using simulations and case studies.

Exploring the effectiveness of virtual product placement on recall and recognition of new brands

This paper investigates the effectiveness of virtual product placement as a marketing tool by examining the relationship between brand recall and recognition and virtual product placement. It also aims to address a gap in the existing academic literature by focusing on the impact of product placement on recall and recognition of new brands. The growing importance of product placement is discussed and a review of previous research on product placement and virtual product placement is provided. The research methodology used to study the recall and recognition effects of virtual product placement are described and key findings presented. Finally, implications are discussed and recommendations for future research provided.

Interactive architecture

This chapter explores the development of concepts of interactive environments by comparing two major projects that frame the period of this book. The Fun Palace of 1960 and the Generator of 1980 both proposed interactive environments responsive to the needs and behaviour of their users, but the contrast in terms of the available technology and what it enabled could not be more marked. The Fun Palace broke new architectural, organizational and social ground and was arguably the first proposition for cybernetic architecture; the Generator demonstrated how it could be achieved. Both projects are now acknowledged as seminal architectural propositions of the twentieth century, and both were designed by Cedric Price.