论文标题
DHOST模型中的迟到时间宇宙学演变
Late time cosmological evolution in DHOST models
论文作者
论文摘要
我们研究了宇宙学的晚期演变，从非依赖主义物质占据了时代到黑暗能量时代，在由退化的高阶标量张量（DHOST）理论描述的改良重力模型中。它们代表了传播单个标量自由度的最通用的标量调整理论，其中包括Horndeski和Horndeski理论之外。我们为任何二次DHOST理论提供均匀的演化方程，而不局限于引力波速度与光相吻合的理论，因为目前的限制适用于比宇宙学量表小得多的波长。为了说明这些理论中宇宙学背景演变的潜在丰富性，我们考虑了一个简单的移位对称模型家族，其特征是三个参数，并计算了暗能量的演变及其状态方程。我们还标识了模型稳定的参数空间中的区域。
We study the late cosmological evolution, from the nonrelativistic matter dominated era to the dark energy era, in modified gravity models described by Degenerate Higher-Order Scalar-Tensor (DHOST) theories. They represent the most general scalar-tensor theories propagating a single scalar degree of freedom and include Horndeski and Beyond Horndeski theories. We provide the homogeneous evolution equations for any quadratic DHOST theory, without restricting ourselves to theories where the speed of gravitational waves coincides with that of light since the present constraints apply to wavelengths much smaller than cosmological scales. To illustrate the potential richness of the cosmological background evolution in these theories, we consider a simple family of shift-symmetric models, characterized by three parameters and compute the evolution of dark energy and of its equation of state. We also identify the regions in parameter space where the models are perturbatively stable.
