SU(3) constraints on cryptoexotic pentaquarks

We examine SU(3) constraints on the spectrum and decay widths of cryptoexotic nucleon-like states in antidecuplet of pentaquarks. We show that in the ideal mixing scenario the number of free matrix elements describing splittings reduces from 4 to 2. Model-independent sum rules are derived. Using as input $\Theta^+$ and $\Xi_{3/2}$ masses we show that it is difficult to interpret Roper and $N^{\ast}(1710)$ nucleon resonances as cryptoexotic pentaquarks. Large $N_c$ limit for antidecuplet and accompanying octet in the diqaurk picture and the analogy with the soliton model is also discussed.