{"title":"On dense, locally finite subgroups of the automorphism group of certain homogeneous structures","authors":"Gábor Sági","doi":"10.1002/malq.202200060","DOIUrl":"10.1002/malq.202200060","url":null,"abstract":"<p>Let <span></span><math>\u0000 <semantics>\u0000 <mi>A</mi>\u0000 <annotation>$mathcal {A}$</annotation>\u0000 </semantics></math> be a countable structure such that each finite partial isomorphism of it can be extended to an automorphism. Evans asked if the age (set of finite substructures) of <span></span><math>\u0000 <semantics>\u0000 <mi>A</mi>\u0000 <annotation>$mathcal {A}$</annotation>\u0000 </semantics></math> satisfies Hrushovski's extension property, then is it true that the automorphism group <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <mo>Aut</mo>\u0000 </mrow>\u0000 <mo>(</mo>\u0000 <mi>A</mi>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$operatorname{{it Aut}}(mathcal {A})$</annotation>\u0000 </semantics></math> of <span></span><math>\u0000 <semantics>\u0000 <mi>A</mi>\u0000 <annotation>$mathcal {A}$</annotation>\u0000 </semantics></math> contains a dense, locally finite subgroup? In order to investigate this question, in the previous decades a coherent variant of Hrushovski's extension property has been introduced and studied. Among other results, we provide equivalent conditions for the existence of a dense, locally finite subgroup of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <mo>Aut</mo>\u0000 </mrow>\u0000 <mo>(</mo>\u0000 <mi>A</mi>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$operatorname{{it Aut}}(mathcal {A})$</annotation>\u0000 </semantics></math> in terms of a (new) variant of the coherent extension property. We also compare our notion with other coherent extension properties.</p>","PeriodicalId":49864,"journal":{"name":"Mathematical Logic Quarterly","volume":"70 2","pages":"162-172"},"PeriodicalIF":0.4,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/malq.202200060","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Division of Logic, Methodology and Philosophy of Science and Technology of the International Union of History and Philosophy of Science and Technology Bulletin no. 24","authors":"","doi":"10.1002/malq.202400004","DOIUrl":"https://doi.org/10.1002/malq.202400004","url":null,"abstract":"<p><i>Assessors</i>:</p><p>Hanne Andersen, Copenhagen, Denmark. Rachel Ankeny, Adelaide, Australia. Valeria de Paiva, Mountain View CA, U.S.A. Gerhard Heinzmann, Nancy, France. Concha Martinez Vidal, Santiago de Compostela, Spain. Tomáš Marvan, Prague, Czech Republic. Dhruv Raina, Delhi, India. Cheng Sumei, Shanghai, China. Alasdair Urquhart, Toronto, Canada. Andrés Villaveces, Bogotá, Colombia.</p><p><i>Former Presidents: († = deceased)</i></p><p>Menachem Magidor (Israel), Elliott Sober (United States of America), Wilfrid Hodges (United Kingdom), Adolf Grünbaum† (United States of America), Michael Rabin (United States of America), Wesley Salmon† (United States of America), Jens-Erik Fenstad† (Norway), Lawrence J. Cohen† (United Kingdom), Dana S. Scott (United States of America), Jerzy Łoś† (Poland). Patrick Suppes† (United States of America), Jaakko Hintikka† (Finland & United States of America), Andrzej Mostowski† (Poland), Stephan Körner† (United Kingdom), Yehoshua Bar-Hillel† (Israel), Georg Henrik von Wright† (Finland), Stephen C. Kleene† (United States of America).</p><p>Former president Jens Erik Fenstad passed away on 14 April 2020.</p><p>The <i>Executive Committee</i> of the Division is composed of the President, the Vice-Presidents, the Secretary-General, the Treasurer, and the immediate Past President. The <i>Council</i> consists of the Executive Committee plus the Assessors.</p><p><i>Ordinary Members Present</i> (number of votes and names of delegates in parentheses; total votes: 68 before <b>Agenda item 5</b>; 69 after <b>Agenda item 5</b>). Argentina (2; 1 after <b>Agenda item 5</b>; Víctor Rodríguez), Australia (3; Pamela Robinson), Austria (1; Georg Schiemer), Belgium (1; Peter Verdée), Brazil (2; Elaine Pimentel), Canada (3; Zeyad El Nabolsy), P. R. China (3; Chen Bo), Czech Republic (2; Libor Behounek, Robin Kopecký), Denmark (2; Magdalena Malecka), Estonia (1; Peeter Müürsepp), Finland (2; Uskali Müki), France (4; Andrew Arana, Paola Cantu, Karine Chemla, Gerhard Heinzmann), Germany (4; Benedikt Löwe), Iran (1; Benedikt Löwe), Italy (4; Daniele Molinini), Japan (4; Mitsuhiro Okada), Republic of Korea (2; Insok Ko), Mexico (2; Atocha Aliseda, Ambrosio Velasco-Gómez), The Netherlands (2; Benedikt Löwe), Poland (2; Piotr Błaszczyk), Romania (1; Sorin Costreie), Russian Federation (3; Ilya Kasavin, Andrei Rodin, Lada Shipovalova), South Africa (1; Sean Muller), Spain (2; José A. Díez Calzada), Sweden (3; Valentin Goranko), Taiwan (2; Husan-Chih Lin, Kok-Yong Lee), United Kingdom (4; Robin Hendry), and United States of America (5; Hasok Chang, Philip Kircher, Helen Longino). After <b>Agenda item 5</b>, the number of votes of Argentina was reduced to 1 and the new Ordinary Member Portugal (2; João Luis Cordovil, Joan Bertran-San-Millán) was admitted; therefore, the number of votes of ordinary members increased by one.</p><p><i>Ordinary Members Absent</i>. Eire (cf. <b>Agenda item 5</b>), Hungary (1), India (1), Israel (1), Moldov","PeriodicalId":49864,"journal":{"name":"Mathematical Logic Quarterly","volume":"70 1","pages":"5-36"},"PeriodicalIF":0.3,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/malq.202400004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141286966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A weak theory of building blocks","authors":"Juvenal Murwanashyaka","doi":"10.1002/malq.202300015","DOIUrl":"10.1002/malq.202300015","url":null,"abstract":"<p>We apply the mereological concept of parthood to the coding of finite sequences. We propose a first-order theory in which coding finite sequences is intuitive and transparent. We compare this theory with Robinson arithmetic, adjunctive set theory and weak theories of finite strings and finite trees using interpretability.</p>","PeriodicalId":49864,"journal":{"name":"Mathematical Logic Quarterly","volume":"70 2","pages":"233-254"},"PeriodicalIF":0.4,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/malq.202300015","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141167711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Compactness in team semantics","authors":"Joni Puljujärvi, Davide Emilio Quadrellaro","doi":"10.1002/malq.202200072","DOIUrl":"10.1002/malq.202200072","url":null,"abstract":"<p>We provide two proofs of the compactness theorem for extensions of first-order logic based on team semantics. First, we build upon Lück's [16] ultraproduct construction for team semantics and prove a suitable version of Łoś' Theorem. Second, we show that by working with suitably saturated models, we can generalize the proof of Kontinen and Yang [13] to sets of formulas with arbitrarily many variables.</p>","PeriodicalId":49864,"journal":{"name":"Mathematical Logic Quarterly","volume":"70 2","pages":"142-161"},"PeriodicalIF":0.4,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/malq.202200072","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141167755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Formal model theory and higher topology","authors":"Ivan Di Liberti","doi":"10.1002/malq.202300006","DOIUrl":"10.1002/malq.202300006","url":null,"abstract":"<p>We study the 2-categories BIon, of (generalized) bounded ionads, and <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mtext>Acc</mtext>\u0000 <mi>ω</mi>\u0000 </msub>\u0000 <annotation>$text{Acc}_omega$</annotation>\u0000 </semantics></math>, of accessible categories with directed colimits, as an abstract framework to approach formal model theory. We relate them to topoi and (lex) geometric sketches, which serve as categorical specifications of geometric theories. We provide reconstruction and completeness-like results. We relate abstract elementary classes to locally decidable topoi. We introduce the notion of categories of saturated objects and relate it to atomic topoi.</p>","PeriodicalId":49864,"journal":{"name":"Mathematical Logic Quarterly","volume":"70 1","pages":"111-125"},"PeriodicalIF":0.3,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/malq.202300006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141167709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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