Positive Entropy Through Pointwise Dynamics

We define some pointwise properties of topological dynamical systems and give pointwise conditions for such a system possesses positive topological entropy. We give sufficient conditions to obtain positive topological entropy for maps which are approximated by maps with the shadowing property in a uniform way.Comment: 8 page

Fractional Exclusion Statistics and the Universal Quantum of Thermal Conductance: A Unifying Approach

We introduce a generalized approach to one-dimensional (1D) conduction based on Haldane's concept of fractional statistics (FES) and the Landauer formulation of transport theory. We show that the 1D ballistic thermal conductance is independent of the statistics obeyed by the carriers and is governed by the universal quantum $(\pi^2 k^2_B T)/(3h)$ in the degenerate regime. By contrast, the electrical conductance of FES systems is statistics-dependent. This work unifies previous theories of electron and phonon systems and explains an interesting commonality in their behavior.Comment: 7 pages (Tex source file) + 2 ps figure

Universities and economically depressed regions: how ‘attractive’ is the University of Évora?

As it is well known, universities constitute sources of important multiplier effects on the economic activity of the regions where they are located. Plainly, in the case of economically depressed regions, the importance of universities becomes higher. This is certainly the case with the University of Évora as being located in the Alentejo, one of the poorest regions at the European Union level, it have been contributing to the attraction of economic activity. Besides the direct effect on the economic activity of the Alentejo, the University of Évora also have been exerting demographic effects, on the one hand, by allowing people to become residents on the region and, on the other hand, by attracting students which normally become residents during the period of time required to conclude their academic degrees. The paper explores this last effect by the analysis of how and why the University of Évora is chosen by students coming from all over the country (and from abroad). This analysis, which is done through the use of econometric techniques, also indicates which are the decisive factors for the attraction exerted by the University of Évora, in general, and by its degree courses, in particular, on the candidate students. KEYWORDS: Decision Analysis, Discrete Choice Models, Portugal, Universities JEL CLASSIFICATION: C21, R12, R23

Universities and economically depressed regions: how strong is the influence of the University of Évora in the regional human capital?

Universities are a source of significant multiplier effects upon local and regional economic activity. In the case of economically depressed regions, the importance of universities is enhanced. This is the case of the University of Évora, located in Alentejo (Portugal), one of the poorest EU regions, where it has been a key element to the dynamics of local economic activity. Apart from a direct impact upon the economic activity of Alentejo, the University of Évora has also been promoting demographic effects, both by encouraging new permanent residents to the area, and also by attracting a fluctuating mass of students which usually become residents during the period of time required to obtain their degrees. In this paper a population of former University of Évora students is analysed with the objective of answering questions related to their connections with the city of Évora, and its surrounding areas, after graduation, and also to analyse their impact upon the regional economic activity and their contribution to the improvement of the regional labour force. The University of Évora is also assessed from the perspective of its relationships with other regional agents, in terms of knowledge and innovation transference. It is concluded that one of the main contributions of the University of Évora to the regional economic activity occurs via the employment of its graduates in local and regional schools, enterprises and other institutions. KEY-WORDS: Human Capital, Regional Development, Universities JEL CLASSIFICATION: O15, O18, R12

Non-linear generalization of the sl(2) algebra

We present a generalization of the sl(2) algebra where the algebraic relations are constructed with the help of a general function of one of the generators. When this function is linear this algebra is a deformed sl(2) algebra. In the non-linear case, the finite dimensional representations are constructed in two different ways. In the first case, which provides finite dimensional representations only for the non-linear case, these representations come from solutions to a dynamical equation and we show how to construct explicitly these representations for a general quadratic non-linear function. The other type of finite dimensional representation comes from solutions to a cut condition equation. We give examples of solutions of this type in the non-linear case as well.Comment: 13 pages, 3 EPS figures, Late

Quantum energy flow, dissipation and decoherence in mesoscopic dielectric structures

We first present a summary of recent results concerning the phononic energy transport properties of mesoscopic, suspended dielectric wires. We then discuss some related open problems concerning the fundamental lower limits on the vibrational damping rates of submicron-sized cantilever structures and also the possibility to create and detect quantum superpositions of spatially separated states for such structures.Comment: To appear in Physica B, Proceedings of the 9th International Conference on Phonon Scattering (Phonons 98

Interactive Unawareness Revisited

We analyze a model of interactive unawareness introduced by Heifetz, Meier and Schipper (HMS). We consider two axiomatizations for their model, which capture different notions of validity. These axiomatizations allow us to compare the HMS approach to both the standard (S5) epistemic logic and two other approaches to unawareness: that of Fagin and Halpern and that of Modica and Rustichini. We show that the differences between the HMS approach and the others are mainly due to the notion of validity used and the fact that the HMS is based on a 3-valued propositional logic.Comment: 26 page

Characterizing the NP-PSPACE Gap in the Satisfiability Problem for Modal Logic

There has been a great of work on characterizing the complexity of the satisfiability and validity problem for modal logics. In particular, Ladner showed that the validity problem for all logics between K, T, and S4 is {\sl PSPACE}-complete, while for S5 it is {\sl NP}-complete. We show that, in a precise sense, it is \emph{negative introspection}, the axiom \neg K p \rimp K \neg K p, that causes the gap. In a precise sense, if we require this axiom, then the satisfiability problem is {\sl NP}-complete; without it, it is {\sl PSPACE}-complete.Comment: 6 page