Two fermion relativistic bound states

We consider the relativistic quantum mechanics of a two interacting fermions system. We first present a covariant formulation of the kinematics of the problem and give a short outline of the classical results. We then quantize the system with a general interaction potential and deduce the explicit equations in a spherical basis. The case of the Coulomb interaction is studied in detail by numerical methods, solving the eigenvalue problem for J=0, J=1, J=2 and determining the spectral curves for a varying ratio of the mass of the interacting particles. Details of the computations, together with a perturbative approach in the mass ratio and an extended description of the ground states of the Para- and Orthopositronium are given in Appendix.Comment: 26 pages, 6 figure

Non-linear fe modelling of seismic pounding and damped-mitigating interconnection between a r/c tower and a masonry church

The finite element analysis of pounding represents one of the most critical issues for the assessment of the seismic performance of R/C structures built at poor distance from adjacent buildings. The effects of pounding can be particularly severe in slender R/C heritage structures, including civic or bell towers. An emblematic case study falling in this class of structures, i.e. a monumental R/C bell tower constructed in the early 1960s in Florence, is analyzed in this paper. Pounding collisions are simulated with a multi-link viscoelastic contact model originally implemented in this study. The results of the non-linear dynamic enquiry carried out with this model show that pounding affects the seismic response of the bell tower and the adjacent church as early as an input seismic action scaled at the amplitude of the normative basic design earthquake level. A retrofit hypothesis to prevent pounding is then proposed, which consists in linking the two structures by means of a pair of fluid-viscous dissipaters. Thanks to the supplemental damping action produced by these devices, the impacts are totally annulled, bringing the structural members of the tower to safe levels

Unified covariant treatment of hyperfine splitting for heavy and light mesons

This paper aims at proving the fundamental role of a relativistic formulation for quarkonia models. We present a completely covariant description of a two-quark system interacting by the Cornell potential with a Breit term describing the hyperfine splitting. Using an appropriate procedure to calculate the Breit correction, we find heavy meson masses in excellent agreement with experimental data. Moreover, also when applied to light quarks and even taking average values of the running coupling constant, we prove that covariance properties and hyperfine splitting are sufficient to explain the light mesons spectrum and to give a very good agreement with the data.Comment: 4 page

Relativistic two-body calculation of bbˉb\bar{b}-mesons radiative decays

This paper is a prosecution of a previous work where we presented a unified two-fermion covariant scheme which produced very precise results for the masses of light and heavy mesons. We extend the analysis to some radiative decays of mesons $\Upsilon,\,\chi_{b2}\,,h_b\,,\chi_{b1}\,,\chi_{b0}\,,\eta_b\,$ and we calculate their branching ratios and their widths. For most of them we can make a comparison with experimental data finding a good agreement.For the decays for which data are not available we compare ours with other recent theoretical previsions.Comment: 7 pages, 1 figur

The European Parliament is more representative of European citizens than we give it credit for

Does the European Parliament adequately represent the views of European citizens? Drawing on a recent study, Miriam Sorace illustrates that while the Parliament is often criticised for being too distant from its voters, it is far more representative of the views of voters than commonly thought. Nevertheless, a lack of information about European election campaigns, as well as a tendency for some voters to cast protest votes, can lead to individual voters being less well represented

Brexit pushes European lawmakers to reform the EU

Brexit has pushed European lawmakers to seriously talk about rebuilding the EU. In December 2016, the Committee on Constitutional Affairs of the European Parliament endorsed a report on adjustments to the institutional set-up of the EU, which was then ratified by the full house. This article argues that calls for democratising the EU political system have to be addressed immediately, ..

Taking back control, actually: reforming the European Parliament elections

Brexit has pushed European law-makers to seriously talk about rebuilding the EU. In December 2016, the Committee on Constitutional Affairs of the European Parliament endorsed a report on adjustments to the institutional set-up of the EU, which was then ratified by the full house. This article argues that calls for democratising the EU political system have to be addressed immediately, and that priority should be given to reforms of the European elections. Miriam Sorace advocates for a uniform Open-List Proportional Representation System with small constituencies and the possibility for national parties to run all over Europe as the ‘ideal- type’. She then outlines its beneficial effects in terms of accountability and the formation of a European public sphere