Pub Date : 2026-04-01Epub Date: 2025-12-04DOI: 10.1016/j.jalgebra.2025.12.005
Xin Lü , Peng Sun
Let be a non-trivial semi-stable fibration of genus with s singular fibers over the complex numbers. Tan conjectured that if . We study this conjecture for irregular surfaces. More precisely, we prove that if the irregularity .
{"title":"Tan's conjecture on irregular family over P1","authors":"Xin Lü , Peng Sun","doi":"10.1016/j.jalgebra.2025.12.005","DOIUrl":"10.1016/j.jalgebra.2025.12.005","url":null,"abstract":"<div><div>Let <span><math><mi>f</mi><mo>:</mo><mspace></mspace><mi>S</mi><mo>→</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup></math></span> be a non-trivial semi-stable fibration of genus <span><math><mi>g</mi><mo>≥</mo><mn>2</mn></math></span> with <em>s</em> singular fibers over the complex numbers. Tan conjectured that <span><math><mi>s</mi><mo>≥</mo><mn>6</mn></math></span> if <span><math><mi>g</mi><mo>≫</mo><mn>0</mn></math></span>. We study this conjecture for irregular surfaces. More precisely, we prove that <span><math><mi>s</mi><mo>≥</mo><mn>6</mn></math></span> if the irregularity <span><math><mi>q</mi><mo>(</mo><mi>S</mi><mo>)</mo><mo>≥</mo><mn>2</mn></math></span>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 488-503"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733659","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 : 2026-04-01Epub Date: 2025-12-05DOI: 10.1016/j.jalgebra.2025.11.019
Dmitriy Voloshyn
We study the decomposition of a generic element of a connected reductive complex algebraic group G in the form where and are rational maps onto a unipotent subgroup and a Borel subgroup opposite to , and is a representative of a Weyl group element u. We introduce a class of rational Weyl group elements that give rise to such decompositions, and study their various properties.
{"title":"Multiple rational normal forms in Lie theory","authors":"Dmitriy Voloshyn","doi":"10.1016/j.jalgebra.2025.11.019","DOIUrl":"10.1016/j.jalgebra.2025.11.019","url":null,"abstract":"<div><div>We study the decomposition of a generic element <span><math><mi>g</mi><mo>∈</mo><mi>G</mi></math></span> of a connected reductive complex algebraic group <em>G</em> in the form <span><math><mi>g</mi><mo>=</mo><mi>N</mi><mo>(</mo><mi>g</mi><mo>)</mo><mi>B</mi><mo>(</mo><mi>g</mi><mo>)</mo><mover><mrow><mi>u</mi></mrow><mrow><mo>¯</mo></mrow></mover><mi>N</mi><msup><mrow><mo>(</mo><mi>g</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> where <span><math><mi>N</mi><mo>:</mo><mi>G</mi><mo>⇢</mo><msub><mrow><mi>N</mi></mrow><mrow><mo>−</mo></mrow></msub></math></span> and <span><math><mi>B</mi><mo>:</mo><mi>G</mi><mo>⇢</mo><msub><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msub></math></span> are rational maps onto a unipotent subgroup <span><math><msub><mrow><mi>N</mi></mrow><mrow><mo>−</mo></mrow></msub></math></span> and a Borel subgroup <span><math><msub><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msub></math></span> opposite to <span><math><msub><mrow><mi>N</mi></mrow><mrow><mo>−</mo></mrow></msub></math></span>, and <span><math><mover><mrow><mi>u</mi></mrow><mrow><mo>¯</mo></mrow></mover></math></span> is a representative of a Weyl group element <em>u</em>. We introduce a class of rational Weyl group elements that give rise to such decompositions, and study their various properties.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 453-487"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733660","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 : 2026-04-01Epub Date: 2025-12-04DOI: 10.1016/j.jalgebra.2025.11.025
P.S. Kolesnikov , B.K. Sartayev
The classical Dong Lemma for distributions over a Lie algebra lies in the foundation of the theory of vertex and conformal algebras. In this paper, we find necessary and sufficient condition for a variety of nonassociative algebras with binary operations to satisfy the analogue of the Dong Lemma. In particular, it turns out that for alternative, Novikov, and Novikov–Poisson algebras the Dong Lemma holds true. The criterion is stated in the language of operads, so we determine for which binary quadratic operads the Dong Lemma holds in the corresponding class of algebras. As an application, we show the black Manin product of such Dong operads is also a Dong operad.
{"title":"On the Dong Property for a binary quadratic operad","authors":"P.S. Kolesnikov , B.K. Sartayev","doi":"10.1016/j.jalgebra.2025.11.025","DOIUrl":"10.1016/j.jalgebra.2025.11.025","url":null,"abstract":"<div><div>The classical Dong Lemma for distributions over a Lie algebra lies in the foundation of the theory of vertex and conformal algebras. In this paper, we find necessary and sufficient condition for a variety of nonassociative algebras with binary operations to satisfy the analogue of the Dong Lemma. In particular, it turns out that for alternative, Novikov, and Novikov–Poisson algebras the Dong Lemma holds true. The criterion is stated in the language of operads, so we determine for which binary quadratic operads the Dong Lemma holds in the corresponding class of algebras. As an application, we show the black Manin product of such Dong operads is also a Dong operad.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 428-452"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733662","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 : 2026-04-01Epub Date: 2025-12-05DOI: 10.1016/j.jalgebra.2025.11.032
Clara Franchi , Mario Mainardis
We use Majorana representations to study the subalgebras of the Griess algebra that have shape and whose associated Miyamoto groups are isomorphic to . We prove that these subalgebras exist only if . The case was already treated by Ivanov, Seress, McInroy, and Shpectorov. In case we prove that these algebras are all isomorphic and provide their precise description. In case we prove that these algebras do not arise from standard Majorana representations.
{"title":"On subalgebras of the Griess algebra with alternating Miyamoto group","authors":"Clara Franchi , Mario Mainardis","doi":"10.1016/j.jalgebra.2025.11.032","DOIUrl":"10.1016/j.jalgebra.2025.11.032","url":null,"abstract":"<div><div>We use Majorana representations to study the subalgebras of the Griess algebra that have shape <span><math><mo>(</mo><mn>2</mn><mi>B</mi><mo>,</mo><mn>3</mn><mi>A</mi><mo>,</mo><mn>5</mn><mi>A</mi><mo>)</mo></math></span> and whose associated Miyamoto groups are isomorphic to <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>. We prove that these subalgebras exist only if <span><math><mi>n</mi><mo>∈</mo><mo>{</mo><mn>5</mn><mo>,</mo><mn>6</mn><mo>,</mo><mn>8</mn><mo>}</mo></math></span>. The case <span><math><mi>n</mi><mo>=</mo><mn>5</mn></math></span> was already treated by Ivanov, Seress, McInroy, and Shpectorov. In case <span><math><mi>n</mi><mo>=</mo><mn>6</mn></math></span> we prove that these algebras are all isomorphic and provide their precise description. In case <span><math><mi>n</mi><mo>=</mo><mn>8</mn></math></span> we prove that these algebras do not arise from standard Majorana representations.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 811-854"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733717","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 : 2026-04-01Epub Date: 2025-11-20DOI: 10.1016/j.jalgebra.2025.11.017
Alessandro Contu
In 2021, Kashiwara–Kim–Oh–Park constructed cluster algebra structures on the Grothendieck rings of certain monoidal subcategories of the category of finite-dimensional representations of a quantum loop algebra, generalizing Hernandez–Leclerc's pioneering work from 2010. They stated the problem of finding explicit quivers for the seeds they used. We provide a solution by using Palu's generalized mutation rule applied to the cluster categories associated with certain algebras of global dimension at most 2, for example tensor products of path algebras of representation-finite quivers. Thus, our method is based on (and contributes to) the bridge, provided by cluster combinatorics, between the representation theory of quantum groups and that of quivers with relations.
{"title":"Solution of a problem in monoidal categorification by additive categorification","authors":"Alessandro Contu","doi":"10.1016/j.jalgebra.2025.11.017","DOIUrl":"10.1016/j.jalgebra.2025.11.017","url":null,"abstract":"<div><div>In 2021, Kashiwara–Kim–Oh–Park constructed cluster algebra structures on the Grothendieck rings of certain monoidal subcategories of the category of finite-dimensional representations of a quantum loop algebra, generalizing Hernandez–Leclerc's pioneering work from 2010. They stated the problem of finding explicit quivers for the seeds they used. We provide a solution by using Palu's generalized mutation rule applied to the cluster categories associated with certain algebras of global dimension at most 2, for example tensor products of path algebras of representation-finite quivers. Thus, our method is based on (and contributes to) the bridge, provided by cluster combinatorics, between the representation theory of quantum groups and that of quivers with relations.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 128-185"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145616566","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 : 2026-04-01Epub Date: 2025-11-15DOI: 10.1016/j.jalgebra.2025.10.049
Satoshi Naito , Yujin Suzuki , Hideya Watanabe
The Naito–Sagaki conjecture asserts that the branching rule for the restriction of finite-dimensional, irreducible polynomial representations of to amounts to the enumeration of certain “rational paths” satisfying specific conditions. This conjecture can be thought of as a non-Levi type analog of the Levi type branching rule, stated in terms of the path model due to Littelmann, and was proved combinatorially in 2018 by Schumann–Torres. In this paper, we give a new proof of the Naito–Sagaki conjecture independently of Schumann–Torres, using the branching rule based on the crystal basis theory for ıquantum groups of type . Here, note that ıquantum groups are certain coideal subalgebras of a quantized universal enveloping algebra obtained by q-deforming symmetric pairs, and also regarded as a generalization of quantized universal enveloping algebras; these were defined by Letzter in 1999, and since then their representation theory has become an active area of research. The main ingredients of our approach are certain combinatorial operations, such as promotion operators and Kashiwara operators, which are well-suited to the representation theory of complex semisimple Lie algebras.
{"title":"A proof of the Naito–Sagaki conjecture via the branching rule for ıquantum groups","authors":"Satoshi Naito , Yujin Suzuki , Hideya Watanabe","doi":"10.1016/j.jalgebra.2025.10.049","DOIUrl":"10.1016/j.jalgebra.2025.10.049","url":null,"abstract":"<div><div>The Naito–Sagaki conjecture asserts that the branching rule for the restriction of finite-dimensional, irreducible polynomial representations of <span><math><mi>G</mi><msub><mrow><mi>L</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span> to <span><math><mi>S</mi><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span> amounts to the enumeration of certain “rational paths” satisfying specific conditions. This conjecture can be thought of as a non-Levi type analog of the Levi type branching rule, stated in terms of the path model due to Littelmann, and was proved combinatorially in 2018 by Schumann–Torres. In this paper, we give a new proof of the Naito–Sagaki conjecture independently of Schumann–Torres, using the branching rule based on the crystal basis theory for <em>ı</em>quantum groups of type <span><math><mi>A</mi><msub><mrow><mi>II</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub></math></span>. Here, note that <em>ı</em>quantum groups are certain coideal subalgebras of a quantized universal enveloping algebra obtained by <em>q</em>-deforming symmetric pairs, and also regarded as a generalization of quantized universal enveloping algebras; these were defined by Letzter in 1999, and since then their representation theory has become an active area of research. The main ingredients of our approach are certain combinatorial operations, such as promotion operators and Kashiwara operators, which are well-suited to the representation theory of complex semisimple Lie algebras.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 32-87"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145616988","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 : 2026-04-01Epub Date: 2025-12-08DOI: 10.1016/j.jalgebra.2025.12.001
Shengkai Mao
Let be an isogeny between linear algebraic groups over a number field E, S be a finite set of places of E. In this note, we give some criteria for when a S-congruence subgroup of has S-congruence image in following [7].
{"title":"Isogenies and congruence subgroups","authors":"Shengkai Mao","doi":"10.1016/j.jalgebra.2025.12.001","DOIUrl":"10.1016/j.jalgebra.2025.12.001","url":null,"abstract":"<div><div>Let <span><math><mi>π</mi><mo>:</mo><mi>G</mi><mo>→</mo><mi>H</mi></math></span> be an isogeny between linear algebraic groups over a number field <em>E</em>, <em>S</em> be a finite set of places of <em>E</em>. In this note, we give some criteria for when a <em>S</em>-congruence subgroup of <span><math><mi>G</mi><mo>(</mo><mi>E</mi><mo>)</mo></math></span> has <em>S</em>-congruence image in <span><math><mi>H</mi><mo>(</mo><mi>E</mi><mo>)</mo></math></span> following <span><span>[7]</span></span>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 781-810"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733716","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 : 2026-04-01Epub Date: 2025-11-20DOI: 10.1016/j.jalgebra.2025.10.054
Jiuzhao Hua
Kac's conjecture, now a theorem, asserts that the polynomial which counts the isomorphism classes of absolutely indecomposable representations of a quiver over a finite field, for any given dimension vector, has only non-negative integer coefficients. In this paper, we provide a refinement of the Kac polynomial for quivers with enough loops, expressing it as a sum of refined Kac polynomials indexed by tuples of partitions. These refined polynomials also have non-negative integer coefficients. We conclude by suggesting several avenues for future research.
{"title":"Refined Kac polynomials for quivers with enough loops","authors":"Jiuzhao Hua","doi":"10.1016/j.jalgebra.2025.10.054","DOIUrl":"10.1016/j.jalgebra.2025.10.054","url":null,"abstract":"<div><div>Kac's conjecture, now a theorem, asserts that the polynomial which counts the isomorphism classes of absolutely indecomposable representations of a quiver over a finite field, for any given dimension vector, has only non-negative integer coefficients. In this paper, we provide a refinement of the Kac polynomial for quivers with enough loops, expressing it as a sum of refined Kac polynomials indexed by tuples of partitions. These refined polynomials also have non-negative integer coefficients. We conclude by suggesting several avenues for future research.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 292-309"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682381","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 : 2026-04-01Epub Date: 2025-12-02DOI: 10.1016/j.jalgebra.2025.10.056
Xin Huang
We introduce a new type of equivalence between blocks of finite group algebras called an almost isotypy. An almost isotypy restricts to a weak isotypy in Broué's original definition [8, Définition 4.6], and it is slightly weaker than Linckelmann's version [17, Definition 9.5.1]. We show that a bimodule of two block algebras of finite groups - which has an endopermutation module as a source and which induces a Morita equivalence - gives rise, via slash functors, to an almost isotypy if the character values of a (hence any) source are rational integers. Consequently, if two blocks are Morita equivalent via a bimodule with endopermutation source, then they are almost isotypic. We also explain why the notion of almost isotypies is reasonable.
{"title":"On Morita equivalences with endopermutation source and isotypies","authors":"Xin Huang","doi":"10.1016/j.jalgebra.2025.10.056","DOIUrl":"10.1016/j.jalgebra.2025.10.056","url":null,"abstract":"<div><div>We introduce a new type of equivalence between blocks of finite group algebras called an <em>almost isotypy</em>. An almost isotypy restricts to a weak isotypy in Broué's original definition <span><span>[8, Définition 4.6]</span></span>, and it is slightly weaker than Linckelmann's version <span><span>[17, Definition 9.5.1]</span></span>. We show that a bimodule of two block algebras of finite groups - which has an endopermutation module as a source and which induces a Morita equivalence - gives rise, via slash functors, to an almost isotypy if the character values of a (hence any) source are rational integers. Consequently, if two blocks are Morita equivalent via a bimodule with endopermutation source, then they are almost isotypic. We also explain why the notion of almost isotypies is reasonable.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 376-408"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682384","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 : 2026-04-01Epub Date: 2025-12-03DOI: 10.1016/j.jalgebra.2025.10.059
Arpan Dutta, Rumi Ghosh
Let be a valued field. Take an extension of v to a fixed algebraic closure of K. In this paper we show that an element admits a complete distinguished chain over K if and only if the extension is unibranched and defectless. This characterization generalizes the known result in the henselian case. In particular, our result shows that if a admits a complete distinguished chain over K, then it also admits one over the henselization ; however the converse may not be true. The main tool employed in our analysis is the stability of the j-invariant associated to a valuation transcendental extension under passage to the henselization.
We also explore the stability of defectless simple extensions in the following sense: let be a valuation transcendental extension with a pair of definition . Assume that either is a defectless extension, or that is a key polynomial for , where is the minimal polynomial of b over K. We show that then the extension is defectless. In particular, the extension is always defectless whenever is a minimal pair of definition for w over K.
{"title":"On defectless unibranched simple extensions, complete distinguished chains and certain stability results","authors":"Arpan Dutta, Rumi Ghosh","doi":"10.1016/j.jalgebra.2025.10.059","DOIUrl":"10.1016/j.jalgebra.2025.10.059","url":null,"abstract":"<div><div>Let <span><math><mo>(</mo><mi>K</mi><mo>,</mo><mi>v</mi><mo>)</mo></math></span> be a valued field. Take an extension of <em>v</em> to a fixed algebraic closure <span><math><mover><mrow><mi>K</mi></mrow><mo>‾</mo></mover></math></span> of <em>K</em>. In this paper we show that an element <span><math><mi>a</mi><mo>∈</mo><mover><mrow><mi>K</mi></mrow><mo>‾</mo></mover></math></span> admits a complete distinguished chain over <em>K</em> if and only if the extension <span><math><mo>(</mo><mi>K</mi><mo>(</mo><mi>a</mi><mo>)</mo><mo>|</mo><mi>K</mi><mo>,</mo><mi>v</mi><mo>)</mo></math></span> is unibranched and defectless. This characterization generalizes the known result in the henselian case. In particular, our result shows that if <em>a</em> admits a complete distinguished chain over <em>K</em>, then it also admits one over the henselization <span><math><msup><mrow><mi>K</mi></mrow><mrow><mi>h</mi></mrow></msup></math></span>; however the converse may not be true. The main tool employed in our analysis is the stability of the <em>j</em>-invariant associated to a valuation transcendental extension under passage to the henselization.</div><div>We also explore the stability of defectless simple extensions in the following sense: let <span><math><mo>(</mo><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo><mo>|</mo><mi>K</mi><mo>,</mo><mi>w</mi><mo>)</mo></math></span> be a valuation transcendental extension with a pair of definition <span><math><mo>(</mo><mi>b</mi><mo>,</mo><mi>γ</mi><mo>)</mo></math></span>. Assume that either <span><math><mo>(</mo><mi>K</mi><mo>(</mo><mi>b</mi><mo>)</mo><mo>|</mo><mi>K</mi><mo>,</mo><mi>v</mi><mo>)</mo></math></span> is a defectless extension, or that <span><math><mi>f</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is a key polynomial for <span><math><mo>(</mo><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo><mo>|</mo><mi>K</mi><mo>,</mo><mi>w</mi><mo>)</mo></math></span>, where <span><math><mi>f</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is the minimal polynomial of <em>b</em> over <em>K</em>. We show that then the extension <span><math><mo>(</mo><mi>K</mi><mo>(</mo><mi>b</mi><mo>,</mo><mi>X</mi><mo>)</mo><mo>|</mo><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo><mo>,</mo><mi>w</mi><mo>)</mo></math></span> is defectless. In particular, the extension <span><math><mo>(</mo><mi>K</mi><mo>(</mo><mi>b</mi><mo>,</mo><mi>X</mi><mo>)</mo><mo>|</mo><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo><mo>,</mo><mi>w</mi><mo>)</mo></math></span> is always defectless whenever <span><math><mo>(</mo><mi>b</mi><mo>,</mo><mi>γ</mi><mo>)</mo></math></span> is a minimal pair of definition for <em>w</em> over <em>K</em>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 352-375"},"PeriodicalIF":0.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682385","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}