On the spectrum of closed k=2 flux tubes in D=2+1 SU(N) gauge theories

Understand

We calculate the energy spectrum of a k=2 flux tube that is closed around a spatial torus, as a function of its length l.

• We do so for SU(4) and SU(5) gauge theories in 2 space dimensions.
• We find that to a very good approximation the eigenstates belong to the irreducible representations of the SU(N) group rather than just to its center, Z_N.
• We obtain convincing evidence that the low-lying states are, for l not too small, very close to those of the Nambu-Goto free string theory (in flat space-time).