{"title":"Finite time blow-up for a heat equation in [formula omitted]","authors":"Kaiqiang Zhang","doi":"10.1016/j.aml.2024.109441","DOIUrl":null,"url":null,"abstract":"We consider the semilinear heat equation <ce:display><ce:formula><mml:math altimg=\"si1.svg\" display=\"block\"><mml:mrow><mml:msub><mml:mrow><mml:mi>u</mml:mi></mml:mrow><mml:mrow><mml:mi>t</mml:mi></mml:mrow></mml:msub><mml:mo linebreak=\"goodbreak\">−</mml:mo><mml:mi>Δ</mml:mi><mml:mi>u</mml:mi><mml:mo linebreak=\"goodbreak\">=</mml:mo><mml:msup><mml:mrow><mml:mrow><mml:mo>|</mml:mo><mml:mi>u</mml:mi><mml:mo>|</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mi>p</mml:mi><mml:mo linebreak=\"badbreak\">−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:mi>u</mml:mi><mml:mo linebreak=\"goodbreak\">+</mml:mo><mml:mi>λ</mml:mi><mml:mi>u</mml:mi><mml:mo>,</mml:mo><mml:mspace width=\"1em\"></mml:mspace><mml:mspace width=\"1em\"></mml:mspace><mml:mtext>on</mml:mtext><mml:mspace width=\"1em\"></mml:mspace><mml:msup><mml:mrow><mml:mi mathvariant=\"double-struck\">R</mml:mi></mml:mrow><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math></ce:formula></ce:display>where <mml:math altimg=\"si2.svg\" display=\"inline\"><mml:mrow><mml:mi>p</mml:mi><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">></mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>, and <mml:math altimg=\"si3.svg\" display=\"inline\"><mml:mrow><mml:mi>λ</mml:mi><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">∈</mml:mo><mml:mi mathvariant=\"double-struck\">R</mml:mi></mml:mrow></mml:math> is a parameter. When <mml:math altimg=\"si4.svg\" display=\"inline\"><mml:mrow><mml:mi>λ</mml:mi><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">=</mml:mo><mml:mn>0</mml:mn></mml:mrow></mml:math>, the equation reduces to the classical heat equation. We reveal that the parameter <mml:math altimg=\"si5.svg\" display=\"inline\"><mml:mi>λ</mml:mi></mml:math> in the linear term plays an important role in the blow-up conditions. Although the solution may blow up in finite time due to the cumulative effect of the nonlinearities, interestingly, we find that for <mml:math altimg=\"si6.svg\" display=\"inline\"><mml:mrow><mml:mi>λ</mml:mi><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">></mml:mo><mml:mfrac><mml:mrow><mml:mi>n</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mfrac></mml:mrow></mml:math>, all non-negative solutions blow up in finite time, which shows that the Fujita exponent is equal to <mml:math altimg=\"si7.svg\" display=\"inline\"><mml:mrow><mml:mo>+</mml:mo><mml:mi>∞</mml:mi></mml:mrow></mml:math>. Our result extends the Theorem 17.1 in Quittner and Souplet (2007). In addition, for <mml:math altimg=\"si8.svg\" display=\"inline\"><mml:mrow><mml:mi>λ</mml:mi><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\"><</mml:mo><mml:mn>0</mml:mn></mml:mrow></mml:math>, we provide a new sufficient condition for the finite time blow-up solution.","PeriodicalId":55497,"journal":{"name":"Applied Mathematics Letters","volume":"4 1","pages":""},"PeriodicalIF":2.9000,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Mathematics Letters","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1016/j.aml.2024.109441","RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS, APPLIED","Score":null,"Total":0}
引用次数: 0
Abstract
We consider the semilinear heat equation ut−Δu=|u|p−1u+λu,onRnwhere p>1, and λ∈R is a parameter. When λ=0, the equation reduces to the classical heat equation. We reveal that the parameter λ in the linear term plays an important role in the blow-up conditions. Although the solution may blow up in finite time due to the cumulative effect of the nonlinearities, interestingly, we find that for λ>n2, all non-negative solutions blow up in finite time, which shows that the Fujita exponent is equal to +∞. Our result extends the Theorem 17.1 in Quittner and Souplet (2007). In addition, for λ<0, we provide a new sufficient condition for the finite time blow-up solution.
期刊介绍:
The purpose of Applied Mathematics Letters is to provide a means of rapid publication for important but brief applied mathematical papers. The brief descriptions of any work involving a novel application or utilization of mathematics, or a development in the methodology of applied mathematics is a potential contribution for this journal. This journal''s focus is on applied mathematics topics based on differential equations and linear algebra. Priority will be given to submissions that are likely to appeal to a wide audience.