A gravitational realization of Courant--Hilbert deformations
Abstract
Courant--Hilbert (CH) deformations unify broad classes of solvable stress-tensor flows including TT̅ and root-TT̅. However, a gravitational action that systematically yields such general deformations has remained unknown. In this Letter, we construct a two-dimensional massive gravity theory whose on-shell action reproduces the complete CH deformation. The gravity sector is defined via an arbitrary function of the eigenvalue ratio y of the relative zweibein. To bypass the technical difficulty of directly eliminating the auxiliary zweibein, we reformulate the matter sector using a 2 × 2 spectral decomposition involving y and a rank-one projector K. Sequentially solving the equations of motion---first for K and subsequently for y---naturally maps the system onto the Russo-Townsend form of the CH flow. Our work extends Tolley's massive gravity formulation of TT̅ flows to the CH landscape, providing a clear geometric mechanism for solvable stress-tensor flows.
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BibTeX
@misc{fukushima2026gravitational,
title = {{A gravitational realization of Courant--Hilbert deformations}},
author = {Osamu Fukushima and Miyabi Kurihara and Takaki Matsumoto and Kentaroh Yoshida},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.35452},
eprint = {2609.35452},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.35452},
}
RIS
TY - UNPB
TI - A gravitational realization of Courant--Hilbert deformations
AU - Osamu Fukushima
AU - Miyabi Kurihara
AU - Takaki Matsumoto
AU - Kentaroh Yoshida
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2609.35452
UR - https://arxiv.org/abs/2609.35452
AB - Courant--Hilbert (CH) deformations unify broad classes of solvable stress-tensor flows including TT̅ and root-TT̅. However, a gravitational action that systematically yields such general deformations has remained unknown. In this Letter, we construct a two-dimensional massive gravity theory whose on-shell action reproduces the complete CH deformation. The gravity sector is defined via an arbitrary function of the eigenvalue ratio y of the relative zweibein. To bypass the technical difficulty of directly eliminating the auxiliary zweibein, we reformulate the matter sector using a 2 × 2 spectral decomposition involving y and a rank-one projector K. Sequentially solving the equations of motion---first for K and subsequently for y---naturally maps the system onto the Russo-Townsend form of the CH flow. Our work extends Tolley's massive gravity formulation of TT̅ flows to the CH landscape, providing a clear geometric mechanism for solvable stress-tensor flows.
ER -