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arXiv 1010.1964hep-thhep-ph
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来自紧致第五维的光标量

Light scalars from a compact fifth dimension

Daniel Elander, Maurizio Piai

摘要:

我们考虑与重力耦合的一般五维西格玛模型,具有任意数量的标量以及一般西格玛模型度量和势。我们详细讨论的标量波动的边界条件的问题,在第五维是紧凑的情况下,并提供一个简单的(和非常一般的)算法程序计算的频谱的物理标量波动的完全反反应系统。特别关注的条件下,标量激发(胶球)的频谱包含参数轻态,我们应用的形式主义,一些特别简单的玩具模型,这可以被认为是规范/引力强耦合,非共形四维规范理论。我们的例子是在唯象有效场论的构造(自下而上的方法)和超引力极限下十维弦论的一致截断(自上而下的方法)的背景下选择的。在其中一个例子中,尽管在深红外中存在一个坏的裸奇点,但光谱中仍然存在一个轻的光子,在这附近,对偶理论的RG流肯定远离任何固定点。如果这一特征在奇异性得到解决的完整模型中持续存在,这将证明至少在某些行走的彩色理论中可以预料到轻膨胀子。我们在这里提供了所有的技术细节,以测试这一声明,一旦这样一个完整的模型被确定。

英文摘要:

We consider a general five-dimensional sigma-model coupled to gravity, with any number of scalars and general sigma-model metric and potential. We discuss in detail the problem of the boundary conditions for the scalar fluctuations, in the case where the fifth dimension is compact, and provide a simple (and very general) algorithmic procedure for computing the spectrum of physical scalar fluctuations of the fully back-reacted system. Focusing in particular on the conditions under which the spectrum of scalar excitations (glueballs) contains parametrically light states, we apply the formalism to some especially simple toy models, which can be thought of as the gauge/gravity duals of strongly-coupled, non-conformal four-dimensional gauge theories. Our examples are chosen both within the context of phenomenological effective field theory constructions (bottom-up approach), and within the context of consistent truncations of ten-dimensional string theories in the supergravity limit (top-down approach). In one of the examples, a light dilaton is present in the spectrum in spite of the presence of a bad naked singularity in the deep IR, near which the RG flow of the dual theory is certainly very far away from any fixed point. If this feature were to persist in a complete model in which the singularity is resolved, this would prove that a light dilaton is to be expected in at least certain walking technicolor theories. We provide here all the technical details for testing this statement, once such a complete model is identified.

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