Submitted to Phys. Rev. Lett.
Detailed measurements on the static and dynamic stripes have been done in an optimally doped high-temperature superconductor, La2CuO4+y. It was found that the dynamic stripes do not disperse towards the static stripes in the limit of vanishing energy transfer. It is concluded that the dynamic stripes observed in neutron scattering experiments are not the Goldstone modes associated with the broken symmetry of the simultaneously observed static stripes, but rather that the signals originate from different domains in the sample.