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Mehdi Tavakol

Publications and source records attributed to Mehdi Tavakol.

15 recordsLinked to original sources
arXiv2020

Airy structures and deformations of curves in surfaces

An embedded curve in a symplectic surface $\Sigma\subset X$ defines a smooth deformation space $\mathcal{B}$ of nearby embedded curves. A key idea of Kontsevich and Soibelman arXiv:1701.09137 [math.AG], is to equip the symplectic surface $X$ with a foliation in order to study the deformation space $\mathcal{B}$. The foliation, together with a vector space $V_\Sigma$ of meromorphic differentials on $\Sigma$, endows an embedded curve $\Sigma$ with the structure of the initial data of topological recursion, which defines a collection of symmetric tensors on $V_\Sigma$. Kontsevich and Soibelman define an Airy structure on $V_\Sigma$ to be a formal quadratic Lagrangian $\mathcal{L}\subset T^*(V_\Sigma^*)$ which leads to an alternative construction of the tensors of topological recursion. In this paper we produce a formal series $\theta$ on $\mathcal{B}$ of meromorphic differentials on $\Sigma$ which takes it values in $\mathcal{L}$, and use this to produce the Donagi-Markman cubic from a natural cubic tensor on $V_\Sigma$, giving a generalisation of a result of Baraglia and Huang, arXiv:1707.04975 [math.DG].

math.AG↗
arXiv2020

Tautological classes with twisted coefficients

Let $M_g$ be the moduli space of smooth genus $g$ curves. We define a notion of Chow groups of $M_g$ with coefficients in a representation of $Sp(2g)$, and we define a subgroup of tautological classes in these Chow groups with twisted coefficients. Studying the tautological groups of $M_g$ with twisted coefficients is equivalent to studying the tautological rings of all fibered powers $C_g^n$ of the universal curve $C_g \to M_g$ simultaneously. By taking the direct sum over all irreducible representations of the symplectic group in fixed genus, one obtains the structure of a twisted commutative algebra on the tautological classes. We obtain some structural results for this twisted commutative algebra, and we are able to calculate it explicitly when $g \leq 4$. Thus we completely determine the tautological rings of all fibered powers of the universal curve over $M_g$ in these genera. We also give some applications to the Faber conjecture.

math.AG↗
arXiv2019

An action of the Polishchuk differential operator via punctured surfaces

For a family of Jacobians of smooth pointed curves there is a notion of tautological algebra. There is an action of $\mathfrak{sl}_2$ on this algebra. We define and study a lifting of the Polishchuk operator, corresponding to $f\in \mathfrak{sl}_2$, on an algebra consisting of punctured Riemann surfaces. As an application we prove that a collection of tautological relations on moduli of curves, discovered by Faber and Zagier, come from a class of relations on the universal Jacobian.

math.AG↗
arXiv2019

A differential model for B-type Landau-Ginzburg theories

We describe a mathematically rigorous differential model for B-type open-closed topological Landau-Ginzburg theories defined by a pair $(X,W)$, where $X$ is a non-compact Kählerian manifold with holomorphically trivial canonical line bundle and $W$ is a complex-valued holomorphic function defined on $X$ and whose critical locus is compact but need not consist of isolated points. We also show how this construction specializes to the case when $X$ is Stein and $W$ has finite critical set, in which case one recovers a simpler mathematical model.

math.DG↗
arXiv2018

B-type Landau-Ginzburg models with one-dimensional target

We summarize the main results of our investigation of B-type topological Landau-Ginzburg models whose target is an arbitrary open Riemann surface. Such a Riemann surface need not be affine algebraic and in particular it may have infinite genus or an infinite number of Freudenthal ends. Under mild conditions on the Landau-Ginzburg superpotential, we give a complete description of the triangulated structure of the category of topological D-branes in such models as well as counting formulas for the number of topological D-branes considered up to relevant equivalence relations.

hep-th↗
arXiv2018

Differential models for B-type open-closed topological Landau-Ginzburg theories

We propose a family of differential models for B-type open-closed topological Landau-Ginzburg theories defined by a pair $(X,W)$, where $X$ is any non-compact Calabi-Yau manifold and $W$ is any holomorphic complex-valued function defined on $X$ whose critical set is compact. The models are constructed at cochain level using smooth data, including the twisted Dolbeault algebra of polyvector valued forms and a twisted Dolbeault category of holomorphic factorizations of $W$. We give explicit proposals for cochain level versions of the bulk and boundary traces and for the bulk-boundary and boundary-bulk maps of the Landau-Ginzburg theory. We prove that most of the axioms of an open-closed topological field theory are satisfied on cohomology and conjecture that the remaining axioms are also satisfied.

math.DG↗
arXiv2018

On B-type open-closed Landau-Ginzburg theories defined on Calabi-Yau Stein manifolds

We consider the bulk algebra and topological D-brane category arising from the differential model of the open-closed B-type topological Landau-Ginzburg theory defined by a pair $(X,W)$, where $X$ is a non-compact Calabi-Yau manifold and $W$ has compact critical set. When $X$ is a Stein manifold (but not restricted to be a domain of holomorphy), we extract equivalent descriptions of the bulk algebra and of the category of topological D-branes which are constructed using only the analytic space associated to $X$. In particular, we show that the D-brane category is described by projective matrix factorizations defined over the ring of holomorphic functions of $X$. We also discuss simplifications of the analytic models which arise when $X$ is holomorphically parallelizable and illustrate these analytic models in a few classes of examples.

math.DG↗
arXiv2018

Matrix factorizations over elementary divisor domains

We study the homotopy category $\mathrm{hmf}(R,W)$ of matrix factorizations of non-zero elements $W\in R^\times$, where $R$ is an elementary divisor domain. When $R$ has prime elements and $W$ factors into a square-free element $W_0$ and a finite product of primes of multiplicity greater than one and which do not divide $W_0$, we show that $\mathrm{hmf}(R,W)$ is triangle-equivalent with an orthogonal sum of the triangulated categories of singularities $\mathrm{D}_{\mathrm sing}(A_n(p))$ of the local Artinian rings $A_n(p)=R/\langle p^n\rangle$, where $p$ runs over the prime divisors of $W$ of order $n\geq 2$. This result holds even when $R$ is not Noetherian. The triangulated categories $\mathrm{D}_{\mathrm sing}(A_n(p))$ are Krull-Schmidt and we describe them explicitly. We also study the cocycle category $\mathrm{zmf}(R,W)$, showing that it is additively generated by elementary matrix factorizations. Finally, we discuss a few classes of examples.

math.AC↗
arXiv2018

Elementary matrix factorizations over Bézout domains

We study the homotopy category $\mathrm{hef}(R,W)$ (and its $\mathbb{Z}_2$-graded version $\mathrm{HEF}(R,W)$) of elementary factorizations, where $R$ is a Bézout domain which has prime elements and $W=W_0 W_c$, where $W_0\in R^\times$ is a square-free element of $R$ and $W_c\in R^\times$ is a finite product of primes with order at least two. In this situation, we give criteria for detecting isomorphisms in $\mathrm{hef}(R,W)$ and $\mathrm{HEF}(R,W)$ and formulas for the number of isomorphism classes of objects. We also study the full subcategory $\mathbf{hef}(R,W)$ of the homotopy category $\mathrm{hmf}(R,W)$ of finite rank matrix factorizations of $W$ which is additively generated by elementary factorizations. We show that $\mathbf{hef}(R,W)$ is Krull-Schmidt and we conjecture that it coincides with $\mathrm{hmf}(R,W)$. Finally, we discuss a few classes of examples.

math.AC↗
arXiv2017

A conjectural connection between R^*(C_g^n) and R^*(M_{g,n}^rt)

Let M_{g,n}^rt be the moduli space of stable n-pointed curves of genus g>1 with rational tails. We also consider the space C_g^n classifying smooth curves of genus g with not necessarily distinct n ordered points. There is a natural proper map from M_{g,n}^rt to C_g^n which contracts all rational components. Tautological classes on these spaces are natural algebraic cycles reflecting the geometry of curves. In this short note we study the connection between tautological classes on M_{g,n}^rt and C_g^n. We show that there is a natural filtration on the tautological ring of M_{g,n}^rt consisting of g-2+n steps. A conjectural dictionary between tautological relations on M_{g,n}^rt and C_g^n is presented. Our conjecture predicts that the space of relations in R^*(M_{g,n}^rt) is generated by relations in R^*(C_g^n) together with a class of relations obtained from the geometry of blow-ups. This conjecture is equivalent to the the independence of certain tautological classes in Chow. We prove the analogue version of our conjecture for the Gorenstein quotients of tautological rings.

math.AG↗
arXiv2016

The moduli space of curves and its invariants

This note is about invariants of moduli spaces of curves. It includes their intersection theory and cohomology. Our main focus in on the distinguished piece containing the so called tautological classes. These are the most natural classes on the moduli space. We give a review of known results and discuss their conjectural descriptions.

math.AG↗
arXiv2014

Tautological classes on the moduli space of hyperelliptic curves with rational tails

We study tautological classes on the moduli space of stable $n$-pointed hyperelliptic curves of genus $g$ with rational tails. Our result gives a complete description of tautological relations. The method is based on the approach of Yin in comparing tautological classes on the moduli of curves and the universal Jacobian. It is proven that all relations come from the Jacobian side. The intersection pairings are shown to be perfect in all degrees. We show that the tautological algebra coincides with its image in cohomology via the cycle class map. The latter is identified with monodromy invariant classes in cohomology. The connection with recent conjectures by Pixton is also discussed.

math.AG↗
arXiv2011

The tautological ring of the moduli space M_{2,n}^rt

We study the tautological ring of the moduli space of stable n-pointed curves of genus two with rational tails. The algebra is described in terms of explicit generators and relations. It is proven that this algebra is Gorenstein.

math.AG↗
arXiv2011

The Chow ring of the moduli space of curves of genus zero

After recalling several constructions of the moduli space of curves of genus zero by different people we give our alternative construction of the moduli space. This gives a simple description of the intersection ring of this space. We give a basis for the Chow groups and an explicit duality between the Chow groups in complementary degrees. There is a recursive description of this algebra by S. Keel. Our presentation is simpler in the sense that there are fewer generators and fewer relations and our description is explicit.

math.AG↗