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A Grushin problem for Bismut's hypoelliptic Laplacian

Francis Nier, Xingfeng Sang and Francis White

Vol. 8 (2026), No. 1, 41–120
Abstract

The name “Grushin problem” refers here to the variation of Schur complement technique introduced by J. Sjöstrand in his early works, which is now a commonly used tool in spectral analysis (see Acta. Math. 130 (1973), 1–51 and Ann. Inst. Fourier 57:7 (2007), 2095–2141). Recently Q. Ren and Z. Tao proposed such an approach for the analysis of the low-lying eigenvalues in the large friction limit for a simple scalar kinetic model. Inspired by this work and the introduction of functional spaces adapted to the analysis of geometric Kramers–Fokker–Planck operators in a previous article, here we study the combined asymptotic analysis of Bismut’s hypoelliptic Laplacian in the high friction b 0+ and possibly low temperature h 0+ regimes.

Keywords
Bismut's hypoelliptic Laplacian, Grushin problem, spectral convergence, multiscale analysis, large friction, low temperature
Mathematical Subject Classification
Primary: 35H10, 35H20, 35K65, 35R01, 47D06
Secondary: 58J50, 58J65, 60J65, 82C31, 82C40
Milestones
Received: 17 May 2024
Revised: 19 May 2025
Accepted: 7 October 2025
Published: 29 December 2025
Authors
Francis Nier
LAGA, UMR-CNRS 7539
Université de Paris XIII
Paris
France
Xingfeng Sang
LAGA, UMR-CNRS 7539
Université de Paris XIII
Paris
France
Francis White
Department of Mathematics
University of California, Los Angeles
Los Angeles, CA
United States