{"title":"关于幂的尾部投影","authors":"Samuel M. Corson, Saharon Shelah","doi":"10.1515/forum-2022-0375","DOIUrl":null,"url":null,"abstract":"Let 𝜅 be an inaccessible cardinal, 𝔘 a universal algebra, and <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mo>∼</m:mo> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0001.png\" /> <jats:tex-math>\\sim</jats:tex-math> </jats:alternatives> </jats:inline-formula> the equivalence relation on <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:msup> <m:mi mathvariant=\"fraktur\">U</m:mi> <m:mi>κ</m:mi> </m:msup> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0002.png\" /> <jats:tex-math>\\mathfrak{U}^{\\kappa}</jats:tex-math> </jats:alternatives> </jats:inline-formula> of eventual equality. From mild assumptions on 𝜅, we give general constructions of <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mrow> <m:mi mathvariant=\"script\">E</m:mi> <m:mo>∈</m:mo> <m:mi>End</m:mi> <m:mrow> <m:mo stretchy=\"false\">(</m:mo> <m:msup> <m:mi mathvariant=\"fraktur\">U</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo rspace=\"0em\">/</m:mo> <m:mo lspace=\"0em\" rspace=\"0em\">∼</m:mo> <m:mo stretchy=\"false\">)</m:mo> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0003.png\" /> <jats:tex-math>\\mathcal{E}\\in\\operatorname{End}(\\mathfrak{U}^{\\kappa}/{\\sim})</jats:tex-math> </jats:alternatives> </jats:inline-formula> satisfying <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mrow> <m:mrow> <m:mi mathvariant=\"script\">E</m:mi> <m:mo lspace=\"0.222em\" rspace=\"0.222em\">∘</m:mo> <m:mi mathvariant=\"script\">E</m:mi> </m:mrow> <m:mo>=</m:mo> <m:mi mathvariant=\"script\">E</m:mi> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0004.png\" /> <jats:tex-math>\\mathcal{E}\\circ\\mathcal{E}=\\mathcal{E}</jats:tex-math> </jats:alternatives> </jats:inline-formula> which do not descend from <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mrow> <m:mi mathvariant=\"normal\">Δ</m:mi> <m:mo>∈</m:mo> <m:mrow> <m:mi>End</m:mi> <m:mo></m:mo> <m:mrow> <m:mo stretchy=\"false\">(</m:mo> <m:msup> <m:mi mathvariant=\"fraktur\">U</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo stretchy=\"false\">)</m:mo> </m:mrow> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0005.png\" /> <jats:tex-math>\\Delta\\in\\operatorname{End}(\\mathfrak{U}^{\\kappa})</jats:tex-math> </jats:alternatives> </jats:inline-formula> having small strong supports. As an application, there exists an <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mrow> <m:mi mathvariant=\"script\">E</m:mi> <m:mo>∈</m:mo> <m:mi>End</m:mi> <m:mrow> <m:mo stretchy=\"false\">(</m:mo> <m:msup> <m:mi mathvariant=\"double-struck\">Z</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo rspace=\"0em\">/</m:mo> <m:mo lspace=\"0em\" rspace=\"0em\">∼</m:mo> <m:mo stretchy=\"false\">)</m:mo> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0006.png\" /> <jats:tex-math>\\mathcal{E}\\in\\operatorname{End}(\\mathbb{Z}^{\\kappa}/{\\sim})</jats:tex-math> </jats:alternatives> </jats:inline-formula> which does not come from a <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mrow> <m:mi mathvariant=\"normal\">Δ</m:mi> <m:mo>∈</m:mo> <m:mrow> <m:mi>End</m:mi> <m:mo></m:mo> <m:mrow> <m:mo stretchy=\"false\">(</m:mo> <m:msup> <m:mi mathvariant=\"double-struck\">Z</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo stretchy=\"false\">)</m:mo> </m:mrow> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_forum-2022-0375_ineq_0007.png\" /> <jats:tex-math>\\Delta\\in\\operatorname{End}(\\mathbb{Z}^{\\kappa})</jats:tex-math> </jats:alternatives> </jats:inline-formula>.","PeriodicalId":12433,"journal":{"name":"Forum Mathematicum","volume":"45 1","pages":""},"PeriodicalIF":1.0000,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"On projections of the tails of a power\",\"authors\":\"Samuel M. Corson, Saharon Shelah\",\"doi\":\"10.1515/forum-2022-0375\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Let 𝜅 be an inaccessible cardinal, 𝔘 a universal algebra, and <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:mo>∼</m:mo> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0001.png\\\" /> <jats:tex-math>\\\\sim</jats:tex-math> </jats:alternatives> </jats:inline-formula> the equivalence relation on <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:msup> <m:mi mathvariant=\\\"fraktur\\\">U</m:mi> <m:mi>κ</m:mi> </m:msup> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0002.png\\\" /> <jats:tex-math>\\\\mathfrak{U}^{\\\\kappa}</jats:tex-math> </jats:alternatives> </jats:inline-formula> of eventual equality. From mild assumptions on 𝜅, we give general constructions of <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:mrow> <m:mi mathvariant=\\\"script\\\">E</m:mi> <m:mo>∈</m:mo> <m:mi>End</m:mi> <m:mrow> <m:mo stretchy=\\\"false\\\">(</m:mo> <m:msup> <m:mi mathvariant=\\\"fraktur\\\">U</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo rspace=\\\"0em\\\">/</m:mo> <m:mo lspace=\\\"0em\\\" rspace=\\\"0em\\\">∼</m:mo> <m:mo stretchy=\\\"false\\\">)</m:mo> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0003.png\\\" /> <jats:tex-math>\\\\mathcal{E}\\\\in\\\\operatorname{End}(\\\\mathfrak{U}^{\\\\kappa}/{\\\\sim})</jats:tex-math> </jats:alternatives> </jats:inline-formula> satisfying <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:mrow> <m:mrow> <m:mi mathvariant=\\\"script\\\">E</m:mi> <m:mo lspace=\\\"0.222em\\\" rspace=\\\"0.222em\\\">∘</m:mo> <m:mi mathvariant=\\\"script\\\">E</m:mi> </m:mrow> <m:mo>=</m:mo> <m:mi mathvariant=\\\"script\\\">E</m:mi> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0004.png\\\" /> <jats:tex-math>\\\\mathcal{E}\\\\circ\\\\mathcal{E}=\\\\mathcal{E}</jats:tex-math> </jats:alternatives> </jats:inline-formula> which do not descend from <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:mrow> <m:mi mathvariant=\\\"normal\\\">Δ</m:mi> <m:mo>∈</m:mo> <m:mrow> <m:mi>End</m:mi> <m:mo></m:mo> <m:mrow> <m:mo stretchy=\\\"false\\\">(</m:mo> <m:msup> <m:mi mathvariant=\\\"fraktur\\\">U</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo stretchy=\\\"false\\\">)</m:mo> </m:mrow> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0005.png\\\" /> <jats:tex-math>\\\\Delta\\\\in\\\\operatorname{End}(\\\\mathfrak{U}^{\\\\kappa})</jats:tex-math> </jats:alternatives> </jats:inline-formula> having small strong supports. As an application, there exists an <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:mrow> <m:mi mathvariant=\\\"script\\\">E</m:mi> <m:mo>∈</m:mo> <m:mi>End</m:mi> <m:mrow> <m:mo stretchy=\\\"false\\\">(</m:mo> <m:msup> <m:mi mathvariant=\\\"double-struck\\\">Z</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo rspace=\\\"0em\\\">/</m:mo> <m:mo lspace=\\\"0em\\\" rspace=\\\"0em\\\">∼</m:mo> <m:mo stretchy=\\\"false\\\">)</m:mo> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0006.png\\\" /> <jats:tex-math>\\\\mathcal{E}\\\\in\\\\operatorname{End}(\\\\mathbb{Z}^{\\\\kappa}/{\\\\sim})</jats:tex-math> </jats:alternatives> </jats:inline-formula> which does not come from a <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\\\"http://www.w3.org/1998/Math/MathML\\\"> <m:mrow> <m:mi mathvariant=\\\"normal\\\">Δ</m:mi> <m:mo>∈</m:mo> <m:mrow> <m:mi>End</m:mi> <m:mo></m:mo> <m:mrow> <m:mo stretchy=\\\"false\\\">(</m:mo> <m:msup> <m:mi mathvariant=\\\"double-struck\\\">Z</m:mi> <m:mi>κ</m:mi> </m:msup> <m:mo stretchy=\\\"false\\\">)</m:mo> </m:mrow> </m:mrow> </m:mrow> </m:math> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" xlink:href=\\\"graphic/j_forum-2022-0375_ineq_0007.png\\\" /> <jats:tex-math>\\\\Delta\\\\in\\\\operatorname{End}(\\\\mathbb{Z}^{\\\\kappa})</jats:tex-math> </jats:alternatives> </jats:inline-formula>.\",\"PeriodicalId\":12433,\"journal\":{\"name\":\"Forum Mathematicum\",\"volume\":\"45 1\",\"pages\":\"\"},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2024-04-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Forum Mathematicum\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://doi.org/10.1515/forum-2022-0375\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Forum Mathematicum","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1515/forum-2022-0375","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
摘要
让 𝜅 是一个不可访问的红心,𝔘 是一个普遍代数,∼ \sim 是 U κ \mathfrak{U}^{\kappa} 上最终相等的等价关系。根据对𝜅、我们给出了 E∈ End ( U κ / ∼ ) 的一般构造 \mathcal{E}\in\operatorname{End}(\mathfrak{U}^{\kappa}/{\sim}) 满足 E ∘ E = E \mathcal{E}\circ\mathcal{E}=\mathcal{E} 它不会从具有小强支持的 Δ∈ End ( U κ ) \Delta\in\operatorname{End}(\mathfrak{U}^{\kappa}) 下降。作为应用,存在一个 E∈ End ( Z κ / ∼ ) ( (mathcal{E}\in\operatorname{End}(\mathbb{Z}^{\kappa}}/{\sim})),它不是来自一个 Δ∈ End ( Z κ ) ( (Delta\in\operatorname{End}(\mathbb{Z}^{\kappa}))。
Let 𝜅 be an inaccessible cardinal, 𝔘 a universal algebra, and ∼\sim the equivalence relation on Uκ\mathfrak{U}^{\kappa} of eventual equality. From mild assumptions on 𝜅, we give general constructions of E∈End(Uκ/∼)\mathcal{E}\in\operatorname{End}(\mathfrak{U}^{\kappa}/{\sim}) satisfying E∘E=E\mathcal{E}\circ\mathcal{E}=\mathcal{E} which do not descend from Δ∈End(Uκ)\Delta\in\operatorname{End}(\mathfrak{U}^{\kappa}) having small strong supports. As an application, there exists an E∈End(Zκ/∼)\mathcal{E}\in\operatorname{End}(\mathbb{Z}^{\kappa}/{\sim}) which does not come from a Δ∈End(Zκ)\Delta\in\operatorname{End}(\mathbb{Z}^{\kappa}).
期刊介绍:
Forum Mathematicum is a general mathematics journal, which is devoted to the publication of research articles in all fields of pure and applied mathematics, including mathematical physics. Forum Mathematicum belongs to the top 50 journals in pure and applied mathematics, as measured by citation impact.