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arXiv 1203.2116hep-lathep-ph
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强耦合额外维理论中的光标量

Light scalars in strongly-coupled extra-dimensional theories

Luigi Del Debbio, Alistair Hart, Enrico Rinaldi

摘要:

在S^1上紧致化的五维杨-米尔斯理论的低能动力学可以用四维规范理论与规范群伴随表象中的标量场耦合来描述。微扰计算表明,这个基本标量场的质量受到幂次发散的保护,并且由额外维度R的大小控制。作为微扰理论之外的这一现象的研究的第一步,我们研究了SU(2)杨米尔斯理论在各向异性晶格上的五维正则化的相图,我们确定了相关的物理尺度的比率。晶格系统显示了一个维度减少的阶段,其中四维相关长度远大于额外维度的大小,但仍然小于四维体积。在裸参数空间的这个区域中,在低于1/R的能量处,非微扰谱包含\emph{light}标量态。该状态的质量与截止无关,并且与胶球算符有少量重叠。我们的研究结果表明,光标量场可以引入到晶格理论使用紧致额外的维度,而不是微调裸质量参数。

英文摘要:

The low-energy dynamics of five-dimensional Yang-Mills theories compactified on S^1 can be described by a four-dimensional gauge theory coupled to a scalar field in the adjoint representation of the gauge group. Perturbative calculations suggest that the mass of this elementary scalar field is protected against power divergences, and is controlled by the size of the extra dimension R. As a first step in the study of this phenomenon beyond perturbation theory, we investigate the phase diagram of a SU(2) Yang-Mills theory in five dimensions regularized on anisotropic lattices and we determine the ratios of the relevant physical scales. The lattice system shows a dimensionally reduced phase where the four-dimensional correlation length is much larger than the size of the extra dimension, but still smaller than the four-dimensional volume. In this region of the bare parameter space, at energies below 1/R, the non-perturbative spectrum contains a \emph{light} scalar state. This state has a mass that is independent of the cut-off, and a small overlap with glueball operators. Our results suggest that light scalar fields can be introduced in a lattice theory using compactified extra dimensions, rather than fine tuning the bare mass parameter.

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