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arXiv 2005.06494hep-thgr-qc
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在字符串紧化中没有什么是确定的

Nothing is certain in string compactifications

Iñaki García Etxebarria, Miguel Montero, Kepa Sousa, Irene Valenzuela

摘要:

空无一物的气泡是一种时空不稳定性,在这种不稳定性中,一个紧凑的维度坍塌了。成核后,它以光速膨胀,留下“什么”。我们认为,拓扑和动力学机制,可以保护一个紧化对衰变到没有似乎是缺乏弦紧化一旦超对称性破缺。拓扑障碍在于一个bordism组,令人惊讶的是,它可以消失,甚至超对称兼容的自旋结构。作为一个原则的证明,我们构建了一个明确的泡沫没有$T^3$与完全周期性(超对称兼容)的自旋结构在Einstein的量子高斯-邦纳理论,这是在某些杂化和II型通量紧致化的低能量极限。在没有拓扑保护的情况下,超对称紧化完全由Coleman-deLuccia机制稳定,该机制依赖于一定的局部能量条件。在我们的例子中,非超对称GB项违反了这一点。在通量的存在下,这种能量条件得到修改,其违反可能与弱引力猜想有关。我们希望我们的技术可以被用来构建大量的新的泡沫没有在任何设置的低能量bordism组消失,包括II型紧化$CY_3$,AdS通量紧化5-流形上,和M理论7-流形。这进一步证明了任何非超对称的量子引力真空最终都是不稳定的。

英文摘要:

A bubble of nothing is a spacetime instability where a compact dimension collapses. After nucleation, it expands at the speed of light, leaving "nothing" behind. We argue that the topological and dynamical mechanisms which could protect a compactification against decay to nothing seem to be absent in string compactifications once supersymmetry is broken. The topological obstruction lies in a bordism group and, surprisingly, it can disappear even for a SUSY-compatible spin structure. As a proof of principle, we construct an explicit bubble of nothing for a $T^3$ with completely periodic (SUSY-compatible) spin structure in an Einstein dilaton Gauss-Bonnet theory, which arises in the low-energy limit of certain heterotic and type II flux compactifications. Without the topological protection, supersymmetric compactifications are purely stabilized by a Coleman-deLuccia mechanism, which relies on a certain local energy condition. This is violated in our example by the nonsupersymmetric GB term. In the presence of fluxes this energy condition gets modified and its violation might be related to the Weak Gravity Conjecture. We expect that our techniques can be used to construct a plethora of new bubbles of nothing in any setup where the low-energy bordism group vanishes, including type II compactifications on $CY_3$, AdS flux compactifications on 5-manifolds, and M-theory on 7-manifolds. This lends further evidence to the conjecture that any non-supersymmetric vacuum of quantum gravity is ultimately unstable.

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