Sine-square deformation and its relevance to string theory

Sine-square deformation, a recently found modulation of the coupling strength in certain statistical models, is discussed in the context of two-dimensional (2D) conformal field theories (CFTs), with particular attention to open/closed string duality. This deformation is shown to be nontrivial and leads to a divergence in the worldsheet metric. The structure of the vacua of the deformed theory is also investigated. The approach advocated here may provide an understanding of string duality through the worldsheet dynamics.