Local tropical linear spaces

In this paper we study general tropical linear spaces locally: For any basis B of the matroid underlying a tropical linear space L, we define the local tropical linear space L_B to be the subcomplex of L consisting of all vectors v that make B a basis of maximal v-weight. The tropical linear space L can then be expressed as the union of all its local tropical linear spaces, which we prove are homeomorphic to Euclidean space. Local tropical linear spaces have a simple description in terms of polyhedral matroid subdivisions, and we prove that they are dual to mixed subdivisions of Minkowski sums of simplices. Using this duality we produce tight upper bounds for their f-vectors. We also study a certain class of tropical linear spaces that we call conical tropical linear spaces, and we give a simple proof that they satisfy Speyer's f-vector conjecture.Comment: 13 pages, 1 figure. Some results are stated in a bit more generality. Minor corrections were also mad

Formalising Confluence in PVS

Confluence is a critical property of computational systems which is related with determinism and non ambiguity and thus with other relevant computational attributes of functional specifications and rewriting system as termination and completion. Several criteria have been explored that guarantee confluence and their formalisations provide further interesting information. This work discusses topics and presents personal positions and views related with the formalisation of confluence properties in the Prototype Verification System PVS developed at our research group.Comment: In Proceedings DCM 2015, arXiv:1603.0053

Financial Globalization, Economic Growth, and Macroeconomic Volatility

This paper evaluates the effects of financial globalization on growth and macroeconomic volatility, from 1984 to 2003, for a sample of 43 countries. Particular attention is given to those effects on the member countries of the Latin American Reserve Fund (FLAR): Bolivia, Colombia, Costa Rica, Ecuador, Peru, and Venezuela. The findings show that financial globalization spurs growth, when the countries’ income level is controlled; it does not increase macroeconomic volatility, as it is commonly stated, but does not reduce it either. Belonging to FLAR does not seem to make a difference in terms of growth and macroeconomic volatility; however, the findings of a strong negative effect on the volatility of consumption might be related to the fact that those countries have an insurer (FLAR) that has helped them to smooth consumption during periods of adverse external shocks.Financial globalization; Economic growth; Macroeconomic volatility; Crosssection regression; Panel data regressions. Classification JEL:F30; F41; F43; G15; G18; C51.

Minimal Geometric Deformation in a cloud of strings

We find new exact analytical solutions in three-dimensional gravity applying the Minimal Geometric Deformation approach in a cloud of strings.Comment: 6 pages, 3 figures, accepted for publication in EPJ

Hopf-Lax formula for variational problems with non-constant discount

We provide a Hop-Lax formula for variational problems with non-constant discount and deduce a dynamic programming equation. We also study some regularity properties of the value function.Comment: 12 pages; corrected typo

International Conference. 20th Century New Towns. Archetypes and Uncertainties

Producción CientíficaThe paper aims to revalue and to compare two urban phenomena of growth and change during the second half of the 20th century: the Mat Building and the Gated City. On the one hand, Mat Building is analysed as a modern strategy of spatial and formal organization in architecture, which is related to the concept of Mat Urbanism. This idea is rooted in the interest of TEAM X in the traditional cities of North Africa, Japan and China, among others, during the late 1950s and 1960s. In 1974 Alison Smithson defined this urban structure using the model of Arab fortresses called Kasbah: “where the functions come to enrich the fabric, and the individual gains new freedoms of action through a new shuffled order, based on interconnection, close knit patterns of association and possibilities for growth, diminution and change.” Alison Smithson formulated an alternative to the functional city described in the CIAM´s Athens Charter. But she also proposed a new urban form, closed and opened at the same time, a kind of urban structure based on the necessity of identity and mobility. On the other hand, the phenomenon of the Gated City is also closely related to the idea of urban identity. The CIDs (Common-Interest-Developments) began to emerge at the end of the 1970s, but actually, that idea was put into practice during the 19th century, as a reaction of utopian socialism to environmental and social consequences of the Industrial Revolution. In the context of the sprawling city, during second half of the 20th century, the New Urbanism also established its criticism to the urban ideology of the Modern Movement, as the TEAM X had done before them. However, unlike the previous one, this current used the paradigm of the walled medieval city, or Gated City, which was indebted to the anti-industrial manifesto of Rob and Leon Krier. They wrote: “function follows form”, and not the opposite, as Louis Sullivan had said. Therefore, a purely picturesque approach to urban form was adopted, against the rationalism of the modern post-war planning. The paper compares both strategies through European and North American urban developments. It analyses their spatial and social structures pointing their own relevance in contemporary urban discourse, and it provides a critical relationship between them, which is full of paradoxes and contradictions for the sustainable urbanism and the landuse planning challenges

Greybody factors and quasinormal modes for a nonminimally coupled scalar field in a cloud of strings in (2+1)-dimensional background

We study the propagation of a probe massless nonminimally coupled scalar field in a fixed gravitational background of a cloud of strings in (2+1) dimensions. We obtain exact analytical expressions for the reflection coefficient, the absorption cross section, the decay rate as well as the quasinormal frequencies. The impact of the nonminimal coupling is investigated in detail. Our results show that Universality is not respected in general, and that scalar perturbations are stable.Comment: References adde