Solid evidence exists that confinement in quenched QCD (~MXY gauge SU(3) thwry) is prodwed by condensation of magnetic monopoles [ 1,2]. The t.ool lused t.o produce t.hat. evidence is a, disorder parameter (!L), whidr is the TWXUIII expectation value of an operator carrying a non zero magnetic charge, a.s defined by wme abelian projwtion. Kurnerical results show that (p} is independent on the choice of the abeliw projection [3], a prop&y &at. has been recently proven a,rialytitally [4]. The result is that (pi} # 0 in the confined phase, indicating Eggs breaking of a mi~gnrtic 1J( 1) symrnetrg; (p} = 0 in thr deconfined phase, where t;he magnetic charge is super-selected. 14 is au X(3), gauge irrvariarit, singlet operator. It is also invariant under the magnetic U(1) gauge symmetry, but has a global magnetic clra~ge~ it is in fact a Dirac operator 151. All this confirms the original idea [G,7] that &e vacuum is a dual superconductor in the confined phase, in which the electric field between a ye pair is channeled into an Abrikosov flux tube, so that the energy is propostional to the distance, E = al& The disorder parameter ,u can be eq~w,lly well defined in full QCD, i.e. in the presence of dynamical quarks [8].
In the pure ga,uge theor there exists it t,raditional order lwarneter, the Polyalsov line {L) ,