Editing Lambert W function (section)

=== Exact solution of QCD coupling constant ===
In [[Quantum chromodynamics]], the [[quantum field theory]] of the [[Strong interaction]], the [[coupling constant]] <math>\alpha_\text{s}</math> is computed perturbatively, the order n corresponding to [[Feynman diagrams]] including n quantum loops.<ref name=PPNG_review_2016>{{cite journal | arxiv=1604.08082 | doi=10.1016/j.ppnp.2016.04.003 | title=The QCD running coupling | year=2016 | last1=Deur | first1=Alexandre | last2=Brodsky | first2=Stanley J. | last3=De Téramond | first3=Guy F. | journal=Progress in Particle and Nuclear Physics | volume=90 | pages=1–74 | bibcode=2016PrPNP..90....1D | s2cid=118854278 }}</ref> The first order, {{math|1=''n'' = 1}}, solution is exact (at that order) and analytical. At higher orders, {{math|1=''n'' > 1}}, there is no exact and analytical solution and one typically uses an [[iterative method]] to furnish an approximate solution. However, for second order, {{math|1=''n'' = 2}}, the Lambert function provides an exact (if non-analytical) solution.<ref name=PPNG_review_2016 />