Higher-order Lorentz-invariance violation, quantum gravity and fine-tuning

The issue of Lorentz fine-tuning in effective theories containing higher-order operators is studied. To this end, we focus on the Myers-Pospelov extension of QED with dimension-five operators in the photon sector and standard fermions. We compute the fermion self-energy at one-loop order considering its even and odd $CPT$ contributions. In the even sector we find small radiative corrections to the usual parameters of QED which also turn to be finite. In the odd sector the axial operator is shown to contain unsuppressed effects of Lorentz violation leading to a possible fine-tuning. We use dimensional regularization to deal with the divergencies and a generic preferred four-vector. Taking the first steps in the renormalization procedure for Lorentz violating theories we arrive to acceptable small corrections allowing to set the bound $\xi<6 \times10^{-3}$.Comment: 11 pages, new version with the correct pole extractio

Income Distribution, Factor Endowments, and Trade Revisited: The Role of Non-Tradable Goods

We return to the traditional theme of the distributive consequences of international prices and trade policies, focusing on economies relatively abundant in natural resources with a large non-tradable-goods sector. Changes in international prices create an aggregate demand effect which impacts on the earnings of factors employed in the non-traded goods sector. We show that, in economies highly specialized in the production of tradable goods and where the import-competing sector is small, under standard assumptions, terms-of- trade shifts have a neutral effect on factor prices and thus lack distributive effects, quite differently from Stolper-Samuelson scenarios. In economies with sizable import-competing sectors and two ?urban? productive factors (e.g. skilled and unskilled labor), changes in the terms of trade do induce distributional tensions through two channels: (i) the exogenous shift in the relative price of tradable goods, and (ii) the endogenous displacement of the demand for non-tradables. We illustrate how, according to the structure of the economy, different patterns of income distribution may arise. Next, we analyze the introduction of trade duties. Trade taxes change relative prices between tradable goods as a terms-of-trade shock does, but also introduce an additional demand mechanism, that depends on the use the government gives to the revenues. If the tax revenues are transferred back to the private sector, the resulting reallocation of spending favors those factors used intensively in the production of non-tradables.Fil: Galiani, Sebastian. University of Maryland; Estados UnidosFil: Heymann, Carlos Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Interdisciplinario de Economía Politica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto Interdisciplinario de Economía Politica de Buenos Aires; ArgentinaFil: Magud, Nicolas E.. International Monetary Fund.; Estados Unido

Polymer quantization, stability and higher-order time derivative terms

The stability of higher-order time derivative theories using the polymer extension of quantum mechanics is studied. First, we focus on the well-known Pais-Uhlenbeck model and by casting the theory into the sum of two decoupled The possibility that fundamental discreteness implicit in a quantum gravity theory may act as a natural regulator for ultraviolet singularities arising in quantum field theory has been intensively studied. Here, along the same expectations, we investigate whether a nonstandard representation, called polymer representation can smooth away the large amount of negative energy that afflicts the Hamiltonians of higher-order time derivative theories; rendering the theory unstable when interactions come into play. We focus on the fourth-order Pais-Uhlenbeck model which can be reexpressed as the sum of two decoupled harmonic oscillators one producing positive energy and the other negative energy. As expected, the Schrodinger quantization of such model leads to the stability problem or to negative norm states called ghosts. Within the framework of polymer quantization we show the existence of new regions where the Hamiltonian can be defined well bounded from below.Comment: 13 pages, 2 figure

Land-Rich Economies, Education and Economic Development

We analyze the emergence of large-scale education systems in a framework where growth is associated with changes in the conguration of the economy. We model the incentives that the economic elite could have (collectively) to accept taxation destined to nance the education of credit-constrained workers. Contrary to previous work, in our model this incentive does not necessarily arise from a complementarity between physical and human capital in manufacturing. Instead, we emphasize the demand for human-capital-intensive services by highincome groups. Our model seems capable to account for salient features of the development of Latin America in the 19th century, where, in particular, land-rich countries such as Argentina established an extensive public education system and developed a sophisticated service sector before starting signicant manufacturing activities.

Classical and quantum-linearized descriptions of degenerate optomechanical parametric oscillators

Recent advances in the development of modern quantum technologies have opened the possibility of studying the interplay between spontaneous parametric down-conversion and optomechanics, two of the most fundamental nonlinear optical processes. Apart from practical reasons, such scenario is very interesting from a fundamental point of view, because it allows exploring the optomechanical interaction in the presence of a strongly quantum-correlated field, the spontaneously down-converted mode. In this work we analyze such problem from two approximate but valuable perspectives: the classical limit and the limit of small quantum fluctuations. We show that, in the presence of optomechanical coupling, the well-known classical phase diagram of the optical problem gets modified by the appearance of new dynamical instabilities. As for the quantum-mechanical description, we prove the ability of the squeezed down-converted field to cool down the mechanical motion not only to thermal but also to squeezed thermal mechanical states, and in a way that can be much less sensitive to parameters (e.g., detuning of the driving laser) than standard sideband cooling.Comment: New version including the quantum linearized description of the system and appendices. Accepted in Physical Review