{"title":"关于希尔伯特空间算子的非超循环向量的说明","authors":"Masoumeh Faghih-Ahmadi, Karim Hedayatian","doi":"10.1016/j.exco.2023.100131","DOIUrl":null,"url":null,"abstract":"<div><p>In this note it is shown that there is a bounded linear operator <span><math><mi>T</mi></math></span> on the Hardy Hilbert space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> and a vector <span><math><mi>f</mi></math></span> in <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> such that the closure of the set <span><math><mrow><mo>{</mo><mi>α</mi><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><mi>f</mi><mo>:</mo><mi>α</mi><mo>∈</mo><mi>ℂ</mi><mo>,</mo><mspace></mspace><mi>n</mi><mo>≥</mo><mn>0</mn><mo>}</mo></mrow></math></span> is not <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>, but for every subsequence <span><math><msubsup><mrow><mrow><mo>(</mo><msub><mrow><mi>n</mi></mrow><mrow><mi>k</mi></mrow></msub><mo>)</mo></mrow></mrow><mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>∞</mi></mrow></msubsup></math></span> the closed linear span of <span><math><mrow><mo>{</mo><msup><mrow><mi>T</mi></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mi>k</mi></mrow></msub></mrow></msup><mi>f</mi><mo>:</mo><mi>k</mi><mo>≥</mo><mn>1</mn><mo>}</mo></mrow></math></span> is the whole space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>. Furthermore, the closure of <span><math><mrow><mo>{</mo><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><mi>g</mi><mo>:</mo><mi>n</mi><mo>≥</mo><mn>0</mn><mo>}</mo></mrow></math></span> is <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> for some <span><math><mrow><mi>g</mi><mo>∈</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"5 ","pages":"Article 100131"},"PeriodicalIF":0.0000,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X23000332/pdfft?md5=d5b92bb3f23309e6fdacec6aceef1367&pid=1-s2.0-S2666657X23000332-main.pdf","citationCount":"0","resultStr":"{\"title\":\"A note on non-supercyclic vectors of Hilbert space operators\",\"authors\":\"Masoumeh Faghih-Ahmadi, Karim Hedayatian\",\"doi\":\"10.1016/j.exco.2023.100131\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>In this note it is shown that there is a bounded linear operator <span><math><mi>T</mi></math></span> on the Hardy Hilbert space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> and a vector <span><math><mi>f</mi></math></span> in <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> such that the closure of the set <span><math><mrow><mo>{</mo><mi>α</mi><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><mi>f</mi><mo>:</mo><mi>α</mi><mo>∈</mo><mi>ℂ</mi><mo>,</mo><mspace></mspace><mi>n</mi><mo>≥</mo><mn>0</mn><mo>}</mo></mrow></math></span> is not <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>, but for every subsequence <span><math><msubsup><mrow><mrow><mo>(</mo><msub><mrow><mi>n</mi></mrow><mrow><mi>k</mi></mrow></msub><mo>)</mo></mrow></mrow><mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>∞</mi></mrow></msubsup></math></span> the closed linear span of <span><math><mrow><mo>{</mo><msup><mrow><mi>T</mi></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mi>k</mi></mrow></msub></mrow></msup><mi>f</mi><mo>:</mo><mi>k</mi><mo>≥</mo><mn>1</mn><mo>}</mo></mrow></math></span> is the whole space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>. Furthermore, the closure of <span><math><mrow><mo>{</mo><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><mi>g</mi><mo>:</mo><mi>n</mi><mo>≥</mo><mn>0</mn><mo>}</mo></mrow></math></span> is <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> for some <span><math><mrow><mi>g</mi><mo>∈</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>.</p></div>\",\"PeriodicalId\":100517,\"journal\":{\"name\":\"Examples and Counterexamples\",\"volume\":\"5 \",\"pages\":\"Article 100131\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-01-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S2666657X23000332/pdfft?md5=d5b92bb3f23309e6fdacec6aceef1367&pid=1-s2.0-S2666657X23000332-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Examples and Counterexamples\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S2666657X23000332\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Examples and Counterexamples","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2666657X23000332","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
A note on non-supercyclic vectors of Hilbert space operators
In this note it is shown that there is a bounded linear operator on the Hardy Hilbert space and a vector in such that the closure of the set is not , but for every subsequence the closed linear span of is the whole space . Furthermore, the closure of is for some .