Pub Date : 2025-02-01DOI: 10.1016/j.aim.2024.110095
Matt Bowen
We show that any 2-coloring of contains infinitely many monochromatic sets of the form , and more generally monochromatic sets of the form for any . Along the way we prove a monochromatic products of sums theorem that extends Hindman's theorem and a colorful variant of this result that holds in any ‘balanced’ coloring.
{"title":"Monochromatic products and sums in 2-colorings of N","authors":"Matt Bowen","doi":"10.1016/j.aim.2024.110095","DOIUrl":"10.1016/j.aim.2024.110095","url":null,"abstract":"<div><div>We show that any 2-coloring of <span><math><mi>N</mi></math></span> contains infinitely many monochromatic sets of the form <span><math><mo>{</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>,</mo><mi>x</mi><mi>y</mi><mo>,</mo><mi>x</mi><mo>+</mo><mi>y</mi><mo>}</mo></math></span>, and more generally monochromatic sets of the form <span><math><mo>{</mo><msub><mrow><mi>x</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>,</mo><mo>∏</mo><msub><mrow><mi>x</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>,</mo><mo>∑</mo><msub><mrow><mi>x</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>:</mo><mi>i</mi><mo>≤</mo><mi>n</mi><mo>}</mo></math></span> for any <span><math><mi>n</mi><mo>∈</mo><mi>N</mi></math></span>. Along the way we prove a monochromatic products of sums theorem that extends Hindman's theorem and a colorful variant of this result that holds in any ‘balanced’ coloring.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"462 ","pages":"Article 110095"},"PeriodicalIF":1.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.aim.2024.110076
Yongbin Ruan , Cheng Shu
We study the geometry of singular -Hitchin fibres over the elliptic locus. We show that orbifold singularities appear in the -moduli space exactly when the side has a reducible Hitchin fibre. Our main theorem shows that the Fourier-Mukai transform of a skyscraper sheaf supported at an orbifold singularity in satisfies a version of the fractional Hecke eigenproperty, as conjectured by Frenkel and Witten.
{"title":"Mirror of orbifold singularities in the Hitchin fibration: The case (SLn,PGLn)","authors":"Yongbin Ruan , Cheng Shu","doi":"10.1016/j.aim.2024.110076","DOIUrl":"10.1016/j.aim.2024.110076","url":null,"abstract":"<div><div>We study the geometry of singular <span><math><msub><mrow><mi>SL</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>-Hitchin fibres over the elliptic locus. We show that orbifold singularities appear in the <span><math><msub><mrow><mi>PGL</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>-moduli space <span><math><msubsup><mrow><mi>M</mi></mrow><mrow><mi>C</mi></mrow><mrow><mi>e</mi><mi>l</mi><mi>l</mi></mrow></msubsup><mo>(</mo><msub><mrow><mi>PGL</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo></math></span> exactly when the <span><math><msub><mrow><mi>SL</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> side <span><math><msubsup><mrow><mi>M</mi></mrow><mrow><mi>C</mi></mrow><mrow><mi>e</mi><mi>l</mi><mi>l</mi></mrow></msubsup><mo>(</mo><msub><mrow><mi>SL</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo></math></span> has a reducible Hitchin fibre. Our main theorem shows that the Fourier-Mukai transform of a skyscraper sheaf supported at an orbifold singularity in <span><math><msubsup><mrow><mi>M</mi></mrow><mrow><mi>C</mi></mrow><mrow><mi>e</mi><mi>l</mi><mi>l</mi></mrow></msubsup><mo>(</mo><msub><mrow><mi>PGL</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo></math></span> satisfies a version of the fractional Hecke eigenproperty, as conjectured by Frenkel and Witten.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"461 ","pages":"Article 110076"},"PeriodicalIF":1.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.aim.2024.110079
A. Boralevi , E. Carlini , M. Michałek , E. Ventura
In this article, we study permanental varieties, i.e., varieties defined by the vanishing of permanents of fixed size of a generic matrix. Permanents and their varieties play an important, and sometimes poorly understood, role in combinatorics. However, there are essentially no geometric results about them in the literature, in very sharp contrast to the well-behaved and ubiquitous case of determinants and minors. Motivated by the study of the singular locus of the permanental hypersurface, we focus on the codimension of these varieties. We introduce a -action on matrices and prove a number of results. In particular, we improve a lower bound on the codimension of the aforementioned singular locus established by von zur Gathen in 1987.
{"title":"On the codimension of permanental varieties","authors":"A. Boralevi , E. Carlini , M. Michałek , E. Ventura","doi":"10.1016/j.aim.2024.110079","DOIUrl":"10.1016/j.aim.2024.110079","url":null,"abstract":"<div><div>In this article, we study <em>permanental varieties</em>, i.e., varieties defined by the vanishing of permanents of fixed size of a generic matrix. Permanents and their varieties play an important, and sometimes poorly understood, role in combinatorics. However, there are essentially no geometric results about them in the literature, in very sharp contrast to the well-behaved and ubiquitous case of determinants and minors. Motivated by the study of the singular locus of the permanental hypersurface, we focus on the codimension of these varieties. We introduce a <span><math><msup><mrow><mi>C</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>-action on matrices and prove a number of results. In particular, we improve a lower bound on the codimension of the aforementioned singular locus established by von zur Gathen in 1987.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"461 ","pages":"Article 110079"},"PeriodicalIF":1.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.aim.2024.110077
Benjamin Biaggi , Chia-Yu Chang , Jan Draisma , Filip Rupniewski
We show that the border subrank of a sufficiently general tensor in is for . Since this matches the growth rate for the generic (non-border) subrank recently established by Derksen-Makam-Zuiddam, we find that the generic border subrank has the same growth rate. In our proof, we use a generalisation of the Hilbert-Mumford criterion that we believe will be of independent interest.
{"title":"Border subrank via a generalised Hilbert-Mumford criterion","authors":"Benjamin Biaggi , Chia-Yu Chang , Jan Draisma , Filip Rupniewski","doi":"10.1016/j.aim.2024.110077","DOIUrl":"10.1016/j.aim.2024.110077","url":null,"abstract":"<div><div>We show that the border subrank of a sufficiently general tensor in <span><math><msup><mrow><mo>(</mo><msup><mrow><mi>C</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo></mrow><mrow><mo>⊗</mo><mi>d</mi></mrow></msup></math></span> is <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>1</mn><mo>/</mo><mo>(</mo><mi>d</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>)</mo></math></span> for <span><math><mi>n</mi><mo>→</mo><mo>∞</mo></math></span>. Since this matches the growth rate <span><math><mi>Θ</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>1</mn><mo>/</mo><mo>(</mo><mi>d</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>)</mo></math></span> for the generic (non-border) subrank recently established by Derksen-Makam-Zuiddam, we find that the generic border subrank has the same growth rate. In our proof, we use a generalisation of the Hilbert-Mumford criterion that we believe will be of independent interest.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"461 ","pages":"Article 110077"},"PeriodicalIF":1.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.aim.2024.110074
Shaunak V. Deo
Let be a prime, N be an integer not divisible by p, be a reducible, odd and semi-simple representation of of dimension 2 and be a set of primes not dividing Np. After assuming that a certain Selmer group has dimension at most 1, we find sufficient conditions for the existence of a cuspidal eigenform f of level and appropriate weight lifting such that f is new at every . Moreover, suppose for some . Then, after assuming that a certain Selmer group vanishes, we find sufficient conditions for the existence of a cuspidal eigenform of level and appropriate weight which is new at every and which lifts . As a consequence, we prove a conjecture of Billerey–Menares in many cases.
{"title":"Non-optimal levels of some reducible mod p modular representations","authors":"Shaunak V. Deo","doi":"10.1016/j.aim.2024.110074","DOIUrl":"10.1016/j.aim.2024.110074","url":null,"abstract":"<div><div>Let <span><math><mi>p</mi><mo>≥</mo><mn>5</mn></math></span> be a prime, <em>N</em> be an integer not divisible by <em>p</em>, <span><math><msub><mrow><mover><mrow><mi>ρ</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub></math></span> be a reducible, odd and semi-simple representation of <span><math><msub><mrow><mi>G</mi></mrow><mrow><mi>Q</mi><mo>,</mo><mi>N</mi><mi>p</mi></mrow></msub></math></span> of dimension 2 and <span><math><mo>{</mo><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>⋯</mo><mo>,</mo><msub><mrow><mi>ℓ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>}</mo></math></span> be a set of primes not dividing <em>Np</em>. After assuming that a certain Selmer group has dimension at most 1, we find sufficient conditions for the existence of a cuspidal eigenform <em>f</em> of level <span><math><mi>N</mi><msubsup><mrow><mo>∏</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>r</mi></mrow></msubsup><msub><mrow><mi>ℓ</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> and appropriate weight lifting <span><math><msub><mrow><mover><mrow><mi>ρ</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub></math></span> such that <em>f</em> is new at every <span><math><msub><mrow><mi>ℓ</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span>. Moreover, suppose <span><math><mi>p</mi><mo>|</mo><msub><mrow><mi>ℓ</mi></mrow><mrow><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msub><mo>+</mo><mn>1</mn></math></span> for some <span><math><mn>1</mn><mo>≤</mo><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≤</mo><mi>r</mi></math></span>. Then, after assuming that a certain Selmer group vanishes, we find sufficient conditions for the existence of a cuspidal eigenform of level <span><math><mi>N</mi><msubsup><mrow><mi>ℓ</mi></mrow><mrow><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow><mrow><mn>2</mn></mrow></msubsup><msub><mrow><mo>∏</mo></mrow><mrow><mi>j</mi><mo>≠</mo><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msub><msub><mrow><mi>ℓ</mi></mrow><mrow><mi>j</mi></mrow></msub></math></span> and appropriate weight which is new at every <span><math><msub><mrow><mi>ℓ</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> and which lifts <span><math><msub><mrow><mover><mrow><mi>ρ</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub></math></span>. As a consequence, we prove a conjecture of Billerey–Menares in many cases.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"461 ","pages":"Article 110074"},"PeriodicalIF":1.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-31DOI: 10.1016/j.aim.2025.110125
Jiyuan Han , Yaxiong Liu
In this paper, we prove that on a smooth Kähler manifold, the -coercivity of the weighted Mabuchi functional implies the existence of the -weighted-cscK (extremal) metric with v log-concave (firstly studied in [33]), e.g., extremal metrics, Kähler–Ricci solitons, μ-cscK metrics.
{"title":"On the existence of weighted-cscK metrics","authors":"Jiyuan Han , Yaxiong Liu","doi":"10.1016/j.aim.2025.110125","DOIUrl":"10.1016/j.aim.2025.110125","url":null,"abstract":"<div><div>In this paper, we prove that on a smooth Kähler manifold, the <span><math><mi>G</mi></math></span>-coercivity of the weighted Mabuchi functional implies the existence of the <span><math><mo>(</mo><mi>v</mi><mo>,</mo><mi>w</mi><mo>)</mo></math></span>-weighted-cscK (extremal) metric with v log-concave (firstly studied in <span><span>[33]</span></span>), e.g., extremal metrics, Kähler–Ricci solitons, <em>μ</em>-cscK metrics.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"463 ","pages":"Article 110125"},"PeriodicalIF":1.5,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-30DOI: 10.1016/j.aim.2025.110117
Michael Chapman , Alexander Lubotzky
Coboundary expansion (with coefficients), and variations on it, have been the focus of intensive research in the last two decades. It was used to study random complexes, property testing, and above all Gromov's topological overlapping property.
In part I of this paper, we extended the notion of coboundary expansion (and its variations) to cochains with permutation coefficients, equipped with the normalized Hamming distance. We showed that this gives a unified language for studying covering stability of complexes, as well as stability of group homomorphisms — a topic that drew a lot of attention in recent years.
In this part, we extend the theory to the permutation coefficients setting. This gives some new results, even for coefficients, opens several new directions of research, and suggests a pattern to proving the existence of non-sofic groups. Along the way, we solve the dimension 2 case of a problem of Gromov, exhibiting a family of bounded degree coboundary expanders with coefficients.
{"title":"Stability of homomorphisms, coverings and cocycles II: Examples, applications and open problems","authors":"Michael Chapman , Alexander Lubotzky","doi":"10.1016/j.aim.2025.110117","DOIUrl":"10.1016/j.aim.2025.110117","url":null,"abstract":"<div><div>Coboundary expansion (with <span><math><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> coefficients), and variations on it, have been the focus of intensive research in the last two decades. It was used to study random complexes, property testing, and above all Gromov's topological overlapping property.</div><div>In part I of this paper, we extended the notion of coboundary expansion (and its variations) to cochains with <strong>permutation coefficients</strong>, equipped with the normalized Hamming distance. We showed that this gives a unified language for studying covering stability of complexes, as well as stability of group homomorphisms — a topic that drew a lot of attention in recent years.</div><div>In this part, we extend the theory to the permutation coefficients setting. This gives some new results, even for <span><math><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> coefficients, opens several new directions of research, and suggests a pattern to proving the existence of non-sofic groups. Along the way, we solve the dimension 2 case of a problem of Gromov, exhibiting a family of bounded degree coboundary expanders with <span><math><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> coefficients.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"463 ","pages":"Article 110117"},"PeriodicalIF":1.5,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143163842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-30DOI: 10.1016/j.aim.2025.110118
Charles D. Frohman , Joanna Kania-Bartoszynska , Thang T.Q. Lê
The sliced skein algebra of a closed surface of genus g with m punctures, , is the quotient of the Kauffman bracket skein algebra corresponding to fixing the scalar values of its peripheral curves. We show that the sliced skein algebra of a finite type surface is a domain if the ground ring is a domain. When the quantum parameter ξ is a root of unity we calculate the center of the sliced skein algebra and its PI-degree. Among applications we show that any smooth point of a sliced character variety is an Azumaya point of the skein algebra .
For any -representation ρ of the fundamental group of an oriented connected 3-manifold M and a root of unity ξ with the order of odd, we introduce the ρ-reduced skein module . We show that has dimension 1 when M is closed and ρ is irreducible. We also show that if ρ is irreducible the ρ-reduced skein module of a handlebody, as a module over the skein algebra of its boundary, is simple and has the dimension equal to the PI-degree of the skein algebra of its boundary.
{"title":"Sliced skein algebras and geometric Kauffman bracket","authors":"Charles D. Frohman , Joanna Kania-Bartoszynska , Thang T.Q. Lê","doi":"10.1016/j.aim.2025.110118","DOIUrl":"10.1016/j.aim.2025.110118","url":null,"abstract":"<div><div>The sliced skein algebra of a closed surface of genus <em>g</em> with <em>m</em> punctures, <span><math><mi>S</mi><mo>=</mo><msub><mrow><mi>Σ</mi></mrow><mrow><mi>g</mi><mo>,</mo><mi>m</mi></mrow></msub></math></span>, is the quotient of the Kauffman bracket skein algebra <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>ξ</mi></mrow></msub><mo>(</mo><mi>S</mi><mo>)</mo></math></span> corresponding to fixing the scalar values of its peripheral curves. We show that the sliced skein algebra of a finite type surface is a domain if the ground ring is a domain. When the quantum parameter <em>ξ</em> is a root of unity we calculate the center of the sliced skein algebra and its PI-degree. Among applications we show that any smooth point of a sliced character variety is an Azumaya point of the skein algebra <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>ξ</mi></mrow></msub><mo>(</mo><mi>S</mi><mo>)</mo></math></span>.</div><div>For any <span><math><mi>S</mi><msub><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span>-representation <em>ρ</em> of the fundamental group of an oriented connected 3-manifold <em>M</em> and a root of unity <em>ξ</em> with the order of <span><math><msup><mrow><mi>ξ</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> odd, we introduce the <em>ρ</em>-reduced skein module <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>ξ</mi><mo>,</mo><mi>ρ</mi></mrow></msub><mo>(</mo><mi>M</mi><mo>)</mo></math></span>. We show that <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>ξ</mi><mo>,</mo><mi>ρ</mi></mrow></msub><mo>(</mo><mi>M</mi><mo>)</mo></math></span> has dimension 1 when <em>M</em> is closed and <em>ρ</em> is irreducible. We also show that if <em>ρ</em> is irreducible the <em>ρ</em>-reduced skein module of a handlebody, as a module over the skein algebra of its boundary, is simple and has the dimension equal to the PI-degree of the skein algebra of its boundary.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"463 ","pages":"Article 110118"},"PeriodicalIF":1.5,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.aim.2025.110128
Benjamin Enriquez , Hidekazu Furusho
In earlier work, we constructed a pair of “Betti” and “de Rham” Hopf algebras and a pair of module-coalgebras over this pair, as well as the bitorsors related to both structures (which will be called the “module” and “algebra” stabilizer bitorsors). We showed that Racinet's torsor constructed out of the double shuffle and regularization relations between multiple zeta values is essentially equal to the “module” stabilizer bitorsor, and that the latter is contained in the “algebra” stabilizer bitorsor. In this paper, we show the equality of the “algebra” and “module” stabilizer bitorsors. We reduce the proof to showing the equality of the associated “algebra” and “module” graded Lie algebras. The argument for showing this equality involves the relation of the “algebra” Lie algebra with the kernel of a linear map, the expression of this linear map as a composition of three linear maps, the relation of one of them with the “module” Lie algebra and the computation of the kernel of the other one by discrete topology arguments.
{"title":"The stabilizer bitorsors of the module and algebra harmonic coproducts are equal","authors":"Benjamin Enriquez , Hidekazu Furusho","doi":"10.1016/j.aim.2025.110128","DOIUrl":"10.1016/j.aim.2025.110128","url":null,"abstract":"<div><div>In earlier work, we constructed a pair of “Betti” and “de Rham” Hopf algebras and a pair of module-coalgebras over this pair, as well as the bitorsors related to both structures (which will be called the “module” and “algebra” stabilizer bitorsors). We showed that Racinet's torsor constructed out of the double shuffle and regularization relations between multiple zeta values is essentially equal to the “module” stabilizer bitorsor, and that the latter is contained in the “algebra” stabilizer bitorsor. In this paper, we show the equality of the “algebra” and “module” stabilizer bitorsors. We reduce the proof to showing the equality of the associated “algebra” and “module” graded Lie algebras. The argument for showing this equality involves the relation of the “algebra” Lie algebra with the kernel of a linear map, the expression of this linear map as a composition of three linear maps, the relation of one of them with the “module” Lie algebra and the computation of the kernel of the other one by discrete topology arguments.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"463 ","pages":"Article 110128"},"PeriodicalIF":1.5,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.aim.2025.110126
Klaus Hulek , Yota Maeda
The moduli space of 8 points on , a so-called ancestral Deligne-Mostow space, is, by work of Kondō, also a moduli space of K3 surfaces. We prove that the Deligne-Mostow isomorphism does not lift to a morphism between the Kirwan blow-up of the GIT quotient and the unique toroidal compactification of the corresponding ball quotient. Moreover, we show that these spaces are not K-equivalent, even though they are natural blow-ups at the unique cusps and have the same cohomology. This is analogous to the work of Casalaina-Martin-Grushevsky-Hulek-Laza on the moduli space of cubic surfaces. The moduli spaces of ordinary stable maps, that is the Fulton-MacPherson compactification of the configuration space of points on , play an important role in the proof. We further relate our computations to new developments in the minimal model program and the recent work of Odaka. We briefly discuss other cases of moduli space of points on where a similar behaviour can be observed, hinting at a more general, but not yet fully understood phenomenon.
{"title":"Revisiting the moduli space of 8 points on P1","authors":"Klaus Hulek , Yota Maeda","doi":"10.1016/j.aim.2025.110126","DOIUrl":"10.1016/j.aim.2025.110126","url":null,"abstract":"<div><div>The moduli space of 8 points on <span><math><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup></math></span>, a so-called ancestral Deligne-Mostow space, is, by work of Kondō, also a moduli space of K3 surfaces. We prove that the Deligne-Mostow isomorphism does not lift to a morphism between the Kirwan blow-up of the GIT quotient and the unique toroidal compactification of the corresponding ball quotient. Moreover, we show that these spaces are not <em>K</em>-equivalent, even though they are natural blow-ups at the unique cusps and have the same cohomology. This is analogous to the work of Casalaina-Martin-Grushevsky-Hulek-Laza on the moduli space of cubic surfaces. The moduli spaces of ordinary stable maps, that is the Fulton-MacPherson compactification of the configuration space of points on <span><math><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup></math></span>, play an important role in the proof. We further relate our computations to new developments in the minimal model program and the recent work of Odaka. We briefly discuss other cases of moduli space of points on <span><math><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup></math></span> where a similar behaviour can be observed, hinting at a more general, but not yet fully understood phenomenon.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"463 ","pages":"Article 110126"},"PeriodicalIF":1.5,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}