Comments on Baryon-like Operators in N=6 Chern-Simons-matter theory of ABJM

We show that baryon-like operators exist in the N=6 superconformal Chern-Simons-matter theory constructed by Aharony, Bergman, Jafferis and Maldacena (ABJM). This involves the introduction of Wilson(or 't Hooft) lines ending on baryon-like operators and we show that the presence of such lines cannot be detected by the fields in the theory. The same construction can be used to make magnetic monopoles charged under the diagonal U(1) gauge group with arbitrary non-integral charge. If we do not include such monopole configurations in the path integral, the moduli space is known to be given by the symmetric N copies of C^4/Z_k. However, if we allow for such monopole configurations, the flux quantization conditions change so that we do not have a discrete gauge symmetry and effectively the (SU(N)xSU(N))/Z_N gauge theory remains. We discuss the possibility of the level-rank duality of the theory.
Comment: 19 pages, 3 figures; v2: references added; v3: comments added in the introduction and discussion; v4: a footnote added in p.6