论文标题
抑制耦合矢量调节理论的宇宙增长
Suppressed cosmic growth in coupled vector-tensor theories
论文作者
论文摘要
我们研究了一个耦合的暗能量方案，其中大量向量场$a_μ$带有损坏的$ u（1）$ gauge对称性与四速度$ u_c^μ$冷暗物质（CDM）通过标量产品$ z = -U_C^μA__$。这种新的耦合对应于动量传递，因此背景矢量和CDM连续性方程没有类似于能量交换的明确相互作用项。因此，与$λ$ CDM模型相对于$λ$ CDM模型的观察性偏好仍然可以保持在背景级别。同时，相同的耦合强烈影响宇宙扰动的演变。尽管CDM的有效音速消失了，但$a_μ$的纵向标量和CDM NO-GHOST条件的繁殖速度和无孔状态受到Lagrangian中的$ Z $依赖性的非平凡修改。我们提出了一个具体的暗能量模型，并表明与大规模结构线性生长相关的尺度上的重力相互作用可能小于低红移时的牛顿常数。这导致抑制CDM和总物质密度扰动的增长率，因此我们的模型允许一种有趣的可能性来减少物质密度对比度的张力$σ_8$之间的高红移测量值之间的张力。
We study a coupled dark energy scenario in which a massive vector field $A_μ$ with broken $U(1)$ gauge symmetry interacts with the four-velocity $u_c^μ$ of cold dark matter (CDM) through the scalar product $Z=-u_c^μ A_μ$. This new coupling corresponds to the momentum transfer, so that the background vector and CDM continuity equations do not have explicit interacting terms analogous to the energy exchange. Hence the observational preference of uncoupled generalized Proca theories over the $Λ$CDM model can be still maintained at the background level. Meanwhile, the same coupling strongly affects the evolution of cosmological perturbations. While the effective sound speed of CDM vanishes, the propagation speed and no-ghost condition of a longitudinal scalar of $A_μ$ and the CDM no-ghost condition are subject to nontrivial modifications by the $Z$ dependence in the Lagrangian. We propose a concrete dark energy model and show that the gravitational interaction on scales relevant to the linear growth of large-scale structures can be smaller than the Newton constant at low redshifts. This leads to the suppression of growth rates of both CDM and total matter density perturbations, so our model allows an interesting possibility for reducing the tension of matter density contrast $σ_8$ between high- and low-redshift measurements.
