arXiv 1906.027642019-06-06hep-phhep-th

暴涨中轴子衰变常数的增强与弱引力猜想

Enhancement of the Axion Decay Constant in Inflation and the Weak Gravity Conjecture

Pran Nath, Maksim Piskunov

备注：: 29 pages, 4 figures

摘要：

基于单一余弦势的轴子暴胀模型要求轴子衰变常数$f$的大小是超普朗克的。然而，$f > M_{Pl}$不受弱引力猜想（WGC）的青睐。然后，我们可以问，是否可以构造符合WGC的轴子暴胀模型。在这项工作中，我们假设WGC的微观拉格朗日，使$f < M_{Pl}$。然而，暴胀是由一个远低于普朗克尺度的有效拉格朗日量控制的，其中暴胀子是一个与有效衰变常数$f_e$相关的有效轴子场，该常数可能与$f$非常不同。在这项工作中，我们提出了一个相干增强机制（CEM）的慢滚膨胀控制的平坦的潜力，可以产生$f_e \gg M_{Pl}$，而$f < M_{Pl}$。在分析中，我们认为景观的手征领域下收取的$U\left(1\right)$全球移动对称性，并考虑破缺的$U\left(1\right)$对称性的瞬子型对称性破缺条款。在破缺相中，有一个轻的赝南布-戈德斯通玻色子（pNGB）充当暴胀子。我们表明，与适当的选择对称性破缺项的暴胀子潜在的是一个叠加的许多余弦和条件，它们产生一个平坦的潜力允许一个增强$f_e$，使$f_e / M_{Pl} \gg 1$。我们讨论的效用，这种机制的各种暴胀模型起源于超对称性和超引力。相干增强机制允许人们通过扩展视界出口发生的场点附近的势，并将扩展系数与自然暴胀的扩展系数相匹配，将具有任意势的暴胀模型简化为有效的自然暴胀模型，即具有单个余弦。

英文摘要：

Models of axion inflation based on a single cosine potential require the axion decay constant $f$ to be super-Planckian in size. However, $f > M_{Pl}$ is disfavored by the Weak Gravity Conjecture (WGC). It is then pertinent to ask if one can construct axion inflation models in conformity with WGC. In this work we assume that WGC holds for the microscopic Lagrangian so that $f < M_{Pl}$. However, inflation is controlled by an effective Lagrangian much below the Planck scale where the inflaton is an effective axionic field associated with an effective decay constant $f_e$ which could be very different from $f$. In this work we propose a Coherent Enhancement Mechanism (CEM) for slow roll inflation controlled by flat potentials which can produce $f_e \gg M_{Pl}$ while $f < M_{Pl}$. In the analysis we consider a landscape of chiral fields charged under a $U\left(1\right)$ global shift symmetry and consider breaking of the $U\left(1\right)$ symmetry by instanton type symmetry breaking terms. In the broken phase there is one light pseudo-Nambu-Goldstone-Boson (pNGB) which acts as the inflaton. We show that with an appropriate choice of symmetry breaking terms the inflaton potential is a superposition of many cosines and the condition that they produce a flat potential allows one to enhance $f_e$ so that $f_e / M_{Pl} \gg 1$. We discuss the utility of this mechanism for a variety of inflaton models originating in supersymmetry and supergravity. The Coherent Enhancement Mechanism allows one to reduce an inflation model with an arbitrary potential to an effective model of natural inflation, i.e. with a single cosine, by expanding the potential near a field point where horizon exit occurs, and matching the expansion coefficients to those of natural inflation.

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摘要：

英文摘要：

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