Within the bottom-up holographic approach to QCD, the highly excited hadrons are identified with the bulk normal modes in the fifth “holographic” dimension. We show that additional states in the same mass range can appear also from taking into consideration the 5D fields dual to higher dimensional QCD operators. The possible effects of these operators have not been taken into account in virtually any phenomenological applications. Using the scalar case as the simplest example, we demonstrate that the additional higher dimensional operators lead to a large degeneracy of highly excited states in the soft wall holographic model, and in the hard wall holographic model, they result in a proliferation of excited states. The considered model can be viewed as the first analytical toy model predicting a one-to-one mapping of the excited meson states to definite QCD operators, to which they prefer to couple.

中文翻译：

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高维QCD算子对自下而上全息模型光谱的影响

在自下而上的QCD全息方法中，高激发强子在第五个“全息”维度上具有体态正态。我们表明，通过将5D场对偶到更高维的QCD算符，还可以出现相同质量范围内的其他状态。实际上，在任何现象学应用中都没有考虑到这些运算符的可能影响。使用标量情况作为最简单的例子，我们证明了额外的高维算子会导致软壁全息模型中高激发态的大量退化，而在硬壁全息模型中，它们导致激发态的扩散。