WAVELET BASED NONLINEAR SEPARATION OF IMAGES

This work addresses a real-life problem corresponding to the separation of the nonlinear mixture of images which arises when we scan a paper document and the image from the back page shows through. The proposed solution consists of a non-iterative procedure that is based on two simple observations: (1) the high frequency content of images is sparse, and (2) the image printed on each side of the paper appears more strongly in the mixture acquired from that side than in the mixture acquired from the opposite side. These ideas had already been used in the context of nonlinear denoising source separation (DSS). However, in that method the degree of separation achieved by applying these ideas was relatively weak, and the separation had to be improved by iterating within the DSS scheme. In this paper the application of these ideas is improved by changing the competition function and the wavelet transform that is used. These improvements allow us to achieve a good separation in one shot, without the need to integrate the process into an iterative DSS scheme. The resulting separation process is both nonlinear and non-local. We present experimental results that show that the method achieves a good separation quality

Referendum Design, Quorum Rules and Turnout

In this article, we focus on the consequences of quorum requirements for turnout in referendums. We use a rational choice, decision theoretic voting model to demonstrate that participation quorums change the incentives some electors face, inducing those who oppose changes in the status quo and expect to be in the minority to abstain. As a result, paradoxically, participation quorums decrease electoral participation. We test our model’s predictions using data for all referendums held in current European Union countries from 1970 until 2007, and show that the existence of a participation quorums increases abstention by more than ten percentage points.Referendum Design; Voter turnout

Schwarzschild-like black holes: Light-like trajectories and massless scalar absorption

Black holes are among the most intriguing objects in nature. They are believed to be fully described by General Relativity (GR), and the astrophysical black holes are expected to belong to the Kerr family, obeying the no-hair theorems. Alternative theories of gravity or parameterized deviations of GR allow black hole solutions, which have additional parameters other than mass and angular momentum. We analyze a Schwarzschild-like metric, proposed by Johannsen and Psaltis, characterized by its mass and a deformation parameter. We compute the absorption cross section of massless scalar waves for different values of this deformation parameter and compare it with the corresponding scalar absorption cross section of the Schwarzschild black hole. We also present analytical approximations for the absorption cross section in the high-frequency regime. We check the consistence of our results comparing the numerical and analytical approaches, finding excellent agreement.Comment: 8 pages, 14 figure

Growth, Centrism and Semi-Presidentialism: Forecasting the Portuguese General Elections

Electoral behaviour in recently established democracies has been more frequently treated from the point of view of its unpredictability, volatility and personalistic elements than that of its "fundamentals". In this paper, we wish to contribute to redress this imbalance by advancing a forecasting model for general elections in a young democracy, Portugal. Building on the very familiar notion that the vote for the incumbent can be predicted on the basis of "economics" and "politics", we capture "economics" through a nonlinear specification of economic growth. Furthermore, we include two structural features of Portuguese politics, which have entailed a systematic electoral punishment for the centre-left Socialist Party as the incumbent and for all incumbents involved in political conflicts with the elected president in Portugal's semi-presidentialism.Forecasting; Portuguese general elections; Economics and elections; Semi-Presidentialism

How quorum rules distort referendum outcomes: evidence from a pivotal voter model

In many jurisdictions, whether referendum results are binding depend on certain legally defined quorum requirements. With a pivotal-voter model, we examine how quorum requirements affect voter’s behavior. We conclude that quorums can be the cause of lower turnout and that they can deliver outcomes that are an inadequate basis to make inferences about collective preferences. We further conclude that quorums may help minorities to impose their will on majorities and that they may create a bias against the status quo. Finally, they generate situations under which the secrecy of the vote is called into question.