Journal of High Energy Physics (Jan 2024)
Free fermions, KdV charges, generalised Gibbs ensembles, modular transforms and line defects
Abstract
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.
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