QCD string

In quantum chromodynamics, or more generally, quantum gauge theories with a connection which are confining, stringlike degrees of freedom called QCD strings or QCD flux tubes form. These stringlike excitations are responsible for the confinement of color charges since they are always attached to at least a string and the strings have tension. Their existence can be predicted from the dual spin network/spin foam models (this duality is exact over a lattice). To a surprisingly good approximation, these strings are described phenomenologically by the Polyakov action, making them noncritical strings.