Research output: Contribution to journal › Journal article › peer-review

Published

<mark>Journal publication date</mark> | 05/2013 |
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<mark>Journal</mark> | Communications in Mathematical Physics |

Issue number | 1 |

Volume | 320 |

Number of pages | 26 |

Pages (from-to) | 275-300 |

Publication Status | Published |

<mark>Original language</mark> | English |

We study the representation theory of a conformal net A on S 1 from a K-theoretical point of view using its universal C*-algebra C∗(A) . We prove that if A satisfies the split property then, for every representation π of A with finite statistical dimension, π(C∗(A)) is weakly closed and hence a finite direct sum of type I∞ factors. We define the more manageable locally normal universal C*-algebra C∗ln(A) as the quotient of C∗(A) by its largest ideal vanishing in all locally normal representations and we investigate its structure. In particular, if A is completely rational with n sectors, then C∗ln(A) is a direct sum of n type I∞ factors. Its ideal KA of compact operators has nontrivial K-theory, and we prove that the DHR endomorphisms of C∗(A) with finite statistical dimension act on KA , giving rise to an action of the fusion semiring of DHR sectors on K0(KA) . Moreover, we show that this action corresponds to the regular representation of the associated fusion algebra.