{"title":"On positivity of the CM line bundle on K-moduli spaces","authors":"Chenyang Xu, Ziquan Zhuang","doi":"10.4007/annals.2020.192.3.7","DOIUrl":"https://doi.org/10.4007/annals.2020.192.3.7","url":null,"abstract":"In this paper, we consider the CM line bundle on the K-moduli space, i.e., the moduli space parametrizing K-polystable Fano varieties. We prove it is ample on any proper subspace parametrizing reduced uniformly K-stable Fano varieties which conjecturally should be the entire moduli space. As a corollary, we prove that the moduli space parametrizing smoothable K-polystable Fano varieties is projective. During the course of proof, we develop a new invariant for filtrations which can be used to test various K-stability notions of Fano varieties.","PeriodicalId":8134,"journal":{"name":"Annals of Mathematics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46527886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Inscribed rectangles in a smooth Jordan curve attain at least one\u0000 third of all aspect ratios","authors":"Cole Hugelmeyer","doi":"10.4007/annals.2021.194.2.3","DOIUrl":"https://doi.org/10.4007/annals.2021.194.2.3","url":null,"abstract":"We prove that for every smooth Jordan curve $gamma$, if $X$ is the set of all $r in [0,1]$ so that there is an inscribed rectangle in $gamma$ of aspect ratio $tan(rcdot pi/4)$, then the Lebesgue measure of $X$ is at least $1/3$. To do this, we study disjoint Mobius strips bounding a $(2n,n)$-torus link in the solid torus times an interval. We prove that any such set of Mobius strips can be equipped with a natural total ordering. We then combine this total ordering with some additive combinatorics to prove that $1/3$ is a sharp lower bound on the probability that a Mobius strip bounding the $(2,1)$-torus knot in the solid torus times an interval will intersect its rotation by a uniformly random angle.","PeriodicalId":8134,"journal":{"name":"Annals of Mathematics","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2019-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44833876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}