Contents: Basic Concepts and Consequences of Stochastic Vacuum Model (H G Dosch)Variational Approximations for Correlation Functions in Quantum Field Theories (C Martin)SU(2) Gauge Theory in Covariant (Maximal) Abelian Gauges (M Schaden)The Vacuum Wave Function in Supersymmetric Matrix Theory (C M Sommerfield)HERA Results on Elastic Hadronic and Sub-Hadronic Diffraction (G Knies)Deriving Effective Transport Equations for Non-Abelian Plasmas (D F Litim)Aspects of Non-Commutativity in ADS/CFT (A Jevicki)Thermal Field Theory in Equilibrium (J O Andersen)Puzzling Aspects of Hot Quantum Fields (T Grandou)DIS Results from HERA (C M Ginsburg)Electroproduction of Vector Mesons (T Teubner)New Developments in Cosmology (J W Moffat)Heavy-Light Physics from Lattice NRQCD (T Onogi)Non-Relativistic Effective Theory for Perturbative Heavy Quark-Antiquark Systems (A H Hoang)The Spin Dependence of Swift Proton Collisions (N H Buttimore)Numerical Investigation of Domain-Wall QCD on CP-PACS (S Aoki)When is It Possible to Use Perturbation Technique in Field Theory? (T N Truong)and other papers Readership: Researchers in high energy physics. Keywords:

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.