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arXiv 1104.0461hep-thhep-ph
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超对称QCD:精确结果和强耦合

Supersymmetric QCD: Exact Results and Strong Coupling

Michael Dine, Guido Festuccia, Lawrence Pack, Chang-Soon Park, Lorenzo Ubaldi, Weitao Wu

摘要:

我们重新审视了超对称规范理论中两个长期存在的难题。第一个问题的全纯性的耦合,并与此相关的可能定义的一个确切的(NSVZ)β函数。第二个是关于纯胶子动力学中的瞬子,它似乎对某些关联函数给出了合理的、精确的结果,但这些结果与用系统弱耦合展开法得到的结果不同。对于第一个问题,我们扩展了Arkani-Hamed和Murayama的早期建议,表明如果他们的调节作用量写得合适,耦合的全纯性是明显的,并且很容易确定NSVZ公式适用的重整化方案。然而,这个方案被看作是一个无限类的方案,每一个导致一个确切的β函数; NSVZ方案,虽然简单,没有选择任何令人信服的物理考虑。对于第二个问题,我们解释了为什么在纯超对称规范理论中的瞬子计算是不可靠的,即使在短距离。关于瞬子的半经典展开是纯粹形式的;如果出现红外发散,它们会破坏基于全纯性的论证。我们证明,红外发散不发生在瞬子的微扰膨胀,但解释说,没有理由认为这捕获所有的贡献与单位拓扑电荷的部门。人们期望通过稀释气体修正来说明额外的贡献。这些都是红外发散的,所以很难定义,但如果非零给一阶,全纯,更正领先的结果。利用戴维斯等人的早期分析,我们证明了在理论中紧化的半径β的圆,由于红外效应,有限的贡献确实出现,这是不可见的正式限制,β走向无穷大。

英文摘要:

We revisit two longstanding puzzles in supersymmetric gauge theories. The first concerns the question of the holomorphy of the coupling, and related to this the possible definition of an exact (NSVZ) beta function. The second concerns instantons in pure gluodynamics, which appear to give sensible, exact results for certain correlation functions, which nonetheless differ from those obtained using systematic weak coupling expansions. For the first question, we extend an earlier proposal of Arkani-Hamed and Murayama, showing that if their regulated action is written suitably, the holomorphy of the couplings is manifest, and it is easy to determine the renormalization scheme for which the NSVZ formula holds. This scheme, however, is seen to be one of an infinite class of schemes, each leading to an exact beta function; the NSVZ scheme, while simple, is not selected by any compelling physical consideration. For the second question, we explain why the instanton computation in the pure supersymmetric gauge theory is not reliable, even at short distances. The semiclassical expansion about the instanton is purely formal; if infrared divergences appear, they spoil arguments based on holomorphy. We demonstrate that infrared divergences do not occur in the perturbation expansion about the instanton, but explain that there is no reason to think this captures all contributions from the sector with unit topological charge. That one expects additional contributions is illustrated by dilute gas corrections. These are infrared divergent, and so difficult to define, but if non-zero give order one, holomorphic, corrections to the leading result. Exploiting an earlier analysis of Davies et al, we demonstrate that in the theory compactified on a circle of radius beta, due to infrared effects, finite contributions indeed arise which are not visible in the formal limit that beta goes to infinity.

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