A new perspective on the Cosmological Constant Problem (CCP) is proposed and discussed within the multiverse approach of Quantum Cosmology. It is assumed that each member of the ensemble of universes has a characteristic scale a that can be used as integration variable in the partition function. An averaged characteristic scale of the ensemble is estimated by using only members that satisfy the Einstein field equations. The averaged characteristic scale is compatible with the Planck length when considering an ensemble of solutions to the Einstein field equations with an effective cosmological constant. The multiverse ensemble is split in Planck-seed universes with vacuum energy density of order one; thus, $\tilde{\Lambda }\approx 8\pi$ in Planck units and a-derivable universes. For a-derivable universe with a characteristic scale of the order of the observed Universe $a\approx 8\times {10}^{60}$, the cosmological constant $\Lambda =\tilde{\Lambda }/a^2$ is in the range ${10}^{-121}$–${10}^{-122}$, which is close in magnitude to the observed value ${10}^{-123}$. We point out that the smallness of $\Lambda$ can be viewed to be natural if its value is associated with the entropy of the Universe. This approach to the CCP reconciles the Planck-scale huge vacuum energy–density predicted by QFT considerations, as valid for Planck-seed universes, with the observed small value of the cosmological constant as relevant to an a-derivable universe as observed.

中文翻译：

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重新审视量子宇宙学中的宇宙常数问题

在量子宇宙学的多宇宙方法中，提出并讨论了宇宙常数问题（CCP）的新观点。假定宇宙整体的每个成员都有一个特征尺度a，可以用作分区函数中的积分变量。通过仅使用满足爱因斯坦场方程的成员来估计集合的平均特征尺度。当考虑具有有效宇宙学常数的爱因斯坦场方程的解的整体时，平均特征尺度与普朗克长度兼容。多元宇宙集合在普朗克种子宇宙中被分裂，真空能量密度为一阶。从而，$\stackrel{〜}{\Lambda }\approx 8\pi$以普朗克单位和可衍生宇宙为单位。对于具有观察到的宇宙数量级特征尺度的可衍生宇宙$\mathrm{一种}\approx 8\times {10}^{60}$，宇宙常数 $\Lambda =\stackrel{〜}{\Lambda }/{\mathrm{一种}}^2$ 在范围内 ${10}^{-121}$–${10}^{-122}$，其大小接近于观测值 ${10}^{-123}$。我们指出，$\Lambda$如果其值与宇宙的熵相关联，则可以视为自然。这种做法对CCP调和普朗克规模巨大的真空能量密度由QFT考虑预测的那样有效普朗克种子宇宙，与宇宙常数作为相关的所涉及的观测值小一个-derivable宇宙所观察到的。