• DOI:10.1007/JHEP04(2021)213
• Corpus ID: 233714259

Non-equilibrium effective field theory and second sound

@article{Landry2020NonequilibriumEF,
  title={Non-equilibrium effective field theory and second sound},
  author={Michael Landry},
  journal={Journal of High Energy Physics},
  year={2020},
  volume={2021}
}

• Michael Landry
• Published 26 August 2020
• Physics
• Journal of High Energy Physics

We investigate the phenomenon of second sound in various states of matter from the perspective of non-equilibrium effective field theory (EFT). In particular, for each state of matter considered, we find that at least two (though sometimes multiple) qualitatively different EFTs exist at finite temperature such that there is always at least one EFT with a propagating second-sound wave and at least one with no such second-sound wave. To aid in the construction of these EFTs, we use the method of cosets developed for non-equilibrium systems. It turns out that the difference between the EFTs with and without second-sound modes can be understood as arising from different choices of a new kind of inverse Higgs constraint. Finally, we demonstrate that it is possible to bypass the need for new inverse Higgs constraints by formulating EFTs on a new kind of manifold that is like the usual fluid worldvolume, but with reduced gauge symmetries.