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We study 5d and 6d SCFTs with eight supercharges by using 5-brane web diagrams in Type IIB string theory. There are two important properties of the web diagram. One is that it enables us to compute the exact partition function of the 5d theory on the 5-brane web. Even though the web diagram is not dual to a toric geometry, we develop a technique to compute the partition function by using the topological vertex. The other is that a new class of the 5-brane web diagram is conjectured to imply that the corresponding 5d theory has a 6d superconformal fixed point at high energies. Such a web diagram is called Tao web diagram. By using the Tao web diagram, we conjecture new 5d theories whose UV completion is a 6d SCFT. Moreover, we can show that a brane configuration realizing the 6d SCFT may reduce to the Tao web diagram, giving a direct way of identifying the 6d description of the 5d theory. This construction also indicates various dualities of the 5d theories.

Using the method of flux fusion anomaly test recently developed by M. Hermele and X. Chen (arXiv:1508.00573), we show that the possible ways of fractionalize crystal symmetry is greatly restricted if we assume the spin liquid has an SU(2) spin rotation symmetry and the spinon carries a half-integer spin. For a Z_2 spin liquid, under these assumptions the vison can only take the crystal symmetry fractionalization described by the Ising gauge theory. For a chiral spin liquid these assumptions imply that the spinon must also take fractionalized quantum numbers of crystal symmetries.