It is called vacuum field equation, where yes ricci tensor 。 The vacuum field equation is Einstein field equation A special case of Dynamic tensor 。 Einstein's field equation is , the left and right sides of the equation are inversely combined by the gauge , due to , combined with Ritchie scalar expression , i.e , where Is the trace obtained by the dynamic tensor with the help of the metric When happen now and then , so , obtained by substituting the entrance equation The Min metric is the simplest and exact solution of the vacuum field equation, because the Min metric Cartesian coordinate system Components in are constant everywhere Therefore, the Kirschner symbol and its partial derivative are both 0, so the Ritchie tensor is 0, which satisfies the vacuum field equation
Other well-known exact solutions of the vacuum field equation include the description of space-time around static spherically symmetric stars [1] Schwarzschild gauge And static axisymmetric stars kerr metric 。 
