{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T21:25:09Z","timestamp":1775856309967,"version":"3.50.1"},"reference-count":5,"publisher":"Cambridge University Press (CUP)","issue":"1","license":[{"start":{"date-parts":[[2014,3,12]],"date-time":"2014-03-12T00:00:00Z","timestamp":1394582400000},"content-version":"unspecified","delay-in-days":12429,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. symb. log."],"published-print":{"date-parts":[[1980,3]]},"abstract":"<jats:p>The properties of small cardinals such as \u2135<jats:sub>1<\/jats:sub> tend to be much more complex than those of large cardinals, so that properties of \u2135<jats:sub>1<\/jats:sub> may often be better understood by viewing them as large cardinal properties. In this paper we show that the existence of a precipitous ideal on \u2135<jats:sub>1<\/jats:sub> is essentially the same as measurability.<\/jats:p><jats:p>If <jats:italic>I<\/jats:italic> is an ideal on <jats:italic>P<\/jats:italic>(<jats:italic>\u03ba<\/jats:italic>) then <jats:italic>R(I)<\/jats:italic> is the notion of forcing whose conditions are sets <jats:italic>x<\/jats:italic> \u2208 <jats:italic>P<\/jats:italic>(<jats:italic>\u03ba<\/jats:italic>)\/<jats:italic>I<\/jats:italic>, with <jats:italic>x<\/jats:italic> \u2264 <jats:italic>x<\/jats:italic>\u2032 if <jats:italic>x<\/jats:italic> \u2286 <jats:italic>x<\/jats:italic>\u2032. Thus a set <jats:italic>D R<\/jats:italic>(<jats:italic>I<\/jats:italic>)-generic over the ground model <jats:italic>V<\/jats:italic> is an ultrafilter on <jats:italic>P<\/jats:italic>(<jats:italic>\u03ba<\/jats:italic>) \u22c2 <jats:italic>V<\/jats:italic> extending the filter dual to <jats:italic>I<\/jats:italic>. The ideal <jats:italic>I<\/jats:italic> is said to be <jats:italic>precipitous<\/jats:italic> if \u03ba \u22a8<jats:sub><jats:italic>R<\/jats:italic>(<jats:italic>I<\/jats:italic>)<\/jats:sub>(<jats:italic>V<jats:sup>\u03ba<\/jats:sup><\/jats:italic>\/<jats:italic>D<\/jats:italic> is wellfounded).<\/jats:p><jats:p>One example of a precipitous ideal is the ideal dual to a <jats:italic>\u03ba<\/jats:italic>-complete ultrafilter <jats:italic>U<\/jats:italic> on <jats:italic>\u03ba<\/jats:italic>. This example is trivial since the generic ultrafilter <jats:italic>D<\/jats:italic> is equal to <jats:italic>U<\/jats:italic> and is already in the ground model. A generic set may be viewed as one that can be worked with in the ground model even though it is not actually in the ground model, so we might expect that cardinals such as \u2135<jats:sub>1<\/jats:sub> that cannot be measurable still might have precipitous ideals, and such ideals might correspond closely to measures.<\/jats:p>","DOI":"10.2307\/2273349","type":"journal-article","created":{"date-parts":[[2006,5,6]],"date-time":"2006-05-06T17:51:56Z","timestamp":1146937916000},"page":"1-8","source":"Crossref","is-referenced-by-count":41,"title":["Precipitous ideals"],"prefix":"10.1017","volume":"45","author":[{"given":"T.","family":"Jech","sequence":"first","affiliation":[]},{"given":"M.","family":"Magidor","sequence":"additional","affiliation":[]},{"given":"W.","family":"Mitchell","sequence":"additional","affiliation":[]},{"given":"K.","family":"Prikry","sequence":"additional","affiliation":[]}],"member":"56","published-online":{"date-parts":[[2014,3,12]]},"reference":[{"key":"S0022481200047101_ref005","unstructured":"Mitchell W. , The core model for sequences of ultrafilters (in preparation)."},{"key":"S0022481200047101_ref003","unstructured":"Jech T. and Prikry K. , Bulletin of the American Mathematical Society (to appear)."},{"key":"S0022481200047101_ref001","first-page":"285","volume":"43","author":"Galvin","year":"1978","journal-title":"An ideal game"},{"key":"S0022481200047101_ref002","doi-asserted-by":"publisher","DOI":"10.1090\/memo\/0214"},{"key":"S0022481200047101_ref004","doi-asserted-by":"publisher","DOI":"10.1016\/0003-4843(70)90013-6"}],"container-title":["Journal of Symbolic Logic"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.cambridge.org\/core\/services\/aop-cambridge-core\/content\/view\/S0022481200047101","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2019,5,26]],"date-time":"2019-05-26T15:36:20Z","timestamp":1558884980000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.cambridge.org\/core\/product\/identifier\/S0022481200047101\/type\/journal_article"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1980,3]]},"references-count":5,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1980,3]]}},"alternative-id":["S0022481200047101"],"URL":"https:\/\/doi.org\/10.2307\/2273349","relation":{},"ISSN":["0022-4812","1943-5886"],"issn-type":[{"value":"0022-4812","type":"print"},{"value":"1943-5886","type":"electronic"}],"subject":[],"published":{"date-parts":[[1980,3]]}}}