{"title":"锥体的彩色正基分解和赫利型结果","authors":"Grigory Ivanov","doi":"arxiv-2407.20961","DOIUrl":null,"url":null,"abstract":"We prove the following colorful Helly-type result: Fix $k \\in [d-1]$. Assume\n$\\mathcal{A}_1, \\dots, \\mathcal{A}_{d+(d-k)+1}$ are finite sets (colors) of\nnonzero vectors in $\\R^d$. If for every rainbow sub-selection $R$ from these\nsets of size at most $\\max \\{d+1, 2(d-k+1)\\}$, the system $\\langle {a},{x}\n\\rangle \\leq 0,\\; a \\in R$ has at least $k$ linearly independent solutions,\nthen at least one of the systems $\\langle {a},{x} \\rangle \\leq 0,\\; a \\in\n\\mathcal{A}_i,$ $i \\in [d+(d-k)+1]$ has at least $k$ linearly independent\nsolutions. A \\emph{rainbow sub-selection} from several sets refers to choosing at most\none element from each set (color). The Helly-number $\\max \\{d+1, 2(d-k+1)\\}$ and the number of colors\n$d+(d-k)+1$ are optimal. Our key observation is a certain colorful Carath\\'eodory-type result for\npositive bases.","PeriodicalId":501444,"journal":{"name":"arXiv - MATH - Metric Geometry","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Colorful positive bases decomposition and Helly-type results for cones\",\"authors\":\"Grigory Ivanov\",\"doi\":\"arxiv-2407.20961\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We prove the following colorful Helly-type result: Fix $k \\\\in [d-1]$. Assume\\n$\\\\mathcal{A}_1, \\\\dots, \\\\mathcal{A}_{d+(d-k)+1}$ are finite sets (colors) of\\nnonzero vectors in $\\\\R^d$. If for every rainbow sub-selection $R$ from these\\nsets of size at most $\\\\max \\\\{d+1, 2(d-k+1)\\\\}$, the system $\\\\langle {a},{x}\\n\\\\rangle \\\\leq 0,\\\\; a \\\\in R$ has at least $k$ linearly independent solutions,\\nthen at least one of the systems $\\\\langle {a},{x} \\\\rangle \\\\leq 0,\\\\; a \\\\in\\n\\\\mathcal{A}_i,$ $i \\\\in [d+(d-k)+1]$ has at least $k$ linearly independent\\nsolutions. A \\\\emph{rainbow sub-selection} from several sets refers to choosing at most\\none element from each set (color). The Helly-number $\\\\max \\\\{d+1, 2(d-k+1)\\\\}$ and the number of colors\\n$d+(d-k)+1$ are optimal. Our key observation is a certain colorful Carath\\\\'eodory-type result for\\npositive bases.\",\"PeriodicalId\":501444,\"journal\":{\"name\":\"arXiv - MATH - Metric Geometry\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-07-30\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"arXiv - MATH - Metric Geometry\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/arxiv-2407.20961\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - MATH - Metric Geometry","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2407.20961","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Colorful positive bases decomposition and Helly-type results for cones
We prove the following colorful Helly-type result: Fix $k \in [d-1]$. Assume
$\mathcal{A}_1, \dots, \mathcal{A}_{d+(d-k)+1}$ are finite sets (colors) of
nonzero vectors in $\R^d$. If for every rainbow sub-selection $R$ from these
sets of size at most $\max \{d+1, 2(d-k+1)\}$, the system $\langle {a},{x}
\rangle \leq 0,\; a \in R$ has at least $k$ linearly independent solutions,
then at least one of the systems $\langle {a},{x} \rangle \leq 0,\; a \in
\mathcal{A}_i,$ $i \in [d+(d-k)+1]$ has at least $k$ linearly independent
solutions. A \emph{rainbow sub-selection} from several sets refers to choosing at most
one element from each set (color). The Helly-number $\max \{d+1, 2(d-k+1)\}$ and the number of colors
$d+(d-k)+1$ are optimal. Our key observation is a certain colorful Carath\'eodory-type result for
positive bases.