Research On Energy, Momentum, Angular Momentum And Theirs Guage Property Of Gravitational Field

Gravity, which is known and studied by human for a long time, is one of four foundmental forces in nature. The main theory of gravity can be summarized as follow: Newton’s Gravity in1687in classic physics region and Einstein’s General Relativity in1915in morden physics region, which is equivalent to Newton’s gravity in classic physics limit. Gauge Field Theory, which is widely recognized as the most powerful theoretical tool to study foundmental forces in nature, has been successful in helping human understanding the nature of electromagnetic, weak and strong interaction. We will use Gauge Field Theory to study gravitational interaction in this paper. Specificly, we analyze the gauge problem of gravitational field via using the Gauge-Invariance Principle of Gauge Field Theory to General Relativity. The aim is that the three important quantities-gauge invariance energy, momentum and angular momentum of gravitational field can be constructed.General Covariance Principle says introducing a localized non-inertial frame can eliminate gravity in any point in General Relativity. The general understanding of above sentence is the uncertain existence of gravitational field in any frame. We want to claim: the effect of gravitational field can be local eliminated, but the gravitational field itself (gravity energy) can’t. Based on this point of view, we attribut the property of the effect of gravitational field can be locally eliminated to the redundant non-physical degrees of freedom exist in gravitational field. Then, two methods that can eliminate the non-physical degrees of freedom in gravitational field are presented in this paper. Enlightened by the radiation gauge in Abelian Gauge Field can totally eliminate all the redundant non-physical degrees of freedom of vector field, the first way is to find the simlar "radiation gauge"’for gravity. Unfortunately, the "radiation gauge" for gravity is not unique. We prove that there does exist a general "radiation gauge" for gravity and all the radiation gauges can eliminate the non-physical degrees of freedom of gravitational field. We discuss the differences among these general "radiation gauges" and find that the non-unique of "radiation gauge" is the unique nature of tensor field. The second way is to use physical decomposition of gauge fields to eliminate the redundant non-physical degrees of freedom of Abelian Gauge Field and Non-Abelian Gauge Field, which is gradually built up in recent years by Chen and co-workers. We extend this physical decomposition of gauge field approach to gravity by separating metric tensor to pure physical metric and pure gauge metric and, then finding their respectively unique solution in mathematics. In principle, one can construct pure physical energy, momentum and angular momentum by using the pure physical metric.