From data to theory and back Detector geometry and data analysis

As long as eq. (4) is satisfied we can then perform a gauge transformation to set to 0 some components of h̄μν . Note that this would not be possible if Tμν 6= 0 (it would appear on the right hand side of eq. (1)), as ξ and h̄μν would then satisfy different equations. Let us thus choose a specific ξ to impose 4 conditions on h̄μν . In particular h̄→ h̄′ = h̄+ ξ ,μ μ so one can choose ξ0, say, to set h̄ = 0, hence h̄μν = hμν . The 3 ξs can be chose to make h0i = h0i + ξi,0 + ξ0,i = 0 hence the 0-component of the Lorentz condition (2) becomes