{"title":"Sufficient conditions for the minimality of biconcave functions","authors":"M. Novikov","doi":"10.1090/spmj/1781","DOIUrl":null,"url":null,"abstract":"This paper describes sufficient conditions under which a biconcave function <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"script upper B colon German upper S equals StartSet left-parenthesis x comma y right-parenthesis element-of double-struck upper R squared colon x minus 2 less-than-or-equal-to y less-than-or-equal-to x plus 2 EndSet right-arrow double-struck upper R\"> <mml:semantics> <mml:mrow> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi class=\"MJX-tex-caligraphic\" mathvariant=\"script\">B</mml:mi> </mml:mrow> <mml:mo>:<!-- : --></mml:mo> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi mathvariant=\"fraktur\">S</mml:mi> </mml:mrow> <mml:mo>=</mml:mo> <mml:mo fence=\"false\" stretchy=\"false\">{</mml:mo> <mml:mo stretchy=\"false\">(</mml:mo> <mml:mi>x</mml:mi> <mml:mo>,</mml:mo> <mml:mi>y</mml:mi> <mml:mo stretchy=\"false\">)</mml:mo> <mml:mo>∈<!-- ∈ --></mml:mo> <mml:msup> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi mathvariant=\"double-struck\">R</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>:<!-- : --></mml:mo> <mml:mi>x</mml:mi> <mml:mo>−<!-- − --></mml:mo> <mml:mn>2</mml:mn> <mml:mo>≤<!-- ≤ --></mml:mo> <mml:mi>y</mml:mi> <mml:mo>≤<!-- ≤ --></mml:mo> <mml:mi>x</mml:mi> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> <mml:mo fence=\"false\" stretchy=\"false\">}</mml:mo> <mml:mo stretchy=\"false\">→<!-- → --></mml:mo> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi mathvariant=\"double-struck\">R</mml:mi> </mml:mrow> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">\\mathcal {B}\\colon \\mathfrak {S}=\\{ (x,y)\\in \\mathbb {R}^2\\colon x-2\\le y\\le x+2 \\}\\to \\mathbb {R}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is minimal with respect to an obstacle <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper L colon German upper S right-arrow left-bracket negative normal infinity comma plus normal infinity right-parenthesis\"> <mml:semantics> <mml:mrow> <mml:mi>L</mml:mi> <mml:mo>:<!-- : --></mml:mo> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi mathvariant=\"fraktur\">S</mml:mi> </mml:mrow> <mml:mo stretchy=\"false\">→<!-- → --></mml:mo> <mml:mo stretchy=\"false\">[</mml:mo> <mml:mo>−<!-- − --></mml:mo> <mml:mi mathvariant=\"normal\">∞<!-- ∞ --></mml:mi> <mml:mo>,</mml:mo> <mml:mo>+</mml:mo> <mml:mi mathvariant=\"normal\">∞<!-- ∞ --></mml:mi> <mml:mo stretchy=\"false\">)</mml:mo> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">L\\colon \\mathfrak {S}\\to [-\\infty ,+\\infty )</mml:annotation> </mml:semantics> </mml:math> </inline-formula>, that is, it is the pointwise minimal among all biconcave functions <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper B colon German upper S right-arrow double-struck upper R\"> <mml:semantics> <mml:mrow> <mml:mi>B</mml:mi> <mml:mo>:<!-- : --></mml:mo> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi mathvariant=\"fraktur\">S</mml:mi> </mml:mrow> <mml:mo stretchy=\"false\">→<!-- → --></mml:mo> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi mathvariant=\"double-struck\">R</mml:mi> </mml:mrow> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">B\\colon \\mathfrak {S}\\to \\mathbb {R}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> that satisfy the inequality <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper B greater-than-or-equal-to upper L\"> <mml:semantics> <mml:mrow> <mml:mi>B</mml:mi> <mml:mo>≥<!-- ≥ --></mml:mo> <mml:mi>L</mml:mi> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">B\\ge L</mml:annotation> </mml:semantics> </mml:math> </inline-formula>.","PeriodicalId":51162,"journal":{"name":"St Petersburg Mathematical Journal","volume":" 9","pages":"0"},"PeriodicalIF":0.7000,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"St Petersburg Mathematical Journal","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1090/spmj/1781","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 1
Abstract
This paper describes sufficient conditions under which a biconcave function B:S={(x,y)∈R2:x−2≤y≤x+2}→R\mathcal {B}\colon \mathfrak {S}=\{ (x,y)\in \mathbb {R}^2\colon x-2\le y\le x+2 \}\to \mathbb {R} is minimal with respect to an obstacle L:S→[−∞,+∞)L\colon \mathfrak {S}\to [-\infty ,+\infty ), that is, it is the pointwise minimal among all biconcave functions B:S→RB\colon \mathfrak {S}\to \mathbb {R} that satisfy the inequality B≥LB\ge L.
期刊介绍:
This journal is a cover-to-cover translation into English of Algebra i Analiz, published six times a year by the mathematics section of the Russian Academy of Sciences.