Astroparticle Physics

16 Glossary 327Quantum anomalies can arise if a classical symmetry is broken inthe process of quantization and renormalization.QCD; theory of strong interactions of quarks and gluons.Quantum-mechanical theory applied to systems that have an infinitenumber of degrees of freedom. Quantum field theory also describesprocesses, in which particles can be created or annihilated.Frothy character of the space-time fabrique on ultramicroscopicscales.Quantum theory of gravitation aiming at the unification with theother types of interactions.Quantum mechanics describes the laws of physics which hold atvery small distances. The main feature of quantum mechanics isthat, for example, the electric charge, the energies, and the angularmomenta come in discrete amounts, which are called quanta.quantum anomaliesquantum chromodynamicsquantum field theoryquantum foamquantum gravitationquantum mechanicsq; a fundamental fermion subject to strong interactions. Quarks quarkcarry the electric charge of either + 2 3 (up, charm, top) or − 1 3(down, strange, bottom) in units, in which the electric charge ofaprotonis+1.Quasistellar radio sources; galaxies at large redshifts with an activenucleus which outshines the whole galaxy and therefore makes thequasar appear like a bright star.A scalar field model for the dark energy. In contrast to the cosmologicalconstant the energy density in the quintessence field representsa time-varying inhomogeneous component with a negativepressure which satisfies −1