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Claude Sabbah

Publications and source records attributed to Claude Sabbah.

At least 55 records · Page 3Linked to original sources
arXiv2011

Flat meromorphic connections of Frobenius manifolds with tt*-structure

The base space of a semi-universal unfolding of a hypersurface singularity carries a rich geometric structure, which was axiomatized as a CDV-structure by C. Hertling. For any CDV-structure on a Frobenius manifold M, the pull-back of the (1,0)-tangent bundle of M to the product of M by the complex line carries two natural holomorphic structures equipped with flat meromorphic connections. We show that, for any semi-simple CDV-structure, there is a formal isomorphism between these two bundles compatible with connections. Moreover, if we assume that the super-symmetric index Q vanishes, we give a necessary and sufficient condition for such a formal isomorphism to be convergent, and we make it explicit for dim M = 2.

math.DG↗
arXiv2010

Une remarque sur l'article "Un théorème à la "Thom-Sebastiani" pour les intégrales-fibres" de D. Barlet

Dans cette note, nous donnons une autre démonstration du résultat démontré par D. Barlet dans http://aif.cedram.org/aif-bin/fitem?id=AIF_2010__60_1_319_0 (arXiv:0809.4981), en nous appuyant sur la transformation de Mellin et des propriétés classiques des fonctions de Bessel (au lieu de la convolution). Le théoréme principal de cette note est un peu plus précis que l'énoncé donné dans loc. cit. [English: In this article, we give another proof of the result shown by D. Barlet in http://aif.cedram.org/aif-bin/fitem?id=AIF_2010__60_1_319_0 (arXiv:0809.4981), relying on the Mellin transform and on classical properties of Bessel functions (instead of convolution). The main theorem of this note is somewhat more precise than the statement given in loc. cit.]

math.CV↗
arXiv2010

Examples of non-commutative Hodge structures

We show that if the Stokes matrix of a connection with a pole of order two and no ramification gives rise, when added to its adjoint, to a positive semi-definite Hermitian form, then the associated integrable twistor structure (or TERP structure, or non-commutative Hodge structure) is pure and polarized.

math.AG↗
arXiv2009

Fourier-Laplace transform of a variation of polarized complex Hodge structure, II

We show that the limit, by rescaling, of the `new supersymmetric index' attached to the Fourier-Laplace transform of a polarized variation of Hodge structure on a punctured affine line is equal to the spectral polynomial attached to the same object. We also extend the definition by Deligne of a Hodge filtration on the de Rham cohomology of a exponentially twisted polarized variation of complex Hodge structure and prove a E_1 degeneration property for it.

math.AG↗
arXiv2008

Wild twistor D-modules

We propose a definition of (polarized) wild twistor D-modules, generalizing to objects with irregular singularities that of (polarized) regular twistor D-modules. We give a precise analysis in dimension one.

math.AG↗
arXiv2008

Universal unfoldings of Laurent polynomials and tt* structures

This article surveys the relations between harmonic Higgs bundles and Saito structures which lead to tt* geometry on Frobenius manifolds. We give the main lines of the proof of the existence of a canonical tt* structure on the base space of the universal unfolding of convenient and nondegenerate Laurent polynomials.

math.AG↗
arXiv2007

Fourier-Laplace transform of irreducible regular differential systems on the Riemann sphere

We show that the Fourier-Laplace transform of an irreducible regular differential system on the Riemann sphere underlies, when one only considers the part at finite distance, a polarizable regular twistor $\mathcal{D}$-module. The associated holomorphic bundle out of the origin is therefore equipped with a natural harmonic metric with a tame behaviour near the origin.

math.AG↗
arXiv2007

Quantum cohomology of the Grassmannian and alternate Thom-Sebastiani

We introduce the notion of alternate product of Frobenius manifolds and we give, after [math.AG/0610265], an interpretation of the Frobenius manifold structure canonically attached to the quantum cohomology of G(r,n+1) in terms of alternate products. We also investigate the relationship with the alternate Thom-Sebastiani product of Laurent polynomials.

math.AG↗
arXiv2006

The Abelian/Nonabelian Correspondence and Frobenius Manifolds

We propose an approach via Frobenius manifolds to the study (began in math.AG/0407254) of the relation between rational Gromov-Witten invariants of nonabelian quotients X//G and those of the corresponding ``abelianized'' quotients X//T, for T a maximal torus in G. The ensuing conjecture expresses the Gromov-Witten potential of X//G in terms of the potential of X//T. We prove this conjecture when the nonabelian quotients are partial flag manifolds.

math.AG↗
arXiv2005

Polarizable twistor D-modules

We prove a Decomposition Theorem for the direct image of an irreducible local system on a smooth complex projective variety under a morphism with values in another smooth complex projective variety. For this purpose, we construct a category of polarized twistor D-modules and show a Decomposition Theorem in this category.

math.AG↗
arXiv2003

Gauss-Manin systems, Brieskorn lattices and Frobenius structures (I)

We associate to any convenient nondegenerate Laurent polynomial on the complex torus (C^*)^n a canonical Frobenius-Saito structure on the base space of its universal unfolding. According to the method of K. Saito (primitive forms) and of M. Saito (good basis of the Gauss-Manin system), the main problem, which is solved in this article, is the analysis of the Gauss-Manin system of the Laurent polynomial (or its universal unfolding) and of the corresponding Hodge theory.

math.AG↗
arXiv2003

Gauss-Manin systems, Brieskorn lattices and Frobenius structures (II)

We give an explicit description of the canonical Frobenius structure attached (by the results of the first part of this article) to the polynomial f(u_0,...,u_n)=w_0u_0+...+w_nu_n restricted to the torus u_0^{w_0}...u_n^{w_n}=1, for any family of positive integers w_0,...,w_n such that gcd(w_0,...,w_n)=1.

math.AG↗
arXiv1999

Vanishing cycles and Hermitian duality

We show the compatibility between the moderate or nearby cycle functor for regular holonomic $\mathcal{D}$-modules, as defined by Beilinson, Kashiwara and Malgrange, and the Hermitian duality functor, as defined by Kashiwara.

math.AG↗
arXiv1999

Harmonic metrics and connections with irregular singularities

We identify the holomorphic de Rham complex of the minimal extension of a meromorphic vector bundle with connexion on a compact Riemann surface X with the L^2 complex relative to a suitable metric on the bundle and a complete metric on the punctured Riemann surface. Applying results of C. Simpson, we show the existence of a harmonic metric on this vector bundle, giving the same L^2 complex. As a consequence, we obtain a Hard Lefschetz-type theorem.

math.AG↗
arXiv1998

Semicontinuity of the spectrum at infinity

We prove that, for an analytic family of ``weakly tame'' regular functions on an affine manifold, the spectrum at infinity of each function of the family is semicontinuous in the sense of Varchenko.

math.AG↗