标题： 关于通过宇宙共形年龄测量的动态暗能量的备注 显示英文标题

标题： Remarks on Dynamical Dark Energy Measured by the Conformal Age of the Universe

摘要： 我们详细阐述了一个共形暗能量模型（由宇宙的共形年龄测量的动力学暗能量），该模型最近在[ H. Wei 和 R.G. Cai, arXiv:0708.0884 ]中提出，其中现今的暗能量密度被取为$\rho_q \equiv 3 \alpha^2 m_P^2/\eta^2$，其中$\eta$是共形时间，$\alpha$是一个数值常数。 在普通物质和暗能量场$q$之间不存在相互作用的情况下，如果数值常数$\alpha$取一个合理大的值，$\alpha\gtrsim 2.6$，该模型可以调整为当前的暗能量密度分数$\Omega\Z{q} \simeq 0.73$和状态方程参数$w\Z{q} < -0.78$。 然而，在存在非平凡的引力耦合的情况下，$q$场与物质，比如$\widetilde{Q}$，模型可能被调整为$\Omega\Z{q}\simeq 0.73$和$w\Z{q}\simeq -1$，即使$\alpha\sim {\cal O}(1)$，只要$\widetilde{Q}$的当前值很大。 与[R.G.中的模型不同 蔡，arXiv:0707.4049]，在大爆炸核合成（BBN）期间的界限$\Omega\Z{q} <0.1$可能对于几乎任何值的$\alpha$都可以满足。 这里我们讨论该提议作为可行暗能量模型的一些其他限制。 该模型与全息暗能量有一些相似之处；我们也将简要评论后者模型。 显示英文摘要

摘要： We elaborate on a model of conformal dark energy (dynamical dark energy measured by the conformal age of the universe) recently proposed in [H. Wei and R.G. Cai, arXiv:0708.0884] where the present-day dark energy density was taken to be $\rho_q \equiv 3 \alpha^2 m_P^2/\eta^2$, where $\eta$ is the conformal time and $\alpha$ is a numerical constant. In the absence of an interaction between the ordinary matter and dark energy field $q$, the model may be adjusted to the present values of the dark energy density fraction $\Omega\Z{q} \simeq 0.73$ and the equation of state parameter $w\Z{q} < -0.78$, if the numerical constant $\alpha$ takes a reasonably large value, $\alpha\gtrsim 2.6$. However, in the presence of a nontrivial gravitational coupling of $q$-field to matter, say $\widetilde{Q}$, the model may be adjusted to the values $\Omega\Z{q}\simeq 0.73$ and $w\Z{q}\simeq -1$, even if $\alpha\sim {\cal O}(1)$, given that the present value of $\widetilde{Q}$ is large. Unlike for the model in [R.G. Cai, arXiv:0707.4049], the bound $\Omega\Z{q} <0.1$ during big bang nucleosynthesis (BBN) may be satisfied for almost any value of $\alpha$. Here we discuss some other limitations of this proposal as a viable dark energy model. The model draws some parallels with the holographic dark energy; we also briefly comment on the latter model.