Considered is the standard 4-dimensional ${ \cal N}=1\,\,SU(N_c)$ SQCD with $1\leq N_F\leq N_c$ quark flavors with masses $m_{ Q,i}$. { \bf The gauge invariant order parameter $\rho$ is introduced in \cite{ ch1} distinguishing confinement (with $\rho=0$) and higgs (with $\rho\neq 0$) phases}. Using a number of independent arguments for different variants of transition between the confinement and higgs regimes in these theories, it is shown that { \bf transitions between these regimes are not crossovers but the phase transitions}. In \cite{ FS} the very special $SU(N_c)$ QCD theory with $N_F=N_c$ defective scalar "quarks" was considered by E.Fradkin and S.H.Shenker. The conclusion of \cite{ FS} was that { \bf the transition between the confinement and higgs regimes is the analytic crossover}. And although the theory considered in \cite{ FS} was very specific, the experience shows that up to now there is a widely spread opinion that this conclusion has general applicability. This model \cite{ FS} is criticized in \cite{ ch1},\cite{ ch2} as incompatible with and very different from the standard non-SUSY $SU(N_c)\,\,N_F=N_c$ QCD theory with standard scalar quarks with all their physical degrees of freedom. It is emphasized that this model \cite{ FS} is really { \bf the Stuckelberg $SU(N_c)$ YM-theory with no dynamical electric quarks and massive all $N_c^2-1$ electric gluons with fixed by hands nonzero masses}. There is no genuine confinement in this theory, it stays permanently in the completely higgsed (i.e. condensed) by hands phase only. And this is a reason for a crossover in this theory. While in the theory with standard scalar quarks there is the phase transition between the confinement (at $0 < |v|\ll \Lambda_{ QCD}$) and higgs (at $|v|\gg\Lambda_{ QCD}$) regimes.
Categories: hep-th