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arXiv 0710.0863hep-phhep-th
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高激发介子、线性Regge轨线和手征对称性的实现模式

Highly Excited Mesons, Linear Regge Trajectories and the Pattern of the Chiral Symmetry Realization

M. Shifman, A. Vainshtein

摘要:

QCD的手征对称性在短欧氏距离或高温下以线性Weyl-Wigner模式出现。另一方面,低位强子态表现出非线性Nambu-Goldstone模。提出了一个有趣的问题,是否线性实现的手征对称性是渐近恢复高度激发态。我们以多种方式处理这一问题。在唯象方面,我们认为,在一定程度上观察到的介子Regge轨迹是线性和等距的,外尔-维格纳模式是没有实现的。这幅图得到了准经典论据的支持,这意味着在高激发下夸克自旋相互作用很弱,轨道是线性的,并且没有手征对称性恢复。然后我们使用弦/规范对偶。在自上而下的Sakai-Sugimoto结构中,建立了手征对称性的非线性实现。在Erlich等人的自底向上AdS/QCD构建中,和Karch等人的情况更加模糊。然而,在这种方法中,可以自然地实现Regge轨迹的线性和等距,具有Nambu-Goldstone模式中的手征对称性。如果在$n,J$的"中间窗口"中的Regge轨迹的非线性(收敛)超出了所探索的域,则渐近手征对称性恢复可能是可能的。这将标志着准古典图景的失败。

英文摘要:

The chiral symmetry of QCD shows up in the linear Weyl--Wigner mode at short Euclidean distances or at high temperatures. On the other hand, low-lying hadronic states exhibit the nonlinear Nambu--Goldstone mode. An interesting question was raised as to whether the linear realization of the chiral symmetry is asymptotically restored for highly excited states. We address it in a number of ways. On the phenomenological side we argue that to the extent the meson Regge trajectories are observed to be linear and equidistant, the Weyl--Wigner mode is not realized. This picture is supported by quasiclassical arguments implying that the quark spin interactions in high excitations are weak, the trajectories are linear, and there is no chiral symmetry restoration. Then we use the string/gauge duality. In the top-down Sakai--Sugimoto construction the nonlinear realization of the chiral symmetry is built in. In the bottom-up AdS/QCD construction by Erlich et al., and Karch et al. the situation is more ambiguous. However, in this approach linearity and equidistance of the Regge trajectories can be naturally implemented, with the chiral symmetry in the Nambu--Goldstone mode. Asymptotic chiral symmetry restoration might be possible if a nonlinearity (convergence) of the Regge trajectories in an "intermediate window" of $n,J$, beyond the explored domain, takes place. This would signal the failure of the quasiclassical picture.

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