标题： 自然通胀模型中的自旋odal效应 显示英文标题

标题： Spinodal effect in the natural inflation model

摘要： 近日，科米尔和霍尔曼指出，在具有势能$V(\phi)$的{\it 自旋odal膨胀}模型中，膨胀子场$\phi$的涨落显著增强，其中第二导数$V^{(2)}(\phi)$发生变号。作为该模型的一个应用，我们利用平均场近似法研究了自然膨胀模型中势能为$V(\phi)=m^4 [1+\cos (\phi/f)]$的粒子产生情况。 对于典型的质量尺度$f \sim m_{\rm pl} \sim 10^{19}$GeV 和$m \sim m_{\rm GUT} \sim 10^{16}$GeV，我们发现与膨胀子初始值$\phi(0)<0.1 m_{\rm pl}$相关的波动增长显著发生。特别是当$\phi(0)<10^{-6}m_{\rm pl}$时，最大波动非常大，以至于由产生的波动引发了二次膨胀。在这种情况下，获得的折叠数$e$远大于忽略自旋odal不稳定性效应的情况下的折叠数。 显示英文摘要

摘要： Recently, Cormier and Holman pointed out that fluctuations of an inflaton field $\phi$ are significantly enhanced in the model of {\it spinodal inflation} with a potential $V(\phi)$ for which the second derivative $V^{(2)}(\phi)$ changes sign. As an application of this model, we investigate particle production in the natural inflation model with a potential $V(\phi)=m^4 [1+\cos (\phi/f)]$ by making use of the Hartree approximation. For typical mass scales $f \sim m_{\rm pl} \sim 10^{19}$GeV, and $m \sim m_{\rm GUT} \sim 10^{16}$GeV, we find that growth of fluctuations relevantly occurs for the initial value of inflaton $\phi(0)<0.1 m_{\rm pl}$. Especially for $\phi(0)<10^{-6}m_{\rm pl}$, maximum fluctuations are so large that secondary inflation takes place by produced fluctuations. In this case, the achieved number of $e$-folding becomes much larger than in the case where an effect of spinodal instability is neglected.