pub fn klein_gordon_kernel(
psi_manifold: &Manifold<f64, f64>,
mass: f64,
) -> Result<CausalTensor<f64>, PhysicsError>Expand description
Calculates the Klein-Gordon operator action: $(\Delta + m^2)\psi$.
Computes the action of the Klein-Gordon operator on a scalar field $\psi$. The result is the “source” or “force” required to maintain that field configuration, or zero if the field satisfies the free equation.
§Sign Convention
This implementation uses the Euclidean/Riemannian convention where the Laplacian $\Delta$ is positive-definite (akin to $k^2$). The equation is $(\Delta + m^2)\psi = 0$.
If Manifold contains a Lorentzian metric, the laplacian method (defined via Hodge stars)
naturally becomes the d’Alembertian $\square$ (Laplace-Beltrami). In that case, the equation
form $(\square + m^2)\psi = 0$ is preserved if the signature (+—) is handled by the metric.
§Arguments
psi_manifold- Manifold containing the scalar field $\psi$ (0-form).mass- Mass $m$.
§Returns
Result<CausalTensor<f64>, PhysicsError>- The result of applying the operator $O(\psi)$.