Entry, Costs Reduction, and Competition in the Portuguese Mobile Telephony Industry

We study the effect of entry on costs and competition in the Portuguese mobile telephony industry.\ We construct and estimate a model that includes demand, network, and cost equations. The latter accounts for inefficiency and cost reducing effort. Our results suggest that the entry of a third operator in 1998 lead to significant cost reductions, and fostered competition. We also show that failure to account for cost reducing effort leads to biased estimates of competition in the industry. Finally, we also find that our estimated price-cost margins are similar to hypothetical Nash margins, if firms are patient, and have optimistic beliefs about the industry growth.

Weak-lensing BB-modes as a probe of the isotropy of the universe

We compute the angular power spectrum of the $B$-modes of the weak-lensing shear in a spatially anisotropic spacetime. We find that there must also exist off-diagonal correlations between the $E$-modes, $B$-modes, and convergence that allow one to reconstruct the eigendirections of expansion. Focusing on future surveys such as Euclid and SKA, we show that observations can constrain the geometrical shear in units of the Hubble rate at the percent level, or even better, offering a new and powerful method to probe our cosmological model.Comment: 4 pages, 3 figures. This version matches the published on

Entry, Costs Reduction, and Competition in the Portuguese Mobile Telephony Industry

We study the effect of entry on costs and competition in the Portuguese mobile telephony industry. We construct and estimate a model that includes demand, network, and cost equations. The latter accounts for inefficiency and cost reducing effort. Our results suggest that the entry of a third operator in 1998 lead to significant cost reductions and fostered competition. We also show that failure to account for cost reducing effort leads to biased estimates of competition in the industry. Finally, we also find that our estimated price–cost margins are similar to hypothetical Nash margins, if firms are patient and have optimistic beliefs about the industry growth.Ministerio de Educación y Ciencia (SEJ2004-00670)Publicad

The effect of firms' size on business cycle

Treball de fi de Grau en Economia. Codi: EC1049. Curs acadèmic 2014-2015In this paper I analyse the cross–correlation between the effects of firms´ size on the business cycle, a phenomenon called granularity. I follow Gabaix´s research which argues that idiosyncratic firm-level shocks can explain an important part of aggregate movements and provide a microfoundation for aggregate shocks. The variable used in my research is the operating revenue. I consider this variable as a proxy of firms' size. Furthermore, the aggregate volatility of GDP is determined by the volatility of operating revenue of large firms. Hence, I can predict the GDP volatility via the operating revenue fluctuations of large firms. This paper shows that the forces of randomness at micro level create an inexorable amount of volatility at macro level

Weak lensing B-modes on all scales as a probe of local isotropy

This article derives a multipolar hierarchy for the propagation of the weak-lensing shear and convergence in a general spacetime. The origin of B-modes, in particular on large angular scales, is related to the local isotropy of space. Known results assuming a Friedmann-Lema\^itre background are naturally recovered. The example of a Bianchi I spacetime illustrates our formalism and its implications for future observations are stressed.Comment: 10 pages, 2 figures. Replaced to match published versio

A Possibility to Enhance Rural Electrification with Small Solar Home Systems Using Light Emitting Diodes

This paper presents a study done in Uganda using LED lights instead of the conventional CFLs.In order to make Solar PV technology available to people living in rural areas, there is the need to reduce the initial investment in Solar Home Systems (SHS), without compromising quality and life span. This paper presents a study done in Uganda using LED lights instead of the conventional CFLs. This option makes it possible to use small sealed deep cycle batteries, low Wattage panels and avoids using charge-controller. Ten of these LED-SHS were installed in a community far from the grid. For three months research assistants were in touch with the users to provide awareness, technical support and gauge customer satisfaction. The test was a success. At the end of the period all users decided to purchase the system and another bigger group manifested interest in replacing their paraffin lamps by LED -SHS. Following the evaluation, a number of improvements have been proposed. The next step is to involve a micro-finance institution to avail the initial capital to pay in one go the USD 150 for the system. Future development includes hiring a designer to make the product more marketable and negotiations with Government and NGOs for possible subsidies

Predictions from an anisotropic inflationary era

This article investigates the predictions of an inflationary phase starting from a homogeneous and anisotropic universe of the Bianchi I type. After discussing the evolution of the background spacetime, focusing on the number of e-folds and the isotropization, we solve the perturbation equations and predict the power spectra of the curvature perturbations and gravity waves at the end of inflation. The main features of the early anisotropic phase is (1) a dependence of the spectra on the direction of the modes, (2) a coupling between curvature perturbations and gravity waves, and (3) the fact that the two gravity waves polarisations do not share the same spectrum on large scales. All these effects are significant only on large scales and die out on small scales where isotropy is recovered. They depend on a characteristic scale that can, but a priori must not, be tuned to some observable scale. To fix the initial conditions, we propose a procedure that generalises the one standardly used in inflation but that takes into account the fact that the WKB regime is violated at early times when the shear dominates. We stress that there exist modes that do not satisfy the WKB condition during the shear-dominated regime and for which the amplitude at the end of inflation depends on unknown initial conditions. On such scales, inflation loses its predictability. This study paves the way to the determination of the cosmological signature of a primordial shear, whatever the Bianchi I spacetime. It thus stresses the importance of the WKB regime to draw inflationary predictions and demonstrates that when the number of e-folds is large enough, the predictions converge toward those of inflation in a Friedmann-Lemaitre spacetime but that they are less robust in the case of an inflationary era with a small number of e-folds.Comment: 48 page

From Infra-Humanization to Discrimination: The Mediation of Symbolic Threat Needs Egalitarian Norms

This set of studies tests the link between infra-humanization, symbolic threat, and discrimination within normative contexts. In two experiments, manipulating the degree of humanity of a disliked outgroup has an effect upon the discrimination towards it. The infra-humanized outgroup is more discriminated than the humanized one. Also, the perception of symbolic threat plays the role of a justifying factor for discrimination, and mediates the relationship between degrees of humanity and discrimination. Study 2 further shows that this mediation occurs only when an egalitarian norm is activated, and not when meritocracy is made salient. The discussion focuses on factors likely to prevent infra-humanization of outgroups. It also considers how norms may change the role of threat

I.C.E.: An Ultra-Cold Atom Source for Long-Baseline Interferometric Inertial Sensors in Reduced Gravity

The accuracy and precision of current atom-interferometric inertialsensors rival state-of-the-art conventional devices using artifact-based test masses . Atomic sensors are well suited for fundamental measurements of gravito-inertial fields. The sensitivity required to test gravitational theories can be achieved by extending the baseline of the interferometer. The I.C.E. (Interf\'erom\'etrie Coh\'erente pour l'Espace) interferometer aims to achieve long interrogation times in compact apparatus via reduced gravity. We have tested a cold-atom source during airplane parabolic flights. We show that this environment is compatible with free-fall interferometric measurements using up to 4 second interrogation time. We present the next-generation apparatus using degenerate gases for low release-velocity atomic sources in space-borne experiments