An elliptic equation may have coefficients smooth enough to control its solutions, yet that does not guarantee that a single estimate constant will work for an entire family of equations. In a preprint posted to arXiv on October 15, 2026, Tian Lan addresses this gap by proving uniform estimates for divergence-form elliptic systems whose coefficients belong to a critical Sobolev–Lorentz class.
Consider the divergence-form operator \(Lu=\partial_\alpha(A^{\alpha\beta}\partial_\beta u)\). The coef
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