Landau坐标条件与Mφller坐标条件

LANDAU COORDINATE CONDITIONS AND MLLER COORDINATE CONDITIONS

Ｌａｎｄａｕ坐标条件保持时空度规号差，但不保持度规矩阵对角项的符号差．坐标条件保持这２种号差。由坐标条件推出了Ｌａｎｄａｕ坐标条件，Ｌａｎｄａｕ坐标条件的主要前提是光沿闭合回路的平均速度是常数ｃ．坐标条件的主要前提是在惯性系中光速为常数ｃ．由于Ｅｉｎｓｔｅｉｎ相对论的前提之一是在惯性系中光速为常数ｃ，所以在Ｅｉｎｓｔｅｉｎ相对论中应用坐标条件是更有效更方便的．在已知的Ｅｉｎｓｔｅｉｎ场方程所有解中，度规矩阵对角项的符号差都为＋２（或－２），其原因就在这里．

Landau coordinate conditions keep the signature of a space time metric, however do not keep the signature of the diagnal terms of the metric matrix. coordinate conditions keep these signatures. Landau coordinate conditions are derived from coordinate conditions. The essential presuppositon of landau coordinate conditions is that the average speed of light over a closed path is the constant c. The essential presupposition of coordinate conditions is that light speed in an inertial system is the constant c. It pointed that coordinate conditions are more available and more convenient in Einstein relativity, because on of the presupposition of Einstein relativity is also light speed in a inertial system is the constant c. This is why the signature of the diagnal of a metric matrixis +2(or-2) in all known solutions of Einstein field equations.