Nonminimally coupled scalar field
= Nonminimally coupled scalar field
A nonminimal scalar coupling includes an interaction between the field and spacetime curvature, such as $-\xi R\Phi^2$ in the <Lagrangian density>. The <Euler-Lagrange field equation> for $\mathcal L=-\frac12(\nabla\Phi)^2-\xi R\Phi^2$ is $\Box\Phi-2\xi R\Phi=0$. The coefficient is convention dependent: an action written with $-\frac12\xi R\Phi^2$ has $\xi$ instead of $2\xi$.