Bulletin of the London Mathematical Society最新文献

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Linear independence of coherent systems associated to discrete subgroups
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2025-01-08 DOI: 10.1112/blms.13226
Ulrik Enstad, Jordy Timo van Velthoven
{"title":"Linear independence of coherent systems associated to discrete subgroups","authors":"Ulrik Enstad,&nbsp;Jordy Timo van Velthoven","doi":"10.1112/blms.13226","DOIUrl":"https://doi.org/10.1112/blms.13226","url":null,"abstract":"<p>This note considers the finite linear independence of coherent systems associated to discrete subgroups. We show by simple arguments that such coherent systems of amenable groups are linearly independent whenever the associated twisted group ring does not contain any nontrivial zero divisors. We verify the latter for discrete subgroups in nilpotent Lie groups. For the particular case of time-frequency translates of Euclidean space, our approach provides a simple and self-contained proof of the Heil–Ramanathan–Topiwala conjecture for subsets of arbitrary discrete subgroups.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"315-329"},"PeriodicalIF":0.8,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/blms.13226","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A finiteness theorem for universal m $m$ -gonal forms
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2025-01-02 DOI: 10.1112/blms.13217
Byeong Moon Kim, Dayoon Park
{"title":"A finiteness theorem for universal \u0000 \u0000 m\u0000 $m$\u0000 -gonal forms","authors":"Byeong Moon Kim,&nbsp;Dayoon Park","doi":"10.1112/blms.13217","DOIUrl":"https://doi.org/10.1112/blms.13217","url":null,"abstract":"<p>In this paper, we study the universal <span></span><math>\u0000 <semantics>\u0000 <mi>m</mi>\u0000 <annotation>$m$</annotation>\u0000 </semantics></math>-gonal forms. More precisely, we study the growth of the size of the finite set <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>{</mo>\u0000 <mn>1</mn>\u0000 <mo>,</mo>\u0000 <mn>2</mn>\u0000 <mo>,</mo>\u0000 <mtext>…</mtext>\u0000 <mo>,</mo>\u0000 <msub>\u0000 <mi>γ</mi>\u0000 <mi>m</mi>\u0000 </msub>\u0000 <mo>}</mo>\u0000 </mrow>\u0000 <annotation>$lbrace 1,2,ldots, gamma _mrbrace$</annotation>\u0000 </semantics></math> (<span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mi>γ</mi>\u0000 <mi>m</mi>\u0000 </msub>\u0000 <annotation>$gamma _m$</annotation>\u0000 </semantics></math> asymptotically increases as <span></span><math>\u0000 <semantics>\u0000 <mi>m</mi>\u0000 <annotation>$m$</annotation>\u0000 </semantics></math> increases) which characterize the universality of <span></span><math>\u0000 <semantics>\u0000 <mi>m</mi>\u0000 <annotation>$m$</annotation>\u0000 </semantics></math>-gonal forms.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"625-637"},"PeriodicalIF":0.8,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/blms.13217","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The Lelek fan admits a completely scrambled weakly mixing homeomorphism 勒勒克扇形承认一个完全扰乱的弱混合同构
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-31 DOI: 10.1112/blms.13205
Piotr Oprocha
{"title":"The Lelek fan admits a completely scrambled weakly mixing homeomorphism","authors":"Piotr Oprocha","doi":"10.1112/blms.13205","DOIUrl":"https://doi.org/10.1112/blms.13205","url":null,"abstract":"<p>We prove that the Lelek fan admits a completely scrambled weakly mixing homeomorphism. This is then used to show that for every <span></span><math>\u0000 <semantics>\u0000 <mi>n</mi>\u0000 <annotation>$n$</annotation>\u0000 </semantics></math> there is a continuum of topological dimension <span></span><math>\u0000 <semantics>\u0000 <mi>n</mi>\u0000 <annotation>$n$</annotation>\u0000 </semantics></math> admitting a weakly mixing completely scrambled homeomorphism. This provides a final answer to a question from 2001.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"432-443"},"PeriodicalIF":0.8,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/blms.13205","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fast Goodstein walks
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-27 DOI: 10.1112/blms.13210
David Fernández-Duque, Andreas Weiermann
{"title":"Fast Goodstein walks","authors":"David Fernández-Duque,&nbsp;Andreas Weiermann","doi":"10.1112/blms.13210","DOIUrl":"https://doi.org/10.1112/blms.13210","url":null,"abstract":"<p>We introduce a family <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <msub>\u0000 <mi>A</mi>\u0000 <mi>k</mi>\u0000 </msub>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 <mo>&lt;</mo>\u0000 <mi>ω</mi>\u0000 </mrow>\u0000 </msub>\u0000 <annotation>$(mathbb {A}_k)_{k&lt;omega }$</annotation>\u0000 </semantics></math> of fast-growing functions based on <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mi>ε</mi>\u0000 <mn>0</mn>\u0000 </msub>\u0000 <annotation>$varepsilon _0$</annotation>\u0000 </semantics></math> and use these to define a variant of the Goodstein process. We show that this variant terminates and that this fact is not provable in Kripke–Platek set theory (or other theories of Bachmann–Howard strength). We, moreover, show that this Goodstein process is of maximal length, so that any alternative Goodstein process based on the same fast-growing functions will also terminate.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"510-533"},"PeriodicalIF":0.8,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/blms.13210","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143363023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Torsion-free connections of second-order maximally superintegrable systems
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-24 DOI: 10.1112/blms.13213
Andreas Vollmer
{"title":"Torsion-free connections of second-order maximally superintegrable systems","authors":"Andreas Vollmer","doi":"10.1112/blms.13213","DOIUrl":"https://doi.org/10.1112/blms.13213","url":null,"abstract":"<p>Second-order (maximally) conformally superintegrable systems play an important role as models of mechanical systems, including systems such as the Kepler–Coulomb system and the isotropic harmonic oscillator. This paper is dedicated to understanding non- and semi-degenerate systems. We obtain “projective flatness” results for two torsion-free connections naturally associated to such systems. This viewpoint sheds some light onto the interrelationship of properly and conformally (second-order maximally) superintegrable systems from a geometrical perspective. It is shown that the semi-degenerate secondary structure tensor can be viewed as the Ricci curvature of a natural torsion-free connection defined by the primary structure tensor (and similarly in the non-degenerate case). It is also shown that properly semi-degenerate systems are characterised, similar to the non-degenerate case, by the vanishing of the secondary structure tensor.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"565-581"},"PeriodicalIF":0.8,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/blms.13213","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143363054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Associahedra as moment polytopes
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-20 DOI: 10.1112/blms.13212
Michael Gekhtman, Hugh Thomas
{"title":"Associahedra as moment polytopes","authors":"Michael Gekhtman,&nbsp;Hugh Thomas","doi":"10.1112/blms.13212","DOIUrl":"https://doi.org/10.1112/blms.13212","url":null,"abstract":"<p>Generalized associahedra are a well-studied family of polytopes associated with a finite-type cluster algebra and a choice of starting cluster. We show that the generalized associahedra constructed by Padrol, Palu, Pilaud, and Plamondon, building on ideas from Arkani-Hamed, Bai, He, and Yan, can be naturally viewed as moment polytopes for an open patch of the quotient of the cluster <span></span><math>\u0000 <semantics>\u0000 <mi>A</mi>\u0000 <annotation>$mathcal {A}$</annotation>\u0000 </semantics></math>-variety with universal coefficients by its maximal natural torus action. We prove our result by showing that the construction of Padrol, Palu, Pilaud, and Plamondon can be understood on the basis of the way that moment polytopes behave under symplectic reduction.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"551-564"},"PeriodicalIF":0.8,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143363059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the order of the classical Erdős–Rogers functions
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-20 DOI: 10.1112/blms.13214
Dhruv Mubayi, Jacques Verstraete
{"title":"On the order of the classical Erdős–Rogers functions","authors":"Dhruv Mubayi,&nbsp;Jacques Verstraete","doi":"10.1112/blms.13214","DOIUrl":"https://doi.org/10.1112/blms.13214","url":null,"abstract":"&lt;p&gt;For an integer &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mo&gt;⩾&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$n geqslant 1$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, the Erdős–Rogers function &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;f&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$f_{s,s+1}(n)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; is the maximum integer &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;annotation&gt;$m$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; such that every &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;annotation&gt;$n$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-vertex &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;K&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;annotation&gt;$K_{s+1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-free graph has a &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;K&lt;/mi&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;annotation&gt;$K_s$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-free induced subgraph with &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;annotation&gt;$m$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; vertices. It is known that for all &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mo&gt;⩾&lt;/mo&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$s geqslant 3$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;f&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mi&gt;Ω&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 ","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"582-598"},"PeriodicalIF":0.8,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143363060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Multiple solutions with sign information for double-phase problems with unbalanced growth
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-20 DOI: 10.1112/blms.13218
Nikolaos S. Papageorgiou, Vicenţiu D. Rădulescu, Wen Zhang
{"title":"Multiple solutions with sign information for double-phase problems with unbalanced growth","authors":"Nikolaos S. Papageorgiou,&nbsp;Vicenţiu D. Rădulescu,&nbsp;Wen Zhang","doi":"10.1112/blms.13218","DOIUrl":"https://doi.org/10.1112/blms.13218","url":null,"abstract":"<p>We consider a double-phase Dirichlet problem with unbalanced growth and a reaction term which is <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mi>p</mi>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$(p-1)$</annotation>\u0000 </semantics></math>-sublinear and has partial interaction with the first eigenvalue of the weighted differential operator <span></span><math>\u0000 <semantics>\u0000 <msubsup>\u0000 <mi>Δ</mi>\u0000 <mi>p</mi>\u0000 <mi>a</mi>\u0000 </msubsup>\u0000 <annotation>$Delta _{p}^{a}$</annotation>\u0000 </semantics></math> (nonuniform nonresonance). Using the Nehari method, we show that the problem has at least three nontrivial bounded solutions, positive, negative and nodal (sign-changing). This paper extends and complements the main results in the recent paper Papageorgiou–Pudelko–Rădulescu (<i>Math. Annalen</i> <b>385</b> (2023) 1707–1745). </p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 2","pages":"638-656"},"PeriodicalIF":0.8,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143363061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fixed points for group actions on 2-dimensional affine buildings
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-18 DOI: 10.1112/blms.13197
Jeroen Schillewaert, Koen Struyve, Anne Thomas
{"title":"Fixed points for group actions on 2-dimensional affine buildings","authors":"Jeroen Schillewaert,&nbsp;Koen Struyve,&nbsp;Anne Thomas","doi":"10.1112/blms.13197","DOIUrl":"https://doi.org/10.1112/blms.13197","url":null,"abstract":"<p>We prove a local-to-global result for fixed points of finitely generated groups acting on 2-dimensional affine buildings of types <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mover>\u0000 <mi>A</mi>\u0000 <mo>∼</mo>\u0000 </mover>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <annotation>$tilde{A}_2$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mover>\u0000 <mi>C</mi>\u0000 <mo>∼</mo>\u0000 </mover>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <annotation>$tilde{C}_2$</annotation>\u0000 </semantics></math>. Our proofs combine building-theoretic arguments with standard results for <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>CAT</mo>\u0000 <mo>(</mo>\u0000 <mn>0</mn>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$operatorname{CAT}(0)$</annotation>\u0000 </semantics></math> spaces.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 1","pages":"285-301"},"PeriodicalIF":0.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Monotone versus non-monotone projective operators
IF 0.8 3区 数学
Bulletin of the London Mathematical Society Pub Date : 2024-12-17 DOI: 10.1112/blms.13194
J. P. Aguilera, P. D. Welch
{"title":"Monotone versus non-monotone projective operators","authors":"J. P. Aguilera,&nbsp;P. D. Welch","doi":"10.1112/blms.13194","DOIUrl":"https://doi.org/10.1112/blms.13194","url":null,"abstract":"&lt;p&gt;For a class of operators &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;Γ&lt;/mi&gt;\u0000 &lt;annotation&gt;$Gamma$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, let &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;mi&gt;Γ&lt;/mi&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$|Gamma |$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; denote the closure ordinal of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;Γ&lt;/mi&gt;\u0000 &lt;annotation&gt;$Gamma$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-inductive definitions. We give upper bounds on the values of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$|Sigma ^{1,mon}_{2n+1}|$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;Π&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;o&lt;/mi&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$|Pi ^{1,mon}_{2n+2}|$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; under the assumption that all projective sets of reals are determined, significantly improving the known results. In particular, the bounds show that &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;|&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;msubsup&gt;\u0000 ","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"57 1","pages":"256-264"},"PeriodicalIF":0.8,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/blms.13194","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143115892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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