Parties and Ballot Access in Latin America: a new trend in a new political context

For the last ten years a group of Latin American countries have passed legal reforms raising ballot access requirements. Although each of these reforms have been profusely discussed in every one of the countries involved, so far, they have not been linked as constituting a regional trend. Firstly this paper shows that this trend actually exists, so reversing the dominant leaning on reforms in this field during the 1980s and 1990s. Secondly, the paper shows that the ongoing regional trend emerges in the aftermath of a legitimacy crisis which has been surmounted in every one of the cases. More specifically, the paper identifies a common sequence followed by four countries (Argentina, Colombia, Mexico and Peru) which leads to the raise of ballot access requirements. The sequence involves the following stages: first, a legitimacy crisis which paves the way to reforms opening up the political system; second, once the legitimacy crisis is left behind, a consensus emerges on the negative consequences of the previous reforms; and third, this consensus culminates with the introduction of the restrictive reforms which have dominated the Latin American landscape for the last decade. Every case is analyzed by observing the coalescence of what Matthew Shugart (2001) defined as the inherent and contingent conditions necessary to account for the passing of electoral reforms.Fil: Scherlis Perel, Gerardo Ezequiel. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Stacking of oligo and polythiophenes cations in solution: surface tension and dielectric saturation

The stacking of positively charged (or doped) terthiophene oligomers and quaterthiophene polymers in solution is investigated applying a recently developed unified electrostatic and cavitation model for first-principles calculations in a continuum solvent. The thermodynamic and structural patterns of the dimerization are explored in different solvents, and the distinctive roles of polarity and surface tension are characterized and analyzed. Interestingly, we discover a saturation in the stabilization effect of the dielectric screening that takes place at rather small values of $\epsilon_0$. Moreover, we address the interactions in trimers of terthiophene cations, with the aim of generalizing the results obtained for the dimers to the case of higher-order stacks and nanoaggregates

Simulation of Heme using DFT+U: a step toward accurate spin-state energetics

We investigate the DFT+U approach as a viable solution to describe the low-lying states of ligated and unligated iron heme complexes. Besides their central role in organometallic chemistry, these compounds represent a paradigmatic case where LDA, GGA, and common hybrid functionals fail to reproduce the experimental magnetic splittings. In particular, the imidazole pentacoordinated heme is incorrectly described as a triplet by all usual DFT flavors. In this study we show that a U parameter close to 4 eV leads to spin transitions and molecular geometries in quantitative agreement with experiments, and that DFT+U represents an appealing tool in the description of iron porphyrin complexes, at a much reduced cost compared to correlated quantum-chemistry methods. The possibility of obtaining the U parameter from first-principles is explored through a self-consistent linear-response formulation. We find that this approach, which proved to be successful in other iron systems, produces in this case some overestimation with respect to the optimal values of U.Comment: To be published in The Journal of Physical Chemistry B 30 pages, 15 figure

Hedgehog Bases for A_n Cluster Polylogarithms and An Application to Six-Point Amplitudes

Multi-loop scattering amplitudes in N=4 Yang-Mills theory possess cluster algebra structure. In order to develop a computational framework which exploits this connection, we show how to construct bases of Goncharov polylogarithm functions, at any weight, whose symbol alphabet consists of cluster coordinates on the $A_n$ cluster algebra. Using such a basis we present a new expression for the 2-loop 6-particle NMHV amplitude which makes some of its cluster structure manifest.Comment: 32 pages; v2: minor corrections and clarification

Presidents and parties in Latin America: the exceptionality of peronism in the Latin American context

Los partidos políticos han dejado de cumplir funciones representativas significativas para legitimarse a partir de su rol como agencias de gobierno. Esto ha implicado la creciente inter- penetración entre partidos y estados, así como la concentración de recursos en los líderes que ocupan cargos ejecutivos. En el contexto latinoamericano, estas características alcanzan mayor intensidad en los partidos de gobierno de países en los que se ha producido el colapso o la dilu- ción del valor de la etiqueta de los partidos tradicionales. En estos casos, el presidente controla al partido de gobierno, mientras la estructura partidaria realmente existente se constituye sobre la base de las redes reclutadas por el líder electo para el ejercicio del gobierno.El argumento central del artículo consiste en que el peronismo es la única fuerza política que ha logrado adaptarse exitosamente a las condiciones de la competencia electoral en la Argentina contemporánea. La autonomía del presidente en términos de orientación de políticas públicas frente a una máquina partidaria sostenida sobre la base del control de los estados subnacionales hace posible escindir la legitimidad del partido respecto a la de su coyuntural liderazgo. Esto provee al peronismo de un exitoso mecanismo de preservación, excepcional en el contexto latinoamericano.Political parties have ceased fulfilling substantial representative functions. Their legitimacy lies now on their role as governmental agencies. This led to an increasing interpenetration between parties and the states, and to the empowerment of those leaders that occupy executive offices. In the Latin American context these features are particularly intense in the case of ruling parties in countries where traditional parties collapsed or suffered significant brand dilution. In these cases the president controls the ruling party, while the «really existent» party organization is built up on the basis of networks recruited by the elected leader to run the government. The central argument of this article is that Peronism is the sole political force which has managed to adapt successfully to the conditions of electoral competition in contemporary Argentina. The president´s autonomy in terms of public policies´ in relation to a political machine sustained on the basis of the control of sub-national states makes it possible to disentangle the legitimacy of the party from that of its current national leadership. This scheme provides Peronism with a successful self-preservation mechanism, which is exceptional in the Latin American context.Fil: Scherlis Perel, Gerardo Ezequiel. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin