## Abstract

In this paper we study critical sets of solutions (Formula presented.) of second-order elliptic equations in divergence form with rapidly oscillating and periodic coefficients. Under some condition on the first-order correctors, we show that the (Formula presented.) -dimensional Hausdorff measures of the critical sets are bounded uniformly with respect to the period ε, provided that doubling indices for solutions are bounded. The key step is an estimate of “turning” of an approximate tangent map, the projection of a non-constant solution (Formula presented.) onto the subspace of spherical harmonics of order ℓ, when the doubling index for (Formula presented.) on a sphere (Formula presented.) is trapped between (Formula presented.) and (Formula presented.), for r between 1 and a minimal radius (Formula presented.). This estimate is proved by using harmonic approximation successively. With a suitable L^{2} renormalization as well as rescaling we are able to control the accumulated errors introduced by homogenization and projection. Our proof also gives uniform bounds for Minkowski contents of the critical sets.

Original language | English |
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Journal | Communications on Pure and Applied Mathematics |

DOIs | |

State | Accepted/In press - 2023 |

### Bibliographical note

Publisher Copyright:© 2023 Wiley Periodicals LLC.

### Funding

Fanghua Lin supported in part by NSF grant DMS‐1955249. Zhongwei Shen supported in part by NSF grant DMS‐1856235 and by Simons Fellowship.

Funders | Funder number |
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National Science Foundation (NSF) | DMS‐1955249, DMS‐1856235 |

## ASJC Scopus subject areas

- General Mathematics
- Applied Mathematics