Can the Nambu-Goldstone boson live on the light front?

We show that the Nambu-Goldstone(NG) boson restricted on the lightfront(LF) can only exist if we regularize the theory by introducing the explicit breaking NG-boson mass m . The NG-boson zero mode, when integrated over the LF, must have a singular behavior 1=m in the symmetric limit of m ! 0. In the discretized LF quantization this peculiarity is clari ed in terms of the zero-mode constraints in the linear model. The LF charge annihilates the vacuum, while it is not conserved in the symmetric limit in the NG phase. E-mail address: [email protected] E-mail address: [email protected] E-mail address: [email protected]