Yutaka Matsui, Kiyoshi Takeuchi
We propose a new sheaf-theoretical method for the calculation of the monodromy zeta functions of Milnor fibrations. As an application, classical formulas of Kushnirenko and Varchenko etc. concerning polynomials on $\CC^n$ will be generalized to polynomial functions on any toric variety.
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The category of finite Milnor-Witt correspondences, introduced by Calmès and Fasel, provides a new type of correspondences closer to the motivic homotopy theoretic framework than Suslin-Voevodsky's correspondences. A fundamental result of the theory of ordinary correspondences concerns homotopy invariance of sheaves with transfers, and in the present paper we address this question in the setting of Milnor-Witt correspondences. Employing techniques due to Druzhinin, Fasel-Østvær and Garkusha-Panin, we show that homotopy invariance of presheaves with Milnor-Witt transfers is preserved under Nisn…
We study function germs on toric varieties which are nondegenerate for their Newton diagram. We express their motivic Milnor fibre in terms of their Newton diagram. We extend a formula for the motivic nearby fibre to the case of a toroidal degeneration. We illustrate this by some examples.
In this note, we provide a quick introduction to the study of the Milnor fibration via the derived category and perverse sheaves. This is primarily a dictionary for translating from the standard topological setting to the derived category and/or the Abelian category of perverse sheaves.
We note that Theorem 5.4 of the paper ``Characteristic cycles of perverse sheaves and Milnor fibers" (by P. Nang and K. Takeuchi, published online in Math. Zeitschrift, October 15, 2004) holds for "any" non-zero complex number $a$.
Decomposition of toric sheaves
本文证明相干环簇层范畴由不变子簇上的一秩自反层的推出生成，并将Klyachko的同调结果推广至相干环簇层。
Equivariant sheaves on toric prevarieties
本文研究紧致化预变种上等变准 coherent sheaves 的组合描述，扩展了Klyachko关于等变torsion free sheaves 的框架。
Toric sheaves and polyhedra
本文从多面体视角研究光滑射影环面簇上的环面层，通过多面体包含/排除序列构造nef线丛的泛扩张，并建立双复形与谱序列以计算环面层上同调。
We explain a method for calculating the cohomology of line bundles on a toric variety in terms of the cohomology of certain constructible sheaves on the polytope. We show its effective use by means of some examples.
Perverse sheaves on smooth toric varieties and stacks
本文将光滑环面簇及其轨道分层上的反常层范畴显式刻画为某代数上的有限维模范畴，并推广到等变情形以描述环面轨形上的反常层，同时比较了相关导出范畴。
We discuss some results on parameterized hypersurfaces which follow quickly from results in the category of perverse sheaves
Toric sheaves and flips
本文研究了toric flip诱导的等变反常层范畴等价下斜率稳定性的行为，分别提出了固定toric sheaf斜率稳定性保持的数值判据和对数toric sheaves满子范畴中多项稳定性保持的刻画。
The Euler characteristic of Milnor fibers over 2-generic symmetric determinantal varieties
本文推导了非退化函数f:X→C的米尔诺纤维欧拉特征公式，通过描述概形的托尔结构和计算牛顿多面体体积，应用Matsui-Takeuchi公式得出结果，并探讨了局部欧拉阻挠与多项式米尔诺数的关系。
Constructible sheaves on toric varieties
本文针对环面簇上的可构造层范畴给出显式计算，既简化了复数域上Braden与Lunts的相关描述，又首次在正特征下对任意域分裂环面簇的驯分歧可构造平展层完成了平展外定理的显式计算。
Acyclic toric sheaves
本文基于Perlman和Smith的定理，证明了在光滑射影的环形变种上，通过Weil装饰给出典范sheaf无环的显式充分条件。
In this note we derive a formalism for describing equivariant sheaves over toric varieties. This formalism is a generalization of a correspondence due to Klyachko, which states that equivariant vector bundles on toric varieties are equivalent to certain sets of filtrations of vector spaces. We systematically construct the theory from the point of view of graded ring theory and this way we clarify earlier constructions of Kaneyama and Klyachko. We also connect the formalism to the theory of fine-graded modules over Cox' homogeneous coordinate ring of a toric variety. As an application we constr…
Constructible sheaves of abelian groups on a stratified space can be equivalently described in terms of representations of the exit-path category. In this work, we provide a similar presentation of the abelian category of perverse sheaves on a stratified surface in terms of representations of the so-called paracyclic category of the surface. The category models a hybrid exit-entrance behaviour with respect to chosen sectors of direction, placing it "in between" exit and entrance path categories. In particular, this perspective yields an intrinsic definition of perverse sheaves as an abelian ca…
We provide a stacky fan description of the total space of certain split vector bundles, as well as their projectivization, over toric Deligne-Mumford stacks. We then specialize to the case of Hirzebruch orbifold $\mathcal{H}_{r}^{ab}$ obtained by projectivizing $\mathcal{O} \oplus \mathcal{O}(r)$ over the weighted projective line $\mathbb{P}(a,b)$. Next, we give a combinatorial description of toric sheaves on $\mathcal{H}_{r}^{ab}$ and investigate their basic properties. With fixed choice of polarization and a generating sheaf, we describe the fixed point locus of the moduli scheme of $μ$-stab…
Broken Toric Varieties and Cell-Compatible Sheaves
本文利用常值层到多面体复形的导出前推研究破碎环面簇的上同调，证明Deligne型分解定理和谱序列退化，并给出部分情形的Betti数显式公式。
We combine work of Cox on the total coordinate ring of a toric variety and results of Eisenbud-Mustata-Stillman and Mustata on cohomology of toric and monomial ideals to obtain a formula for computing the Euler characteristic of a Weil divisor D on a complete simplicial toric variety in terms of graded pieces of the Cox ring and Stanley-Reisner ring. The main point is to use Alexander duality to pass from the toric irrelevant ideal, which appears in the computation of the Euler characteristic of D, to the Stanley-Reisner ideal of the fan, which is used in defining the Chow ring. The formula al…
A note on stable toric sheaves of low rank
本文构造了极化环面簇上低秩稳定等变自反层的显式例子，证明其奇异轨迹维数严格受 $n-r$ 限制，与高秩向量丛必分裂的已知结论形成对比。
Stable toric sheaves. I : Chern classes
本文研究复射影空间上秩为2的环面等变无挠层，通过自反层的陈多项式公式和基于初等单射的迭代构造方法指定陈类，在$\mathbb{P}^n$（$n\geq 3$）上得到满足已知约束的无穷多显式例子，并给出可光滑化的障碍。
Given a smooth toric variety $X$, the action of the torus $T$ lifts to the moduli space $\mathcal{M}$ of stable sheaves on $X$. Using the pioneering work of Klyacho, a fairly explicit combinatorial description of the fixed point locus $\mathcal{M}^T$ can be given (as shown by earlier work of the author). In this paper, we apply this description to the case of torsion free sheaves on a smooth toric surface $S$. A general expression for the generating function of the Euler characteristics of such moduli spaces is obtained. The generating function is expressed in terms of Euler characteristics of…
Derived category of equivariant coherent sheaves on a smooth toric variety and Koszul duality
本文通过定义光滑环面簇扇上的分次代数层，建立组合Koszul对偶等价，并用模层描述等变凝聚层范畴，最终将完备情形下的对偶解释为Serre函子。
Toric sheaves, stability and fibrations
本文研究了极化环面簇上等变反射层沿环面纤维化拉回的斜率稳定性，证明了在绝热极化下稳定性得以保持，给出了严格半稳定情形的充要条件，并展示了其在切层稳定扰动及模空间单射映射中的应用。
Fixed point loci of moduli spaces of sheaves on toric varieties
该研究推广前人工作给出非奇异环面簇上纯等变层的组合描述，借助GIT构造对应模空间，显式表出Gieseker稳定层模空间的环面作用不动点轨迹，构造出对应Gieseker稳定性的等变线丛，并得到μ-稳定自反层模空间不动点轨迹的组合描述，可用于计算相关欧拉示性数生成函数。
We consider for structure groups ${\rm SU}(n)\,\subset\, {\rm SL}(n,\mathbb C)$ a densely defined toric structure on the moduli of framed parabolic sheaves on a three-punctured sphere, which degenerates to an actual toric structure. In combination with previous degeneration results, these extend to similar moduli for arbitrary Riemann surfaces.
We show that certain categories of perverse sheaves on a pair of affine toric varieties defined by dual cones are Koszul dual in the sense of Beilinson, Ginzburg and Soergel. The functor expressing this duality is constructed explicitly using a combinatorial model for mixed sheaves on toric varieties.
Stability of Equivariant Logarithmic Tangent Sheaves on Toric Varieties of Picard Rank Two
本文研究了正规环面簇上等变对数切层的斜率稳定性，并完整刻画了Picard秩为一或二时除子与极化使得该层（半）稳定的条件。
Using the homogeneous coordinate ring construction of a toric variety IP defined by a complete simplicial fan and the methods of local cohomology theory we develop a framework for the calculation of cohomology groups H^{*}(IP, O(p)) of twisting sheaves O(p) on IP.
A correspondence between quasicoherent sheaves on toric schemes and graded modules over some homogeneous coordinate ring is presented, and the behaviour of several finiteness properties under this correspondence is investigated.
We characterise and investigate co-Higgs sheaves and associated algebraic and combinatorial invariants on toric varieties. In particular, we compute explicit examples.
Given a smooth projective toric variety $X_Σ$ of complex dimension $n$, Fang-Liu-Treumann-Zaslow \cite{FLTZ} showed that there is a quasi-embedding of the differential graded (dg) derived category of coherent sheaves $Coh(X_Σ)$ into the dg derived category of constructible sheaves on a torus $Sh(T^n, Λ_Σ)$. Recently, Kuwagaki \cite{Ku2} proved that the quasi-embedding is a quasi-equivalence, and generalized the result to toric stacks. Here we give a different proof in the smooth projective case, using non-characteristic deformation of sheaves to find twisted polytope sheaves that co-represent …
The purpose of this paper is to calculate the support of the multiplier ideal sheaves derived from the Kähler-Ricci flow on certain toric Fano manifolds with large symmetry. The early idea of this paper has already been in Appendix of \cite{futaki-sano0711}.
Geometric monodromies, mixed Hodge numbers of motivic Milnor fibers and Newton polyhedra
本文引入多项式上同调群中局部与全局单值理论，结合环面几何与动机Milnor纤维，用Newton多面体描述等变混合Hodge数。
We use Altmann's toric fan description of P-resolutions to formulate a new description of deformation theory invariants for two-dimensional cyclic quotient singularities. In particular, we show how to calculate the dimensions of the (reduced) versal base space components as well as Milnor numbers of smoothings over them.
In this work we construct global resolutions for general coherent equivariant sheaves over toric varieties. For this, we use the framework of sheaves over posets. We develop a notion of gluing of posets and of sheaves over posets, which we apply to construct global resolutions for equivariant sheaves. Our constructions give a natural correspondence between resolutions for reflexive equivariant sheaves and free resolutions of vector space arrangements.
For a variety X which admits a Cox ring we introduce a functor from the category of quasi-coherent sheaves on $X$ to the category of graded modules over the homogeneous coordinate ring of $X$. We show that this functor is right-adjoint to the sheafification functor and therefore left-exact. Moreover, we show that this functor preserves torsion-freeness and reflexivity. For the case of toric sheaves we give a combinatorial characterization of its right-derived functors in terms of certain right-derived limit functors.
For (X,L) a polarized toric variety and G a torus of automorphisms of (X,L), denote by Y the GIT quotient X/G. We define a family of fully faithful functors from the category of torus equivariant reflexive sheaves on Y to the category of torus equivariant reflexive sheaves on X. We show, under a genericity assumption on G, that slope stability is preserved by these functors if and only if the pair ((X, L), G) satisfies a combinatorial criterion. As an application, when (X,L) is a polarized toric orbifold of dimension n, we relate stable equivariant reflexive sheaves on (X, L) to stable equivar…
Rouquier dimension is Krull dimension for normal toric varieties
本文借助凝聚—可构造对应，证明任意正规环面簇的凝聚层有界导出范畴的 Rouquier 维数与其 Krull 维数相等。
Morelli's computation of the K-theory of a toric variety X associates a polyhedrally constructible function on a real vector space to every equivariant vector bundle E on X. The coherent-constructible correspondence lifts Morelli's constructible function to a complex of constructible sheaves kappa(E). We show that certain filtrations of the cohomology of kappa(E) coming from Morse theory coincide with the Klyachko filtrations of the generic stalk of E. We give Morse-theoretic (i.e. microlocal) conditions for a complex of constructible sheaves to correspond to a vector bundle, and to a nef vect…
We prove two theorems on the derived categories of toric varieties, the existence of an exceptional collection consisting of sheaves for a divisorial extraction and the finiteness of Fourier-Mukai partners.
We extend Nadel's results on some conditions for the multiplier ideal sheaves to satisfy which are described in terms of an obstruction defined by the first author. Applying our extension we can determine the multiplier ideal sheaves on toric del Pezzo surfaces which do not admit Kähler-Einstein metrics. We also show that one can define multiplier ideal sheaves for Kähler-Ricci solitons and extend the result of Nadel using the holomorphic invariant defined by Tian and Zhu.
The Seshadri Constants of Tangent Sheaves on Toric Varieties
本文研究环面簇上切丛的 Seshadri 常数，给出其正性的判别条件，并证明光滑射影环面簇若在某点处该常数为正则同构于射影空间，验证了 Fulger-Murayama 猜想的一个特例。
We study equivariant resolutions and local cohomologies of toric sheaves for affine toric varieties, where our focus is on the construction of new examples of decomposable maximal Cohen-Macaulay modules of higher rank. A result of Klyachko states that the category of reflexive toric sheaves is equivalent to the category of vector spaces together with a certain family of filtrations. Within this setting, we develop machinery which facilitates the construction of minimal free resolutions for the smooth case as well as resolutions which are acyclic with respect to local cohomology functors for th…
Vanishing Cycles for Zariski-Constructible Sheaves on Rigid Analytic Varieties
本文在非阿基米德域上建立了Zariski可构造层的近环与消失环理论，证明其保持可构造性、具有Milnor纤维解释、满足Beilinson粘合、perverse t-精确且与Verdier对偶交换。
In this paper we give an inherently toric description of a special class of sheaves (known as equivariant sheaves) over toric varieties, due in part to A. A. Klyachko. We apply this technology to heterotic compactifications, in particular to the (0,2) models of Distler, Kachru, and also discuss how knowledge of equivariant sheaves can be used to reconstruct information about an entire moduli space of sheaves. Many results relevant to heterotic compactifications previously known only to mathematicians are collected here -- for example, results concerning whether the restriction of a stable shea…
Invertible sheaves and $Π$-invertible sheaves on the isomeric supergrassmannian and its toric subvarieties
本文证明了同构超格拉斯曼流形的 Picard 群和 $Π$-Picard 集除特定 $Π$-射影空间外均为平凡，并扩展该技术通过单纯形因子计数计算超环面轨道闭包的相应群集，最后将非平凡层构造为 tautological 层的对称幂。
We study global primary decompositions in the category of sheaves on a scheme which are equivariant under the action of an algebraic group. We show that equivariant primary decompositions exist if the group is connected. As main application we consider the case of varieties which are quotients of a quasi-affine variety by the action of a diagonalizable group and thus admit a homogeneous coordinate ring, such as toric varieties. Comparing these decompositions with primary decompositions of graded modules over the homogeneous coordinate ring, we show that these are equivalent if the action of th…
Suppose that the critical locus $Σ$ of a complex analytic function $f$ on affine space is, itself, a space with an isolated singular point at the origin $\0$, and that the Milnor number of $f$ restricted to normal slices of $Σ-\{\0\}$ is constant. Then, the general theory of perverse sheaves puts severe restrictions on the cohomology of the Milnor fiber of $f$ at $\0$, and even more surprising restrictions on the cohomology of the Milnor fiber of generic hyperplane slices.
We study the bounded derived categories of torus-equivariant coherent sheaves on smooth toric varieties and Deligne-Mumford stacks. We construct and describe full exceptional collections in these categories. We also observe that these categories depend only on the PL homeomorphism type of the corresponding simplicial complex.
Toric Foliated Minimal Model Program
本文利用Klyachko滤过理论，将Spicer的结果推广至任意秩，证明了环簇叶状极小模型纲领的存在性。
In each dimension n>2 there are many projective simplicial toric varieties whose Grothendieck groups of vector bundles are at least as big as the ground field. In particular, the conjecture that the Grothendieck groups of locally trivial sheaves and coherent sheaves on such varieties are rationally isomorphic fails badly.
If $X$ is a smooth toric variety over an algebraically closed field of positive characteristic and $L$ is an invertible sheaf on $X$, it is known that $F_* L$, the push-forward of $L$ along the Frobenius morphism of $X$, is a direct sum of invertible sheaves. We show that this property characterizes smooth projective toric varieties.
Studying toric varieties from a scheme-theoretical point of view leads to toric schemes, i.e. "toric varieties over arbitrary base rings". It is shown how the base ring affects the geometry of a toric scheme. Moreover, generalisations of results by Cox and Mustata allow to describe quasicoherent sheaves on toric schemes in terms of graded modules. Finally, a toric version of the Serre-Grothendieck correspondence relates cohomology of quasicoherent sheaves on toric schemes to local cohomology of graded modules.
Proto-Exact Categories of Matroids over Idylls and Tropical Toric Reflexive Sheaves
本文证明idyll上拟阵范畴是proto-exact和proto-abelian，并由此推出热带环面自反层范畴也具有这些性质，进而研究其稳定性与Harder-Narasimhan滤过。
In the first part of this paper, we study the properties of some particular plurisubharmonic functions, namely the toric ones. The main result of this part is a precise description of their multiplier ideal sheaves, which generalizes the algebraic case studied by Howald. In the second part, almost entirely independent of the first one, we generalize the notion of the adjoint ideal sheaf used in algebraic geometry to the analytic setting. This enables us to give an analogue of Howald's theorem for adjoint ideals attached to monomial ideals. Finally, using the local Ohsawa-Takegoshi-Manivel theo…
Let X be the toric scheme over a ring R associated with a fan Sigma. It is shown that there are a group B, a B-graded R-algebra S and a graded ideal I of S such that there is an essentially surjective, exact functor ~ from the category of B-graded S-modules to the category of quasicoherent O_X-modules that vanishes on I-torsion modules and that induces for every B-graded S-module F a surjection Xi_F from the set of I-saturated graded sub-S-modules of F onto the set of quasicoherent sub-O_X-modules of ~F. If Sigma is simplicial, the above data can be chosen such that ~ vanishes precisely on I-t…
Achar has recently introduced a family of t-structures on the derived category of equivariant coherent sheaves on a $G$-scheme, generalizing the perverse coherent t-structures of Bezrukavnikov and Deligne. They are called \emph{staggered} t-structures, and their main point of interest so far is that they are more often self-dual. In this paper we investigate these t-structures on the $T$-equivariant derived category of a toric variety.
We study the local cohomology modules H^i_B(R) for a reduced monomial ideal B in a polynomial ring R=k[X_1,...,X_n]. We consider a grading on R which is coarser than the Z^n-grading such that each component of H^i_B(R) is finite dimensional and we give an effective way to compute these components. Using Cox's description for sheaves on toric varieties, we apply these results to compute the cohomology of coherent sheaves on toric varieties. We give algorithms for this computation which have been implemented in the Macaulay 2 system. We obtain also a topological description for the cohomology of…
This work discusses combinatorial and arithmetic aspects of cohomology vanishing for divisorial sheaves on toric varieties. We obtain a refined variant of the Kawamata-Viehweg theorem which is slightly stronger. Moreover, we prove a new vanishing theorem related to divisors whose inverse is nef and has small Kodaira dimension. Finally, we give a new criterion for divisorial sheaves for being maximal Cohen-Macaulay.
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