{"title":"A geometric characterization of toric singularities","authors":"Joaquin Moraga , Roberto Svaldi","doi":"10.1016/j.matpur.2024.103620","DOIUrl":"10.1016/j.matpur.2024.103620","url":null,"abstract":"<div><div>Given a projective contraction <span><math><mi>π</mi><mo>:</mo><mi>X</mi><mo>→</mo><mi>Z</mi></math></span> and a log canonical pair <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>B</mi><mo>)</mo></math></span> such that <span><math><mo>−</mo><mo>(</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>X</mi></mrow></msub><mo>+</mo><mi>B</mi><mo>)</mo></math></span> is nef over a neighborhood of a closed point <span><math><mi>z</mi><mo>∈</mo><mi>Z</mi></math></span>, one can define an invariant, the complexity of <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>B</mi><mo>)</mo></math></span> over <span><math><mi>z</mi><mo>∈</mo><mi>Z</mi></math></span>, comparing the dimension of <em>X</em> and the relative Picard number of <span><math><mi>X</mi><mo>/</mo><mi>Z</mi></math></span> with the sum of the coefficients of those components of <em>B</em> intersecting the fiber over <em>z</em>. We prove that, in the hypotheses above, the complexity of the log pair <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>B</mi><mo>)</mo></math></span> over <span><math><mi>z</mi><mo>∈</mo><mi>Z</mi></math></span> is non-negative and that when it is zero then <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mo>⌊</mo><mi>B</mi><mo>⌋</mo><mo>)</mo><mo>→</mo><mi>Z</mi></math></span> is formally isomorphic to a morphism of toric varieties around <span><math><mi>z</mi><mo>∈</mo><mi>Z</mi></math></span>. In particular, considering the case when <em>π</em> is the identity morphism, we get a geometric characterization of singularities that are formally isomorphic to toric singularities, thus resolving a conjecture due to Shokurov.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"195 ","pages":"Article 103620"},"PeriodicalIF":2.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143155111","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}
{"title":"A mean curvature flow arising in adversarial training","authors":"Leon Bungert , Tim Laux , Kerrek Stinson","doi":"10.1016/j.matpur.2024.103625","DOIUrl":"10.1016/j.matpur.2024.103625","url":null,"abstract":"<div><div>We connect adversarial training for binary classification to a geometric evolution equation for the decision boundary. Relying on a perspective that recasts adversarial training as a regularization problem, we introduce a modified training scheme that constitutes a minimizing movements scheme for a nonlocal perimeter functional. We prove that the scheme is monotone and consistent as the adversarial budget vanishes and the perimeter localizes, and as a consequence we rigorously show that the scheme approximates a weighted mean curvature flow. This highlights that the efficacy of adversarial training may be due to locally minimizing the length of the decision boundary. In our analysis, we introduce a variety of tools for working with the subdifferential of a supremal-type nonlocal total variation and its regularity properties.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"192 ","pages":"Article 103625"},"PeriodicalIF":2.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659252","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}
Charles Bertucci , Jean-Michel Lasry , Pierre-Louis Lions
{"title":"A spectral dominance approach to large random matrices: Part II","authors":"Charles Bertucci , Jean-Michel Lasry , Pierre-Louis Lions","doi":"10.1016/j.matpur.2024.103630","DOIUrl":"10.1016/j.matpur.2024.103630","url":null,"abstract":"<div><div>This paper is the second of a series devoted to the study of the dynamics of the spectrum of large random matrices. We precise and extend some results of the first part. We study general extensions of the partial differential equation arising to characterize the limit spectral measure of the Dyson Brownian motion. We provide a regularizing result for those generalizations. We also show that several results of part I extend to cases in which there is no spectral dominance property. We then provide several modeling extensions of such models as well as several identities for the Dyson Brownian motion.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"192 ","pages":"Article 103630"},"PeriodicalIF":2.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700825","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}
Bruno Colbois , Corentin Léna , Luigi Provenzano , Alessandro Savo
{"title":"A reverse Faber-Krahn inequality for the magnetic Laplacian","authors":"Bruno Colbois , Corentin Léna , Luigi Provenzano , Alessandro Savo","doi":"10.1016/j.matpur.2024.103632","DOIUrl":"10.1016/j.matpur.2024.103632","url":null,"abstract":"<div><div>We consider the first eigenvalue of the magnetic Laplacian in a bounded and simply connected planar domain, with uniform magnetic field and Neumann boundary conditions. We investigate the reverse Faber-Krahn inequality conjectured by S. Fournais and B. Helffer, stating that this eigenvalue is maximized by the disk for a given area. Using the method of level lines, we prove the conjecture for small enough values of the magnetic field (those for which the corresponding eigenfunction in the disk is radial).</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"192 ","pages":"Article 103632"},"PeriodicalIF":2.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659251","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}
{"title":"Monotonicity, asymptotics and level sets for principal eigenvalues of some elliptic operators with shear flow","authors":"Shuang Liu , Yuan Lou","doi":"10.1016/j.matpur.2024.103622","DOIUrl":"10.1016/j.matpur.2024.103622","url":null,"abstract":"<div><div>We investigate the joint effects of diffusion and advection on principal eigenvalues of some elliptic operators with shear flow. Some monotonicity and asymptotic behaviors of principal eigenvalues, with respect to diffusion rate and flow amplitude, are established. These analyses lead to a classification of topological structures of level sets for principal eigenvalues, as a function of diffusion rate and flow amplitude. Our analytical results provide a unifying viewpoint to understand mixing enhancement and dispersal-induced growth, which are apparently two unrelated phenomena, one in fluid mechanics and the other in population dynamics. In our analysis, some limiting Hamilton-Jacobi equations, blowup argument and limiting generalized principal eigenvalue problems play critical roles.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"191 ","pages":"Article 103622"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655419","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}
{"title":"Optimal regularity for the 2D Euler equations in the Yudovich class","authors":"Nicola De Nitti , David Meyer , Christian Seis","doi":"10.1016/j.matpur.2024.103631","DOIUrl":"10.1016/j.matpur.2024.103631","url":null,"abstract":"<div><div>We analyze the optimal regularity that is exactly propagated by a transport equation driven by a velocity field with a BMO gradient. As an application, we study the 2D Euler equations in case the initial vorticity is bounded. The sharpness of our result for the Euler equations follows from a variation of Bahouri and Chemin's vortex patch example.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"191 ","pages":"Article 103631"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655671","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}
{"title":"New perspectives on categorical Torelli theorems for del Pezzo threefolds","authors":"Soheyla Feyzbakhsh , Zhiyu Liu , Shizhuo Zhang","doi":"10.1016/j.matpur.2024.103627","DOIUrl":"10.1016/j.matpur.2024.103627","url":null,"abstract":"<div><div>Let <span><math><msub><mrow><mi>Y</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span> be a del Pezzo threefold of Picard rank one and degree <span><math><mi>d</mi><mo>≥</mo><mn>2</mn></math></span>. In this paper, we apply two different viewpoints to study <span><math><msub><mrow><mi>Y</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span> via a particular admissible subcategory of its bounded derived category, called the Kuznetsov component:<ul><li><span>(i)</span><span><div>Brill–Noether reconstruction. We show that <span><math><msub><mrow><mi>Y</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span> can be uniquely recovered as a Brill–Noether locus of Bridgeland stable objects in its Kuznetsov component.</div></span></li><li><span>(ii)</span><span><div>Exact equivalences. We prove that up to composing with an explicit auto-equivalence, any Fourier–Mukai type equivalence of Kuznetsov components of two del Pezzo threefolds of degree <span><math><mn>2</mn><mo>≤</mo><mi>d</mi><mo>≤</mo><mn>4</mn></math></span> can be lifted to an equivalence of their bounded derived categories. As a result, we obtain a complete description of the group of Fourier–Mukai type auto-equivalences of the Kuznetsov component of <span><math><msub><mrow><mi>Y</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>.</div></span></li></ul></div><div>In an appendix, we classify instanton sheaves on quartic double solids, generalizing a result of Druel.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"191 ","pages":"Article 103627"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655418","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}
{"title":"Transition of the semiclassical resonance widths across a tangential crossing energy-level","authors":"Marouane Assal , Setsuro Fujiié , Kenta Higuchi","doi":"10.1016/j.matpur.2024.103634","DOIUrl":"10.1016/j.matpur.2024.103634","url":null,"abstract":"<div><div>We consider a 1D <span><math><mn>2</mn><mo>×</mo><mn>2</mn></math></span> matrix-valued operator <span><span>(1.1)</span></span> with two semiclassical Schrödinger operators on the diagonal entries and small interactions on the off-diagonal ones. When the two potentials cross at a turning point with contact order <em>n</em>, the corresponding two classical trajectories at the crossing level intersect at one point in the phase space with contact order 2<em>n</em>. Below this level, they have no intersection, which suggests exponentially small widths of resonances (see e.g., <span><span>[1]</span></span>, <span><span>[2]</span></span>), while above this level, on the contrary, they intersect at two points, which implies a polynomial order of the widths as proved in <span><span>[3]</span></span>. We prove that the transition of the resonance widths near the crossing level is described in terms of a generalized Airy function. This result generalizes <span><span>[4]</span></span> to the tangential crossing and <span><span>[3]</span></span> to the crossing at a turning point. Our approach is based on the computation of the microlocal transfer matrix at the crossing point between the incoming and outgoing microlocal solutions.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"191 ","pages":"Article 103634"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655424","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}
Paolo Antonelli , Pierangelo Marcati , Raffaele Scandone
{"title":"Existence and stability of almost finite energy weak solutions to the quantum Euler-Maxwell system","authors":"Paolo Antonelli , Pierangelo Marcati , Raffaele Scandone","doi":"10.1016/j.matpur.2024.103629","DOIUrl":"10.1016/j.matpur.2024.103629","url":null,"abstract":"<div><div>In this paper we prove the existence of global in time, finite energy weak solutions to the quantum magnetohydrodynamics (QMHD) system, for a large class of initial data that are slightly more regular than being of finite energy. No restriction is given on their size or the uniform positivity of the mass density. The QMHD system is a well-established model in superconductivity due to Feynman, and is intimately related to a nonlinear Maxwell-Schrödinger (NLMS) system via the Madelung transformations. The lack of global well-posedness (GWP) results for the NLMS system in the energy norm provides an obstruction to stability of its solutions, and consequently to the use of approximation arguments to make rigorous the Madelung approach. We implement here a new strategy, that derives weak solutions to QMHD starting from weak solutions to NLMS, by exploiting its Duhamel formulation. This derivation is rigorously justified by means of suitable dispersive/smoothing estimates for almost finite energy weak solutions to NLMS. The corresponding weak solutions to QMHD satisfy a generalized irrotationality condition, that allows for the presence of non-trivial vorticity (e.g., vortex filaments) concentrated in the vacuum region. This is in sharp contrast with the Euler-Maxwell system where the dispersion is not able to deal with the vorticity transport, therefore almost GWP (for regular solutions that are small perturbations of constant states) holds only in a lifespan, reciprocal of the size of the initial vorticity. Moreover, we also prove a stability property in the energy norm of the weak solutions constructed by our approach. This result follows from new local smoothing estimates for NLMS that are also of independent interest. As a byproduct, we also show the stability for the electromagnetic Lorentz force.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"191 ","pages":"Article 103629"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655421","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}
{"title":"The soliton resolution conjecture for the Boussinesq equation","authors":"C. Charlier , J. Lenells","doi":"10.1016/j.matpur.2024.103621","DOIUrl":"10.1016/j.matpur.2024.103621","url":null,"abstract":"<div><div>We analyze the Boussinesq equation on the line with Schwartz initial data belonging to the physically relevant class of global solutions. In a recent paper, we determined ten main asymptotic sectors describing the large <span><math><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo></math></span>-behavior of the solution, and for each of these sectors we provided the leading order asymptotics in the case when no solitons are present. In this paper, we give a formula valid in the asymptotic sector <span><math><mi>x</mi><mo>/</mo><mi>t</mi><mo>∈</mo><mo>(</mo><mn>1</mn><mo>,</mo><mi>M</mi><mo>]</mo></math></span>, where <em>M</em> is a large positive constant, in the case when solitons are present. Combined with earlier results, this validates the soliton resolution conjecture for the Boussinesq equation everywhere in the <span><math><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo></math></span>-plane except in a number of small transition zones.</div></div>","PeriodicalId":51071,"journal":{"name":"Journal de Mathematiques Pures et Appliquees","volume":"191 ","pages":"Article 103621"},"PeriodicalIF":2.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655423","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}