hi_class background evolution, initial conditions and approximation schemes
hi_class background evolution, initial conditions and approximation schemes
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DOI：
10.1088/1475-7516/2020/02/008
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发表时间：
2019-09
影响因子：
6.4
通讯作者：
E. Bellini;I. Sawicki;M. Zumalac'arregui
中科院分区：
文献类型：
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作者：
E. Bellini;I. Sawicki;M. Zumalac'arregui
宇宙学数据集在阐明暗能量的性质和在可供观测的最大尺度上测试重力方面具有巨大的潜力。理论预测可以用hi_CLASS(www.hiclass-code.net)计算，这是一个准确、快速和灵活的线性宇宙学程序，结合了广泛的暗能量理论和对广义相对论的修改。我们在Hi_CLASS中引入了三个新的功能：(1)支持基于协变拉格朗日的模型，包括背景演化的约束保持积分方案和一系列已完成的例子：Galileon，NKGB，QuintEssence(Monomial，Tracker)和Brans-Dicke。(2)在深辐射时代标量场扰动的一致初始条件，确定了修正重力等温扰动可能比绝热模式增长得更快从而导致预报性丧失的条件。(3)自动准静态近似方案，允许在不牺牲大类模型精度的情况下将计算性能提高数量级。这些改进使暗能量和修正的重力模型的处理达到了可与限于标准Λ清洁发展机制宇宙学的软件工具相媲美的详细程度。Hi_(https://github.com/miguelzuma/hi_class_public)，代码是公开可用的，可以随时查看当前数据并为下一代实验做准备。
Cosmological datasets have great potential to elucidate the nature of dark energy and test gravity on the largest scales available to observation. Theoretical predictions can be computed with hi_class (www.hiclass-code.net), an accurate, fast and flexible code for linear cosmology, incorporating a wide range of dark energy theories and modifications to general relativity. We introduce three new functionalities into hi_class: (1) Support for models based on covariant Lagrangians, including a constraint-preserving integration scheme for the background evolution and a series of worked-out examples: Galileon, nKGB, quintessence (monomial, tracker) and Brans-Dicke. (2) Consistent initial conditions for the scalar-field perturbations in the deep radiation era, identifying the conditions under which modified-gravity isocurvature perturbations may grow faster than adiabatic modes leading to a loss of predictivity. (3) An automated quasi-static approximation scheme allowing order-of-magnitude improvement in computing performance without sacrificing accuracy for wide classes of models. These enhancements bring the treatment of dark energy and modified gravity models to the level of detail comparable to software tools restricted to standard ΛCDM cosmologies. The hi_class code is publicly available (https://github.com/miguelzuma/hi_class_public), ready to explore current data and prepare for next-generation experiments.