{"title":"A porous medium equation with spatially inhomogeneous absorption. Part I: Self-similar solutions","authors":"Razvan Gabriel Iagar , Diana-Rodica Munteanu","doi":"10.1016/j.jmaa.2024.128965","DOIUrl":null,"url":null,"abstract":"<div><div>This is the first of a two-parts work on the qualitative properties and large time behavior for the following quasilinear equation involving a spatially inhomogeneous absorption<span><span><span><math><msub><mrow><mo>∂</mo></mrow><mrow><mi>t</mi></mrow></msub><mi>u</mi><mo>=</mo><mi>Δ</mi><msup><mrow><mi>u</mi></mrow><mrow><mi>m</mi></mrow></msup><mo>−</mo><mo>|</mo><mi>x</mi><msup><mrow><mo>|</mo></mrow><mrow><mi>σ</mi></mrow></msup><msup><mrow><mi>u</mi></mrow><mrow><mi>p</mi></mrow></msup><mo>,</mo></math></span></span></span> posed for <span><math><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo><mo>∈</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>N</mi></mrow></msup><mo>×</mo><mo>(</mo><mn>0</mn><mo>,</mo><mo>∞</mo><mo>)</mo></math></span>, <span><math><mi>N</mi><mo>≥</mo><mn>1</mn></math></span>, and in the range of exponents <span><math><mn>1</mn><mo><</mo><mi>m</mi><mo><</mo><mi>p</mi><mo><</mo><mo>∞</mo></math></span>, <span><math><mi>σ</mi><mo>></mo><mn>0</mn></math></span>. We give a complete classification of (singular) self-similar solutions of the form<span><span><span><math><mi>u</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo><mo>=</mo><msup><mrow><mi>t</mi></mrow><mrow><mo>−</mo><mi>α</mi></mrow></msup><mi>f</mi><mo>(</mo><mo>|</mo><mi>x</mi><mo>|</mo><msup><mrow><mi>t</mi></mrow><mrow><mo>−</mo><mi>β</mi></mrow></msup><mo>)</mo><mo>,</mo><mspace></mspace><mi>α</mi><mo>=</mo><mfrac><mrow><mi>σ</mi><mo>+</mo><mn>2</mn></mrow><mrow><mi>σ</mi><mo>(</mo><mi>m</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>+</mo><mn>2</mn><mo>(</mo><mi>p</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></mfrac><mo>,</mo><mspace></mspace><mi>β</mi><mo>=</mo><mfrac><mrow><mi>p</mi><mo>−</mo><mi>m</mi></mrow><mrow><mi>σ</mi><mo>(</mo><mi>m</mi><mo>−</mo><mn>1</mn><mo>)</mo><mo>+</mo><mn>2</mn><mo>(</mo><mi>p</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></mfrac><mo>,</mo></math></span></span></span> showing that their form and behavior strongly depends on the critical exponent<span><span><span><math><msub><mrow><mi>p</mi></mrow><mrow><mi>F</mi></mrow></msub><mo>(</mo><mi>σ</mi><mo>)</mo><mo>=</mo><mi>m</mi><mo>+</mo><mfrac><mrow><mi>σ</mi><mo>+</mo><mn>2</mn></mrow><mrow><mi>N</mi></mrow></mfrac><mo>.</mo></math></span></span></span> For <span><math><mi>p</mi><mo>≥</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>F</mi></mrow></msub><mo>(</mo><mi>σ</mi><mo>)</mo></math></span>, we prove that all self-similar solutions have a tail as <span><math><mo>|</mo><mi>x</mi><mo>|</mo><mo>→</mo><mo>∞</mo></math></span> of one of the forms<span><span><span><math><mi>u</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo><mo>∼</mo><mi>C</mi><mo>|</mo><mi>x</mi><msup><mrow><mo>|</mo></mrow><mrow><mo>−</mo><mo>(</mo><mi>σ</mi><mo>+</mo><mn>2</mn><mo>)</mo><mo>/</mo><mo>(</mo><mi>p</mi><mo>−</mo><mi>m</mi><mo>)</mo></mrow></msup><mspace></mspace><mrow><mi>or</mi></mrow><mspace></mspace><mi>u</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo><mo>∼</mo><msup><mrow><mo>(</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mi>p</mi><mo>−</mo><mn>1</mn></mrow></mfrac><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mo>(</mo><mi>p</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>|</mo><mi>x</mi><msup><mrow><mo>|</mo></mrow><mrow><mo>−</mo><mi>σ</mi><mo>/</mo><mo>(</mo><mi>p</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>,</mo></math></span></span></span> while for <span><math><mi>m</mi><mo><</mo><mi>p</mi><mo><</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>F</mi></mrow></msub><mo>(</mo><mi>σ</mi><mo>)</mo></math></span> we add to the previous the <em>existence and uniqueness</em> of a <em>compactly supported very singular solution</em>. These solutions will be employed in describing the large time behavior of general solutions in a forthcoming paper.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"543 1","pages":"Article 128965"},"PeriodicalIF":1.2000,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Mathematical Analysis and Applications","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022247X24008874","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
This is the first of a two-parts work on the qualitative properties and large time behavior for the following quasilinear equation involving a spatially inhomogeneous absorption posed for , , and in the range of exponents , . We give a complete classification of (singular) self-similar solutions of the form showing that their form and behavior strongly depends on the critical exponent For , we prove that all self-similar solutions have a tail as of one of the forms while for we add to the previous the existence and uniqueness of a compactly supported very singular solution. These solutions will be employed in describing the large time behavior of general solutions in a forthcoming paper.
期刊介绍:
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