arXiv subjects

Martin Puchol

Publications and source records attributed to Martin Puchol.

9 recordsLinked to original sources

arXiv2024

Generalized Morse Functions, Excision and Higher Torsions

Comparing invariants from both topological and geometric perspectives is a key focus in index theorem. This paper compares higher analytic and topological torsions and establishes a version of the higher Cheeger-M\"uller/Bismut-Zhang theorem. In fact, Bismut-Goette achieved this comparison assuming the existence of fiberwise Morse functions satisfying the fiberwise Thom-Smale transversality condition (TS condition). To fully generalize the theorem, we should remove this assumption. Notably, unlike fiberwise Morse functions, fiberwise generalized Morse functions (GMFs) always exist, we extend Bismut-Goette's setup by considering a fibration $ M \to S $ with a unitarily flat complex bundle $ F \to M $ and a fiberwise GMF $ f $, while retaining the TS condition. Compared to Bismut-Goette's work, handling birth-death points for a generalized Morse function poses a key difficulty. To deal with this, first, by the work of the author M.P., joint with Zhang and Zhu, we focus on a relative version of the theorem. Here, analytic and topological torsions are normalized by subtracting their corresponding torsions for trivial bundles. Next, using new techniques from by the author J.Y., we excise a small neighborhood around the locus where $f$ has birth-death points. This reduces the problem to Bismut-Goette's settings (or its version with boundaries) via a Witten-type deformation. However, new difficulties arise from very singular critical points during this deformation. To deal with these, we extend methods from Bismut-Lebeau, using Agmon estimates for noncompact manifolds developed by Dai and J.Y.

math.DG↗

arXiv2021

A comparison between the Bismut-Lott torsion and the Igusa-Klein torsion

We consider a fibration with compact fiber together with a unitarily flat complex vector bundle over the total space. Under the assumption that the fiberwise cohomology admits a filtration with unitary factors, we construct Bismut-Lott analytic torsion classes. The analytic torsion classes obtained satisfy Igusa's and Ohrt's axiomatization of higher torsion invariants. As a consequence, we obtain a higher version of the Cheeger-Müller/Bismut-Zhang theorem: for trivial flat line bundles, the Bismut-Lott analytic torsion classes coincide with the Igusa-Klein higher topological torsions up to a normalization.

math.DG↗

arXiv2020

Adiabatic limit, Witten deformation and analytic torsion forms

We consider a smooth fibration equipped with a flat complex vector bundle and a hypersurface cutting the fibration into two pieces. Our main result is a gluing formula relating the Bismut-Lott analytic torsion form of the whole fibration to that of each piece. This result confirms a conjecture proposed in a conference in Goettingen in 2003. Our approach combines an adiabatic limit along the normal direction of the hypersurface and a Witten type deformation on the flat vector bundle. Due to disagreement among authors, author Zhang unilaterally decides to never publish this paper. If you saw this paper published somewhere, it must be without Zhang's approvement.

math.DG↗

arXiv2020

Variance of the volume of random real algebraic submanifolds II

Let $\mathcal{X}$ be a complex projective manifold of dimension $n$ defined over the reals and let $M$ be its real locus. We study the vanishing locus $Z\_{s\_d}$ in $M$ of a random real holomorphic section $s\_d$ of $\mathcal{E} \otimes \mathcal{L}^d$, where $\mathcal{L} \to \mathcal{X}$ is an ample line bundle and $\mathcal{E} \to \mathcal{X}$ is a rank $r$ Hermitian bundle, $r \in \{1,\dots, n\}$. We establish the asymptotic of the variance of the linear statistics associated with $Z\_{s\_d}$, as $d$ goes to infinity. This asymptotic is of order $d^{r-\frac{n}{2}}$. As a special case, we get the asymptotic variance of the volume of $Z\_{s\_d}$. The present paper extends the results of [20], by the first-named author, in essentially two ways. First, our main theorem covers the case of maximal codimension ($r = n$), which was left out in [20]. And second, we show that the leading constant in our asymptotic is positive. This last result is proved by studying the Wiener--It{ō} expansion of the linear statistics associated with the common zero set in $\mathbb{RP}^n$ of $r$ independent Kostlan--Shub--Smale polynomials.

math.MG↗

arXiv2019

Scattering Matrix and Analytic Torsion

For a compact manifold, which has a part isometric to a cylinder of finite length, we consider an adiabatic limit procedure, in which the length of the cylinder tends to infinity. We study the asymptotic of the spectrum of Hodge-Laplacian and the asymptotic of the $L^2$-metric on de Rham cohomology. As an application, we give a pure analytic proof of the gluing formula for analytic torsion.

math.DG↗

arXiv2018

Holomorphic Morse inequalities for orbifolds

We prove that Demailly's holomorphic Morse inequalities hold true for complex orbifolds by using a heat kernel method. Then we introduce the class of Moishezon orbifolds and as an application of our inequalties, we give a geometric criterion for a compact connected orbifold to be a Moishezon orbifolds, thus generalizing Siu's and Demailly's answers to the Grauert-Riemenschneider conjecture to the orbifold case.

math.DG↗

arXiv2017

The first terms in the expansion of the Bergman kernel in higher degrees

We establish the cancellation of the first $2j$ terms in the diagonal asymptotic expansion of the restriction to the $(0,2j)$-forms of the Bergman kernel associated to the spin${}^c$ Dirac operator on high tensor powers of a positive line bundle twisted by a (non necessarily holomorphic) complex vector bundle, over a compact Kähler manifold. Moreover, we give a local formula for the first and the second (non-zero) leading coefficients.

math.DG↗

arXiv2015

G-invariant Holomorphic Morse inequalities

Consider an action of a connected compact Lie group on a compact complex manifold $M$, and two equivariant vector bundles $L$ and $E$ on $M$, with $L$ of rank 1. The purpose of this paper is to establish holomorphic Morse inequalities à la Demailly for the invariant part of the Dolbeault cohomology of tensor powers of $L$ twisted by $E$. To do so, we define a moment map $μ$ by the Kostant formula and we define the reduction of $M$ under a natural hypothesis on $μ^{-1}(0)$. Our inequalities are given in term of the curvature of the bundle induced by $L$ on this reduction.

math.DG↗

arXiv2015

The Asymptotic of the Holomorphic Analytic Torsion Forms

The purpose of this paper is first to give an asymptotic formula for the holomorphic analytic torsion forms of a fibration associated with increasing powers of a given line bundle. Secondly, we generalize this formula, thanks to the theory of Toeplitz operators, in the case where the powers of the line bundle is replaced by the direct image of powers of a line bundle on a bigger manifold. In both cases we have to make fiberwise positivity assumption on the line bundle. This results are the family versions of the results of Bimsut and Vasserot on the asymptotic of the holomorphic torsion.

math.DG↗