Flat-space Dirac factorization
= Flat-space Dirac factorization
{title2=$(i\not\partial+m)(i\not\partial-m)=-(\Box+m^2)$}
The <gamma matrix> <Clifford algebra> and commuting <partial derivatives> give $(\not\partial)^2=\Box$. Thus every free <Dirac equation> solution also solves the <Klein-Gordon equation> componentwise. The converse is false without the first-order <spinor> constraint: the second-order equation alone allows twice as much independent initial data.