Title | A Hopf bundle over a quantum four-sphere from the symplectic group |

Publication Type | Journal Article |

Year of Publication | 2006 |

Authors | Landi, G, Pagani, C, Reina, C |

Journal | Commun. Math. Phys. 263 (2006) 65-88 |

Abstract | We construct a quantum version of the SU(2) Hopf bundle $S^7 \\\\to S^4$. The quantum sphere $S^7_q$ arises from the symplectic group $Sp_q(2)$ and a quantum 4-sphere $S^4_q$ is obtained via a suitable self-adjoint idempotent $p$ whose entries generate the algebra $A(S^4_q)$ of polynomial functions over it. This projection determines a deformation of an (anti-)instanton bundle over the classical sphere $S^4$. We compute the fundamental $K$-homology class of $S^4_q$ and pair it with the class of $p$ in the $K$-theory getting the value -1 for the topological charge. There is a right coaction of $SU_q(2)$ on $S^7_q$ such that the algebra $A(S^7_q)$ is a non trivial quantum principal bundle over $A(S^4_q)$ with structure quantum group $A(SU_q(2))$. |

URL | http://hdl.handle.net/1963/2179 |

DOI | 10.1007/s00220-005-1494-3 |

## A Hopf bundle over a quantum four-sphere from the symplectic group

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