Analysis of QCD by superstring theory

It has been proposed by Sakai and Sugimoto recently to construct QCD by using superstring theory and to analyze on the basis of gauge/gravity correspondence. It is tried here to explain the practical applications of the analyzing method specifically to make it possible for those readers, who are not familiar with the superstring theory, to use this method only by reading this paper. Using the method proposed, the description by five-dimensional gauge theory expressed by the action explained in the text is naturally derived for the effective theory of mesons. Once the expression of the action is accepted, it is no more necessary to refer to the superstring theory and gauge/gravity correspondence. In section 2) Specific Important Points of the Analyses: two subsections are provided. 2.1 Five-dimensional gauge theory to four dimensional meson effective theory, and 2.2 Introduction of external field. In section 3) Main Results, the following subsections are given, 3.1 General notes, 3.2 Meson spectra, 3.3 Spontaneous breaking of chiral symmetry and effective action of pions, 3.4 Vector meson dominance, 3.5 Kawarabayashi-Suzuki-Riazuddin-Fawazuddin (KSRF) relation, 3.6 Pion form factor, 37 Chiral anomaly and Wess-Zumino-Witten term, 3.8 ω meson decay, and 3.9 Other topics. In the summary, an overview of the relation between the superstring theory and QCD is given. (S. Funahashi)