Montani Giovanni, Carlevaro Nakia, De Angelis Mariaveronica
Nuclear Department, ENEA, C.R. Frascati, Via E. Fermi 45, 00044 Frascati, Italy.
Physics Department, "Sapienza" University of Rome, P. le A. Moro 5, 00185 Rome, Italy.
Entropy (Basel). 2024 Aug 4;26(8):662. doi: 10.3390/e26080662.
We consider a dynamic scenario for characterizing the late Universe evolution, aiming to mitigate the Hubble tension. Specifically, we consider a metric f(R) gravity in the Jordan frame which is implemented to the dynamics of a flat isotropic Universe. This cosmological model incorporates a matter creation process, due to the time variation of the cosmological gravitational field. We model particle creation by representing the isotropic Universe (specifically, a given fiducial volume) as an open thermodynamic system. The resulting dynamical model involves four unknowns: the Hubble parameter, the non-minimally coupled scalar field, its potential, and the energy density of the matter component. We impose suitable conditions to derive a closed system for these functions of the redshift. In this model, the vacuum energy density of the present Universe is determined by the scalar field potential, in line with the modified gravity scenario. Hence, we construct a viable model, determining the form of the f(R) theory a posteriori and appropriately constraining the phenomenological parameters of the matter creation process to eliminate tachyon modes. Finally, by analyzing the allowed parameter space, we demonstrate that the Planck evolution of the Hubble parameter can be reconciled with the late Universe dynamics, thus alleviating the Hubble tension.
我们考虑一种用于刻画晚期宇宙演化的动态情景，旨在缓解哈勃张力。具体而言，我们考虑约旦框架下的$f(R)$引力，将其应用于平坦各向同性宇宙的动力学。由于宇宙引力场的时间变化，这个宇宙学模型纳入了物质产生过程。我们通过将各向同性宇宙（具体而言，一个给定的基准体积）表示为一个开放的热力学系统来对粒子产生进行建模。由此产生的动力学模型涉及四个未知数：哈勃参数、非最小耦合标量场、其势以及物质成分的能量密度。我们施加适当条件以导出这些红移函数的封闭系统。在这个模型中，当前宇宙的真空能量密度由标量场势决定，这与修正引力情景一致。因此，我们构建了一个可行模型，后验地确定$f(R)$理论的形式，并适当约束物质产生过程的唯象学参数以消除快子模式。最后，通过分析允许的参数空间，我们证明哈勃参数的普朗克演化可以与晚期宇宙动力学相协调，从而缓解哈勃张力。
