String Field Theory and D-brane Dynamics

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The research results of our project for three academic years in 1998-2000 are as follows :1. String field theory of unoriented open-closed string system : We presented a full order action of the string field theory for the mixed system of open and closed strings and gave a complete proof for its BRS invariance. Anomalous one-loop graphs are identified which are expected to cancel the anomaly. In the course, we proved a generalized version of the GGRT (generalized gluing resmoothing theorem) by Peskin et al.2. Supersymmetric E_6 grand unified model : We constructed a supersymmetric E_6 grand unified model which incorporates the Frogatt-Nielsen mechanism using anomalous U (1) symmetry and can consistently explain all the mass matrices of quark, lepton and neutrino sectors. In the process of analyzing mass matrices, we found an interesting novel relation which holds remarkably well empirically and relates the large lepton mixing angle to the quark masses and a mixing angle.3. Brane world scenario : We pointed out the imporatance of the fluctuation mode of the 3-brane on which our world lies, and proved that the couplings of the higher Kaluza-Klein modes of the bulk gauge field are exponentially suppressed if the brane tension is small. Evaluating the contributions of the fluctuation mode to the fifth force and the supernova cooling process, we obtained the lower bound for the brane tension. As a preparation for investigating the brane world scenario seriously, we first derived a supergravity tensor calculus in 5 dimensions from the known 6-dimensional superconformal tensor calculus, and then explicitly calculated and invariant action for the general system of matter and Yang-Mills supermultiplets coupled to supergravity in 5 dimensions.