Irrational constants in positronium decays
نویسندگان
چکیده
Most of the multi-loop analytical calculations in quantum field theories have been dine for socalled single-scale problems. This means that the evaluated integrals are basicaly expressed as numerical constants up to a trivial scale factor. Examples of such problems include almost all renormalization group calculations, evaluations of the critical exponents, anomalous magnetic moments of the electron and the muon, matching calculations in effective theories (e.g. HQFT, NRQFT) and many others. Usually analytical results involve the so-called Euler–Zagier (EZ) sums of the form
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