Journal of High Energy Physics (Jan 2024)

Free fermions, KdV charges, generalised Gibbs ensembles, modular transforms and line defects

  • Max Downing,
  • Gérard M. T. Watts

DOI
https://doi.org/10.1007/JHEP01(2024)041
Journal volume & issue
Vol. 2024, no. 1
pp. 1 – 26

Abstract

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Abstract In this paper we return to the question of the modular properties of a generalised Gibbs ensemble of a single free fermion. We extend our previous proposals to a GGE containing an arbitrary number of conserved charges and provide a physical interpretation of the result in terms of a line defect. The defect description perfectly explains the product formula for the modular transformation we found previously. We also give a proposal for a Hamiltonian approach to the line defect.

Keywords