01156nas a2200121   4500008004300000245007100043210006800114520075900182100002000941700001900961700001800980856003600998       2006                        en_Ud  00aA Hopf bundle over a quantum four-sphere from the symplectic group0 aHopf bundle over a quantum foursphere from the symplectic group3 aWe 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 $A(SU_q(2))$.1 aLandi, Giovanni1 aPagani, Chiara1 aReina, Cesare  uhttp://hdl.handle.net/1963/2179