This condition is used in the derivation of the Liénard–Wiechert (“l’yay-NARR VEE-curt”) potentials to reduce a degree of freedom in the time-dependent field. For 10 points each:
[10h] Name this condition that sets the four-gradient of the electromagnetic four-potential equal to zero.
ANSWER: Lorenz gauge condition [accept Lorenz gauge fixing; prompt on gauge condition or gauge fixing]
[10e] The Lorenz gauge condition is sometimes used instead of this scientist’s gauge condition because it is Lorentz-invariant. This scientist names an inverse-square force law between charged objects.
ANSWER: Charles-Augustin de Coulomb [accept Coulomb’s law or Coulomb gauge condition]
[10m] The Lorenz gauge allows one to write Maxwell’s equations using the d’Alembertian (“dal-ahm-BARE-shin”), which generalizes this operation to Minkowski space. This operation is the divergence of the gradient and is symbolized “nabla squared.”
ANSWER: Laplacian [or Laplace operator]
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