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## Main Question or Discussion Point

From the action ∫Ldt =∫ι√|g|d

For gravitational field why is this ι is replaced by the Ricci scaler R which yield field equations in vaccum.(R

Is it that the lagrangian density corresponding to vaccum is the Ricci scaler??

^{4}x where |g| is the determinant of the metric .and ι the lagrangian density.For gravitational field why is this ι is replaced by the Ricci scaler R which yield field equations in vaccum.(R

_{ij}-1/2Rg_{ij})=0Is it that the lagrangian density corresponding to vaccum is the Ricci scaler??