EN
We construct $𝓒^{∞}$ maps T on the interval and on the circle which are Lebesgue exact preserving an absolutely continuous infinite measure μ ≪ λ, such that for any probability measure ν ≪ λ the sequence $(n^{-1} ∑_{k=0}^{n-1} ν∘T^{-k})_{n≥1}$ of arithmetical averages of image measures does not converge weakly.