重构Horndeski模型的正界
Positivity bounds on reconstructed Horndeski models
摘要：
正性边界提供了量子场论存在一致UV完备的条件。我们研究它们的应用Horndeski引力模型重建的有效场论（EFT）的暗能量。这使我们能够评估是否特定的现象学参数化的EFT功能重建理论，尊重或违反的积极性界限。我们发现，通常采用的EFT参数化，投在暗能量密度或幂律的标度因子，只满足正界的非平凡区域的参数空间。然后，我们检查参数化的固有稳定的EFT基础上，构造，以避免梯度和鬼不稳定性默认情况下。与此形成鲜明对比的是，在此基础上的积极性界限要么只提供约束的先验不切实际的区域的参数空间或不提供任何约束的参数值。正界的标准EFT函数的共同参数化的应用，因此可以导致人为的结论，可行的Horndeski修改的重力区域是高度约束的。我们的研究结果提供了一个强大的动机，除了默认避免理论不稳定性，而不是采用参数化的固有稳定的EFT基础时，测试暗能量和修改后的重力模型与即将到来的宇宙学调查数据。
英文摘要：
Positivity bounds provide conditions that a consistent UV-completion exists for a quantum field theory. We examine their application to Horndeski gravity models reconstructed from the effective field theory (EFT) of dark energy. This enables us to assess whether particular phenomenological parameterizations of the EFT functions reconstruct theories that respect or violate the positivity bounds. We find that commonly adopted EFT parametrizations, cast in terms of the dark energy density or power laws of the scale factor, only satisfy the positivity bounds in non-trivial regions of the parameter space. We then examine parameterizations of the inherently stable EFT basis, constructed to avoid gradient and ghost instabilities by default. In stark contrast, in this basis the positivity bounds either only provide constraints in a-priori unrealistic regions of the parameter space or do not provide any constraints on parameter values at all. The application of positivity bounds to common parametrizations of the standard EFT functions can therefore lead to artificial conclusions that the region of viable Horndeski modifications of gravity is highly constrained. Our results provide a strong motivation, in addition to the default avoidance of theoretical instabilities, for instead adopting parametrizations of the inherently stable EFT basis when testing dark energy and modified gravity models with forthcoming cosmological survey data.
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