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Exact solutions to the Erdős-Rothschild problem 厄尔多斯-罗斯柴尔德问题的精确解
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-08 DOI: 10.1017/fms.2023.117
Oleg Pikhurko, Katherine Staden
<p>Let <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline1.png"><span data-mathjax-type="texmath"><span>$boldsymbol {k} := (k_1,ldots ,k_s)$</span></span></img></span></span> be a sequence of natural numbers. For a graph <span>G</span>, let <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline2.png"><span data-mathjax-type="texmath"><span>$F(G;boldsymbol {k})$</span></span></img></span></span> denote the number of colourings of the edges of <span>G</span> with colours <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline3.png"><span data-mathjax-type="texmath"><span>$1,dots ,s$</span></span></img></span></span> such that, for every <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline4.png"><span data-mathjax-type="texmath"><span>$c in {1,dots ,s}$</span></span></img></span></span>, the edges of colour <span>c</span> contain no clique of order <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline5.png"><span data-mathjax-type="texmath"><span>$k_c$</span></span></img></span></span>. Write <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline6.png"><span data-mathjax-type="texmath"><span>$F(n;boldsymbol {k})$</span></span></img></span></span> to denote the maximum of <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline7.png"><span data-mathjax-type="texmath"><span>$F(G;boldsymbol {k})$</span></span></img></span></span> over all graphs <span>G</span> on <span>n</span> vertices. There are currently very few known exact (or asymptotic) results for this problem, posed by Erdős and Rothschild in 1974. We prove some new exact results for <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105145234572-0397:S2050509423001172:S2050509423001172_inline8.png"><span data-mathjax-type="texmath"><span>$n to infty $</span></span></img></span></span>: </p><ol><li><p><span>(i)</span> A sufficient condition on <span><span><img data-mimesubtype="png" data-type="" src="https://static.
让 $boldsymbol {k} := (k_1,ldots ,k_s)$ 是一个自然数序列。对于一个图 G,让 $F(G;boldsymbol {k})$ 表示 G 中颜色为 $1,dots,s$的边的着色数,对于 {1,dots ,s}$中的每一个 $c,颜色为 c 的边都不包含阶数为 $k_c$ 的簇。写$F(n;boldsymbol {k})$表示在n个顶点上的所有图G中$F(G;boldsymbol {k})$的最大值。这个问题由 Erdős 和 Rothschild 于 1974 年提出,目前已知的精确(或渐近)结果很少。我们为 $n to infty $ 证明了一些新的精确结果:(i) $boldsymbol {k}$ 上的一个充分条件,它保证了每个极值图都是一个完整的多方图,系统地恢复了所有已有的精确结果。(ii) 针对厄尔多斯和罗斯柴尔德的原始问题,在长度为 $7$ 的 $boldsymbol {k}=(3,ldots ,3)$ 情况下,唯一的极值图是完整的平衡 $8$ 多方图,其着色来自阶数为 $8$ 的哈达玛矩阵。(iii) 在$boldsymbol {k}=(k+1,k)$的情况下,(i)中的充分条件不成立,对于$3 leq k leq 10$,唯一的极值图是完整的k-partite图,其中一部分的大小小于k,其他部分的大小尽可能相等。
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引用次数: 0
Positivity of Schur forms for strongly decomposably positive vector bundles 强可分解正向向量束的舒尔形式的正向性
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-08 DOI: 10.1017/fms.2023.125
Xueyuan Wan

In this paper, we define two types of strongly decomposable positivity, which serve as generalizations of (dual) Nakano positivity and are stronger than the decomposable positivity introduced by S. Finski. We provide the criteria for strongly decomposable positivity of type I and type II and prove that the Schur forms of a strongly decomposable positive vector bundle of type I are weakly positive, while the Schur forms of a strongly decomposable positive vector bundle of type II are positive. These answer a question of Griffiths affirmatively for strongly decomposably positive vector bundles. Consequently, we present an algebraic proof of the positivity of Schur forms for (dual) Nakano positive vector bundles, which was initially proven by S. Finski.

在本文中,我们定义了两类强可分解正定性,它们是(对偶)中野正定性的概括,比 S. 芬斯基引入的可分解正定性更强。我们提供了 I 型和 II 型强可分解正性的标准,并证明了 I 型强可分解正向量束的舒尔形式是弱正性的,而 II 型强可分解正向量束的舒尔形式是正性的。这肯定地回答了格里菲斯关于强可分解正向量束的一个问题。因此,我们对(对偶)中野正向量束的舒尔形式的实在性提出了代数证明,这最初是由 S. 芬斯基证明的。
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引用次数: 0
Hypercontractivity on the symmetric group 对称群的超收缩性
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-08 DOI: 10.1017/fms.2023.118
Yuval Filmus, Guy Kindler, Noam Lifshitz, Dor Minzer
<p>The hypercontractive inequality is a fundamental result in analysis, with many applications throughout discrete mathematics, theoretical computer science, combinatorics and more. So far, variants of this inequality have been proved mainly for product spaces, which raises the question of whether analogous results hold over non-product domains.</p><p>We consider the symmetric group, <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105121623186-0467:S2050509423001184:S2050509423001184_inline1.png"><span data-mathjax-type="texmath"><span>$S_n$</span></span></img></span></span>, one of the most basic non-product domains, and establish hypercontractive inequalities on it. Our inequalities are most effective for the class of <span>global functions</span> on <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105121623186-0467:S2050509423001184:S2050509423001184_inline2.png"><span data-mathjax-type="texmath"><span>$S_n$</span></span></img></span></span>, which are functions whose <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105121623186-0467:S2050509423001184:S2050509423001184_inline3.png"><span data-mathjax-type="texmath"><span>$2$</span></span></img></span></span>-norm remains small when restricting <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105121623186-0467:S2050509423001184:S2050509423001184_inline4.png"><span data-mathjax-type="texmath"><span>$O(1)$</span></span></img></span></span> coordinates of the input, and assert that low-degree, global functions have small <span>q</span>-norms, for <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105121623186-0467:S2050509423001184:S2050509423001184_inline5.png"><span data-mathjax-type="texmath"><span>$q>2$</span></span></img></span></span>.</p><p>As applications, we show the following: </p><ol><li><p><span>1.</span> An analog of the level-<span>d</span> inequality on the hypercube, asserting that the mass of a global function on low degrees is very small. We also show how to use this inequality to bound the size of global, product-free sets in the alternating group <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105121623186-0467:S2050509423001184:S2050509423001184_inline6.png"><span data-mathjax-type="texmath"><span>$A_n$</span></span></img></span></span>.</p></li><li><p><span>2.</span> Isoperimetric inequalities on the transposition Cayley graph of <span><span><img data-mimesubtype="png" data-type="" src="https://static.cambridge.org/binary/version/id/urn:cambridge.or
超收缩不等式是分析学中的一个基本结果,在离散数学、理论计算机科学、组合学等领域有许多应用。迄今为止,这一不等式的变体主要是针对乘积空间证明的,这就提出了一个问题:类似的结果是否适用于非乘积域。我们考虑了对称群 $S_n$,这是最基本的非乘积域之一,并在其上建立了超契约不等式。我们的不等式对 $S_n$ 上的全局函数类最有效,全局函数是指当限制输入的 $O(1)$ 坐标时,其 $2$ 准则仍然很小的函数,并断言低度全局函数在 $q>2$ 时具有很小的 q 准则:1.超立方体上的等差数列不等式,断言低度全局函数的质量非常小。我们还展示了如何利用这个不等式来约束交替群 $A_n$ 中全局无积集的大小。在全局函数 $S_n$ 的转置 Cayley 图上的等周不等式,它类似于 KKL 定理和布尔超立方体中的小集扩展性质。 3. 在参数的某些情况下,克鲁斯卡尔-卡托纳定理的多片和稳定版本的超收缩不等式。
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引用次数: 0
Tropical Fock–Goncharov coordinates for -webs on surfaces I: construction 曲面上-网的热带福克-冈察洛夫坐标 I:构造
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-05 DOI: 10.1017/fms.2023.120
Daniel C. Douglas, Zhe Sun

For a finite-type surface $mathfrak {S}$, we study a preferred basis for the commutative algebra $mathbb {C}[mathscr {R}_{mathrm {SL}_3(mathbb {C})}(mathfrak {S})]$ of regular functions on the $mathrm {SL}_3(mathbb {C})$-character variety, introduced by Sikora–Westbury. These basis elements come from the trace functions associated to certain trivalent graphs embedded in the surface $mathfrak {S}$. We show that this basis can be naturally indexed by nonnegative integer coordinates, defined by Knutson–Tao rhombus inequalities and modulo 3 congruence conditions. These coordinates are related, by the geometric theory of Fock and Goncharov, to the tropical points at infinity of the dual version of the character variety.

对于有限型曲面 $mathfrak {S}$,我们研究了西科拉-韦斯特伯里(Sikora-Westbury)引入的交换代数 $mathbb {C}[mathscr {R}_{mathrm {SL}_3(mathbb {C})}(mathfrak {S})]$上正则函数的优选基。这些基元来自与嵌入表面 $mathfrak {S}$ 的某些三价图相关的迹函数。我们证明,这个基可以自然地用非负整数坐标来索引,这些坐标是由克努森-陶菱形不等式和模 3 全等条件定义的。根据福克和冈察洛夫的几何理论,这些坐标与特征多样性对偶版本的无穷远处的热带点相关。
{"title":"Tropical Fock–Goncharov coordinates for -webs on surfaces I: construction","authors":"Daniel C. Douglas, Zhe Sun","doi":"10.1017/fms.2023.120","DOIUrl":"https://doi.org/10.1017/fms.2023.120","url":null,"abstract":"<p>For a finite-type surface <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104142456266-0825:S2050509423001202:S2050509423001202_inline2.png\"><span data-mathjax-type=\"texmath\"><span>$mathfrak {S}$</span></span></img></span></span>, we study a preferred basis for the commutative algebra <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104142456266-0825:S2050509423001202:S2050509423001202_inline3.png\"><span data-mathjax-type=\"texmath\"><span>$mathbb {C}[mathscr {R}_{mathrm {SL}_3(mathbb {C})}(mathfrak {S})]$</span></span></img></span></span> of regular functions on the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104142456266-0825:S2050509423001202:S2050509423001202_inline4.png\"><span data-mathjax-type=\"texmath\"><span>$mathrm {SL}_3(mathbb {C})$</span></span></img></span></span>-character variety, introduced by Sikora–Westbury. These basis elements come from the trace functions associated to certain trivalent graphs embedded in the surface <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104142456266-0825:S2050509423001202:S2050509423001202_inline5.png\"><span data-mathjax-type=\"texmath\"><span>$mathfrak {S}$</span></span></img></span></span>. We show that this basis can be naturally indexed by nonnegative integer coordinates, defined by Knutson–Tao rhombus inequalities and modulo 3 congruence conditions. These coordinates are related, by the geometric theory of Fock and Goncharov, to the tropical points at infinity of the dual version of the character variety.</p>","PeriodicalId":56000,"journal":{"name":"Forum of Mathematics Sigma","volume":"26 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139105069","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}
引用次数: 0
Every complex Hénon map is exponentially mixing of all orders and satisfies the CLT 每个复 Hénon 映射的所有阶都是指数混合的,并满足 CLT
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-05 DOI: 10.1017/fms.2023.110
Fabrizio Bianchi, Tien-Cuong Dinh

We show that the measure of maximal entropy of every complex Hénon map is exponentially mixing of all orders for Hölder observables. As a consequence, the Central Limit Theorem holds for all Hölder observables.

我们证明,对于赫尔德观测值,每个复赫农图的最大熵的度量在所有阶都是指数混合的。因此,中心极限定理对所有霍尔德观测值都成立。
{"title":"Every complex Hénon map is exponentially mixing of all orders and satisfies the CLT","authors":"Fabrizio Bianchi, Tien-Cuong Dinh","doi":"10.1017/fms.2023.110","DOIUrl":"https://doi.org/10.1017/fms.2023.110","url":null,"abstract":"<p>We show that the measure of maximal entropy of every complex Hénon map is exponentially mixing of all orders for Hölder observables. As a consequence, the Central Limit Theorem holds for all Hölder observables.</p>","PeriodicalId":56000,"journal":{"name":"Forum of Mathematics Sigma","volume":"150 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139105070","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}
引用次数: 0
Modularity of trianguline Galois representations 三角伽罗瓦表示的模块性
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-05 DOI: 10.1017/fms.2023.116
Rebecca Bellovin

We use the theory of trianguline $(varphi ,Gamma )$-modules over pseudorigid spaces to prove a modularity lifting theorem for certain Galois representations which are trianguline at p, including those with characteristic p coefficients. The use of pseudorigid spaces lets us construct integral models of the trianguline varieties of [BHS17], [Che13] after bounding the slope, and we carry out a Taylor–Wiles patching argument for families of overconvergent modular forms. This permits us to construct a patched quaternionic eigenvariety and deduce our modularity results.

我们利用伪原初空间上的三角$(varphi ,Gamma)$模块理论,证明了某些在p处是三角的伽罗华表示的模块性提升定理,包括那些有特征p系数的伽罗华表示。利用伪原型空间,我们可以在限定斜率之后,构建 [BHS17], [Che13] 三角形变体的积分模型,并对过敛积模态族进行泰勒-怀尔斯修补论证。这样,我们就可以构造一个修补的四元数特征变量,并推导出我们的模块性结果。
{"title":"Modularity of trianguline Galois representations","authors":"Rebecca Bellovin","doi":"10.1017/fms.2023.116","DOIUrl":"https://doi.org/10.1017/fms.2023.116","url":null,"abstract":"<p>We use the theory of trianguline <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104083513942-0464:S2050509423001160:S2050509423001160_inline1.png\"><span data-mathjax-type=\"texmath\"><span>$(varphi ,Gamma )$</span></span></img></span></span>-modules over pseudorigid spaces to prove a modularity lifting theorem for certain Galois representations which are trianguline at <span>p</span>, including those with characteristic <span>p</span> coefficients. The use of pseudorigid spaces lets us construct integral models of the trianguline varieties of [BHS17], [Che13] after bounding the slope, and we carry out a Taylor–Wiles patching argument for families of overconvergent modular forms. This permits us to construct a patched quaternionic eigenvariety and deduce our modularity results.</p>","PeriodicalId":56000,"journal":{"name":"Forum of Mathematics Sigma","volume":"150 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139105118","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}
引用次数: 0
Chern classes in equivariant bordism 等边性中的哲恩类
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-05 DOI: 10.1017/fms.2023.124
Stefan Schwede

We introduce Chern classes in $U(m)$-equivariant homotopical bordism that refine the Conner–Floyd–Chern classes in the $mathbf {MU}$-cohomology of $B U(m)$. For products of unitary groups, our Chern classes form regular sequences that generate the augmentation ideal of the equivariant bordism rings. Consequently, the Greenlees–May local homology spectral sequence collapses for products of unitary groups. We use the Chern classes to reprove the $mathbf {MU}$-completion theorem of Greenlees–May and La Vecchia.

我们介绍了$U(m)$-等变同调共生中的切尔恩类,它们完善了$B U(m)$的$mathbf {MU}$-同调中的康纳-弗洛伊德-切尔恩类。对于单元群的乘积,我们的切尔恩类形成正则序列,生成等变边界环的增量理想。因此,对于单元群的乘积,格林列斯-梅局部同源性谱序列会坍缩。我们利用这些哲恩类重新证明了格林列斯-梅和拉韦奇亚的 $mathbf {MU}$-completion 定理。
{"title":"Chern classes in equivariant bordism","authors":"Stefan Schwede","doi":"10.1017/fms.2023.124","DOIUrl":"https://doi.org/10.1017/fms.2023.124","url":null,"abstract":"<p>We introduce Chern classes in <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105024122240-0548:S205050942300124X:S205050942300124X_inline1.png\"><span data-mathjax-type=\"texmath\"><span>$U(m)$</span></span></img></span></span>-equivariant homotopical bordism that refine the Conner–Floyd–Chern classes in the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105024122240-0548:S205050942300124X:S205050942300124X_inline2.png\"><span data-mathjax-type=\"texmath\"><span>$mathbf {MU}$</span></span></img></span></span>-cohomology of <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105024122240-0548:S205050942300124X:S205050942300124X_inline3.png\"><span data-mathjax-type=\"texmath\"><span>$B U(m)$</span></span></img></span></span>. For products of unitary groups, our Chern classes form regular sequences that generate the augmentation ideal of the equivariant bordism rings. Consequently, the Greenlees–May local homology spectral sequence collapses for products of unitary groups. We use the Chern classes to reprove the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240105024122240-0548:S205050942300124X:S205050942300124X_inline4.png\"><span data-mathjax-type=\"texmath\"><span>$mathbf {MU}$</span></span></img></span></span>-completion theorem of Greenlees–May and La Vecchia.</p>","PeriodicalId":56000,"journal":{"name":"Forum of Mathematics Sigma","volume":"25 2","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139105112","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}
引用次数: 0
The stable cohomology of self-equivalences of connected sums of products of spheres 球面积的连通和的自等价稳定同调
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-05 DOI: 10.1017/fms.2023.113
Robin Stoll

We identify the cohomology of the stable classifying space of homotopy automorphisms (relative to an embedded disk) of connected sums of ${mathrm {S}^{k}} times {mathrm {S}^{l}}$, where $3 le k < l le 2k - 2$. The result is expressed in terms of Lie graph complex homology.

我们确定了 ${mathrm {S}^{k}} 的连接和的同调自变量(相对于嵌入盘)的稳定分类空间的同调。times {mathrm {S}^{l}}$, where $3 le k < l le 2k - 2$.这个结果用李图复同调来表示。
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引用次数: 0
Base sizes of primitive groups of diagonal type 对角型原始群的基数大小
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2024-01-04 DOI: 10.1017/fms.2023.121
Hong Yi Huang

Let G be a permutation group on a finite set $Omega $. The base size of G is the minimal size of a subset of $Omega $ with trivial pointwise stabiliser in G. In this paper, we extend earlier work of Fawcett by determining the precise base size of every finite primitive permutation group of diagonal type. In particular, this is the first family of primitive groups arising in the O’Nan–Scott theorem for which the exact base size has been computed in all cases. Our methods also allow us to determine all the primitive groups of diagonal type with a unique regular suborbit.

让 G 是有限集合 $Omega $ 上的一个置换群。 G 的基大小是在 G 中具有琐碎点稳定器的 $Omega $ 子集的最小大小。在本文中,我们扩展了 Fawcett 早期的工作,确定了每个对角型有限基元置换群的精确基大小。特别是,这是奥南-斯科特定理中出现的第一个在所有情况下都计算出精确基大小的原始群族。我们的方法还允许我们确定所有对角类型的原始群,它们都有一个唯一的正则子轨道。
{"title":"Base sizes of primitive groups of diagonal type","authors":"Hong Yi Huang","doi":"10.1017/fms.2023.121","DOIUrl":"https://doi.org/10.1017/fms.2023.121","url":null,"abstract":"<p>Let <span>G</span> be a permutation group on a finite set <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104065504114-0233:S2050509423001214:S2050509423001214_inline1.png\"><span data-mathjax-type=\"texmath\"><span>$Omega $</span></span></img></span></span>. The base size of <span>G</span> is the minimal size of a subset of <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240104065504114-0233:S2050509423001214:S2050509423001214_inline2.png\"><span data-mathjax-type=\"texmath\"><span>$Omega $</span></span></img></span></span> with trivial pointwise stabiliser in <span>G</span>. In this paper, we extend earlier work of Fawcett by determining the precise base size of every finite primitive permutation group of diagonal type. In particular, this is the first family of primitive groups arising in the O’Nan–Scott theorem for which the exact base size has been computed in all cases. Our methods also allow us to determine all the primitive groups of diagonal type with a unique regular suborbit.</p>","PeriodicalId":56000,"journal":{"name":"Forum of Mathematics Sigma","volume":"8 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139094095","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}
引用次数: 0
Lim Ulrich sequences and Boij-Söderberg cones Lim Ulrich 序列和 Boij-Söderberg 锥体
IF 1.7 2区 数学 Q1 MATHEMATICS Pub Date : 2023-12-18 DOI: 10.1017/fms.2023.108
Srikanth B. Iyengar, Linquan Ma, Mark E. Walker

This paper extends the results of Boij, Eisenbud, Erman, Schreyer and Söderberg on the structure of Betti cones of finitely generated graded modules and finite free complexes over polynomial rings, to all finitely generated graded rings admitting linear Noether normalizations. The key new input is the existence of lim Ulrich sequences of graded modules over such rings.

本文将 Boij、Eisenbud、Erman、Schreyer 和 Söderberg 关于多项式环上有限生成的级数模块和有限自由复数的贝蒂锥结构的研究成果,扩展到所有允许线性诺特归一化的有限生成的级数环。关键的新输入是在这些环上存在有级模块的极限乌尔里希序列。
{"title":"Lim Ulrich sequences and Boij-Söderberg cones","authors":"Srikanth B. Iyengar, Linquan Ma, Mark E. Walker","doi":"10.1017/fms.2023.108","DOIUrl":"https://doi.org/10.1017/fms.2023.108","url":null,"abstract":"<p>This paper extends the results of Boij, Eisenbud, Erman, Schreyer and Söderberg on the structure of Betti cones of finitely generated graded modules and finite free complexes over polynomial rings, to all finitely generated graded rings admitting linear Noether normalizations. The key new input is the existence of lim Ulrich sequences of graded modules over such rings.</p>","PeriodicalId":56000,"journal":{"name":"Forum of Mathematics Sigma","volume":"106 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138717512","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}
引用次数: 0
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