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arXiv 1211.4151hep-th
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重整化与渐近安全讲座

Lectures on renormalization and asymptotic safety

Sandor Nagy

摘要:

简要介绍了泛函重整化群方法,着重介绍了它的非微扰性质。该方法能够在量子场论模型中找到非平凡的不动点,使它们不发散,并导致渐近安全的概念。它可以看作是在微扰重整化中起关键作用的渐近自由度的推广。本文对Gross-Neveu模型、非线性$σ$模型、sine-Gordon模型等几个重要的渐近安全模型进行了总结和简要的讨论,并考虑了量子爱因斯坦引力模型,它似乎也是渐近安全的。我们还详细分析了发生自发对称性破缺的标量模型的红外行为。在微扰计算的框架内不能处理破碎相的深红外行为。我们证明了在破缺相中存在一个红外不动点,它在那里产生了一个新的标度区,但它的结构被重整化群方程的奇异性所掩盖.这些模型的理论空间表现出一些相似的性质,即模型具有相同的相位和不动点结构。量子爱因斯坦引力在考虑其理论空间的整体方面时也表现出相似性,因为那里出现的两个相与标量模型的对称相和破缺相具有相似性。这些结果可以用泛函重整化群方法很好地揭示出来.

英文摘要:

A short introduction is given on the functional renormalization group method, putting emphasis on its nonperturbative aspects. The method enables to find nontrivial fixed points in quantum field theoretic models which make them free from divergences and leads to the concept of asymptotic safety. It can be considered as a generalization of the asymptotic freedom which plays a key role in the perturbative renormalization. We summarize and give a short discussion of some important models, which are asymptotically safe such as the Gross-Neveu model, the nonlinear $σ$ model, the sine-Gordon model, and we consider the model of quantum Einstein gravity which seems to show asymptotic safety, too. We also give a detailed analysis of infrared behavior of such scalar models where a spontaneous symmetry breaking takes place. The deep infrared behaviorof the broken phase cannot be treated within the framework of perturbative calculations. We demonstrate that there exists an infrared fixed point in the broken phase whichcreates a new scaling regime there, however its structure is hidden by the singularity of the renormalization group equations. The theory spaces of these models show several similar properties, namely the models have the same phase and fixed point structure. The quantum Einstein gravity also exhibits similarities when considering the global aspects of its theory space since the appearing two phases there show analogies with the symmetric and the broken phases of the scalar models. These results be nicely uncovered by the functional renormalization group method.

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