Closed-loop control strategy with improved current for a flashing ratchet

We show how to switch on and off the ratchet potential of a collective Brownian motor, depending only on the position of the particles, in order to attain a current higher than or at least equal to that induced by any periodic flashing. Maximization of instant velocity turns out to be the optimal protocol for one particle but is nevertheless defeated by a periodic switching when a sufficiently large ensemble of particles is considered. The protocol presented in this article, although not the optimal one, yields approximately the same current as the optimal protocol for one particle and as the optimal periodic switching for an infinite number of them.Comment: 4 pages, 4 figure

Fluctuation theorem for black-body radiation

The fluctuation theorem is verified for black-body radiation, provided the bunching of photons is taken into account appropriately.Comment: 4 pages, 3 figure

Fluctuation symmetry in a two-state Markov model

We show that the scaled cumulant generating and large deviation function, associated to a two-state Markov process involving two processes, obey a symmetry relation reminiscent of the fluctuation theorem, independent from any conditions on the transition rates. The Legendre transform leading from the scaled cumulant generating function to the large deviation function is performed in an ingenious way, avoiding the sign problem associated to taking a square root. Applications to the theory of random walks and to the stochastic thermodynamics for a quantum dot are presented.Comment: 4 pages, 3 figure

Administrating Participatory Budgeting in Porto Alegrestreet-level Officials and Organisational Preconditions

 El Partido de los Trabajadores (PT) desarrolló en Porto Alegre un régimen participativo de gasto, que permitió a los ciudadanos tener una voz sobre la inversión pública a nivel municipal. Éste ha sido aclamado como un modelo de participación en la toma de decisiones que aumenta la transparencia al nivel local. La mayoría de los académicos han mirado este régimen con un enfoque socio-céntrico, enfocándose en los encuentros participativos, y en el rol de la sociedad civil. Sin embargo, poca atención ha sido dada al diseño institucional, el rol crucial de la administración pública, y a los políticos del PT responsables de las mejoras en el servicio público y la infraestructura. Este artículo tiene un enfoque de políticas y redirige la atención hacia los funcionarios y políticos que estuvieron firmemente en el control y llevaron las riendas del régimen. La principal propuesta del artículo es que gran parte del éxito de la administración del PT en Porto Alegre dependió de dedicados militantes nombrados dentro de la administración municipal. Ellos fueron la encarnación del presupuesto participativo intermediado, el que fue un importante instrumento para la participación ciudadana, pero que contaba con una serie de debilidades estructurales, que los militantes del PT fueron capaces de superar durante varios años.The Workers' Party (PT) developed In Porto Alegre a participatory expenditure scheme which allowed citizens to have a say on public investments at municipal level. It has been hailed as a model for participatory decision-making that increases transparency at the local level. Most scholars so far have looked at this scheme with a society-centred approach focusing on the participatory meetings and the role of civil society. However, little attention has been given to the institutional design, the crucial role of the public administration, and PT politicians who were responsible for the increase in public services and infrastructure. This article has a policy approach and redirects the attention toward officials and politicians who were firmly in control and pulled the strings of the scheme. The article's main contention is that much of the success of the PT administration in Porto Alegre hinged upon dedicated partisan members appointed inside the municipal administration. They were the embodiment of the intermediary participatory budget as such was an important instrument for citizens' inclusion, but lacked the showed a number of structural weaknesses which these militant PT members were able to overcome during many years