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arXiv 1109.4192hep-thastro-ph.COgr-qchep-ph
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暴胀有效场论中的耗散效应

Dissipative effects in the Effective Field Theory of Inflation

Diana Lopez Nacir, Rafael A. Porto, Leonardo Senatore, Matias Zaldarriaga

摘要:

我们将单钟暴胀的有效场论推广到包括耗散效应。在幺正规范下,我们在有效作用量中耦合了一组复合算子,该作用量仅受时间依赖的空间非同态下的不变性的约束。我们限制自己的情况下,负责耗散的自由度没有贡献的密度扰动在晚些时候。扰动的动力学被“摩擦”和噪声项的出现所改变,并且假设这些复合算子的格林函数具有一定的局部性,我们证明了存在一个以大摩擦项γ>> H为特征的区域,在该区域中,扰动算子由噪声支配,功率谱可以显著增强。我们还计算了三点函数的广泛的一类模型,并讨论在何种情况下,大摩擦导致非高斯性的水平增加。特别地,在我们的假设下,我们证明了强耗散以及所需的对称性的非线性实现意味着|f_NL| ~ γ/(c_s^2H)>> 1。作为一个典型的例子,我们制定了一个变化的“陷阱通货膨胀”的情况下,当地的响应函数,并执行匹配与我们的有效理论。我们在这里描述的,在暴胀过程中结合耗散效应所产生的一般类型的特征的检测,将教会我们早期宇宙的动力学,也扩展了暴胀模型的参数空间。

英文摘要:

We generalize the effective field theory of single clock inflation to include dissipative effects. Working in unitary gauge we couple a set of composite operators in the effective action which is constrained solely by invariance under time-dependent spatial diffeomorphisms. We restrict ourselves to situations where the degrees of freedom responsible for dissipation do no contribute to the density perturbations at late time. The dynamics of the perturbations is then modified by the appearance of `friction' and noise terms, and assuming certain locality properties for the Green's functions of these composite operators, we show that there is a regime characterized by a large friction term γ>> H in which the ζ-correlators are dominated by the noise and the power spectrum can be significantly enhanced. We also compute the three point function <ζζζ> for a wide class of models and discuss under which circumstances large friction leads to an increased level of non-Gaussianities. In particular, under our assumptions, we show that strong dissipation together with the required non-linear realization of the symmetries implies |f_NL| ~ γ/(c_s^2H) >> 1. As a paradigmatic example we work out a variation of the `trapped inflation' scenario with local response functions and perform the matching with our effective theory. A detection of the generic type of signatures that result from incorporating dissipative effects during inflation, as we describe here, would teach us about the dynamics of the early universe and also extend the parameter space of inflationary models.

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