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arXiv 1406.0939hep-thastro-ph.COgr-qchep-ph
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用有效场论形式研究膜膨胀和标量微扰的理论和观测约束

Theoretical and Observational Constraints on Brane Inflation and Study of Scalar Perturbations through the Effective Field Theory Formalism

Spyros Sypsas

备注：
PhD thesis, 145 p. Defended OCT 2013
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摘要：

本论文由两个主要部分组成，我们研究了D膜暴胀背景下宇宙（超）弦的观测特征以及一般均匀暴胀背景上标量扰动的性质。在第一部分中，我们研究了在两个被广泛应用的D膜暴胀模型$D3/D7$和$D3/\bar{D}3$中宇宙超弦的产生、性质和衰变过程。具体来说，我们表明，在$D3/D7$中产生的字符串是当地的轴子类型，我们把约束的张力，同时认为，该模型的超对称性破缺机制需要改变根据超重力约束恒定费耶特-伊利奥普洛斯条款。此外，我们还研究了宇宙超弦在弯曲背景上的辐射过程。我们认为，把弦的形成在一个自然的背景下，如$D3/\bar{D}3$膨胀，限制了这些对象的可能辐射的形式。这些弦模型，这不可避免地导致在暴胀过程中存在的重模场的激励下，在第二部分中，使用有效场论（EFT）的暴胀，我们构建运营商捕获的影响，大量标量的低能量动力学暴胀子扰动。我们计算定义EFT的有效性窗口的能量尺度，例如紫外线（UV）自由度变得可操作的尺度和EFT变得强耦合的尺度。我们表明，与重场有关的低能量运营商诱导的色散关系的光模式承认两个制度：线性和非线性/色散的。假设这些模式在色散范围内跨越哈勃尺度，我们计算与两点和三点散射相关的观测值，并显示它们如何与紫外物理学的尺度直接相关。

英文摘要：

In this thesis, consisting of two main parts, we study observational signatures of cosmic (super)strings in the context of D-brane inflation and properties of scalar perturbations on generic homogeneous inflating backgrounds. In the first part we study the production, nature and decay processes of cosmic superstrings in two widely used effective models of D-brane inflation, namely the $D3/D7$ and $D3/\bar{D}3$ models. Specifically, we show that the strings produced in $D3/D7$ are of local axionic type and we place constraints on the tension while arguing that the supersymmetry breaking mechanism of the model needs to be altered according to supergravity constraints on constant Fayet-Iliopoulos terms. Moreover, we study radiative processes of cosmic superstrings on warped backgrounds. We argue that placing the string formation in a natural context such as $D3/\bar{D}3$ inflation, restricts the forms of possible radiation from these objects. Motivated by these string models, which inevitably result in the presence of heavy moduli fields during inflation, in the second part, using the Effective Field Theory (EFT) of inflation, we construct operators that capture the effects of massive scalars on the low energy dynamics of inflaton perturbations. We compute the energy scales that define the validity window of the EFT such as the scale where ultra violet (UV) degrees of freedom become operational and the scale where the EFT becomes strongly coupled. We show that the low energy operators related to heavy fields induce a dispersion relation for the light modes admitting two regimes: a linear and a non linear/dispersive one. Assuming that these modes cross the Hubble scale within the dispersive regime, we compute observables related to two- and three-point correlators and show how they are directly connected with the scale of UV physics.

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