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arXiv 1002.5045gr-qcastro-ph.COhep-th
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经典场论中小物体的运动

Motion of Small Bodies in Classical Field Theory

Samuel E. Gralla

摘要:

我展示了优先级如何使用R。瓦尔德在广义相对论中关于测地运动的理论可以推广到四维时空中度量场和其他张量场的经典场论,这些场1)是二阶的,2)是从一个自同态协变的拉格朗日量导出的。该方法是考虑一个参数家庭的解决方案,满足一定的假设,旨在反映存在的身体的大小,质量和各种费用同时缩放到零的场方程。(That这样的解的存在对我们的结果所适用的理论类别施加了进一步的限制。)假设只适用于物体外的时空区域,因此结果既适用于黑洞,也适用于普通物体。由收缩、消失的天体“留下”的世界线被解释为它的最低阶运动。这个世界线的方程来自于理论的“比安奇恒等式”,除了二阶外,没有使用场方程的任何性质。因此,一个理论的力定律的形式只取决于它的各种张量场的秩,而场方程只与从外场确定特定物体的电荷有关。我明确地推导出标量场和矢量场情况下的力定律(和质量演化定律),并给出高阶情况下的配方。注意,矢量力定律相当复杂,只有在麦克斯韦规范对称性存在的情况下才能简化为洛伦兹力定律。结果的例子应用是超越牛顿极限的“变色龙”物体的运动,以及(经典)非阿贝尔规范理论中物体的运动。我还对标度在物体运动普遍性的出现中所起的作用作了一些评论。

英文摘要:

I show how prior work with R. Wald on geodesic motion in general relativity can be generalized to classical field theories of a metric and other tensor fields on four-dimensional spacetime that 1) are second-order and 2) follow from a diffeomorphism-covariant Lagrangian. The approach is to consider a one-parameter-family of solutions to the field equations satisfying certain assumptions designed to reflect the existence of a body whose size, mass, and various charges are simultaneously scaled to zero. (That such solutions exist places a further restriction on the class of theories to which our results apply.) Assumptions are made only on the spacetime region outside of the body, so that the results apply to ordinary bodies as well as black holes. The worldline "left behind" by the shrinking, disappearing body is interpreted as its lowest-order motion. An equation for this worldline follows from the "Bianchi identity" for the theory, without use of any properties of the field equations beyond their being second-order. The form of the force law for a theory therefore depends only on the ranks of its various tensor fields, with the field equations relevant only for determining the charges of a particular body from its exterior fields. I explicitly derive the force law (and mass-evolution law) in the case of scalar and vector fields, and give the recipe in the higher-rank case. Note that the vector force law is quite complicated, simplifying to the Lorentz force law only in the presence of the Maxwell gauge symmetry. Example applications of the results are the motion of "chameleon" bodies beyond the Newtonian limit, and the motion of bodies in (classical) non-Abelian gauge theory. I also make some comments on the role that scaling plays in the appearance of universality in the motion of bodies.

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