标题： 三次准拓扑宇宙学中的能量密度界限 显示英文标题

标题： Energy Density Bounds in Cubic Quasi-Topological Cosmology

摘要： 我们研究了四维三次准拓扑引力（QTG）的宇宙学模型的热力学和因果一致性，以及它们的物理现象后果。 通过要求视界熵为时间的非负、非递减函数，得出了物质密度最大值的具体限制。详细研究了QTG中与爱因斯坦-希尔伯特（EH）引力线性状态方程相对应的模型。这一特定QTG宇宙学模型的一个重要特征是宇宙演化早期出现了新的加速阶段，同时保留了原始EH模型中存在的标准晚期加速。此外，还计算了QTG对因果钻石体积的修正。 显示英文摘要

摘要： We investigate the thermodynamical and causal consistency of cosmological models of the cubic Quasi-Topological Gravity (QTG) in four dimensions, as well as their phenomenological consequences. Specific restrictions on the maximal values of the matter densities are derived by requiring the apparent horizon's entropy to be a non-negative, non-decreasing function of time. The QTG counterpart of the Einstein-Hilbert (EH) gravity model of linear equation of state is studied in detail. An important feature of this particular QTG cosmological model is the new early-time acceleration period of the evolution of the Universe, together with the standard late-time acceleration present in the original EH model. The QTG correction to the causal diamond's volume is also calculated.