Daniel Duarte, Luis Núñez-Betancourt
We prove that the higher Nash blowup of a normal toric variety defined over a field of positive characteristic is an isomorphism if and only if it is non-singular. We also extend a result by R. Toh-Yama which shows that higher Nash blowups do not give a one-step resolution of the $A_3$-singularity. These results were previously known only in characteristic zero.
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We consider the problem of finding an ideal whose blowup defines the Nash blowup of a toric surface and such that its zero locus coincides with the singular set of the toric surface.
Nash blowups of toric varieties in prime characteristic
本文研究素特征域上Nash吹胀的奇点消解性质，证明迭代规范化Nash吹胀可消解正规环面曲面奇点，并引入对数Jacobian理想的素特征版本以实现对任意维环面簇Nash吹胀的组合描述。
The higher Nash blowup of an algebraic variety replaces singular points with limits of certain spaces carrying higher order data associated to the variety at non-singular points. In the case of normal toric varieties we give a combinatorial description of the higher Nash blowup in terms of a Gröbner fan. This description will allow us to prove the analogue of Nobile's theorem on the usual Nash blowup in this context. More precisely, we prove that for a normal toric variety, the higher Nash blowup is an isomorphism if and only if the variety is non-singular.
Classification of normal toric surfaces resolved by a single Nash blowup
本文通过连分数方法对由单次Nash吹胀解析的正常尖点曲面进行了完整分类。
Higher Nash blowups
本文引入高阶纳什爆破概念，详细研究曲线情形，并证明特征零下任何曲线都可由足够高阶的纳什爆破实现去奇异化。
The higher Nash blowup of an algebraic variety replaces singular points with limits of certain spaces carrying higher-order data associated to the variety at non-singular points. In this note we will define a higher-order Jacobian matrix that will allow us to make explicit computations concerning the higher Nash blowup of hypersurfaces. Firstly, we will generalize a known method to compute the fiber of this modification. Secondly, we will give an explicit description of the ideal whose blowup gives the higher Nash blowup. As a consequence, we will deduce a higher-order version of Nobile's theo…
This short note solves the following problem: Given a map of normal toric varieties corresponding to a coherent subdivision of a cone, find an ideal such that the given map is the blowup of that ideal.
Nash blowup fails to resolve singularities in dimensions four and higher
本文证明在任意特征的代数闭域上，对四维及以上代数簇迭代 Nash blowup 或规范化 Nash blowup 均不能消解奇点。
Characteristic-free normalized Nash blowup of toric varieties
本文研究环簇的标准化 Nash 爆破，引入锥体条件使定义多面体不依赖基域特征，从而推导奇点消解性质，恢复正特征已知结果并给出任意特征下非奇异的新族。
Non-normalized Nash blowup fails to resolve singularities in dimension three
本文证明了在特征零域上，迭代非正规化的Nash吹胀未必能消解三维代数簇的奇点。
Flag higher Nash blowups
本文引入另一种更高阶纳什爆破，证明其与乘积和光滑态射相容，并证明曲线乘积可通过两种版本实现去奇异化。
We study Sarkisov links initiated by the toric weighted blowup of a point in $\mathbb{P}^3$ or $\mathbb{P}^4$ using variation of GIT. We completely classify which of these initiate Sarkisov links and describe the links explicitly. Moreover, if $X$ is the toric weighted blowup of $\mathbb{P}^d$ at a point, we give a simple criterion in terms of the weights of the blowup that characterises when $X$ is weak Fano.
Nash blowups of normal toric surfaces: the case of one and two segments
本文研究正规环面曲面奇点的Nash爆破消解问题，证明当对应半群的极小生成集位于一段或两段时迭代Nash爆破可消解奇点，并给出任意多段情形成立的例子。
On a Computational Approach to the Nash Blowup Problem
本文通过计算方法发现纳什吹胀猜想的反例，并提供了无法通过标准化纳什吹胀解析的典范簇例子，同时展示了大量计算证据支持猜想的剩余开放案例。
Nash blowups of 2-generic determinantal varieties in positive characteristic
本文通过显式描述toric结构并证明Nash吹胀组合学无特征依赖，得出正特征域上2-generic行列式簇的Nash吹胀非奇异。
We show that the $ n $-th Nash blowup of the toric surface singularity of type $ A_3 $ is singular for any $ n > 0 $. It was known that the normalization of the $ n $-th Nash blowup of a toric variety is also a toric variety associated to the Gröbner fan of a certain ideal $ J_n $. In our case, we prove that the Gröbner fan contains a non-regular cone. We determine minimal generators of the initial ideal of $ J_n $ with respect to a certain monomial ordering, and show that the reduced Gröbner basis of $ J_n $ has polynomials of certain forms for each $ n $.
We introduce a higher-order version of the tangent map of a morphism and find a matrix representation. We then apply this matrix to solve a conjecture by T. Yasuda regarding the semigroup of the higher Nash blowup of formal curves. We first show that the conjecture is true for toric curves. We conclude by exhibiting a family of non-monomial curves where the conjecture fails.
A one-step counterexample to the normalized Nash blowup conjecture
本文构造了一个五维的正常奇异仿射交错簇，其归一化纳什吹胀已包含与原簇同构的仿射开子簇，从而在五维及以上所有特征下给出单步反例。
F-blowups and essential divisors for toric varieties
本文研究环面簇上本质除子与F-爆破的关系，给出除子出现在极限F-爆破上的充分条件，并证明有余切消解时答案为肯定，还给出非本质除子出现的例子。
We establish a genus zero correspondence between the equivariant Gromov-Witten theory of the Deligne-Mumford stack $[\mathbb{C}^N/G]$ and its blowup at the origin. The relationship generalizes the crepant transformation conjecture of Coates-Iritani-Tseng and Coates-Ruan to the discrepant (non-crepant) setting using asymptotic expansion. Using this result together with quantum Serre duality and the MLK correspondence we prove LG/Fano and LG/general type correspondences for hypersurfaces.
Mather-Yau's type theorem for higher Nash blowup algebras
本文针对任意域上的超曲面奇点，证明其局部环同构类型由高阶Nash爆破代数完全决定，先证该代数在接触等价下的稳定性，再用Samuel经典结果证逆命题，推广了经典Mather-Yau定理。
Counts of holomorphic disks are at the heart of the SYZ approach to mirror symmetry. In the non archimedean framework, these counts are expressed as counts of analytic cylinders. In simple cases, such as cluster varieties, these counts can be extracted from a combinatorial algorithm encoded by a scattering diagram. The relevant scattering diagram encodes information about infinitesimal analytic cylinders. In this paper, we give a formula relating counts of a restricted class of cylinders on affine log Calabi Yau surfaces to counts on a single blowup of a toric surface, using non archimedean Gr…
We initiate the study of Nash blowups in prime characteristic. First, we show that a normal variety is non-singular if and only if its Nash blowup is an isomorphism, extending a theorem by A. Nobile. We also study higher Nash blowups, as defined by T. Yasuda. Specifically, we give a characteristic-free proof of a higher version of Nobile's Theorem for quotient varieties and hypersurfaces. We also prove a weaker version for $F$-pure varieties.
We present a solution for Nash problem for stable toric varieties. We also introduce Nash problem for pairs and prove it for toric pairs.
This paper explores homological mirror symmetry for weighted blowups of toric varieties. It will be shown that both the A-model and B-model categories have natural semiorthogonal decompositions. An explicit equivalence of the right orthogonal categories will be shown for the case of toric surfaces.
We revisit the problem of resolution of singularities of toric curves by iterating Nash modification. We give a bound on the number of iterations required to obtain the resolution. We also introduce a different approach on counting iterations by dividing the combinatorial algorithm of Nash modification of toric curves into several division algorithms.
We show that there exists a strong connection between the generic formal neighborhood at a rational arc lying in the Nash set associated with a toric divisorial valuation on a toric variety and the formal neighborhood at the generic point of the same Nash set. This may be interpreted as the fact that, analytically along such a Nash set, the arc scheme of a toric variety is a product of a finite dimensional singularity and an infinite dimensional affine space.
This paper formulates the Nash problem for a pair consisting of a toric variety and an invariant ideal and gives an affirmative answer to the problem. We also prove that the minimal log-discrepacy is computed by a divisor corresponding to a Nash component, if the minimal log-discrepancy is finite. On the other hand there exists a Nash component such that the corresponding divisor has negative log-discrepancy, if the minimal log-discrepancy is $-/infty$.
Using Frobenius morphisms of noncommutative blowups, we prove that every normal toric singularity has a standard noncommutative resolution.
Exceptional loci of F-blowups and $G$-Hilbert schemes
研究F吹胀正常分形变的例外极子，通过组合数据给出素除子中心维数公式，并探讨F吹胀与三维终端奇点和canonical奇点的关联。
It has been recently shown that the iteration of Nash modification on not necessarily normal toric varieties corresponds to a purely combinatorial algorithm on the generators of the semigroup associated to the toric variety. We will show that for toric surfaces this algorithm stops for certain choices of affine charts of the Nash modification. In addition, we give a bound on the number of steps required for the algorithm to stop in the cases we consider. Let $\C(x_1,x_2)$ be the field of rational functions of a toric surface. Then our result implies that if $ν:\C(x_1,x_2)\rightarrowΓ$ is any v…
Let E be a toric fibration arising from symplectic reduction of a direct sum of line bundles over (almost-) Kähler base B. Then each torus-fixed point of the toric manifold fiber defines a section of the fibration. Let L_a be convex line bundles over B, A_a smooth divisors of B arising as the zero loci of generic sections of L_a, and \a:B\to E a particular fixed-point section of E. Further assume the \{A_a\} to be mutually disjoint. We compute genus-0 Gromov--Witten invariants of the blowup of E along \a(\coprod_a A_a) in terms of genus-0 Gromov--Witten invariants of B and of \{A_a\}, the matr…
A case study of intersections on blowups of the moduli of curves
本文利用对数爆裂与虚拟严格变换，证明曲线模空间中的环面接触环位于tautological环中，并给出其计算方法，推广了Faber–Pandharipande的经典结果。
This paper proposes some material towards a theory of general toric varieties without the assumption of normality. Their combinatorial description involves a fan to which is attached a set of semigroups subjected to gluing-up conditions. In particular it contains a combinatorial construction of the blowing up of a sheaf of monomial ideals on a toric variety. In the second part it is shown that over an algebraically closed base field of zero characteristic the Semple-Nash modification of a general toric variety is isomorphic to the blowing up of the sheaf of logarithmic jacobian ideals and that…
An introduction to real oriented blowups in toric, toroidal and logarithmic geometries
本文介绍了复对数空间取整（Kato-Nakayama实现）在奇点理论中的应用，通过极坐标转换引入仿射环面簇、实定向吹胀、对数结构等概念，并涵盖Nakayama-Ogus关于特殊对数态射取整局部平凡性的定理。
Non-existence of negative derivations on the higher Nash blowup local algebra
本文证明具有孤立奇点的加权齐次多项式的高次Nash爆破局部代数在$n\geq2$时无负加权导子，肯定回答了Hussain-Ma-Yau-Zuo猜想。
In this paper, using the degeneration formula we obtain a blowup formulae of local Gromov-Witten invariants of Fano surfaces. This formula makes it possible to compute the local Gromov-Witten invariants of non-toric Fano surfaces form toric Fano surface, such as del Pezzo surfaces. This formula also verifed an expectation of Chiang-Klemm-Yau-Zaslow.
We consider mirror symmetry for (essentially arbitrary) hypersurfaces in (possibly noncompact) toric varieties from the perspective of the Strominger-Yau-Zaslow (SYZ) conjecture. Given a hypersurface $H$ in a toric variety $V$ we construct a Landau-Ginzburg model which is SYZ mirror to the blowup of $V\times\mathbb{C}$ along $H\times 0$, under a positivity assumption. This construction also yields SYZ mirrors to affine conic bundles, as well as a Landau-Ginzburg model which can be naturally viewed as a mirror to $H$. The main applications concern affine hypersurfaces of general type, for which…
The Nash problem on arc families is affirmatively answered for a toric variety by Ishii and Kollar's paper which also shows the negative answer for general case. The Nash problem is one of questions about the relation between arc families and valuations. In this paper, the relation is described clearly for a toric variety. The arc space of a toric variety admits an action of the group scheme determined by the torus. Each orbit on the arc space corresponds to a lattice point in the cone and therefore corresponds to a toric valuation. The dominant relation among the orbits is described in terms …
It is a long-standing question whether an arbitrary variety is desingularized by finitely many normalized Nash blow-ups. We consider this question in the case of a toric variety. We interpret the normalized Nash blow-up in polyhedral terms, show how continued fractions can be used to give an affirmative answer for a toric surface, and report on a computer investigation in which over a thousand 3- and 4-dimensional toric varieties were successfully resolved.
We study smoothness of toric quiver varieties. When a quiver $Q$ is defined with the identity dimension vector, the corresponding quiver variety is also a toric variety. So it has both fan representation and quiver representation. We work only on quivers with canonical weight and we classify smooth such toric quiver varieties. We show that a variety corresponding to a quiver with the identity dimension vector and the canonical weight is smooth if and only if it is a product of projective spaces or their blowups.
Quadratic generation of ideals defining nonsigular toric 3-folds
针对两类非奇异环三维簇上的丰富线丛，证明其射影正规嵌入对应的理想可由二次元素生成。
This paper shows the affirmative answer to the local Nash problem for a toric singularity and analytically pretoric singularity. As a corollary we obtain the affirmative answer to the local Nash problem for a quasi-ordinary singularity.
We show that the normalization of the Nash blow-up of order n of the toric surface singularity An can be factorized by the minimal resolution of An. The result is obtained using the combinatorial description of these objects.
Toric Elliptic Pairs with Picard Number Three
本文研究皮卡数为三的环面椭圆对，通过分析 $K_X+C$ 的 Zariski 分解中的曲线，证明了不存在 Lang-Trotter 四边形，从而否定回答了已有文献提出的公开问题。
Normal Bundle Splitting Strata of Rational Curves in Toric Varieties
本文研究环面簇中有理曲线法丛分裂型的分层，通过Cox构造和相对上同调态射给出非平衡性数值判据，并应用于射影空间爆破，与已有结果等价。
We prove that, for the jet scheme of a singular hypersurface, the blowup of a certain jet-related module is not an isomorphism. In conjunction with recent developments in the theory of Nash blowups, our result holds over fields of arbitrary characteristic. Our approach is based on explicit presentations given by a higher-order Jacobian matrix combined with a certain jet-related matrix.
Let V be an irreducible affine algebraic variety over a field k of characteristic zero, and let (f_0,...,f_m) be a sequence of elements of the coordinate ring. There is probably no elementary condition on the f_i and their derivatives which determines whether the blowup of V along (f_0,...,f_m) is nonsingular. The result is that there indeed is such an elementary condition, involving the first and second derivatives of the $f_i,$ provided we admit certain singular blowups, all of which can be resolved by an additional Nash blowup. There is is a particular explicit sequence of ideals R=J_0, J_1…
We give a geometric interpretation of cluster varieties in terms of blowups of toric varieties. This enables us to provide, among other results, an elementary geometric proof of the Laurent phenomenon for cluster algebras (of geometric type), extend Speyer's example of an upper cluster algebra which is not finitely generated, and show that the Fock-Goncharov dual basis conjecture is usually false.
Notes on Nash modification
本文围绕代数簇的Nash修改展开，梳理了该领域的若干后续研究，涵盖正规簇推广、高阶Nash修改、环面簇情形及消奇点性质等主题。
We study a graded algebra D=D(L,G) defined by a finite lattice L and a subset G in L, a so-called building set. This algebra is a generalization of the cohomology algebras of hyperplane arrangement compactifications found in work of De Concini and Procesi. Our main result is a representation of D, for an arbitrary atomic lattice L, as the Chow ring of a smooth toric variety that we construct from L and G. We describe this variety both by its fan and geometrically by a series of blowups and orbit removal. Also we find a Groebner basis of the relation ideal of D and a monomial basis of D over Z.
We will describe a one-step "Gorensteinization" process for a Schubert variety by blowing-up along its boundary divisor. The local question involves Kazhdan-Lusztig varieties which can be degenerated to affine toric schemes defined using the Stanley-Reisner ideal of a subword complex. The blow-up along the boundary in this toric case is in fact Gorenstein. We show that there exists a degeneration of the blow-up of the Kazhdan-Lusztig variety to this Gorenstein scheme, allowing us to extend this result to Schubert varieties in general. The potential use of this one-step Gorensteinization to des…
Let (X,0) be a germ of complex analytic normal variety, non-singular outside 0. An essential divisor over (X,0) is a divisorial valuation of the field of meromorphic functions on (X,0), whose center on any resolution of the germ is an irreducible component of the exceptional locus. The Nash map associates to each irreducible component of the space of arcs through 0 on X the unique essential divisor intersected by the strict transform of the generic arc in the component. Nash proved its injectivity and asked if it was bijective. We prove that this is the case if there exists a divisorial resolu…
Higher Jacobian matrix of weighted homogeneous polynomials and derivation algebras
本文证明加权齐次多项式高阶 Jacobian 矩阵极大子式所生成的理想仍为加权齐次，并据此部分回应高阶 Nash 爆破局部代数上不存在负权导子的猜想。
Signature 0 toric varieties, wall crossings, and cross polytope-like structures
本文研究符号差为0的偶维完备环面簇对应的单纯局部凸扇结构，利用壁穿技术揭示其链环、锚定子空间的相交规律，生成覆盖极小对象的诱导4环，推进了对顶γ向量为0情形的理解。
Weight sensitivity in K-stability of Fano varieties
本文证明了特定球面Fano三维簇中加权K-多稳定性等价于加权Futaki不变量消失，并在Mori-Mukai族2-29及高维二次曲面中展示了该性质不成立的显式反例。
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