Y. Hatsuda, A new approach to black hole quasinormal modes

Black holes have characteristic damped oscillatory modes called quasinormal modes. I will review how to compute these frequencies, and will explain a new refined way.

D. Polyakov, Mixed States in String Theory and Higher-Spin Entanglement

Standard vertex operators in string theory define pure states with wavefunctions describing point-like excitations (such as a photon). In my talk, I describe new classes of vertex operators describing ensembles of mixed states in string theory. Acting on the vacuum, these operators define density matrices which eigenvalues describe the entanglement between string modes of different spins. We explicitly construct these operators and compute the related entanglement entropies.

Z. Tsuboi, Reflection equation algebras and Baxter Q-operators for open spin chains

The reflection equation is a fundamental equation in quantum integrable systems with open boundary conditions. I will discuss underlying symmetries of the reflection equation (q-Onsager type algebras) and its solutions (K-matrices). Then I explain how to construct Baxter Q-operators for open spin chains associated with the quantum affine algebra \(U_{q}(\widehat{sl}_2) \).

F. Yagi, Complete prepotential for five dimensional N=1 superconformal field theory

The prepotential for five dimensional N=1 supersymmetric gauge theory at Coulomb branch is known to be perturbatively 1-loop exact and the explicit formula was found by Intriligator, Morrison and Seiberg. It is given by adding the 1-loop corrections from the vector multiplets and the hypermultiplets to the tree level prepotential. Since the instanton particles are known to play important role in these theories, it is natural to ask whether there is contribution from them as non-perturbative effect. We discuss that there are indeed such terms in the prepotential if we consider all the parameter region for the mass deformation from the superconformal field theory realized at the UV fixed point. The enhanced global symmetry also plays an important role.

S. Yamaguchi, Atiyah-Patodi-Singer index from the domain-wall Dirac operator

The Atiyah-Patodi-Singer (APS) index theorem attracts attention for understanding physics on the surface of materials in topological phases. However the APS boundary condition is non-local and hardly realized on the surface of materials. In this talk, we consider the domain-wall fermion Dirac operator with a local boundary condition, which is naturally given by the kink structure in the mass term. We compute the index that appears in the phase of the partition function by Fujikawa's method and find that this index is the same as the APS index. We also give a mathematically rigorous proof of this relation.

H. Zhang, Web of W Algebras

Y. Zhou, Discrete Anomalies in 2d CFT