# electricity and gravity

19 Oct 2016why is there a cosmological constant (even) in the classical Poisson-equation, \(\Delta\Phi = 4\pi G\rho + \lambda\), but no such term in the wave-equation of electrodynamics, \(\Box A^\mu = 4\pi\jmath^\mu\)?

why is there a cosmological constant (even) in the classical Poisson-equation, \(\Delta\Phi = 4\pi G\rho + \lambda\), but no such term in the wave-equation of electrodynamics, \(\Box A^\mu = 4\pi\jmath^\mu\)?