The QNP series of international conferences on Quarks and Nuclear Physics is by now a well established and highly respected forum where the most recent developments in the field are discussed and communicated. QNP 2006 is the forth edition of this biennial meeting. Selected and refereed original contributions of QNP 2006 have been published in The European Physical Journal A - Hadrons and Nuclei (EPJ A), while the present proceedings book, in addition to reprinting the articles published in EPJ A, further includes all other contributions selected and accepted by the organizing committee for publication and archiving.

Quantum chromodynamics is generally accepted to be the quantum field theory which describes the strong interactions in elementary particle physics. However, the question of the mechanism responsible for the “confinement” of the color degrees of freedom of quarks and gluons into hadrons still ranks as one of the most interesting open problems in physics.This proceedings volume summarizes the state of the art in this area of research. Mathematically inclined readers will find the articles based on monopoles, vortices, and topology most interesting. Meanwhile, lattice calculations can be performed for many important physical quantities. Their results can be used as guidelines for developing models of quark confinement. These models are indispensable for theoretical physicists performing calculations with the Bethe-Salpeter equation, Dyson-Schwinger equations, effective Hamiltonians, and potential models. The cross-fertilization of all these subfields of research becomes evident from the articles in this book. A few experimental papers are also included.

Quarks '90 covers various topics in the theory of elementary particles and quantum fields (including perturbative and non-perturbative QCD, sphalerons, topological field theory, strings and superstrings, physics in TeV region), astrophysics and cosmology as related to particle physics.

The following are the topics covered: Relativistic Heavy Ion Collisions; Hadronic Interaction and Particle Production Processes; Transport Theory for Hadrons and Quark-Gluon Plasma; Hadronization Process; Disordered Chiral Condensate; Strangeness Production; Lepton Pair Production; Particle Interferometry, Electromagnetic Signals of QGP; Structure of Hadrons; Nuclear Astrophysics and Solar Neutrino Problem.

The International Conference on Exotic Nuclei and Atomic Masses (ENAM) has gained the status of the premier meeting for the physics of nuclei far from stability. The selected and refereed papers presenting the main results constitute valuable proceedings that offer everyone working in this field an authoritative and comprehensive source of reference.

Valerio Filippini devoted his life to physics. His scientific contributions were provided in the OBELIX and FINUDA experiments. The FINUDA experiment collected physics data immediately after the roll-in, thanks to the reliability and simplicity of the on-line system designed and assembled by the physicist. This work is dedicated to him.