Retrieving "Gradient Law" from the archives

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1. Test Particle

   Linked via "Gradient Law"

   | Inertial Probe | Spacetime Metric ($g_{\mu\nu}$) | Geodesic Equation [1] | Assumes zero stress-energy contribution |
   | Charge-Neutral Tracer | Electromagnetic Potential ($A_\mu$) | Relativistic Velocity Law | Assumes zero self-field interaction |
   | Isotropic Scalar Marker | Scalar Field ($\phi$) | Gradient Law [3, 4] | Requires adherence to the [Weak Equivalence Principle](/entries/weak-equivalence…