{"title":"关于加权三角波雅诺夫-切比雪夫极值问题","authors":"B'ela Nagy, S. R'ev'esz","doi":"10.21538/0134-4889-2023-29-4-193-216","DOIUrl":null,"url":null,"abstract":"We investigate the weighted Bojanov-Chebyshev extremal problem for trigonometric polynomials, that is, the minimax problem of minimizing $\\|T\\|_{w,C({\\mathbb T})}$, where $w$ is a sufficiently nonvanishing, upper bounded, nonnegative weight function, the norm is the corresponding weighted maximum norm on the torus ${\\mathbb T}$, and $T$ is a trigonometric polynomial with prescribed multiplicities $\\nu_1,\\ldots,\\nu_n$ of root factors $|\\sin(\\pi(t-z_j))|^{\\nu_j}$. If the $\\nu_j$ are natural numbers and their sum is even, then $T$ is indeed a trigonometric polynomial and the case when all the $\\nu_j$ are 1 covers the Chebyshev extremal problem. Our result will be more general, allowing, in particular, so-called generalized trigonometric polynomials. To reach our goal, we invoke Fenton's sum of translates method. However, altering from the earlier described cases without weight or on the interval, here we find different situations, and can state less about the solutions.","PeriodicalId":44555,"journal":{"name":"Trudy Instituta Matematiki i Mekhaniki UrO RAN","volume":"114 1","pages":""},"PeriodicalIF":0.4000,"publicationDate":"2023-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"On the weighted trigonometric Bojanov - Chebyshev extremal problem\",\"authors\":\"B'ela Nagy, S. R'ev'esz\",\"doi\":\"10.21538/0134-4889-2023-29-4-193-216\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We investigate the weighted Bojanov-Chebyshev extremal problem for trigonometric polynomials, that is, the minimax problem of minimizing $\\\\|T\\\\|_{w,C({\\\\mathbb T})}$, where $w$ is a sufficiently nonvanishing, upper bounded, nonnegative weight function, the norm is the corresponding weighted maximum norm on the torus ${\\\\mathbb T}$, and $T$ is a trigonometric polynomial with prescribed multiplicities $\\\\nu_1,\\\\ldots,\\\\nu_n$ of root factors $|\\\\sin(\\\\pi(t-z_j))|^{\\\\nu_j}$. If the $\\\\nu_j$ are natural numbers and their sum is even, then $T$ is indeed a trigonometric polynomial and the case when all the $\\\\nu_j$ are 1 covers the Chebyshev extremal problem. Our result will be more general, allowing, in particular, so-called generalized trigonometric polynomials. To reach our goal, we invoke Fenton's sum of translates method. However, altering from the earlier described cases without weight or on the interval, here we find different situations, and can state less about the solutions.\",\"PeriodicalId\":44555,\"journal\":{\"name\":\"Trudy Instituta Matematiki i Mekhaniki UrO RAN\",\"volume\":\"114 1\",\"pages\":\"\"},\"PeriodicalIF\":0.4000,\"publicationDate\":\"2023-09-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Trudy Instituta Matematiki i Mekhaniki UrO RAN\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.21538/0134-4889-2023-29-4-193-216\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"MATHEMATICS, APPLIED\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Trudy Instituta Matematiki i Mekhaniki UrO RAN","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.21538/0134-4889-2023-29-4-193-216","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATHEMATICS, APPLIED","Score":null,"Total":0}
On the weighted trigonometric Bojanov - Chebyshev extremal problem
We investigate the weighted Bojanov-Chebyshev extremal problem for trigonometric polynomials, that is, the minimax problem of minimizing $\|T\|_{w,C({\mathbb T})}$, where $w$ is a sufficiently nonvanishing, upper bounded, nonnegative weight function, the norm is the corresponding weighted maximum norm on the torus ${\mathbb T}$, and $T$ is a trigonometric polynomial with prescribed multiplicities $\nu_1,\ldots,\nu_n$ of root factors $|\sin(\pi(t-z_j))|^{\nu_j}$. If the $\nu_j$ are natural numbers and their sum is even, then $T$ is indeed a trigonometric polynomial and the case when all the $\nu_j$ are 1 covers the Chebyshev extremal problem. Our result will be more general, allowing, in particular, so-called generalized trigonometric polynomials. To reach our goal, we invoke Fenton's sum of translates method. However, altering from the earlier described cases without weight or on the interval, here we find different situations, and can state less about the solutions.