论文标题
定义明确的运动方程，而没有外部来源的限制
Well-defined equations of motion without constraint of external sources
论文作者
论文摘要
我们提出了一种新的方法来限制经典领域，使行动形式主义能够决定外部来源必须如何进入所得的运动方程。如果可以将所断言在各个字段上的对称性建模为在傅立叶空间中的限制，我们证明这些限制会以明确的方式自动应用于外部来源。相反，典型的过程将对称的ansatze插入Euler-Lagrange微分方程中，即使是用于未解决的外部源。这需要对外部来源的临时约束，尽管模型字段和源术语之间的表面一致性，但仍可以向模型系统引入前阶错误。为了证明，我们考虑了一般相对论中的罗伯逊·沃克宇宙学，并证明了类似点样相对论压力源对宇宙学动力学的影响不能被理论上的论点排除在外。
We present a new approach to constrained classical fields that enables the action formalism to dictate how external sources must enter the resulting equations of motion. If symmetries asserted upon the varied fields can be modeled as restrictions in Fourier space, we prove that these restrictions are automatically applied to external sources in an unambiguous way. In contrast, the typical procedure inserts symmetric ansatze into the Euler-Lagrange differential equations, even for external sources not being solved. This requires ad hoc constraint of external sources, which can introduce leading-order errors to model systems despite superficial consistency between model field and source terms. To demonstrate, we consider Robertson-Walker cosmologies within General Relativity and prove that the influence of point-like relativistic pressure sources on cosmological dynamics cannot be excluded by theoretical arguments.
