Topics in light-quark physics

This special issue of the European Journal of Physics: Special Topics entitled Topics in Light Quark Physics collects 8 papers with the intention to discuss problems in physical processes involving the particles (mesons and baryons) comprising the lighter part in the spectrum of strong interactions, though some connections to the heavy-quark sector are also discussed. Active and timely problems in this broad field are introduced and covered by experts who root their contributions in the known aspects at the same time that take us to the frontier of knowledge, while introducing in many instances new techniques for present and future further developments. The nature of the lightest scalar resonances, the hunt for the lightest glueballs, the $$\Lambda (1405)$$ as a paradigmatic example of two-pole resonances, the pion–nucleon sigma term, two- and three-body scattering amplitudes extracted from lattice QCD, the QCD phase diagram, extrapolations in the number of colors of QCD and their use for addressing properties of its spectrum, and new advances to reach renormalized scattering amplitudes with attractive/repulsive singular potentials are all items covered here.