  We investigate baryon-baryon (BB) interactions in the 3-flavor full QCD
simulations with degenerate quark masses for all flavors. The BB potentials in
the orbital S-wave are extracted from the Nambu-Bethe-Salpeter wave functions
measured on the lattice. We observe strong flavor-spin dependences of the BB
potentials at short distances. In particular, a strong repulsive core exists in
the flavor-octet and spin-singlet channel (the 8_s representation), while an
attractive core appears in the flavor singlet channel (the 1 representation).
We discuss a relation of such flavor-spin dependence with the Pauli exclusion
principle in the quark level. Possible existence of an H-dibaryon resonance
above the Lambda-Lambda threshold is also discussed.
