非线性实现对称的Adler零拉格朗日量和有效拉格朗日量
Adler's Zero and Effective Lagrangians for Nonlinearly Realized Symmetry
摘要:
很久以前,Coleman,Callan,Wess和Zumino(CCWZ)通过寻找破缺群G的所有可能的非线性表示,当限制到未破缺群H时,这些非线性表示变成线性表示,构建了非线性实现对称的广义有效拉格朗日量。然而,在对应于破缺U(1)的单个南武-戈德斯通玻色子(NGB)的情况下,有效拉格朗日量也可以通过施加恒定的位移对称性来获得。在这项工作中,我们推广的移位对称的方法,以多个NGB和显示,当他们提供了一个线性表示的H,可以嵌入在一个对称陪集,它是可能的,以获得CCWZ拉格朗日施加1)“阿德勒的零条件”,这需要散射振幅消失时,发射一个单一的软NGB,和2)关闭的移位对称与线性实现的对称;完全不需要知道破群G。仅使用H的生成元,NGB协变导数和相关的规范场可以计算到NGB衰变常数f的所有阶。
英文摘要:
Long ago Coleman, Callan, Wess and Zumino (CCWZ) constructed the general effective lagrangian for nonlinearly realized symmetry by finding all possible nonlinear representations of the broken group G which become linear when restricted to the unbroken group H. However, in the case of a single Nambu-Goldstone boson (NGB), which corresponds to a broken U(1), the effective lagrangian can also be obtained by imposing a constant shift symmetry. In this work we generalize the shift symmetry approach to multiple NGBs and show that, when they furnish a linear representation of H that can be embedded in a symmetric coset, it is possible to derive the CCWZ lagrangian by imposing 1) the "Adler's zero condition," which requires scattering amplitudes to vanish when emitting a single soft NGB, and 2) closure of shift symmetry with the linearly realized symmetry; knowledge of the broken group G is not required at all. Using only generators of H, the NGB covariant derivative and the associated gauge field can be computed to all orders in the NGB decay constant f.
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