标题： 共形Weyl引力中的原始核合成 显示英文标题

标题： Primordial Nucleosynthesis in Conformal Weyl Gravity

摘要： 近期共形Weyl引力被考虑作为一种候选的替代引力理论。 这种四阶理论因其唯一性——即它是唯一在度规的局域共形变换下不变的度规引力理论——而具有吸引力。我们在此理论中计算了原始轻元素丰度。与标准宇宙学的主要不同之处在于，宇宙在核合成时期的膨胀速度要慢得多。{}的 $^4\rm{He}$ 的产生强烈依赖于$\eta$，即重子与光子的比例。 对于$\eta = 10^{-8}$，$^4{\rm He}$的质量分数为$X_4 \simeq 0.25$，而相对于氢的数密度，$^2{\rm H}$、$^3{\rm He}$和$^7{\rm Li}$分别为$n(^2{\rm H})/n({\rm H}) \simeq 9\times 10^{-20}$、$n(^3{\rm He})/n({\rm H})\simeq 4 \times 10^{-18}$和$n(^7{\rm Li})/n({\rm H}) \simeq 10^{-13}$。 这一数值的$\eta$对应于接近标准模型临界密度的重子质量密度。然而，调整$\eta$以得到合理的氦产量会迫使氘和锂的产量变得足够小，以至于该理论无法与观测结果相一致。 显示英文摘要

摘要： Recently conformal Weyl gravity has been considered as a candidate alternative gravity theory. This fourth-order theory is attractive because it is the only metric theory of gravity which is invariant under local conformal transformations of the metric. We calculate the primordial light element abundances in this theory. The major difference {}from the standard cosmology is that the universe expands far more slowly throughout the nucleosynthesis epoch. The production of $^4\rm{He}$ depends strongly on $\eta$, the ratio of baryons to photons. For $\eta = 10^{-8}$ the mass fraction of $^4{\rm He}$ is $X_4 \simeq 0.25$ and the number densities relative to hydrogen for $^2{\rm H}$, $^3{\rm He}$ and $^7{\rm Li}$ are $n(^2{\rm H})/n({\rm H}) \simeq 9\times 10^{-20}$, $n(^3{\rm He})/n({\rm H})\simeq 4 \times 10^{-18}$ and $n(^7{\rm Li})/n({\rm H}) \simeq 10^{-13}$. This value of $\eta$ corresponds to a baryon mass density close to the standard model critical density. However, adjusting $\eta$ to give a reasonable helium yield forces the deuterium and lithium yields to be small enough that the theory cannot be reconciled with observations.