  We calculate the entanglement entropy for a sphere and a massless scalar
field in any dimensions. The reduced density matrix is expressed in terms of
the infinitesimal generator of conformal transformations keeping the sphere
fixed. The problem is mapped to the one of a thermal gas in a hyperbolic space
and solved by the heat kernel approach. The coefficient of the logarithmic term
in the entropy for 2 and 4 spacetime dimensions are in accordance with previous
numerical and analytical results. In particular, the four dimensional result,
together with the one reported by Solodukhin, gives support to the
Ryu-Takayanagi holographic anzats. We also find there is no logarithmic
contribution to the entropy for odd space time dimensions.
