{"title":"随机模型中有一个P-测度","authors":"Piotr Borodulin-Nadzieja, Damian Sobota","doi":"10.4064/fm277-3-2023","DOIUrl":null,"url":null,"abstract":"We say that a finitely additive probability measure $\\mu$ on $\\omega$ is \\emph{a P-measure} if it vanishes on points and for each decreasing sequence $(E_n)$ of infinite subsets of $\\omega$ there is $E\\subseteq\\omega$ such that $E\\subseteq^* E_n$ for each $n\\in\\omega$ and $\\mu(E) = \\lim_{n\\to\\infty}\\mu(E_n)$. Thus, P-measures generalize in a natural way P-points and it is known that, similarly as in the case of P-points, their existence is independent of $\\mathsf{ZFC}$. In this paper we show that there is a P-measure in the model obtained by adding any number of random reals to a model of $\\mathsf{CH}$. As a corollary, we obtain that in the classical random model $\\omega^*$ contains a nowhere dense ccc closed P-set.","PeriodicalId":0,"journal":{"name":"","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"There is a P-measure in the random model\",\"authors\":\"Piotr Borodulin-Nadzieja, Damian Sobota\",\"doi\":\"10.4064/fm277-3-2023\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We say that a finitely additive probability measure $\\\\mu$ on $\\\\omega$ is \\\\emph{a P-measure} if it vanishes on points and for each decreasing sequence $(E_n)$ of infinite subsets of $\\\\omega$ there is $E\\\\subseteq\\\\omega$ such that $E\\\\subseteq^* E_n$ for each $n\\\\in\\\\omega$ and $\\\\mu(E) = \\\\lim_{n\\\\to\\\\infty}\\\\mu(E_n)$. Thus, P-measures generalize in a natural way P-points and it is known that, similarly as in the case of P-points, their existence is independent of $\\\\mathsf{ZFC}$. In this paper we show that there is a P-measure in the model obtained by adding any number of random reals to a model of $\\\\mathsf{CH}$. As a corollary, we obtain that in the classical random model $\\\\omega^*$ contains a nowhere dense ccc closed P-set.\",\"PeriodicalId\":0,\"journal\":{\"name\":\"\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0,\"publicationDate\":\"2022-04-25\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://doi.org/10.4064/fm277-3-2023\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.4064/fm277-3-2023","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
We say that a finitely additive probability measure $\mu$ on $\omega$ is \emph{a P-measure} if it vanishes on points and for each decreasing sequence $(E_n)$ of infinite subsets of $\omega$ there is $E\subseteq\omega$ such that $E\subseteq^* E_n$ for each $n\in\omega$ and $\mu(E) = \lim_{n\to\infty}\mu(E_n)$. Thus, P-measures generalize in a natural way P-points and it is known that, similarly as in the case of P-points, their existence is independent of $\mathsf{ZFC}$. In this paper we show that there is a P-measure in the model obtained by adding any number of random reals to a model of $\mathsf{CH}$. As a corollary, we obtain that in the classical random model $\omega^*$ contains a nowhere dense ccc closed P-set.