Some Aspects of Trace Anomaly
  We review briefly some well known facts about trace anomaly and then concentrate on its 'infrared' manifestation. Among other things we show by means of dispersion relations that dilatations and translations are conflicting symmetries. We discuss the occurrence of some subtraction constants in convergent dispersion relations and illustrate it on the decay process of Higgs to two photons in the electroweak theory. 
M. Schnabl