标题： 有多少暗能量参数？ 显示英文标题

标题： How many dark energy parameters?

摘要： 为了探索加速膨胀宇宙背后的物理机制，一个关键的问题是我们能通过下一代宇宙学实验了解多少动力学信息。 例如，在通过有效状态方程定义暗能量行为时，我们能够实际期望精确限制多少参数？ 通过一般和具体的例子（包括新的参数化方法和主成分分析），我们认为答案是“42”——等等，不是，是两个。 因此，涉及某个时期（例如 \( w_0 \)）的状态方程值的测量以及状态方程变化（例如 \( w' \)）的测量的宇宙学参数分析在预测暗能量参数约束方面是现实可行的。 更复杂的参数化方法可能有一些用途（例如测试偏差或与模型特征进行比较），但不会导致准确测量的暗能量参数。 显示英文摘要

摘要： For exploring the physics behind the accelerating universe a crucial question is how much we can learn about the dynamics through next generation cosmological experiments. For example, in defining the dark energy behavior through an effective equation of state, how many parameters can we realistically expect to tightly constrain? Through both general and specific examples (including new parametrizations and principal component analysis) we argue that the answer is 42 - no, wait, two. Cosmological parameter analyses involving a measure of the equation of state value at some epoch (e.g. w_0) and a measure of the change in equation of state (e.g. w') are therefore realistic in projecting dark energy parameter constraints. More elaborate parametrizations could have some uses (e.g. testing for bias or comparison with model features), but do not lead to accurately measured dark energy parameters.