Irrational constants in positronium decays
  We establish irrational constants, that contribute to the positronium lifetime at $O(\alpha)$ and $O(\alpha^2)$ order. In particular we show, that a new type of constants appear, which are not related to Euler--Zagier sums or multiple $\zeta$ values. 
B. A. Kniehl, A. V. Kotikov, O. L. Veretin