关于完全标量场的一个注记
A note on perfect scalar fields
摘要：
通过要求与标量场相关的固有的、非绝热的压力扰动完全消失，我们推导出了描述一个通用的、单一的、非正则的标量场的拉格朗日密度的条件。基于与理想流体的类比，我们称这种场为理想标量场。众所周知，仅依赖于标量场的动能的模型（通常称为纯动力学模型）不具有非绝热压力扰动。虽然我们能够构建看似依赖于标量场并且也不包含任何非绝热压力扰动的模型，但我们发现我们构建的所有此类模型都允许重新定义场，在此基础上它们简化为纯动力学模型。我们表明，如果一个完美的标量场驱动通货膨胀，那么，在这种情况下，第一个慢滚参数将始终是一个时间的单调递减函数。我们指出，这种行为意味着这些标量场不能导致暴胀标量微扰谱的特征。
英文摘要：
We derive a condition on the Lagrangian density describing a generic, single, non-canonical scalar field, by demanding that the intrinsic, non-adiabatic pressure perturbation associated with the scalar field vanishes identically. Based on the analogy with perfect fluids, we refer to such fields as perfect scalar fields. It is common knowledge that models that depend only on the kinetic energy of the scalar field (often referred to as pure kinetic models) possess no non-adiabatic pressure perturbation. While we are able to construct models that seemingly depend on the scalar field and also do not contain any non-adiabatic pressure perturbation, we find that all such models that we construct allow a redefinition of the field under which they reduce to pure kinetic models. We show that, if a perfect scalar field drives inflation, then, in such situations, the first slow roll parameter will always be a monotonically decreasing function of time. We point out that this behavior implies that these scalar fields can not lead to features in the inflationary, scalar perturbation spectrum.
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