Rainbow Nambu-Goldstone Modes under a Shear Flow

Yuki Minami, Hiroyoshi Nakano, and Yoshimasa Hidaka

We study an OðNÞ scalar model under shear flow and its Nambu-Goldstone modes associated with spontaneous symmetry breaking OðNÞ → OðN − 1Þ. We find that the Nambu-Goldstone mode splits into an infinite number of gapless modes, which we call the rainbow Nambu-Goldstone modes. They have different group velocities and the fractional dispersion relation ω ∼ k2=3 1 , where k1 is the wave number along the flow. Such behaviors do not have counterparts in an equilibrium state.

PHYSICAL REVIEW LETTERS 126, 141601 (2021)

The published article is available at https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.126.141601