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arXiv 2009.08460hep-thgr-qchep-ph
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引力耦合大$N$ QCD中的因果约束

Causality Constraints in Large $N$ QCD Coupled to Gravity

Jared Kaplan, Sandipan Kundu

备注：
7 pages; Some comments are added
发表信息：
Phys. Rev. D 104, 061901 (2021)
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摘要：

约束规范理论包含任意自旋的胶球和介子，这些粒子在大$N$处成为亚稳态。然而，亚稳态的高自旋粒子，当与引力耦合时，与因果关系相冲突。只有当引力相互作用伴随着其他远低于普朗克尺度$M_{\rm pl}$的更高自旋态的相互作用时，这种张力才能避免。这些高自旋态可以来自QCD扇区或引力扇区，但这两个分辨率都有一些令人惊讶的含义。例如，QCD态可以解决这个问题，因为在QCD扇区和引力扇区之间存在非平凡的混合，要求所有粒子在树级与胶球相互作用。如果引力扇区状态恢复了因果关系，那么引力扇区的任何弱耦合UV补全都必须具有许多弦特征，并且弦尺度上有一个上限。在引力是弱耦合的假设下，这两种情况都意味着理论在$N\gtrsim \frac{M_{\rm pl}}{Λ_{\rm QCD}}$之上有一个严格的描述，其中$Λ_{\rm QCD}$是约束尺度。

英文摘要：

Confining gauge theories contain glueballs and mesons with arbitrary spin, and these particles become metastable at large $N$. However, metastable higher spin particles, when coupled to gravity, are in conflict with causality. This tension can be avoided only if the gravitational interaction is accompanied by interactions involving other higher spin states well below the Planck scale $M_{\rm pl}$. These higher spin states can come from either the QCD sector or the gravity sector, but both these resolutions have some surprising implications. For example, QCD states can resolve the problem since there is a non-trivial mixing between the QCD sector and the gravity sector, requiring all particles to interact with glueballs at tree-level. If gravity sector states restore causality, any weakly coupled UV completion of the gravity-sector must have many stringy features, with an upper bound on the string scale. Under the assumption that gravity is weakly coupled, both scenarios imply that the theory has a stringy description above $N\gtrsim \frac{M_{\rm pl}}{Λ_{\rm QCD}}$, where $Λ_{\rm QCD}$ is the confinement scale.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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