A compact metric surface $M$ isometrically fills a closed metric curve $C$ if $\partial M=C$ and $d_M(x,y)=d_C(x,y)$ for every $x,y\in C=\partial M$; that is, $M$ does not introduce any ``shortcuts'' between points on its boundary. Gromov's filling area conjecture in differential geometry from 1983 asserts that among all compact, orientable Riemannian surfaces which isometrically fill the Riemannian circle, the one with the smallest surface area is the hemisphere. Gromov demonstrated that this is indeed the case if $M$ is homeomorphic to the disk. While Gromov's conjecture has since been verified in some other cases, the full conjecture remains unresolved.
In this paper, we consider a discrete analogue of Gromov's problem, which is likely natural to those who study graph embeddings on arbitrary surfaces. Using standard graph-theoretic tools, such as Menger's theorem, we obtain reasonable asymptotic bounds on this discrete variant. We then demonstrate how these discrete bounds can be translated to the continuous setting, showing that any isometric filling of the Riemannian circle of length $2π$ has surface area at least $1.36π$ (the hemisphere has surface area $2π$). This appears to be the first quantitative lower-bound on Gromov's problem that applies to arbitrary isometric fillings.
Gromov's dihedral rigidity conjecture in dimension three
State Key Laboratory of Mathematical Sciences, Academy of Mathematics and Systems Science, Chinese Academy of Sciences(中国科学院数学与系统科学研究院);Department of Mathematics, Texas A&M University(德克萨斯农工大学数学系)
Gromov's Simplicial Volume Vanishing Conjecture for Positive Scalar Curvature
Department of Mathematics, Texas A&M University(德州农工大学数学系);State Key Laboratory of Mathematical Sciences, Academy of Mathematics and Systems Science, Chinese Academy of Sciences(中国科学院数学与系统科学研究院数学科学重点实验室);Yau Mathematical Sciences Center, Tsinghua University(清华大学丘成桐数学科学中心)
School of Mathematical Sciences, Key Laboratory of Intelligent Computing and Applications (Tongji University), Ministry of Education, Tongji University(同济大学数学科学学院,教育部智能计算与应用重点实验室)