Pentaquark Baryons in String Theory

The recently observed pentaquark baryons $\Theta^{+}$ and $\Xi^{--}$ arestudied in the dual gravity theory of QCD. By developing a general formulation useful for studying the branched stringweb in a curved space, simple mass formulae of the pentaquark baryons arederived in the Maldacena prototype model for supersymmetric QCD and a morerealistic model for ordinary QCD. Even though the approximations adopted herein deriving these formulae are extremely naive, the predicted values of themasses do not differ significantly from their experimental values. We thusconclude that this approach is promising for the purpose of obtaining adescription of the observed masses of pentaquarks and of their extremely narrowdecay widths. With the aim of constructing more reliable mass formulae, apreliminary sketch is given of how spin, the hyperfine interaction and parityare considered in the string picture.Comment: 38 pages, 7 figures, LaTex;to be published in Prog. Theor. Phys. Vol.112, No.2, August(2004);in ver2 references are added and Eq.(123) is modified;in ver3 references are added and English is improve