Example image of eyePlorer eyePlorer map for 'Four-current': Charge (physics) Current density Electromagnetism Four-vector General relativity Lorentz covariance Special relativity Conservation law Continuity equation Dimension Four-gradient Spacetime Einstein notation Covariant derivative Covariant formulation of classical electromagnetism Graviton P-form electrodynamics Dirac adjoint Electromagnetic four-potential Weinberg–Witten theorem Conserved current Algebra of physical space Charge conservation D'Alembert operator Electromagnetic tensor Gravitomagnetism Classical electromagnetism and special relativity Magnetic potential Geometrized unit system Classical field theory Physical theories modified by general relativity Nucleon Gauge fixing Mathematical descriptions of the electromagnetic field Theoretical motivation for general relativity Maxwell's equations