Renormalized QCD-inspired model for the pion and mesons

We apply the subtraction method to an effective QCD-inspired model, which includes the Coulomb plus a zero-range hyperfine interactions, to define a renormalized Hamiltonian for mesons. The spectrum of the renormalized Hamiltonian agrees with the one obtained with a smeared hyperfine interaction. The masses of the low-lying pseudo scalar and vector mesons are reasonably described within the model.Comment: 5 pages, 3 figures, 5 references. To be published in Nucl. Phys. B (Proc. Suppl.) Talk presented at the Workshop "Light-cone Physics: Particles and Strings" at ECT* in Trento, Sep 3-11, 200

Semantic Grounding Strategies for Tagbased Recommender Systems

Recommender systems usually operate on similarities between recommended items or users. Tag based recommender systems utilize similarities on tags. The tags are however mostly free user entered phrases. Therefore, similarities computed without their semantic groundings might lead to less relevant recommendations. In this paper, we study a semantic grounding used for tag similarity calculus. We show a comprehensive analysis of semantic grounding given by 20 ontologies from different domains. The study besides other things reveals that currently available OWL ontologies are very narrow and the percentage of the similarity expansions is rather small. WordNet scores slightly better as it is broader but not much as it does not support several semantic relationships. Furthermore, the study reveals that even with such number of expansions, the recommendations change considerably.Comment: 13 pages, 5 figure

Some Facts About the Cyclical Convergence in the Euro Zone

In the context of a single currency and a common monetary policy defined by the European Central Bank for the euro area as a whole, it is important to evaluate the degree of business cycle resemblance among the participant countries. We resort to the association and synchronization concepts to define cyclical convergence. Using a time domain approach, we purport to use several parametric and non-parametric statistics to investigate whether the cycles of these countries have converged to the euro area business cycle during the sample period. The results obtained are in line with those from previous studies and suggest that Italy, Spain, Austria, the Netherlands, Portugal and Greece have cyclically converged to the euro area business cycle. Regarding the United Kingdom, the evidence suggests the existence of a strong degree of association with the euro zone, exhibiting however a lead cycle in the more recent period.

Necessary optimality conditions for fractional action-like problems with intrinsic and observer times

We prove higher-order Euler-Lagrange and DuBois-Reymond stationary conditions to fractional action-like variational problems. More general fractional action-like optimal control problems are also considered