标题： 暗能量材料模型 显示英文标题

标题： Material models of dark energy

摘要： 我们回顾并发展了一类新的“暗能量”模型，在这些模型中，相对论固体理论被用来构建暗能量的材料模型。 这些模型包括在线性化扰动水平上具有明确物理性质的连续介质的影响。 该形式主义是为具有任意对称性的介质构建的，然后专门用于各向同性介质（这将是大多数宇宙学应用的情况）。 我们在考虑到最终希望观测约束材料模型允许属性的同时，发展了相对论各向同性粘弹性介质的理论。 我们通过获得扰动的粘弹性状态方程（熵和各向异性应力）以及确定具有恒定方程状态参数$\dot{w}=0$的理论一致角落来实现这一点。 我们还通过识别构建能量-动量张量所需的两个二次不变量，即雷利耗散函数和扰动的拉格朗日量，将该理论与非相对论固体理论联系起来。 最后，我们提出了一个概念，即介质的粘弹性行为可以被视为一种非最小耦合的引力质量理论。 这也为构建耦合暗能量理论的一致推广提供了一个工具包。 显示英文摘要

摘要： We review and develop a new class of "dark energy" models, in which the relativistic theory of solids is used to construct material models of dark energy. These are models which include the effects of a continuous medium with well defined physical properties at the level of linearized perturbations. The formalism is constructed for a medium with arbitrary symmetry, and then specialised to isotropic media (which will be the case of interest for the majority of cosmological applications). We develop the theory of relativistic isotropic viscoelastic media whilst keeping in mind that we ultimately want to observationally constrain the allowed properties of the material model. We do this by obtaining the viscoelastic equations of state for perturbations (the entropy and anisotropic stress), as well as identifying the consistent corner of the theory which has constant equation of state parameter $\dot{w}=0$. We also connect to the non-relativistic theory of solids, by identifying the two quadratic invariants that are needed to construct the energy-momentum tensor, namely the Rayleigh dissipation function and Lagrangian for perturbations. Finally, we develop the notion that the viscoelastic behavior of the medium can be thought of as a non-minimally coupled massive gravity theory. This also provides a tool-kit for constructing consistent generalizations of coupled dark energy theories.