Exponential suppression of the cosmological constant in nonsupersymmetric string vacua at two loops and beyond
Exponential suppression of the cosmological constant in nonsupersymmetric string vacua at two loops and beyond
复制标题
非超对称弦真空中宇宙常数在两个环及以上的指数抑制
DOI：
10.1103/physrevd.96.106013
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发表时间：
2017
影响因子：
5
通讯作者：
Richard J. Stewart
中科院分区：
文献类型：
--
作者：
S. Abel;Richard J. Stewart
提出了两个独立的标准，它们共同保证非超对称异质弦中双环宇宙学常数的指数抑制。它们是通过在全弦理论及其有效场论中进行计算而得出的，并且分别来自仅涉及物理未扭曲态的贡献和包括轨道扭曲态的贡献。这些标准完全取决于频谱和费用，因此满足这些标准的模型无需微调即可实现。另一个一致性条件（来自所谓的二环图的分离简并极限）是单环宇宙学常数也必须被无质量谱中的玻色-费米简并性抑制。我们评论了剩余指数抑制单环膨胀蝌蚪的影响，得出的结论是，剩余的不稳定性将在通用现象学结构中受到微扰控制。我们注意到，这种对高阶持续指数抑制的理论可以构成“没有超对称性的自然性”思想的弦实现的基础。
Two independent criteria are presented that together guarantee exponential suppression of the two-loop cosmological constant in nonsupersymmetric heterotic strings. They are derived by performing calculations in both the full string theory and in its effective field theory, and come respectively from contributions that involve only physical untwisted states, and contributions that include orbifold twisted states. The criteria depend purely on the spectrum and charges, so a model that satisfies them will do so with no fine-tuning. An additional consistency condition (emerging from the so-called separating degeneration limit of the two-loop diagram) is that the one-loop cosmological constant must also be suppressed, by Bose-Fermi degeneracy in the massless spectrum. We comment on the effects of the residual exponentially suppressed one-loop dilaton tadpole, with the conclusion that the remaining instability would be under perturbative control in a generic phenomenological construction. We remark that theories of this kind, that have continued exponential suppression to higher orders, can form the basis for a string implementation of the “naturalness without supersymmetry” idea.