Artículos con la etiqueta ‘ciencias de la computación’

A Note on the Fixed Points in Justification Logics

Por • 26 mar, 2014 • Category: Educacion

In this note we study the effect of adding fixed points to justification logics. We introduce two extensions of justification logics: extensions by fixed point (or diagonal) operators, and extensions by least fixed points. The former is a justification version of Smory\`{n}ski’s Diagonalization Operator Logic, and the latter is a justification version of Kozen’s modal μ -calculus. We also introduce fixed point extensions of Fitting’s quantified logic of proofs, and formalize the Knower Paradox and the Surprise Test Paradox in these extensions. By interpreting a surprise statement as a statement for which there is no justification, we give a solution to the self-reference version of the Surprise Test Paradox in quantified logic of proofs.



Selection and Influence in Cultural Dynamics

Por • 6 may, 2013 • Category: sociologia

One of the fundamental principles driving diversity or homogeneity in domains such as cultural differentiation, political affiliation, and product adoption is the tension between two forces: influence (the tendency of people to become similar to others they interact with) and selection (the tendency to be affected most by the behavior of others who are already similar). Influence tends to promote homogeneity within a society, while selection frequently causes fragmentation. When both forces are in effect simultaneously, it becomes an interesting question to analyze which societal outcomes should be expected.



How hard is it to control an election by breaking ties?

Por • 29 abr, 2013 • Category: sociologia

We study the computational complexity of the problem of controlling the result of an election by breaking ties. When the chair is only asked to break ties to choose between one of the co-winners, the problem is trivially easy. However, in multi-round elections like STV, we prove that it can be NP-hard for the chair to compute how to break ties to ensure a given result. Our results contain several surprises. For example, whilst it is NP-hard to compute a manipulating vote for a multi-round rule like Nanson, it is polynomial for the chair to control the result by breaking ties. As a second example, it can be NP-hard to control an election by breaking ties even with a simple two-stage voting rule.



The Mathematician’s Bias – and the Return to Embodied Computation

Por • 22 abr, 2013 • Category: Leyes

There are growing uncertainties surrounding the classical model of computation established by G\”odel, Church, Kleene, Turing and others in the 1930s onwards. The mismatch between the Turing machine conception, and the experiences of those more practically engaged in computing, has parallels with the wider one between science and those working creatively or intuitively out in the ‘real’ world. The scientific outlook is more flexible and basic than some understand or want to admit. The science is subject to limitations which threaten careers. We look at embodiment and disembodiment of computation as the key to the mismatch, and find Turing had the right idea all along – amongst a productive confusion of ideas about computation in the real and the abstract worlds.



Paradoxes in Social Networks with Multiple Products

Por • 4 feb, 2013 • Category: Opinion

Recently, we introduced in arXiv:1105.2434 a model for product adoption in social networks with multiple products, where the agents, influenced by their neighbours, can adopt one out of several alternatives. We identify and analyze here four types of paradoxes that can arise in these networks. To this end, we use social network games that we recently introduced in arXiv:1211.5938. These paradoxes shed light on possible inefficiencies arising when one modifies the sets of products available to the agents forming a social network. One of the paradoxes corresponds to the well-known Braess paradox in congestion games and shows that by adding more choices to a node, the network may end up in a situation that is (weakly) worse for everybody.



Knowledge epidemics and population dynamics models for describing idea diffusion

Por • 6 ene, 2012 • Category: Opinion

The diffusion of ideas is often closely connected to the creation and diffusion of knowledge and to the technological evolution of society. Because of this, knowledge creation, exchange and its subsequent transformation into innovations for improved welfare and economic growth is briefly described from a historical point of view. Next, three approaches are discussed for modeling the diffusion of ideas in the areas of science and technology, through (i) deterministic, (ii) stochastic, and (iii) statistical approaches. These are illustrated through their corresponding population dynamics and epidemic models relative to the spreading of ideas, knowledge and innovations. The deterministic dynamical models are considered to be appropriate for analyzing the evolution of large and small societal, scientific and technological systems when the influence of fluctuations is insignificant. Stochastic models are appropriate when the system of interest is small but when the fluctuations become significant for its evolution. Finally statistical approaches and models based on the laws and distributions of Lotka, Bradford, Yule, Zipf-Mandelbrot, and others, provide much useful information for the analysis of the evolution of systems in which development is closely connected to the process of idea diffusion.



Education for Computational Science and Engineering

Por • 24 ago, 2011 • Category: Educacion

Computational science and engineering (CSE) has been misunderstood to advance with the construction of enormous computers. To the contrary, the historical record demonstrates that innovations in CSE come from improvements to the mathematics embodied by computer programs. Whether scientists and engineers become inventors who make these breakthroughs depends on circumstances and the interdisciplinary extent of their educations. The USA currently has the largest CSE professorate, but the data suggest this prominence is ephemeral.



Education for Computational Science and Engineering

Por • 25 feb, 2011 • Category: Educacion

For decades, CSE has been misunderstood to require massive computers, whereas breakthroughs in CSE have historically been the mathematical programs of computing rather than the machines themselves.