Pub Date : 2024-06-11DOI: 10.1016/j.apal.2024.103485
Graham E. Leigh, Dominik Wehr
We consider cyclic proof systems in which derivations are graphs rather than trees. Such systems typically come with a condition that isolates which derivations are admitted as proofs, known as the soundness condition. This soundness condition frequently takes the form of either a global trace condition, a property dependent on all infinite paths in the proof-graph, or a reset condition, a ‘local’ condition depending on the simple cycles only which, as a result, is typically stable under more proof transformations.
In this article we present a general method for constructing cyclic proof systems with reset conditions from systems with global trace conditions. In contrast to previous approaches, this method of generation is entirely independent of logic's semantics, only relying on combinatorial aspects of the notion of ‘trace’ and ‘progress’. We apply this method to present reset proof systems for three cyclic proof systems from the literature: cyclic arithmetic, cyclic Gödel's T and cyclic tableaux for the modal μ-calculus.
{"title":"From GTC to : Generating reset proof systems from cyclic proof systems","authors":"Graham E. Leigh, Dominik Wehr","doi":"10.1016/j.apal.2024.103485","DOIUrl":"10.1016/j.apal.2024.103485","url":null,"abstract":"<div><p>We consider cyclic proof systems in which derivations are graphs rather than trees. Such systems typically come with a condition that isolates which derivations are admitted as proofs, known as the <em>soundness condition</em>. This soundness condition frequently takes the form of either a <em>global trace</em> condition, a property dependent on all infinite paths in the proof-graph, or a <em>reset</em> condition, a ‘local’ condition depending on the simple cycles only which, as a result, is typically stable under more proof transformations.</p><p>In this article we present a general method for constructing cyclic proof systems with reset conditions from systems with global trace conditions. In contrast to previous approaches, this method of generation is entirely independent of logic's semantics, only relying on combinatorial aspects of the notion of ‘trace’ and ‘progress’. We apply this method to present reset proof systems for three cyclic proof systems from the literature: cyclic arithmetic, cyclic Gödel's T and cyclic tableaux for the modal <em>μ</em>-calculus.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168007224000897/pdfft?md5=3f6516f2a534f0fa710275ea2d71b171&pid=1-s2.0-S0168007224000897-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141402450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-06DOI: 10.1016/j.apal.2024.103486
Miloš S. Kurilić , Stevo Todorčević
The poset of copies of a relational structure is the partial order and each similarity of such posets (e.g. isomorphism, forcing equivalence = isomorphism of Boolean completions, ) determines a classification of structures. Here we consider the structures from Lachlan's list of countable ultrahomogeneous tournaments: (the rational line), (the circular tournament), and (the countable homogeneous universal tournament); as well as the ultrahomogeneous digraphs , , and from Cherlin's list.
If (resp. ) denotes the countable homogeneous universal graph (resp. n-labeled linear order), it turns out that and that densely embeds in , for .
Consequently, , where is the poset of perfect subsets of and π an -name such that
关系结构 X 副本的正集是偏序 P(X):=〈{Y⊂X:Y≅X},⊂〉,这种正集的每一个相似性(例如同构、强制等价 = 布尔完成的同构,BX:=rosqP(X))决定了结构的一个分类。在此,我们考虑拉克兰的可数超同调锦标赛列表中的结构:Q(有理线)、S(2)(循环锦标赛)和 T∞(可数同质通用锦标赛);以及谢林列表中的超同质数图 S(3)、Q[In]、S(2)[In]和 T∞[In]。如果 GRado(或 Qn)表示可数同素万能图(或 n 标记线性阶),那么对于 n∈{2,3},P(T∞)≅P(GRado)和 P(Qn)密集嵌入 P(S(n))。因此,BX≅ro(S⁎π),其中 S 是 R 的完全子集的正集,π 是一个 S 名,使得 1S⊩"π 是一个分离式、只要 X 是与 Q、Qn、S(2)、S(3)、Q[In] 或 S(2)[In]等价的可数结构,CH 下的 1S⊩"π≡forc(P(ω)/Fin)+"(因此 1S⊩"π≡forc(P(ω)/Fin)+")。另外,BX≅ro(S⁎π),其中 1S⊩"π是ω-分布强迫",只要 X 是包含 GRado 副本的可数图,或包含 T∞ 副本的可数锦标赛,或 X=T∞[In]。
{"title":"Posets of copies of countable ultrahomogeneous tournaments","authors":"Miloš S. Kurilić , Stevo Todorčević","doi":"10.1016/j.apal.2024.103486","DOIUrl":"https://doi.org/10.1016/j.apal.2024.103486","url":null,"abstract":"<div><p>The <em>poset of copies</em> of a relational structure <span><math><mi>X</mi></math></span> is the partial order <span><math><mi>P</mi><mo>(</mo><mi>X</mi><mo>)</mo><mo>:</mo><mo>=</mo><mo>〈</mo><mo>{</mo><mi>Y</mi><mo>⊂</mo><mi>X</mi><mo>:</mo><mi>Y</mi><mo>≅</mo><mi>X</mi><mo>}</mo><mo>,</mo><mo>⊂</mo><mo>〉</mo></math></span> and each similarity of such posets (e.g. isomorphism, forcing equivalence = isomorphism of Boolean completions, <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>X</mi></mrow></msub><mo>:</mo><mo>=</mo><mrow><mi>ro</mi></mrow><mspace></mspace><mrow><mi>sq</mi></mrow><mspace></mspace><mi>P</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span>) determines a classification of structures. Here we consider the structures from Lachlan's list of countable ultrahomogeneous tournaments: <span><math><mi>Q</mi></math></span> (the rational line), <span><math><mi>S</mi><mo>(</mo><mn>2</mn><mo>)</mo></math></span> (the circular tournament), and <span><math><msup><mrow><mi>T</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span> (the countable homogeneous universal tournament); as well as the ultrahomogeneous digraphs <span><math><mi>S</mi><mo>(</mo><mn>3</mn><mo>)</mo></math></span>, <span><math><mi>Q</mi><mo>[</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>]</mo></math></span>, <span><math><mi>S</mi><mo>(</mo><mn>2</mn><mo>)</mo><mo>[</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>]</mo></math></span> and <span><math><msup><mrow><mi>T</mi></mrow><mrow><mo>∞</mo></mrow></msup><mo>[</mo><msub><mrow><mi>I</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>]</mo></math></span> from Cherlin's list.</p><p>If <span><math><msub><mrow><mi>G</mi></mrow><mrow><mi>Rado</mi></mrow></msub></math></span> (resp. <span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>) denotes the countable homogeneous universal graph (resp. <em>n</em>-labeled linear order), it turns out that <span><math><mi>P</mi><mo>(</mo><msup><mrow><mi>T</mi></mrow><mrow><mo>∞</mo></mrow></msup><mo>)</mo><mo>≅</mo><mi>P</mi><mo>(</mo><msub><mrow><mi>G</mi></mrow><mrow><mi>Rado</mi></mrow></msub><mo>)</mo></math></span> and that <span><math><mi>P</mi><mo>(</mo><msub><mrow><mi>Q</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo></math></span> densely embeds in <span><math><mi>P</mi><mo>(</mo><mi>S</mi><mo>(</mo><mi>n</mi><mo>)</mo><mo>)</mo></math></span>, for <span><math><mi>n</mi><mo>∈</mo><mo>{</mo><mn>2</mn><mo>,</mo><mn>3</mn><mo>}</mo></math></span>.</p><p>Consequently, <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>X</mi></mrow></msub><mo>≅</mo><mrow><mi>ro</mi></mrow><mspace></mspace><mo>(</mo><mi>S</mi><mo>⁎</mo><mi>π</mi><mo>)</mo></math></span>, where <span><math><mi>S</mi></math></span> is the poset of perfect subsets of <span><math><mi>R</mi></math></span> and <em>π</em> an <span><math><mi>S</mi></math></span>-name such that <span><math><msub><mrow><mn>1</mn></mrow><mrow><mi>S</mi></mrow></msub><mo","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141325306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-04DOI: 10.1016/j.apal.2024.103484
Pablo Andújar Guerrero , Will Johnson
We prove some technical results on definable types in p-adically closed fields, with consequences for definable groups and definable topological spaces. First, the code of a definable n-type (in the field sort) can be taken to be a real tuple (in the field sort) rather than an imaginary tuple (in the geometric sorts). Second, any definable type in the real or imaginary sorts is generated by a countable union of chains parameterized by the value group. Third, if X is an interpretable set, then the space of global definable types on X is strictly pro-interpretable, building off work of Cubides Kovacsics, Hils, and Ye [7], [8]. Fourth, global definable types can be lifted (in a non-canonical way) along interpretable surjections. Fifth, if G is a definable group with definable f-generics (dfg), and G acts on a definable set X, then the quotient space is definable, not just interpretable. This explains some phenomena observed by Pillay and Yao [24]. Lastly, we show that interpretable topological spaces satisfy analogues of first-countability and curve selection. Using this, we show that all reasonable notions of definable compactness agree on interpretable topological spaces, and that definable compactness is definable in families.
我们证明了 p-adically closed fields 中可定义类型的一些技术结果,这些结果对可定义群和可定义拓扑空间都有影响。首先,可定义 n 型的代码(在字段排序中)可以被视为实元组(在字段排序中),而不是虚元组(在几何排序中)。其次,在实排序或虚排序中,任何可定义类型都是由值组参数化的链的可数联盟生成的。第三,如果 X 是一个可解释集合,那么 X 上的全局可定义类型空间严格来说是亲可解释的,这是建立在 Cubides Kovacsics、Hils 和 Ye [7], [8] 的工作基础之上的。第四,全局可定义类型可以(以非规范的方式)沿着可解释的投射提升。第五,如果 G 是具有可定义 f 元(dfg)的可定义群,并且 G 作用于可定义集合 X,那么商空间 X/G 是可定义的,而不仅仅是可解释的。这解释了 Pillay 和 Yao [24] 观察到的一些现象。最后,我们证明可解释拓扑空间满足第一可数性和曲线选择的类似条件。由此,我们证明了可定义紧凑性的所有合理概念都与可解释拓扑空间一致,而且可定义紧凑性在族中是可定义的。
{"title":"Around definable types in p-adically closed fields","authors":"Pablo Andújar Guerrero , Will Johnson","doi":"10.1016/j.apal.2024.103484","DOIUrl":"https://doi.org/10.1016/j.apal.2024.103484","url":null,"abstract":"<div><p>We prove some technical results on definable types in <em>p</em>-adically closed fields, with consequences for definable groups and definable topological spaces. First, the code of a definable <em>n</em>-type (in the field sort) can be taken to be a real tuple (in the field sort) rather than an imaginary tuple (in the geometric sorts). Second, any definable type in the real or imaginary sorts is generated by a countable union of chains parameterized by the value group. Third, if <em>X</em> is an interpretable set, then the space of global definable types on <em>X</em> is strictly pro-interpretable, building off work of Cubides Kovacsics, Hils, and Ye <span>[7]</span>, <span>[8]</span>. Fourth, global definable types can be lifted (in a non-canonical way) along interpretable surjections. Fifth, if <em>G</em> is a definable group with definable f-generics (<em>dfg</em>), and <em>G</em> acts on a definable set <em>X</em>, then the quotient space <span><math><mi>X</mi><mo>/</mo><mi>G</mi></math></span> is definable, not just interpretable. This explains some phenomena observed by Pillay and Yao <span>[24]</span>. Lastly, we show that interpretable topological spaces satisfy analogues of first-countability and curve selection. Using this, we show that all reasonable notions of definable compactness agree on interpretable topological spaces, and that definable compactness is definable in families.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141325305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-29DOI: 10.1016/j.apal.2024.103466
Stefan Hoffelner
We show that there are models of where the -uniformization property holds. Further we show that “+ is not inaccessible to reals” outright implies that the -uniformization property is true.
{"title":"Forcing axioms and the uniformization-property","authors":"Stefan Hoffelner","doi":"10.1016/j.apal.2024.103466","DOIUrl":"https://doi.org/10.1016/j.apal.2024.103466","url":null,"abstract":"<div><p>We show that there are models of <span><math><msub><mrow><mi>MA</mi></mrow><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msub></math></span> where the <span><math><msubsup><mrow><mi>Σ</mi></mrow><mrow><mn>3</mn></mrow><mrow><mn>1</mn></mrow></msubsup></math></span>-uniformization property holds. Further we show that “<span><math><mi>BPFA</mi></math></span>+ <span><math><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> is not inaccessible to reals” outright implies that the <span><math><msubsup><mrow><mi>Σ</mi></mrow><mrow><mn>3</mn></mrow><mrow><mn>1</mn></mrow></msubsup></math></span>-uniformization property is true.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168007224000642/pdfft?md5=be051362a938ef048330838dac255f88&pid=1-s2.0-S0168007224000642-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141286509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-28DOI: 10.1016/j.apal.2024.103464
Josiah Jacobsen-Grocott
We prove that there are strong minimal pairs in the enumeration degrees and that the degrees of the left and right sides of strong minimal pairs include degrees, although it is unknown if there is a strong minimal pair in the enumeration degrees. We define a stronger type of minimal pair we call a strong super minimal pair, and show that there are none of these in the enumeration degrees, answering a question of Lempp et al. [6]. We leave open the question of the existence of a super minimal pair in the enumeration degrees.
{"title":"Strong minimal pairs in the enumeration degrees","authors":"Josiah Jacobsen-Grocott","doi":"10.1016/j.apal.2024.103464","DOIUrl":"https://doi.org/10.1016/j.apal.2024.103464","url":null,"abstract":"<div><p>We prove that there are strong minimal pairs in the enumeration degrees and that the degrees of the left and right sides of strong minimal pairs include <span><math><msubsup><mrow><mi>Σ</mi></mrow><mrow><mn>2</mn></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> degrees, although it is unknown if there is a strong minimal pair in the <span><math><msubsup><mrow><mi>Σ</mi></mrow><mrow><mn>2</mn></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> enumeration degrees. We define a stronger type of minimal pair we call a strong super minimal pair, and show that there are none of these in the enumeration degrees, answering a question of Lempp et al. <span>[6]</span>. We leave open the question of the existence of a super minimal pair in the enumeration degrees.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141286571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-20DOI: 10.1016/j.apal.2024.103465
Brian Tyrrell
A field K in a ring language is finitely undecidable if is undecidable for every nonempty finite . We adapt arguments originating with Cherlin-van den Dries-Macintyre/Ershov (for PAC fields) and Haran (for PRC fields) to prove all PAC and PRC fields are finitely undecidable. We describe the difficulties that arise in adapting the proof to PpC fields, and show no bounded PpC field is finitely axiomatisable. This work is drawn from the author's PhD thesis [44, Chapter 4].
{"title":"Finite undecidability in PAC and PRC fields","authors":"Brian Tyrrell","doi":"10.1016/j.apal.2024.103465","DOIUrl":"10.1016/j.apal.2024.103465","url":null,"abstract":"<div><p>A field <em>K</em> in a ring language <span><math><mi>L</mi></math></span> is <em>finitely undecidable</em> if <span><math><mtext>Cons</mtext><mo>(</mo><mi>Σ</mi><mo>)</mo></math></span> is undecidable for every nonempty finite <span><math><mi>Σ</mi><mo>⊆</mo><mtext>Th</mtext><mo>(</mo><mi>K</mi><mo>;</mo><mi>L</mi><mo>)</mo></math></span>. We adapt arguments originating with Cherlin-van den Dries-Macintyre/Ershov (for PAC fields) and Haran (for PRC fields) to prove all PAC and PRC fields are finitely undecidable. We describe the difficulties that arise in adapting the proof to P<em>p</em>C fields, and show no bounded P<em>p</em>C field is finitely axiomatisable. This work is drawn from the author's PhD thesis <span>[44, Chapter 4]</span>.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168007224000630/pdfft?md5=4a33b42fff6d541d26261561103e7ddd&pid=1-s2.0-S0168007224000630-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-13DOI: 10.1016/j.apal.2024.103463
Brent Cody , Philip White
A well-known version of Rowbottom's theorem for supercompactness ultrafilters leads naturally to notions of two-cardinal Ramseyness and corresponding normal ideals introduced herein. Generalizing results of Baumgartner, Feng and the first author, from the cardinal setting to the two-cardinal setting, we study hierarchies associated with a particular version of two-cardinal Ramseyness and a strong version of two-cardinal ineffability, as well as the relationships between these hierarchies and a natural notion of transfinite two-cardinal indescribability.
{"title":"Two-cardinal ideal operators and indescribability","authors":"Brent Cody , Philip White","doi":"10.1016/j.apal.2024.103463","DOIUrl":"10.1016/j.apal.2024.103463","url":null,"abstract":"<div><p>A well-known version of Rowbottom's theorem for supercompactness ultrafilters leads naturally to notions of two-cardinal Ramseyness and corresponding normal ideals introduced herein. Generalizing results of Baumgartner, Feng and the first author, from the cardinal setting to the two-cardinal setting, we study hierarchies associated with a particular version of two-cardinal Ramseyness and a strong version of two-cardinal ineffability, as well as the relationships between these hierarchies and a natural notion of transfinite two-cardinal indescribability.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168007224000617/pdfft?md5=48f3bb6ab30a9410a6aa9d07709c915f&pid=1-s2.0-S0168007224000617-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-13DOI: 10.1016/j.apal.2024.103455
David Fernández-Duque, Andreas Weiermann
Hardy functions are defined by transfinite recursion and provide upper bounds for the growth rate of the provably total computable functions in various formal theories, making them an essential ingredient in many proofs of independence. Their definition is contingent on a choice of fundamental sequences, which approximate limits in a ‘canonical’ way. In order to ensure that these functions behave as expected, including the aforementioned unprovability results, these fundamental sequences must enjoy certain regularity properties.
In this article, we prove that Buchholz's system of fundamental sequences for the ϑ function enjoys such conditions, including the Bachmann property. We partially extend these results to variants of the ϑ function, including a version without addition for countable ordinals. We conclude that the Hardy functions based on these notation systems enjoy natural monotonicity properties and majorize all functions defined by primitive recursion along .
{"title":"Fundamental sequences and fast-growing hierarchies for the Bachmann-Howard ordinal","authors":"David Fernández-Duque, Andreas Weiermann","doi":"10.1016/j.apal.2024.103455","DOIUrl":"10.1016/j.apal.2024.103455","url":null,"abstract":"<div><p>Hardy functions are defined by transfinite recursion and provide upper bounds for the growth rate of the provably total computable functions in various formal theories, making them an essential ingredient in many proofs of independence. Their definition is contingent on a choice of fundamental sequences, which approximate limits in a ‘canonical’ way. In order to ensure that these functions behave as expected, including the aforementioned unprovability results, these fundamental sequences must enjoy certain regularity properties.</p><p>In this article, we prove that Buchholz's system of fundamental sequences for the <em>ϑ</em> function enjoys such conditions, including the Bachmann property. We partially extend these results to variants of the <em>ϑ</em> function, including a version without addition for countable ordinals. We conclude that the Hardy functions based on these notation systems enjoy natural monotonicity properties and majorize all functions defined by primitive recursion along <span><math><mi>ϑ</mi><mo>(</mo><msub><mrow><mi>ε</mi></mrow><mrow><mi>Ω</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>)</mo></math></span>.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168007224000538/pdfft?md5=a9318d0df651509a7116d53069683110&pid=1-s2.0-S0168007224000538-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141061705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-08DOI: 10.1016/j.apal.2024.103456
Paolo Liberatore
Forgetting is removing variables from a logical formula while preserving the constraints on the other variables. In spite of reducing information, it does not always decrease the size of the formula and may sometimes increase it. This article discusses the implications of such an increase and analyzes the computational properties of the phenomenon. Given a propositional Horn formula, a set of variables and a maximum allowed size, deciding whether forgetting the variables from the formula can be expressed in that size is -hard in . The same problem for unrestricted CNF propositional formulae is -hard in .
{"title":"The ghosts of forgotten things: A study on size after forgetting","authors":"Paolo Liberatore","doi":"10.1016/j.apal.2024.103456","DOIUrl":"10.1016/j.apal.2024.103456","url":null,"abstract":"<div><p>Forgetting is removing variables from a logical formula while preserving the constraints on the other variables. In spite of reducing information, it does not always decrease the size of the formula and may sometimes increase it. This article discusses the implications of such an increase and analyzes the computational properties of the phenomenon. Given a propositional Horn formula, a set of variables and a maximum allowed size, deciding whether forgetting the variables from the formula can be expressed in that size is <span><math><msup><mrow><mi>D</mi></mrow><mrow><mi>p</mi></mrow></msup></math></span>-hard in <span><math><msubsup><mrow><mi>Σ</mi></mrow><mrow><mn>2</mn></mrow><mrow><mi>p</mi></mrow></msubsup></math></span>. The same problem for unrestricted CNF propositional formulae is <span><math><msubsup><mrow><mi>D</mi></mrow><mrow><mn>2</mn></mrow><mrow><mi>p</mi></mrow></msubsup></math></span>-hard in <span><math><msubsup><mrow><mi>Σ</mi></mrow><mrow><mn>3</mn></mrow><mrow><mi>p</mi></mrow></msubsup></math></span>.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S016800722400054X/pdfft?md5=664e39c8c02a1bed0bfc7e9414e88499&pid=1-s2.0-S016800722400054X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141063991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-15DOI: 10.1016/j.apal.2024.103453
Miguel A. Cardona , Lukas Daniel Klausner , Diego A. Mejía
Combining creature forcing approaches from [16] and [8], we show that, under ch, there is a proper -bounding poset with ℵ2-cc that forces continuum many pairwise different cardinal characteristics, parametrised by reals, for each one of the following six types: uniformity and covering numbers of Yorioka ideals as well as both kinds of localisation and anti-localisation cardinals, respectively. This answers several open questions from [17].
{"title":"Continuum many different things: Localisation, anti-localisation and Yorioka ideals","authors":"Miguel A. Cardona , Lukas Daniel Klausner , Diego A. Mejía","doi":"10.1016/j.apal.2024.103453","DOIUrl":"10.1016/j.apal.2024.103453","url":null,"abstract":"<div><p>Combining creature forcing approaches from <span>[16]</span> and <span>[8]</span>, we show that, under <span>ch</span>, there is a proper <span><math><msup><mrow><mi>ω</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span>-bounding poset with ℵ<sub>2</sub>-cc that forces continuum many pairwise different cardinal characteristics, parametrised by reals, for each one of the following six types: uniformity and covering numbers of Yorioka ideals as well as both kinds of localisation and anti-localisation cardinals, respectively. This answers several open questions from <span>[17]</span>.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140611495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}