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arXiv 1909.09027hep-thhep-lathep-ph
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类矢量理论中重子色味(BCF)anomaly

On the baryon-color-flavor (BCF) anomaly in vector-like theories

Mohamed M. Anber, Erich Poppitz

摘要:

我们认为最一般的分数背景通量的颜色,味道,和重子数的方向,兼容的忠实行动的全球对称性的一个给定的理论。我们把这种背景对测量对称性的阻碍称为重子色味特胡夫特反常。我们适用于BCF异常矢量理论,与费米子在高维表示的任意N-度,并推导出非平凡的约束其IR动力学。特别是,这类理论享有独立的离散手征对称性,人们可能会问这种对称性的命运在BCF通量的背景。我们表明,在一定的条件下,之间的手征对称性和BCF背景的异常排除了无质量的复合费米子作为唯一的球员在IR:无论是复合材料不形成或额外的贡献匹配的BCF异常是必需的。我们也可以给费米子一个味道对称的质量,小于或等于理论的强标度,并在BCF背景下检验理论的$θ$角周期性。有趣的是,我们发现排除复合物的条件与导致$θ$周期性异常的条件完全相同:当我们将$θ$从$0$改变为$2π$时,大质量理论将经历相变。

英文摘要:

We consider the most general fractional background fluxes in the color, flavor, and baryon number directions, compatible with the faithful action of the global symmetry of a given theory. We call the obstruction to gauging symmetries revealed by such backgrounds the baryon-color-flavor (BCF) 't Hooft anomaly. We apply the BCF anomaly to vector-like theories, with fermions in higher-dimensional representations of arbitrary N-ality, and derive non-trivial constraints on their IR dynamics. In particular, this class of theories enjoys an independent discrete chiral symmetry and one may ask about the fate of this symmetry in the background of BCF fluxes. We show that, under certain conditions, an anomaly between the chiral symmetry and the BCF background rules out massless composite fermions as the sole player in the IR: either the composites do not form or additional contributions to the matching of the BCF anomaly are required. We can also give a flavor-symmetric mass to the fermions, smaller than or of order the strong scale of the theory, and examine the $θ$-angle periodicity of the theory in the BCF background. Interestingly, we find that the conditions that rule out the composites are the exact same conditions that lead to an anomaly of the $θ$ periodicity: the massive theory will experience a phase transition as we vary $θ$ from $0$ to $2π$.

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