PIRSA:26050027 Conference Quantum Information Condensed Matter

DOI10.48660/26050027

Conference/School: Physics of Quantum Information II

Grover, T. (2026). Non-perturbative constraints on phase diagrams of non-equilibrium systems. Perimeter Institute. https://pirsa.org/26050027

Grover, Tarun. Non-perturbative constraints on phase diagrams of non-equilibrium systems. Perimeter Institute, May. 27, 2026, https://pirsa.org/26050027 

@misc{ pirsa_PIRSA:26050027,
  doi = {10.48660/26050027},
  url = {https://pirsa.org/26050027},
  author = {Grover, Tarun},
  keywords = {Quantum Information, Condensed Matter},
  language = {en},
  title = {Non-perturbative constraints on phase diagrams of non-equilibrium systems},
  publisher = {Perimeter Institute},
  year = {2026},
  month = {may},
  note = {PIRSA:26050027 see, \url{https://pirsa.org}}
}

Abstract

In this talk I will discuss constraints on renormalization group (RG) flows and the stability of phases in nonequilibrium systems using information-theoretic inequalities, with examples drawn from both quantum and classical settings. The central quantity underlying these constraints is the conditional mutual information (CMI), which quantifies correlations between spatially separated regions that are not mediated by their surroundings. Assuming a UV-finite and sufficiently regular CMI scaling function, I will argue that a fixed point with smaller CMI cannot be destabilized toward one with larger CMI. I will discuss implications of this result for phase diagrams of classical nonequilibrium steady states, as well as examples involving strong-to-weak symmetry breaking, topological order, and SPT order. Time permitting, I will discuss a bound relating CMI of a convex mixture to the CMI of its pure-state components. I will use this bound to argue for the perturbative stability of spontaneous-symmetry-breaking states against arbitrary p-bounded quantum channels, even when the channel explicitly breaks the symmetry. This implies the existence of steady states with long-range order whose corresponding Liouvillian has no standard 0-form symmetry --- a phenomenon one might call "spontaneous symmetry breaking without symmetry." This work is in collaboration with Yu-Hsueh Chen.

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