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Based on Teichm\"uller theory, we construct a degenerating family $\overline{Y}_g^{orb} \rightarrow \overline{M}_g^{orb}$ over the Deligne-Mumford compactification of the moduli space with the natural orbifold structure such that any…

Algebraic Geometry · Mathematics 2023-01-03 Tadashi Ashikaga , Yukio Matsumoto

We generalize Illusie's result to prove the decomposition of the de Rham complex with smooth horizontal coefficients for a semistable $S$-morphism $f:X\ra Y$ which is liftable over $\Z/p^2\Z$. As an application, we prove the Koll\'ar…

Algebraic Geometry · Mathematics 2011-10-13 Qihong Xie

Motivated by a conjecture of Xiao, we study supporting divisors of fibred surfaces. On the one hand, after developing a formalism to treat one-dimensional families of varieties of any dimension, we give a structure theorem for fibred…

Algebraic Geometry · Mathematics 2016-02-22 Víctor González-Alonso

We use the Decomposition Theorem to derive several generalizations of the Clemens-Schmid sequence, relating asymptotic Hodge theory of a degeneration to the mixed Hodge theory of its singular fiber(s).

Algebraic Geometry · Mathematics 2022-02-08 Matt Kerr , Radu Laza

Deformation theory is treated for locally notherian formal schemes (non necessarily smooth). The cotangent complex is defined in the derived category through the homology localization functor. The basic properties and results of a…

Algebraic Geometry · Mathematics 2024-02-06 Marta Pérez Rodríguez

We study the interaction between Fourier-Mukai transforms and perverse filtrations for a certain class of dualizable abelian fibrations. Multiplicativity of the perverse filtration and the "Perverse $\supset$ Chern" phenomenon for these…

Algebraic Geometry · Mathematics 2025-10-09 Davesh Maulik , Junliang Shen , Qizheng Yin

We study local splitting-type results for general Loday algebroids and use them to obtain a direct proof of the splitting theorem for Courant algebroids. We also discuss the linearization problem and establish a general linearization…

Differential Geometry · Mathematics 2026-05-05 Hudson Lima

This paper contains two results on Hodge loci in the moduli space of curves. The first concerns fibrations over curves with a non-trivial flat part in the Fujita decomposition. If local Torelli theorem holds for the fibres and the fibration…

Algebraic Geometry · Mathematics 2020-07-15 Paola Frediani , Alessandro Ghigi , Gian Pietro Pirola

We consider collections of disjoint simple closed curves in a compact orientable surface which decompose the surface into pairs of pants. The isotopy classes of such curve systems form the vertices of a 2-complex, whose edges correspond to…

Geometric Topology · Mathematics 2007-05-23 Allen Hatcher

We develop the theory of Hodge ideals for Q-divisors by means of log resolutions, extending our previous work on reduced hypersurfaces. We prove local (non-)triviality criteria and a global vanishing theorem, as well as other analogues of…

Algebraic Geometry · Mathematics 2018-11-08 Mircea Mustata , Mihnea Popa

We prove that the cycle-valued logarithmic Gromov--Witten theory of a product of simple normal crossings pairs $X\times Y$ decomposes into a product of pieces coming from $X$ and $Y$, provided that the decomposition is considered over a…

Algebraic Geometry · Mathematics 2022-09-20 Dhruv Ranganathan

In this paper we show Whitney's fibering conjecture in the real and complex, local analytic and global algebraic cases. For a given germ of complex or real analytic set, we show the existence of a stratification satisfying a strong (real…

Algebraic Geometry · Mathematics 2017-01-25 Adam Parusiński , Laurentiu Paunescu

In this paper, we prove that the theta divisor of a smooth hyperelliptic curve has a natural and explicit embedded resolution of singularities using iterated blowups of Brill-Noether subvarieties. We also show that the Brill-Noether…

Algebraic Geometry · Mathematics 2024-12-13 Christian Schnell , Ruijie Yang

We show that if $(X,Y)$ is a simple normal crossings log Calabi--Yau pair, then there is a real torus of dimension equal to the codimension of the smallest stratum of $Y$ which can be used to construct $W_{2k-1}H^k(X \setminus…

Algebraic Geometry · Mathematics 2019-08-15 Andrew Harder

We study the scale and tidy subgroups of an endomorphism of a totally disconnected locally compact group using a geometric framework. This leads to new interpretations of tidy subgroups and the scale function. Foremost, we obtain a…

Group Theory · Mathematics 2018-10-11 Timothy P. Bywaters , Stephan Tornier

We use Kiehl-Verdier's and Houzel's finiteness theorems in the setting of local analytic geometry, and the Whitney-Thom theory of stratified spaces, to prove that fibrewise constructible complex of sheaves have coherent direct images. We…

Algebraic Geometry · Mathematics 2007-05-23 Mauricio D. Garay

We recover the Newton diagram (modulo a natural ambiguity) from the link for any surface hypersurface singularity with non-degenerate Newton principal part whose link is a rational homology sphere. As a corollary, we show that the link…

Algebraic Geometry · Mathematics 2007-05-23 Gabor Braun , Andras Nemethi

We give a simplified proof (in characteristic zero) of the decomposition theorem for complex projective varieties with klt singularities and numerically trivial canonical bundle. The proof rests in an essential way on most of the partial…

Algebraic Geometry · Mathematics 2020-05-13 Frederic Campana

We show that the universal abelian cover of the complement to a germ of a reducible divisor on a complex space $Y$ with isolated singularity is $(dimY-2)$-connected provided that the divisor has normal crossings outside of the singularity…

Algebraic Geometry · Mathematics 2007-05-23 Alexandru Dimca , Anatoly Libgober

We give a framework to produce constructible functions from natural functors between categories, without need of a morphism of moduli spaces to model the functor. We show using the Riemann-Hilbert correspondence that any natural (derived)…

Algebraic Geometry · Mathematics 2021-10-18 Nero Budur , Botong Wang