 NSFPAR ID:
 10428493
 Date Published:
 Journal Name:
 Journal of High Energy Physics
 Volume:
 2023
 Issue:
 4
 ISSN:
 10298479
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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null (Ed.)A bstract Twodimensional SU( N ) gauge theory coupled to a Majorana fermion in the adjoint representation is a nice toy model for higherdimensional gauge dynamics. It possesses a multitude of “gluinoball” bound states whose spectrum has been studied using numerical diagonalizations of the lightcone Hamiltonian. We extend this model by coupling it to N f flavors of fundamental Dirac fermions (quarks). The extended model also contains mesonlike bound states, both bosonic and fermionic, which in the large N limit decouple from the gluinoballs. We study the large N meson spectrum using the Discretized LightCone Quantization (DLCQ). When all the fermions are massless, we exhibit an exact $$ \mathfrak{osp} $$ osp (14) symmetry algebra that leads to an infinite number of degeneracies in the DLCQ approach. More generally, we show that many singletrace states in the theory are threshold bound states that are degenerate with multitrace states. These exact degeneracies can be explained using the KacMoody algebra of the SU( N ) current. We also present strong numerical evidence that additional threshold states appear in the continuum limit. Finally, we make the quarks massive while keeping the adjoint fermion massless. In this case too, we observe some exact degeneracies that show that the spectrum of mesons becomes continuous above a certain threshold. This demonstrates quantitatively that the fundamental string tension vanishes in the massless adjoint QCD 2 without explicit fourfermion operators.more » « less

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