{"title":"On the balanced pantograph equation of mixed type","authors":"G. Derfel, B. V. Brunt","doi":"10.3842/umzh.v75i12.7654","DOIUrl":null,"url":null,"abstract":"<jats:p>UDC 517.9\nWe consider the balanced pantograph equation (BPE) <mml:math>\n<mml:mrow>\n\t<mml:msup>\n\t\t<mml:mi>y</mml:mi>\n\t\t<mml:mo>′</mml:mo>\n\t</mml:msup>\n\t<mml:mrow>\n\t\t<mml:mo form=\"prefix\">(</mml:mo>\n\t\t<mml:mi>x</mml:mi>\n\t\t<mml:mo form=\"postfix\">)</mml:mo>\n\t</mml:mrow>\n\t<mml:mo>+</mml:mo>\n\t<mml:mi>y</mml:mi>\n\t<mml:mrow>\n\t\t<mml:mo form=\"prefix\">(</mml:mo>\n\t\t<mml:mi>x</mml:mi>\n\t\t<mml:mo form=\"postfix\">)</mml:mo>\n\t</mml:mrow>\n\t<mml:mo>=</mml:mo>\n\t<mml:mstyle displaystyle=\"true\">\n\t\t<mml:munderover>\n\t\t\t<mml:mo>∑</mml:mo>\n\t\t\t<mml:mrow>\n\t\t\t\t<mml:mi>k</mml:mi>\n\t\t\t\t<mml:mo>=</mml:mo>\n\t\t\t\t<mml:mn>1</mml:mn>\n\t\t\t</mml:mrow>\n\t\t\t<mml:mi>m</mml:mi>\n\t\t</mml:munderover>\n\t</mml:mstyle>\n\t<mml:msub>\n\t\t<mml:mi>p</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:mi>y</mml:mi>\n\t<mml:mrow>\n\t\t<mml:mo form=\"prefix\">(</mml:mo>\n\t\t<mml:msub>\n\t\t\t<mml:mi>a</mml:mi>\n\t\t\t<mml:mi>k</mml:mi>\n\t\t</mml:msub>\n\t\t<mml:mi>x</mml:mi>\n\t\t<mml:mo form=\"postfix\">)</mml:mo>\n\t</mml:mrow>\n\t<mml:mo>,</mml:mo>\n</mml:mrow>\n</mml:math> where <mml:math>\n<mml:mrow>\n\t<mml:msub>\n\t\t<mml:mi>a</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:mo>,</mml:mo>\n\t<mml:msub>\n\t\t<mml:mi>p</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:mo>></mml:mo>\n\t<mml:mn>0</mml:mn>\n</mml:mrow>\n</mml:math> and <mml:math>\n<mml:mrow>\n\t<mml:mstyle displaystyle=\"true\">\n\t\t<mml:munderover>\n\t\t\t<mml:mo>∑</mml:mo>\n\t\t\t<mml:mrow>\n\t\t\t\t<mml:mi>k</mml:mi>\n\t\t\t\t<mml:mo>=</mml:mo>\n\t\t\t\t<mml:mn>1</mml:mn>\n\t\t\t</mml:mrow>\n\t\t\t<mml:mi>m</mml:mi>\n\t\t</mml:munderover>\n\t</mml:mstyle>\n\t<mml:msub>\n\t\t<mml:mi>p</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:mo>=</mml:mo>\n\t<mml:mn>1.</mml:mn>\n</mml:mrow>\n</mml:math> It is known that if <mml:math>\n<mml:mrow>\n\t<mml:mi>K</mml:mi>\n\t<mml:mo>=</mml:mo>\n\t<mml:mstyle displaystyle=\"true\">\n\t\t<mml:munderover>\n\t\t\t<mml:mo>∑</mml:mo>\n\t\t\t<mml:mrow>\n\t\t\t\t<mml:mi>k</mml:mi>\n\t\t\t\t<mml:mo>=</mml:mo>\n\t\t\t\t<mml:mn>1</mml:mn>\n\t\t\t</mml:mrow>\n\t\t\t<mml:mi>m</mml:mi>\n\t\t</mml:munderover>\n\t</mml:mstyle>\n\t<mml:msub>\n\t\t<mml:mi>p</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:mi>ln</mml:mi>\n\t<mml:msub>\n\t\t<mml:mi>a</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:mo>≤</mml:mo>\n\t<mml:mn>0</mml:mn>\n</mml:mrow>\n</mml:math> then, under mild technical conditions, the BPE does not have bounded solutions that are not constant, whereas for <mml:math>\n<mml:mrow>\n\t<mml:mi>K</mml:mi>\n\t<mml:mo>></mml:mo>\n\t<mml:mn>0</mml:mn>\n</mml:mrow>\n</mml:math> these solutions exist. In the present paper, we deal with a BPE of <em>mixed type</em>, i.e., <mml:math>\n<mml:mrow>\n\t<mml:msub>\n\t\t<mml:mi>a</mml:mi>\n\t\t<mml:mn>1</mml:mn>\n\t</mml:msub>\n\t<mml:mo><</mml:mo>\n\t<mml:mn>1</mml:mn>\n\t<mml:mo><</mml:mo>\n\t<mml:msub>\n\t\t<mml:mi>a</mml:mi>\n\t\t<mml:mi>m</mml:mi>\n\t</mml:msub>\n\t<mml:mo>,</mml:mo>\n</mml:mrow>\n</mml:math> and prove that, in this case, the BPE has a nonconstant solution <mml:math>\n<mml:mrow>\n\t<mml:mi>y</mml:mi>\n</mml:mrow>\n</mml:math> and that <mml:math>\n<mml:mrow>\n\t<mml:mi>y</mml:mi>\n\t<mml:mrow>\n\t\t<mml:mo form=\"prefix\">(</mml:mo>\n\t\t<mml:mi>x</mml:mi>\n\t\t<mml:mo form=\"postfix\">)</mml:mo>\n\t</mml:mrow>\n\t<mml:mo>∼</mml:mo>\n\t<mml:mi>c</mml:mi>\n\t<mml:msup>\n\t\t<mml:mi>x</mml:mi>\n\t\t<mml:mi>σ</mml:mi>\n\t</mml:msup>\n</mml:mrow>\n</mml:math> as <mml:math>\n<mml:mrow>\n\t<mml:mi>x</mml:mi>\n\t<mml:mo>→</mml:mo>\n\t<mml:mo>∞</mml:mo>\n\t<mml:mo>,</mml:mo>\n</mml:mrow>\n</mml:math> where <mml:math>\n<mml:mrow>\n\t<mml:mi>c</mml:mi>\n\t<mml:mo>></mml:mo>\n\t<mml:mn>0</mml:mn>\n</mml:mrow>\n</mml:math> and <mml:math>\n<mml:mrow>\n\t<mml:mi>σ</mml:mi>\n</mml:mrow>\n</mml:math> is the unique positive root of the characteristic equation <mml:math>\n<mml:mrow>\n\t<mml:mi>P</mml:mi>\n\t<mml:mrow>\n\t\t<mml:mo form=\"prefix\">(</mml:mo>\n\t\t<mml:mi>s</mml:mi>\n\t\t<mml:mo form=\"postfix\">)</mml:mo>\n\t</mml:mrow>\n\t<mml:mo>=</mml:mo>\n\t<mml:mn>1</mml:mn>\n\t<mml:mo>-</mml:mo>\n\t<mml:mstyle displaystyle=\"true\">\n\t\t<mml:munderover>\n\t\t\t<mml:mo>∑</mml:mo>\n\t\t\t<mml:mrow>\n\t\t\t\t<mml:mi>k</mml:mi>\n\t\t\t\t<mml:mo>=</mml:mo>\n\t\t\t\t<mml:mn>1</mml:mn>\n\t\t\t</mml:mrow>\n\t\t\t<mml:mi>m</mml:mi>\n\t\t</mml:munderover>\n\t</mml:mstyle>\n\t<mml:msub>\n\t\t<mml:mi>p</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t</mml:msub>\n\t<mml:msubsup>\n\t\t<mml:mi>a</mml:mi>\n\t\t<mml:mi>k</mml:mi>\n\t\t<mml:mrow>\n\t\t\t<mml:mo>-</mml:mo>\n\t\t\t<mml:mi>s</mml:mi>\n\t\t</mml:mrow>\n\t</mml:msubsup>\n\t<mml:mo>=</mml:mo>\n\t<mml:mn>0.</mml:mn>\n</mml:mrow>\n</mml:math> We also show that <mml:math>\n<mml:mrow>\n\t<mml:mi>y</mml:mi>\n</mml:mrow>\n</mml:math> is unique (up to a multiplicative constant) among the solutions of the BPE that decay to zero as <mml:math>\n<mml:mrow>\n\t<mml:mi>x</mml:mi>\n\t<mml:mo>→</mml:mo>\n\t<mml:mo>∞</mml:mo>\n\t<mml:mo>.</mml:mo>\n</mml:mrow>\n</mml:math></jats:p>","PeriodicalId":163365,"journal":{"name":"Ukrains’kyi Matematychnyi Zhurnal","volume":"38 2","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Ukrains’kyi Matematychnyi Zhurnal","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3842/umzh.v75i12.7654","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
UDC 517.9
We consider the balanced pantograph equation (BPE) y′(x)+y(x)=∑k=1mpky(akx), where ak,pk>0 and ∑k=1mpk=1. It is known that if K=∑k=1mpklnak≤0 then, under mild technical conditions, the BPE does not have bounded solutions that are not constant, whereas for K>0 these solutions exist. In the present paper, we deal with a BPE of mixed type, i.e., a1<1<am, and prove that, in this case, the BPE has a nonconstant solution y and that y(x)∼cxσ as x→∞, where c>0 and σ is the unique positive root of the characteristic equation P(s)=1-∑k=1mpkak-s=0. We also show that y is unique (up to a multiplicative constant) among the solutions of the BPE that decay to zero as x→∞.