### Abstract

We study the conformal field theory of a free massless scalar field living on the half-line with interactions introduced via a periodic potential at the boundary. An SU(2) current algebra underlies this system and the interacting boundary state is given by a global SU(2) rotation of the left-moving fields in the zero-potential (Neumann) boundary state. As the potential strength varies from zero to infinity, the boundary state interpolates between the Neumann and the Dirichlet values. The full S-matrix for scattering from the boundary, with arbitrary particle production, is explicitly computed. To maintain unitarity, it is necessary to attribute a hidden discrete "soliton" degree of freedom to the boundary. The same unitarity puzzle occurs in the Kondo problem, and we anticipate a similar solution.

Original language | English (US) |
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Pages (from-to) | 417-448 |

Number of pages | 32 |

Journal | Nuclear Physics, Section B |

Volume | 422 |

Issue number | 3 |

DOIs | |

State | Published - Jul 11 1994 |

### All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics

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## Cite this

*Nuclear Physics, Section B*,

*422*(3), 417-448. https://doi.org/10.1016/0550-3213(94)90440-5