= Minimally coupled scalar field
{title2=$L=-\tfrac12g^{ab}\nabla_a\phi\nabla_b\phi-V(\phi)$}
A real <scalar field> is minimally coupled to a <metric tensor> when its kinetic term uses the metric contraction of first derivatives and its <scalar potential> depends only on the field, without an explicit <scalar curvature> coupling. For <metric signature> $(-,+,+,+)$ the displayed <Lagrangian> and volume density $\sqrt{-g}$ give $\Box\phi-V'(\phi)=0$. Its <stress-energy tensor> is $T_{ab}=\nabla_a\phi\nabla_b\phi-g_{ab}[\tfrac12(\nabla\phi)^2+V]$. The <scalar stress-energy divergence identity> explains its conservation on the field equation.
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