Volume 252 - December 2023
Latest volume of Nagoya Mathematical Journal
Contents
Article
A CATEGORIFICATION OF ACYCLIC PRINCIPAL COEFFICIENT CLUSTER ALGEBRAS
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- 22 February 2023, pp. 769-809
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In earlier work, the author introduced a method for constructing a Frobenius categorification of a cluster algebra with frozen variables by starting from the data of an internally Calabi–Yau algebra, which becomes the endomorphism algebra of a cluster-tilting object in the resulting category. In this paper, we construct appropriate internally Calabi–Yau algebras for cluster algebras with polarized principal coefficients (which differ from those with principal coefficients by the addition of more frozen variables) and obtain Frobenius categorifications in the acyclic case. Via partial stabilization, we then define extriangulated categories, in the sense of Nakaoka and Palu, categorifying acyclic principal coefficient cluster algebras, for which Frobenius categorifications do not exist in general. Many of the intermediate results used to obtain these categorifications remain valid without the acyclicity assumption, as we will indicate, and are interesting in their own right. Most notably, we provide a Frobenius version of Van den Bergh’s result that the Ginzburg dg-algebra of a quiver with potential is bimodule
$3$-Calabi–Yau.
KRONECKER LIMIT FUNCTIONS AND AN EXTENSION OF THE ROHRLICH–JENSEN FORMULA
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- 11 April 2023, pp. 810-841
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In [20], Rohrlich proved a modular analog of Jensen’s formula. Under certain conditions, the Rohrlich–Jensen formula expresses an integral of the log-norm
$\log \Vert f \Vert $ of a 
${\mathrm {PSL}}(2,{\mathbb {Z}})$ modular form f in terms of the Dedekind Delta function evaluated at the divisor of f. In [2], the authors re-interpreted the Rohrlich–Jensen formula as evaluating a regularized inner product of 
$\log \Vert f \Vert $ and extended the result to compute a regularized inner product of 
$\log \Vert f \Vert $ with what amounts to powers of the Hauptmodul of 
$\mathrm {PSL}(2,{\mathbb {Z}})$. In the present article, we revisit the Rohrlich–Jensen formula and prove that in the case of any Fuchsian group of the first kind with one cusp it can be viewed as a regularized inner product of special values of two Poincaré series, one of which is the Niebur–Poincaré series and the other is the resolvent kernel of the Laplacian. The regularized inner product can be seen as a type of Maass–Selberg relation. In this form, we develop a Rohrlich–Jensen formula associated with any Fuchsian group 
$\Gamma $ of the first kind with one cusp by employing a type of Kronecker limit formula associated with the resolvent kernel. We present two examples of our main result: First, when 
$\Gamma $ is the full modular group 
${\mathrm {PSL}}(2,{\mathbb {Z}})$, thus reproving the theorems from [2]; and second when 
$\Gamma $ is an Atkin–Lehner group 
$\Gamma _{0}(N)^+$, where explicit computations of inner products are given for certain levels N when the quotient space 
$\overline {\Gamma _{0}(N)^+}\backslash \mathbb {H}$ has genus zero, one, and two.
CONCAVITY PROPERTY OF MINIMAL
$L^{2}$ INTEGRALS WITH LEBESGUE MEASURABLE GAIN
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- 05 June 2023, pp. 842-905
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In this article, we present a concavity property of the minimal
$L^{2}$ integrals related to multiplier ideal sheaves with Lebesgue measurable gain. As applications, we give necessary conditions for our concavity degenerating to linearity, characterizations for 1-dimensional case, and a characterization for the holding of the equality in optimal 
$L^2$ extension problem on open Riemann surfaces with weights may not be subharmonic.
EXTENSIONS OF CHARACTERS IN TYPE D AND THE INDUCTIVE MCKAY CONDITION, I
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- 08 September 2023, pp. 906-958
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This is a contribution to the study of
$\mathrm {Irr}(G)$ as an 
$\mathrm {Aut}(G)$-set for G a finite quasisimple group. Focusing on the last open case of groups of Lie type 
$\mathrm {D}$ and 
$^2\mathrm {D}$, a crucial property is the so-called 
$A'(\infty )$ condition expressing that diagonal automorphisms and graph-field automorphisms of G have transversal orbits in 
$\mathrm {Irr}(G)$. This is part of the stronger 
$A(\infty )$ condition introduced in the context of the reduction of the McKay conjecture to a question about quasisimple groups. Our main theorem is that a minimal counterexample to condition 
$A(\infty )$ for groups of type 
$\mathrm {D}$ would still satisfy 
$A'(\infty )$. This will be used in a second paper to fully establish 
$A(\infty )$ for any type and rank. The present paper uses Harish-Chandra induction as a parametrization tool. We give a new, more effective proof of the theorem of Geck and Lusztig ensuring that cuspidal characters of any standard Levi subgroup of 
$G=\mathrm {D}_{ l,\mathrm {sc}}(q)$ extend to their stabilizers in the normalizer of that Levi subgroup. This allows us to control the action of automorphisms on these extensions. From there, Harish-Chandra theory leads naturally to a detailed study of associated relative Weyl groups and other extendibility problems in that context.
$\tau $-PERPENDICULAR WIDE SUBCATEGORIES
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- 22 August 2023, pp. 959-984
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Let
$\Lambda $ be a finite-dimensional algebra. A wide subcategory of 
$\mathsf {mod}\Lambda $ is called left finite if the smallest torsion class containing it is functorially finite. In this article, we prove that the wide subcategories of 
$\mathsf {mod}\Lambda $ arising from 
$\tau $-tilting reduction are precisely the Serre subcategories of left-finite wide subcategories. As a consequence, we show that the class of such subcategories is closed under further 
$\tau $-tilting reduction. This leads to a natural way to extend the definition of the “
$\tau $-cluster morphism category” of 
$\Lambda $ to arbitrary finite-dimensional algebras. This category was recently constructed by Buan–Marsh in the 
$\tau $-tilting finite case and by Igusa–Todorov in the hereditary case.
Erratum
ERRATUM TO “NON-UNIFORMLY FLAT AFFINE ALGEBRAIC HYPERSURFACES”
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- 06 June 2023, pp. 985-989
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In this erratum, we correct an erroneous result in [PV2] and prove that the affine algebraic hypersurfaces
$xy^2=1$ and 
$z=xy^2$ are not interpolating with respect to the Gaussian weight.
Front Cover (OFC, IFC) and matter
NMJ volume 252 Cover and Front matter
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- 31 October 2023, pp. f1-f3
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Back Cover (OBC, IBC) and matter
NMJ volume 252 Cover and Back matter
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- 31 October 2023, pp. b1-b2
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