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.

This proceedings volume brings together the contributions of experts from different fields within the nuclear physics community. Topics such as rare kaon decays, astrophysics, relativistic heavy ion collisions, and few-GeV electromagnetic probes are covered. The strange quark plays a vital role in understanding such diverse phenomena as CP violation (article by Lincoln Wolfenstein), the ?spin crisis? (article by Brad Filipone), and supernova explosions (article by Chris Fryer). Additional topics of interest are parity violation experiments, strangeness content of the proton, and enhanced strangeness production at CERN and RHIC. This unique blend of recent results, with a focus on the role of the strange quark, shows the prominence of strangeness in nuclear physics over the past 50 years.

The nucleus and its constituents are a challenging problem. The lectures collected in this book present a broad and comprehensive review of the current knowledge about nuclei.They cover topics such as searching for signatures of the quarks in nuclei with electromagnetic probes and, at much higher energies, for signatures of the quark-gluon plasma in ultrarelativistic nuclear collisions. The attempts to obtain new nuclei in the laboratory are also discussed, as well as the central role played by nuclear physics in the development of weak interactions. Progress in all these areas rests on a deeper theoretical handling of the nuclear and nucleon’s structure. The latter can also be addressed by relying on numerical solutions of QCD on a discrete space-time lattice. The advancement of computational capabilities has spurred a growing interest in this approach. Finally, the book deals with different paths toward solving non-perturbative QCD.

This proceedings volume brings together the contributions of experts from different fields within the nuclear physics community. Topics such as rare kaon decays, astrophysics, relativistic heavy ion collisions, and few-GeV electromagnetic probes are covered. The strange quark plays a vital role in understanding such diverse phenomena as CP violation (article by Lincoln Wolfenstein), the “spin crisis” (article by Brad Filipone), and supernova explosions (article by Chris Fryer). Additional topics of interest are parity violation experiments, strangeness content of the proton, and enhanced strangeness production at CERN and RHIC. This unique blend of recent results, with a focus on the role of the strange quark, shows the prominence of strangeness in nuclear physics over the past 50 years.

These proceedings consist of plenary rapporteur talks covering topics of major interest to the high energy physics community and parallel sessions papers which describe recent research results and future plans.