A new formulation of Lee-Wick quantum field theory

The Lee-Wick models are higher-derivative theories that are claimed to be unitary thanks to a peculiar cancelation mechanism. In this paper, we provide a new formulation of the models, to clarify several aspects that have remained quite mysterious, so far. Specifically, we define them as nonanalytically Wick rotated Euclidean theories. The complex energy plane is divided into disconnected regions, which can be related to one another by a well-defined, albeit nonanalytic procedure. Working in a generic Lorentz frame, the models are intrinsically equipped with the right recipe to treat the pinchings of the Lee-Wick poles, with no need of external ad hoc prescriptions. We describe these features in detail by calculating the one-loop bubble diagram and explaining how the key properties generalize to more complicated diagrams. The physical results of our formulation are different from those of the previous ones. The unusual behaviors of the physical amplitudes lead to interesting phenomenological predictions.Comment: 27 pages, 17 figures; v2: details about Lorentz invariance above LW thresholds; v3: minor changes, JHE

Perturbative unitarity of Lee-Wick quantum field theory

We study the perturbative unitarity of the Lee-Wick models, formulated as nonanalytically Wick rotated Euclidean theories. The complex energy plane is divided into disconnected regions and the values of a loop integral in the various regions are related to one another by a nonanalytic procedure. We show that the one-loop diagrams satisfy the expected, unitary cutting equations in each region: only the physical degrees of freedom propagate through the cuts. The goal can be achieved by working in suitable subsets of each region and proving that the cutting equations can be analytically continued as a whole. We make explicit calculations in the cases of the bubble and triangle diagrams and address the generality of our approach. We also show that the same higher-derivative models violate unitarity if they are formulated directly in Minkowski spacetime.Comment: 30 pages, 15 figures; v2: more details and comments on generality of approach; v3: minor changes, PR

The skill bias in Italy: a first report

In this study three possible determinants of the increased demand for skilled workers are tested using a panel of 412 Italian manufacturing firms over the period 1989-1997. The results suggest the statistical significance of the impact of organisational change, while they tend to exclude the roles of R&D spending and foreign direct investment.

Renormalization of Massive Rank-1 Field Theory Nonminimally Coupled to Quantum Gravity

We consider a self-interacting, massive rank-1 field coupled to quantum gravity. The theory is renormalizable by power counting and contains a massive spin-1 field and a massive scalar field. The latter has a propagator with negative residue and it is quantized as a purely virtual particle, namely it cannot appear as external on-shell state but contributes to renormalization. In this way the resulting theory is also unitary, both in flat spacetime and when it is coupled to renormalizable quantum gravity (where purely virtual particles are required as well). We compute the full set of one-loop beta functions, including those of the nonminimal couplings. We show that the gravitational couplings cannot be made asymptotically free in absence of tachyons, even with the addition of the two nonminimal terms. Various aspects of renormalizability are discussed by studying the beta functions. Finally, we compare our model with Proca theory, where renormalizability is spoiled if self interactions are present.Comment: 26 pages, 3 figures, PRD versio

R&D and Employment: Some Evidence from European Microdata

After discussing theory regarding the consequences of technological change on employment and surveying previous microeconometric literature, our aim with this paper is to test the possible job creation effect of business R&D expenditures, using a unique longitudinal database covering 677 European manufacturing and service firms over the period 1990-2008. The main outcome from the whole sample dynamic LSDVC (Least Squared Dummy Variable Corrected) estimate is the labour-friendly nature of companies’ R&D, the coefficient of which turns out to be statistically significant, although not very large in magnitude. However, the positive and significant impact of R&D expenditures on employment is detectable in services and high-tech manufacturing but absent in the more traditional manufacturing sectors. This means that we should not expect positive employment effects from increasing R&D in the majority of industrial sectors. This is something that should be borne in mind by European innovation policy makers having employment as one of their specific aims.manufacturing, employment, innovation, services, LSDVC

How Do Young Innovative Companies Innovate?

This paper discusses the determinants of product innovation in young innovative companies (YICs) by looking at in-house and external R&D and at the acquisition of external technology in embodied and disembodied components. These input-output relationships are tested on a sample of innovative Italian firms. A sample-selection approach is applied. Results show that in-house R&D is linked to the propensity to introduce product innovation both in mature firms and YICs; however, innovation intensity in the YICs is mainly dependent on embodied technical change from external sources, while − in contrast with the incumbent firms − in-house R&D does not play a significant role.R&D, product innovation, embodied technical change, CIS 3, sample selection

The impact of R&D on employment in Europe: a firm-level analysis

The aim of this paper is to test the employment effect of business R&D expenditures, using a unique longitudinal database covering 677 European manufacturing and service firms over the period 1990-2008. Main result from the whole sample dynamic LSDVC (Least Squared Dummy Variable Corrected) estimate is the labour-friendly nature of companies’ R&D, the coefficient of which turns out to be statistically significant, although not very large in magnitude. However, the positive and significant job creation effect of R&D expenditures is detectable in services and high-tech manufacturing but absent in the more traditional manufacturing sectors. This means that we should not expect positive employment effects from increasing R&D in the majority of industrial sectors. This evidence should be kept in mind by European innovation policy makers having employment as one of their specific aims.Innovation, employment, manufacturing, services, LSDVC