Closed flux tubes in higher representations and their string description in D=2+1 SU(N) gauge theories

Understand

We calculate, numerically, the low-lying spectrum of closed confining flux tubes that carry flux in different representations of SU(N).

• We do so for SU(6) at beta=171, where the calculated low-energy physics is very close to the continuum limit and, in many respects, also close to N=infinity.
• We focus on the adjoint, 84, 120, k=2A,2S and k=3A,3M,3S representations and provide evidence that the corresponding flux tubes, albeit mostly unstable, do in fact exist.
• We observe that the ground state of a flux tube with momentum along its axis appears to be well defined in all cases and is well described by the Nambu-Goto free string spectrum, all the way down to very small lengths, just as it is for flux tubes carrying fundamental flux.