Hiroshi Sato, Yusuke Suyama
We show that the second Chern character of any projective toric manifold of Picard number three is not ample. In connection with this result, we give various examples of the positivity of higher Chern characters of projective toric manifolds.
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We show that any toric Fano manifold of dimension at most eight with the positive second Chern character is isomorphic to the projective space by using polymake.
The purpose of this short note is to prove a formula for the Chern-Mather classes of a toric variety in terms of its orbits and the local Euler obstructions at general points of each orbit (Theorem 2). We use the general definition of the Chern-Schwartz-MacPherson classes (see [7]) and their special expression in case of a toric variety (see [2]). As a corollary, we obtain a formula by Matsui-Takeuchi [8, Corollary 1.6]. Alternatively, one could deduce the formula of Theorem 2 from the Matsui-Takeuchi formula, by using our general result [11, Theoreme 3] for the degree of the polar varieties i…
Equivariant Chern Classes of Toric Vector Bundles over a DVR and Bruhat--Tits Buildings
本文定义 DVR 上正常环面格式中环面向量丛的等变陈类，借助多面体复形上的分段多项式函数及扩展 Bruhat–Tits 建筑给出组合刻画，并联系非阿基米德 Arakelov 理论。
Toric vector bundles with trivial Chern class and flag decorations
本文用热带方法研究完备环面簇上Chern类平凡的环面向量丛，证明其可经特征标扭曲后由低维簇拉回，推广了Payne定理，并构造了无此类非平凡丛的例子，引入旗装饰作为关键工具。
Let $\sE$ be an ample rank $r$ bundle on a smooth toric projective surface, $S$, whose topological Euler characteristic is $e(S)$. In this article, we prove a number of surprisingly strong lower bounds for $c_1(\sE)^2$ and $c_2(\sE)$. We also enumerate the exceptions to either the inequality $c_1(\sE)^2\ge 4e(S)$ or the inequality $c_2(\sE)\ge e(S)$ holding.
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。
Chern Classes of Toric Variety Bundles
本文解决了Khovanskii--Monin猜想，给出环簇丛切丛全陈类用基空间与环簇纤维陈类表示的公式，并推广至稳定复拟环流形，应用于环面螺旋球簇及Masuda公式的新证明。
In this notes we classify toric Fano 4-folds having positive second Chern Character.
Topological invariants such as characteristic classes are an important tool to aid in understanding and categorizing the structure and properties of algebraic varieties. In this note we consider the problem of computing a particular characteristic class, the Chern-Schwartz-MacPherson class, of a complete simplicial toric variety X defined by a fan from the combinatorial data contained in the fan. Specifically, we give an effective combinatorial algorithm to compute the Chern-Schwartz-MacPherson class of X, in the Chow ring (or rational Chow ring) of X. This method is formulated by combining, a…
In this paper, we give a construction of the global Chern-Simons functions for toric Calabi-Yau stacks of dimension three using strong exceptional collections. The moduli spaces of sheaves on such stacks can be identified with critical loci of these functions. We give two applications of these functions. First, we prove Joyce's integrality conjecture of generalized DT invariants on local surfaces. Second, we prove a dimension reduction formula for virtual motives, which leads to two recursion formulas for motivic Donaldson-Thomas invariants.
Let X be a normal projective Q-Gorenstein variety with at worst log-terminal singularities. We prove a formula expressing the total stringy Chern class of a generic complete intersection in X via the total stringy Chern class of X. This formula is motivated by its applications to mirror symmetry for Calabi-Yau complete intersections in toric varieties. We compute stringy Chern classes and give a combinatorial interpretation of the stringy Libgober-Wood identity for arbitrary projective Q-Gorenstein toric varieties. As an application we derive a new combinatorial identity relating d-dimensional…
In this paper, we investigate whether the 124 nonsingular toric Fano 4-folds admit totally nondegenerate embeddings from abelian surfaces or not. As a result, we determine the possibilities for such embeddings except for the remaining 21 nonsingular toric Fano 4-folds.
We can run the MMP for any divisor on any $\mathbb{Q}$-factorial projective toric variety. We show that two Mori fiber spaces, which are outputs of the above MMP, are connected by finitely many elementary transforms.
A remark on toric foliations
本文研究射影 Q-因子环面簇上的环面叶状结构，证明当极射线长度超过叶状结构秩时，极收缩为射影空间丛且叶状结构等于其相对切层。
We prove the following result of Bondal's: that there is a fully faithful embedding $κ$ of the perfect derived category of a proper toric variety into the derived category of constructible sheaves on a compact torus. We compare this result to a torus-equivariant version considered in joint work with Fang, Liu, and Zaslow. There we showed that in the torus-equivariant version the image of the embedding is cut out by microlocal conditions. To establish a similar characterization of the image of $κ$ is an open problem.
We show that refined Chern-Simons theory and large N duality can be used to study the refined topological string with and without branes. We derive the refined topological vertex of hep-th/0701156 and hep-th/0502061 from a link invariant of the refined SU(N) Chern-Simons theory on S^3, at infinite N. Quiver-like Chern-Simons theories, arising from Calabi-Yau manifolds with branes wrapped on several minimal S^3's, give a dual description of a large class of toric Calabi-Yau. We use this to derive the refined topological string amplitudes on a toric Calabi-Yau containing a shrinking P^2 surface.…
Toric Fano manifolds that do not admit extremal Kähler metrics
本文构造了维数为 10 的环面 Fano 流形，使其第一陈类中无极值 Kähler 度量，并通过乘积推广到所有 n≥11，回答了 Mabuchi 的问题。
Chern Characteristics and Todd-Hirzebruch Identities for Transpolar Pairs of Toric Spaces
本文研究了通过星形三角化非凸多面体构造非Fano品种的全交集时，Chern特性与Transpolar对的Todd-Hirzebruch恒等式在非代数但光滑的Toric空间中的应用。
We prove that the mean Euler characteristic of a Gorenstein toric contact manifold, i.e. a good toric contact manifold with zero first Chern class, is equal to half the normalized volume of the corresponding toric diagram and give some applications. A particularly interesting one, obtained using a result of Batyrev and Dais, is the following: twice the mean Euler characteristic of a Gorenstein toric contact manifold is equal to the Euler characteristic of any crepant toric symplectic filling, i.e. any toric symplectic filling with zero first Chern class.
We initiate a systematic investigation of the space of 2+1 dimensional quiver gauge theories, emphasising a succinct "forward algorithm". Few "order parametres" are introduced such as the number of terms in the superpotential and the number of gauge groups. Starting with two terms in the superpotential, we find a generating function, with interesting geometric interpretation, which counts the number of inequivalent theories for a given number of gauge groups and fields. We demonstratively list these theories for some low numbers thereof. Furthermore, we show how these theories arise from M2-br…
H-Instanton Bundles on Three-Dimensional Smooth Toric Varieties with Picard Number Two
本文在具有 Picard 数为二的三维光滑 toric 变分上，研究 $H$-瞬子丛的构造与存在性，并推广了经典单调方法。
Vector bundles on proper toric 3-folds and certain other schemes
本研究证明满足特定修改条件的n维正常代数概形（含非射影情形）存在秩为n且顶陈数任意大的非平凡向量丛，应用于环面簇得出三维正常环面簇均有秩3的这类向量丛，并刻画了适用该结果的高维环面簇类。
Starting from the data of a nonsingular complex projective toric variety, we define an associated notion of toric co-Higgs bundle. We provide a Lie-theoretic classification of these objects by studying the interaction between Klyachko's fan filtration and the fiber of the co-Higgs bundle at a closed point in the open orbit of the torus action. This can be interpreted, under certain conditions, as the construction of a coarse moduli scheme of toric co-Higgs bundles of any rank and with any total equivariant Chern class.
In this paper we compute the motivic Chern classes and homology Hirzebruch characteristic classes of (possibly singular) toric varieties, which in the complete case fit nicely with a generalized Hirzebruch-Riemann-Roch theorem. As special cases, we obtain new (or recover well-known) formulae for the Baum-Fulton-MacPherson Todd (or MacPherson-Chern) classes of toric varieties, as well as for the Thom-Milnor L-classes of simplicial projective toric varieties. We present two different perspectives for the computation of these characteristic classes of toric varieties. First, we take advantage of …
This note presents some new information on how the minimum distance of the generalized toric code corresponding to a fixed set of integer lattice points S in R^2 varies with the base field. The main results show that in some cases, over sufficiently large fields, the minimum distance of the code corresponding to a set S will be the same as that of the code corresponding to the convex hull of S. In an example, we will also discuss a [49,12,28] generalized toric code over GF(8), better than any previously known code according to M. Grassl's online tables, as of July 2011.
Kawamata proposed a conjecture predicting that every nef and big line bundle on a smooth projective variety with trivial first Chern class has nontrivial global sections. We verify this conjecture for several cases, including (i) all hyperkähler varieties of dimension $\leq 6$; (ii) all known hyperkähler varieties except for O'Grady's 10-dimensional example; (iii) general complete intersection Calabi-Yau varieties in certain Fano manifolds (e.g. toric ones). Moreover, we investigate the effectivity of Todd classes of hyperkähler varieties and Calabi-Yau varieties. We prove that the fourth Todd…
On the classification of toric $2$-Fano manifolds: generic $\mathbb{P}^2$-bundles
本文通过研究最小投影包络维度m(X)扩展了toric 2-Fano manifold的分类，证明只有当m(X)=2时，X同构于P^2。
An Upper Bound on the Critical Volume in a Class of Toric Sasaki-Einstein Manifolds
该研究证明了一类环面Sasaki-Einstein流形的临界体积存在与对应环面Calabi-Yau簇Gorenstein奇点消解第一陈类相关的上界，刻画了上界可达情形，并提及所用的神经网络与梯度显著性计算工具。
Contact invariants of Q-Gorenstein toric contact manifolds, the Ehrhart polynomial and Chen-Ruan cohomology
本文研究Q-Gorenstein环面接触流形的柱形接触同调不变量，建立其与环面图的Ehrhart（拟）多项式、对应环面孤立奇点的crepant环面轨形消解的Chen-Ruan上同调，以及生成该流形的单调环面辛轨形底空间的Chen-Ruan上同调的关联。
Remarks on the second Chern class of a foliation
本文研究了叶状结构的第二陈类及其奇点方案的度数，提出对于射影空间上的叶状结构，其奇点方案的度数下界为d+1，并探讨了等号成立的条件。
We review the theory of combinatorial intersection cohomology of fans developed by Barthel-Brasselet-Fieseler-Kaup, Bressler-Lunts, and Karu. This theory gives a substitute for the intersection cohomology of toric varieties which has all the expected formal properties but makes sense even for non-rational fans, which do not define a toric variety. As a result, a number of interesting results on the toric $g$ and $h$ polynomials have been extended from rational polytopes to general polytopes. We present explicit complexes computing the combinatorial IH in degrees one and two; the degree two com…
Chern Classes of Tropical Manifolds
本文将拟阵的CSM闭链定义推广到热带流形，证明热带化对应定理和伴随公式，并建立具有Delzant面结构的紧致热带曲面的Noether公式。
We prove that the inverse of a mirror map for a toric Calabi-Yau manifold of the form $K_Y$, where $Y$ is a compact toric Fano manifold, can be expressed in terms of generating functions of genus 0 open Gromov-Witten invariants defined by Fukaya-Oh-Ohta-Ono \cite{FOOO10}. Such a relation between mirror maps and disk counting invariants was first conjectured by Gross and Siebert \cite[Conjecture 0.2 and Remark 5.1]{GS11} as part of their program, and was later formulated in terms of Fukaya-Oh-Ohta-Ono's invariants in the toric Calabi-Yau case in \cite[Conjecture 1.1]{CLL12}.
Let $X$ be a complex toric Fano $n$-fold and ${\cal N}(T)$ the normalizer of a maximal torus $T$ in the group of biholomorphic authomorphisms $Aut(X)$. We call $X$ {\em symmetric} if the trivial character is a single ${\cal N}(T)$-invariant algebraic character of $T$. Using an invariant $α_G(X)$ introduced by Tian, we show that all symmetric toric Fano $n$-folds admit an Einstein-Kähler metric. We remark that so far one doesn't know any example of a toric Fano $n$-fold $X$ such that $Aut(X)$ is reductive, the Futaki character of $X$ vanishes, but $X$ is not symmetric.
Self-dual toric varieties
该研究明确刻画了所有定义自对偶射影环面簇的权重多重集，揭示了其定义理想的弱鲁棒与强鲁棒组合性质及对应Graver基的结构特征。
We provide a contour integral formula for the exact partition function of ${\cal N}=2$ supersymmetric $U(N)$ gauge theories on compact toric four-manifolds by means of supersymmetric localisation. We perform the explicit evaluation of the contour integral for $U(2)$ ${\cal N}=2$ theory on $\mathbb{P}^2$ for all instanton numbers. In the zero mass case, corresponding to the ${\cal N}=4$ supersymmetric gauge theory, we obtain the generating function of the Euler characteristics of instanton moduli spaces in terms of mock-modular forms. In the decoupling limit of infinite mass we find that the ge…
Let $X_Σ$ be a smooth complete toric variety defined by a fan $Σ$ and let $V=V(I)$ be a subscheme of $X_Σ$ defined by an ideal $I$ homogeneous with respect to the grading on the total coordinate ring of $X_Σ$. We show a new expression for the Segre class $s(V,X_Σ)$ in terms of the projective degrees of a rational map specified by the generators of $I$ when each generator corresponds to a numerically effective (nef) divisor. Restricting to the case where $X_Σ$ is a smooth projective toric variety and dehomogenizing the total homogeneous coordinate ring of $X_Σ$ via a dehomogenizing ideal we als…
Chern flow and Chern moment algebras
该研究在任意域上构造了拉斯科、正格罗滕迪克等多项式的可实现体积模型，证明了多个相关支集与牛顿多面体猜想，还得到全局生成丛最高次全陈多项式的可实现性结论。
For a quasi-projective scheme M which carries a perfect obstruction theory, we construct the virtual cobordism class of M. If M is projective, we prove that the corresponding Chern numbers of the virtual cobordism class are given by integrals of the Chern classes of the virtual tangent bundle. Further, we study cobordism invariants of the moduli space of stable pairs introduced by Pandharipande-Thomas. Rationality of the partition function is conjectured together with a functional equation, which can be regarded as a generalization of the rationality and 1/q <-> q symmetry of the Calabi-Yau ca…
A fundamental result of toric geometry is that there is a bijection between toric varieties and fans. More generally, it is known that some class of manifolds having well-behaved torus actions, called topological toric manifolds $M^{2n}$, can be classified in terms of combinatorial data containing simplicial complexes with $m$ vertices. We remark that topological toric manifolds are a generalization of smooth toric varieties. The number $m-n$ is known as the Picard number when $M^{2n}$ is a {compact smooth} toric variety. In this paper, we investigate the relationship between the topological t…
In recent papers, summarized in survey [1], we construct a number of examples of non standard lagrangian tori on compact toric varieties and as well on certain non toric varieties which admit pseudotoric structures. Using this pseudotoric technique we explain how non standard lagrangian tori of Chekanov type can be constructed and what is the topological difference between standard Liouville tori and the non standard ones. However we have not discussed the natural question about the periods of the constructed twist tori; in particular the monotonicity problem for the monotonic case was not stu…
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