Redundancies in Nambu-Goldstone Bosons

Haruki Watanabe and Hitoshi Murayama

Phys. Rev. Lett. 110, 181601 – Published 1 May 2013

Abstract

We propose a simple criterion to identify when Nambu-Goldstone bosons for different symmetries are redundant. It solves an old mystery why crystals have phonons for spontaneously broken translations but no gapless excitations for equally spontaneously broken rotations. Similarly for a superfluid, the Nambu-Goldstone boson for spontaneously broken Galilean symmetry is redundant with phonons. The most nontrivial example is Tkachenko mode for a vortex lattice in a superfluid, where phonons are redundant to the Tkachenko mode which is identified as the Boboliubov mode.

Received 19 February 2013

DOI:https://doi.org/10.1103/PhysRevLett.110.181601

Authors & Affiliations

Haruki Watanabe^1,* and Hitoshi Murayama^1,2,3,†

¹Department of Physics, University of California, Berkeley, California 94720, USA
²Lawrence Berkeley National Laboratory, Theoretical Physics Group, Berkeley, California 94720, USA
³Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583, Japan