Marsh M C David
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom.
Phys Rev Lett. 2017 Jan 6;118(1):011302. doi: 10.1103/PhysRevLett.118.011302. Epub 2017 Jan 5.
Future cosmological surveys will probe the expansion history of the Universe and constrain phenomenological models of dark energy. Such models do not address the fine-tuning problem of the vacuum energy, i.e., the cosmological constant problem (CCP), but can make it spectacularly worse. We show that this is the case for "interacting dark energy" models in which the masses of the dark matter states depend on the dark energy sector. If realized in nature, these models have far-reaching implications for proposed solutions to the CCP that require the number of vacua to exceed the fine-tuning of the vacuum energy density. We show that current estimates of the number of flux vacua in string theory, N_{vac}∼O(10^{272 000}), are far too small to realize certain simple models of interacting dark energy and solve the cosmological constant problem anthropically. These models admit distinctive observational signatures that can be targeted by future gamma-ray observatories, hence making it possible to observationally rule out the anthropic solution to the cosmological constant problem in theories with a finite number of vacua.
未来的宇宙学调查将探究宇宙的膨胀历史，并对暗能量的唯象模型加以限制。这类模型并未解决真空能量的微调问题，即宇宙学常数问题（CCP），反而可能使其显著恶化。我们表明，对于“相互作用暗能量”模型而言正是如此，在这类模型中暗物质态的质量取决于暗能量部分。如果这类模型在自然界中得以实现，那么对于那些要求真空数量超过真空能量密度微调的CCP提议解决方案而言，将具有深远影响。我们表明，弦理论中目前对通量真空数量的估计，即N_{vac} ∼ O(10^{272 000})，远远太小，无法实现某些简单的相互作用暗能量模型，也无法通过人择原理解决宇宙学常数问题。这些模型具有独特的观测特征，未来的伽马射线天文台可以针对这些特征进行观测，从而有可能在具有有限数量真空的理论中，通过观测排除宇宙学常数问题的人择解决方案。
