用Birkhoff定理研究修正引力中的球坍缩
Spherical collapse in modified gravity with the Birkhoff-theorem
摘要：
我们研究结构形成的唯象模型之间的LambdaCDM和唯象DGP重力插值的修改的重力。用Birkhoff定理和修正的增长方程对球形坍缩进行了推广，结果表明，与LambdaCDM模型相比，这些模型中球形坍缩的过密度delta_c显著降低，从而提高了大质量团簇的数密度和团簇合并速率.我们发现delta_c（z）可以很好地用一个形式为delta_c（z）= a-b \exp（-cz）的函数来拟合.我们检查的灵敏度普朗克和SPT的Sunyaev Zel 'dovich调查约束修改后的重力parameterisation，并发现这些实验可以很容易地区分模型与宇宙学常数和修改后的重力，如果事先从CMB温度和偏振各向异性的约束。
英文摘要：
We study structure formation in a phenomenological model of modified gravity which interpolates between LambdaCDM and phenomenological DGP-gravity. Generalisation of spherical collapse by using the Birkhoff-theorem along with the modified growth equation shows that the overdensity for spherical collapse delta_c in these models is significantly lowered compared to LambdaCDM, leading to enhanced number densities of massive clusters and enhanced cluster merging rates. We find that delta_c(z) is well fitted by a function of the form delta_c(z) = a - b\exp(-cz). We examine the sensitivity of PLANCK's and SPT's Sunyaev-Zel'dovich survey to constrain the modified gravity parameterisation and find that these experiments can easily distinguish between models with a cosmological constant and modified gravity, if prior constraints from CMB temperature and polarisation anisotropies are included.
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