Supersymmetry Enhancement and Junctions in S-folds

We study supersymmetry enhancement from ${\cal N}=3$ to ${\cal N}=4$ proposed by Aharony and Tachikawa by using string junctions in S-folds. The central charges carried by junctions play a central role in our analysis. We consider planer junctions in a specific plane. Before the S-folding they carry two complex central charges, which we denote by $Z$ and $\bar Z$. The S-fold projection eliminates $\bar Z$ as well as one of the four supercharges, and when the supersymmetry is enhanced $\bar Z$ should be reproduced by some non-perturbative mechanism. For the models of $\mathbb{Z}_3$ and $\mathbb{Z}_4$ S-folds which are expected to give $SU(3)$ and $SO(5)$ ${\cal N}=4$ theories we compare the junction spectra with those in perturbative brane realization of the same theories. We establish one-to-one correspondence so that $Z$ coincides. By using the correspondence we also give an expression for the enhanced central charge $\bar Z$.Comment: 30 pages, 7 figures, v2: minor corrections, version accepted for publication in JHE

Failure Mode of Columns of Existing R/C Building Damaged During the 2007 Niigata Chuetsu-Oki Earthquake

AbstractThe school building investigated was a 3-story reinforced concrete (R/C) building built in 1963. The building suffered from a great deal of damage during both the 2004 Chuetsu Earthquake and the 2007 Chuetsu-Oki Earthquake. The damage of the first and second floors during Chuetsu Earthquake was light and that by Chuetsu-Oki Earthquake was moderate. The previous study revealed that the anticipated design failure modes of most of the columns of the building were flexure although most of them actually failed in shear during the 2007 earthquake. This is an important problem to be studied. In order to study the reason why the columns failed in shear rather than in flexural, a parametric study was conducted, paying attention to parameters including the strength of concrete, hoop spacing and subjected axial force. But those studies could not explain the real phenomenon clearly. After that the effects of cutoff location of longitudinal reinforcement bars were examined and it was concluded that the diagonal crack generated from cutoff point caused shear failure in these columns