candidate: We will take the cosmological constant Λ equal to zero ( one of the requirements of the properties of the gravitational equations is that they reduce to the free - space field equations when the density of energy in space " Tαγ " is zero , therefore that the cosmological constant λ appearing in this equation is zero ) so the field equation becomes:formula_4where " Rαγ " s the Ricci tensor , " gαγ " is the metric tensor , " R " the scalar curvature and κ is Einstein 's constant we will calculate in the next section ..