We investigate the properties of the deconfining/chiral restoring transition for two flavor QCD in the presence of a uniform background magnetic field. We adopt standard staggered fermions and a lattice spacing of the order of 0.3 fm. We explore different values of the bare quark mass, corresponding to pion masses in the range 200–480 MeV, and magnetic fields up to eB 0.75 GeV^2. The deconfinement and chiral symmetry restoration temperatures remain compatible with each other and rise very slightly ( < 2% for our largest magnetic field) as a function of the magnetic field. On the other hand, the transition seems to become sharper as the magnetic field increases

We study the dual superconductivity of the ground state of SU͑2͒ gauge theory in connection with confinement. We do this measuring on the lattice a disorder parameter describing condensation of monopoles. Confinement appears as a transition to the dual superconductor, independent of the Abelian projection defining monopoles. Some speculation is made on the existence of a more appropriate disorder parameter. A similar study for SU͑3͒ is presented in a companion paper.

In a numerical experiment, we remove center vortices from an ensemble of lattice SU (2) gauge configurations. This removal adds short-range disorder. Nevertheless, we observe long-range order in the modified ensemble: confinement is lost and chiral symmetry is restored (together with trivial topology), proving that center vortices are responsible for both phenomena. As for the Abelian monopoles, they survive but their percolation properties are lost.

We study, by numerical simulations on a lattice, the behaviour of the gauge-invariant two-point correlation functions of the gauge field strengths in the QCD vacuum with dynamical fermions.Comment: 11 pages, LaTeX file, + 2 PS figure