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YanYan Li

Publications and source records attributed to YanYan Li.

68 records · Page 4Linked to original sources

Regularity of the distance function to the boundary

Let $Ω$ be a domain in a smooth complete Finsler manifold, and let $G$ be the largest open subset of $Ω$ such that for every $x$ in $G$ there is a unique closest point from $\partial Ω$ to $x$ (measured in the Finsler metric). We prove that the distance function from $\partial Ω$ is in $C^{k,α}_{loc}(G\cup \partial Ω)$, $k\ge 2$ and $0<α\le 1$, if $\partial Ω$ is in $C^{k,α}$.

math.AP↗

On some conformally invariant fully nonlinear equations

We will report some results concerning the Yamabe problem and the Nirenberg problem. Related topics will also be discussed. Such studies have led to new results on some conformally invariant fully nonlinear equations arising from geometry. We will also present these results which include some Liouville type theorems, Harnack type inequalities, existence and compactness of solutions to some nonlinear version of the Yamabe problem.

math.AP↗

A sharp Sobolev inequality on Riemannian manifolds

Let (M,g) be a smooth compact Riemannian manifold without boundary of dimension n>=6. We prove that {align*} \|u\|_{L^{2^*}(M,g)}^2 \le K^2\int_M\{|\nabla_g u|^2+c(n)R_gu^2\}dv_g +A\|u\|_{L^{2n/(n+2)}(M,g)}^2, {align*} for all u\in H^1(M), where 2^*=2n/(n-2), c(n)=(n-2)/[4(n-1)], R_g is the scalar curvature, $K^{-1}=\inf\|\nabla u\|_{L^2(\R^n)}\|u\|_{L^{2n/(n-2)}(\R^n)}^{-1}$ and A>0 is a constant depending on (M,g) only. The inequality is {\em sharp} in the sense that on any (M,g), $K$ can not be replaced by any smaller number and R_g can not be replaced by any continuous function which is smaller than R_g at some point. If (M,g) is not locally conformally flat, the exponent 2n/(n+2) can not be replaced by any smaller number. If (M,g) is locally conformally flat, a stronger inequality, with 2n/(n+2) replaced by 1, holds in all dimensions n>=3.

math.AP↗