[论文解读] From Axions to Other WISPs.

Andreas Ringwald|arXiv (Cornell University)|Jan 1, 2009

Cosmology and Gravitation Theories被引用 2

一句话总结

本文研究了从弦理论紧化中涌现的轴子及其他非常轻、弱相互作用的亚电子伏特粒子（WISPs），展示了在额外维度紧化后的低能有效理论中，赝标量轴子和隐藏U(1)规范玻色子如何作为无质量或轻量态出现。其主要贡献是从弦论嵌入出发，自上而下推导出WISP候选者，强调了通过异常U(1)对称性和隐藏 sector 动力学，在现实紧化中这些粒子的普遍出现。

ABSTRACT

It is a tantalizing question whether there is new physics below the Standard Model. That is to ask, whether there are new very light particles – apart from the known ones with sub-eV mass, the photon and the neutrinos – which are very weakly coupled to the Standard Model. In fact, embeddings of the latter into more unified theories, in particular into string theory, suggest their possible existence in a so-called hidden sector of the theory. Prominent examples of inhabitants of the latter are the axion and axion-like particles, arising as pseudo NambuGoldstone bosons associated with the breakdown of global anomalous U(1) symmetries. They occur generically in realistic string compactifications, as we will review below. Extra, hidden U(1) gauge bosons are also frequently encountered in string embeddings of the Standard Model, as we will summarize below. There is no reason why some of these hidden U(1) gauge bosons can not be massless or very light, in which case they also belong to the class of very weakly interacting sub-eV particles (WISPs). Further candidates for WISPs are very light hidden sector particles which are charged under the hidden U(1)s. In this contribution, we will take a top-down point of view: we will illustrate how axions and other WISPs arise in the course of compactification of the extra dimensions of string theory. For the bottom-up point of view, i.e. for arguments and phenomenological as well as cosmological hints which point to the possible existence of WISPs, see the contributions of Joerg Jaeckel and Javier Redondo in these proceedings. Axions from string compactifications.– The low-energy effective actions describing the dynamics of the massless bosonic excitations of the heterotic and type II string theories in 9+1 dimensions are summarized in Table 1. As we will see, after compactification of six of the spatial dimensions, pseudo-scalar fields a will generically arise which have a coupling a trG∧G

研究动机与目标

• 理解弦理论中轴子及其他非常轻、弱相互作用的亚电子伏特粒子（WISPs）的理论起源。
• 解释轴子如何作为弦紧化中全局异常U(1)对称性自发性自发破缺的伪Nambu-Goldstone玻色子而出现。
• 证明隐藏U(1)规范玻色子及其潜在轻质量在现实弦紧化中的普遍性。
• 提供一个自上而下的框架，将弦理论紧化与WISPs的涌现（包括轴子样粒子和隐藏 sector 带电粒子）联系起来。
• 通过从基本弦理论推导其低能有效耦合，为WISPs的现象学和宇宙学研究奠定基础。

提出的方法

• 推导异色和II型弦理论在9+1维下的低能有效作用量，重点关注无质量的玻色子激发态。
• 通过紧化六个空间维，导致4维有效理论中出现赝标量场（轴子）。
• 将轴子识别为紧化理论中全局异常U(1)对称性自发破缺所对应的伪Nambu-Goldstone玻色子。
• 通过有效作用量中的项 a trG∧G 分析轴子的耦合结构，该结构控制其与规范场强度的相互作用。
• 将分析扩展至包含隐藏U(1)规范玻色子及其在低能谱中可能的无质量或轻质量特性。
• 包含与隐藏U(1)规范玻色子耦合的带电隐藏 sector 粒子，完整构建有效理论中的WISP谱。

实验结果

研究问题

• RQ1 在弦紧化后的低能有效理论中，轴子如何作为伪Nambu-Goldstone玻色子出现？
• RQ2 有效作用量中 a trG∧G 耦合项的起源是什么？它如何与轴子对规范场的相互作用相关？
• RQ3 为何隐藏U(1)规范玻色子在弦紧化中普遍存在？在何种条件下它们可以保持轻质量或无质量？
• RQ4 在相同框架下，其他WISPs（如隐藏 sector 中的带电粒子）的存在与性质由什么决定？
• RQ5 自上而下的弦论方法如何为现实紧化中轴子及其他WISPs提供统一的起源？

主要发现

• 轴子在弦紧化中普遍出现，作为全局异常U(1)对称性自发破缺的伪Nambu-Goldstone玻色子。
• 有效耦合 a trG∧G 是低能作用量的关键特征，介导轴子与规范场强度的相互作用。
• 隐藏U(1)规范玻色子在弦论嵌入中频繁出现，且可保持轻质量或无质量，符合WISP特征。
• 六个空间维的紧化导致一个丰富的轻量、弱耦合粒子谱，包括轴子和隐藏 sector 状态。
• 与隐藏U(1)规范玻色子耦合的隐藏 sector 带电粒子，是该框架中自然的WISP候选者。
• 该框架从弦理论出发，一致地自上而下推导出WISPs，确立了其在现实紧化中的理论合理性。