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Zhenbo Qin

Publications and source records attributed to Zhenbo Qin.

At least 19 recordsLinked to original sources
arXiv2025

N^d-indexed persistence modules, higher dimensional partitions and rank invariants

We study decomposable N^d-indexed persistence modules via higher dimensional partitions. Their barcodes are defined in terms of the extended interior of the corresponding Young diagrams. For two decomposable N^d-indexed persistence modules, we present a necessary and sufficient condition, in terms of the partitions, for their rank invariants to be the same. This generalizes the well-known fact that for an N-indexed persistence module, its barcode and its rank invariant determine each other, i.e., the rank invariant is a complete invariant.

math.AT↗
arXiv2025

Multiple q-zeta values and traces

Let $(a)_\infty = (a; q)_\infty = \prod_{n=0}^\infty (1-aq^n)$. An elegant result of Bloch and Okounkov [BO] states that if $x = e^z$, then $$ \frac{(xq)_\infty (x^{-1}q)_\infty}{(q)_\infty^2}, $$ which appears in various traces in representation theory and algebraic geometry, is a formal power series in $z^2$ whose coefficient for $z^{2k}$ is a quasi-modular form of weight $2k$. Quasi-modular forms are special types of multiple $q$-zeta values. In this paper, we generalize this result of Bloch and Okounkov and prove that certain other traces are related to multiple $q$-zeta values. A simple case of our main results asserts that if $x = e^z$ and $y = e^w$, then $$ \frac{(xq)_\infty (yq)_\infty}{(q)_\infty (xyq)_\infty}, $$ which appears in [CW, Theorem 5] as a trace (the deformed Bloch-Okounkov $1$-point function), is a formal power series in $z$ and $w$ whose coefficient for $z^mw^n$ is a multiple $q$-zeta value (in the sense of [BK3, Oko]) of weight $(m+n)$.

math.NT↗
arXiv2025

Equivariant Chern character operators and Okounkov's conjecture

In this paper, we study the Chern character operators on the equivariant cohomology of the Hilbert schemes of points in the complex affine plane $C^2$ with the action of the torus $(C^*)^2$, and partially verify Okounkov's Conjecture [Oko, Conjecture 2] in this setting. Our main idea is to apply the connection between the equivariant cohomology of these Hilbert schemes and the ring of symmetric functions, via the deformed vertex operators of Cheng and Wang [CW], (the integral form of) the Jack symmetric functions and the transformed Macdonald symmetric functions of Garsia and Haiman [GH, Hai].

math.AG↗
arXiv2023

Hilbert schemes of points on surfaces and multiple q-zeta values

For a line bundle $L$ on a smooth projective surface $X$ and nonnegative integers $k_1, \ldots, k_N$, Okounkov \cite{Oko} introduced the reduced generating series $\big \langle {\rm ch}_{k_1}^{L} \cdots {\rm ch}_{k_N}^{L} \big \rangle'$ for the intersection numbers among the Chern characters of the tautological bundles over the Hilbert schemes of points on $X$ and the total Chern classes of the tangent bundles of these Hilbert schemes, and conjectured that they are multiple $q$-zeta values of weight at most $\sum_{i=1}^N (k_i + 2)$. The second-named author further conjectured in \cite{Qin2} that these reduced generating series are quasi-modular forms if the canonical divisor of $X$ is numerically trivial. In this paper, we verify these two conjectures for $\big \langle {\rm ch}_2^{L} \big \rangle'$. The main approaches are to apply the procedure laid out in \cite{QY} and to establish various identities for multiple $q$-zeta values and quasi-modular forms.

math.AG↗
arXiv2015

On Okounkov's conjecture connecting Hilbert schemes of points and multiple q-zeta values

We compute the generating series for the intersection pairings between the total Chern classes of the tangent bundles of the Hilbert schemes of points on a smooth projective surface and the Chern characters of tautological bundles over these Hilbert schemes. Modulo the lower weight term, we verify Okounkov's conjecture [Oko] connecting these Hilbert schemes and multiple $q$-zeta values. In addition, this conjecture is completely proved when the surface is abelian. We also determine some universal constants in the sense of Boissi\' ere and Nieper-Wisskirchen [Boi, BN] regarding the total Chern classes of the tangent bundles of these Hilbert schemes. The main approach of this paper is to use the set-up of Carlsson and Okounkov outlined in [Car, CO] and the structure of the Chern character operators proved in [LQW2].

math.AG↗
arXiv2014

The Gromov-Witten invariants of the Hilbert schemes of points on surfaces with $p_g > 0$

In this paper, we study the Gromov-Witten theory of the Hilbert schemes X^{[n]} of points on smooth projective surfaces X with positive geometric genus p_g. Using cosection localization technique due to Y. Kiem and J. Li [KL1, KL2], we prove that if X is a simply connected surface admitting a holomorphic differential two-form with irreducible zero divisor, then all the Gromov-Witten invariants of X^{[n]} defined via the moduli space $\Mbar_{g, r}(X^{[n]}, β)$ vanish except possibly when $β= d_0 β_{K_X} - d β_n$ where d is an integer, $d_0 \ge 0$ is a rational number, and $β_n$ and $β_{K_X}$ are defined in (3.2) and (3.3) respectively. When $n=2$, the exceptional cases can be further reduced to the invariants: $<1>_{0, β_{K_X} - dβ_2}^{X^{[2]}}$ with $K_X^2 = 1$ and $d \le 3$, and $<1>_{1, dβ_2}^{X^{[2]}}$ with $d \ge 1$. We show that when $K_X^2 = 1$, $$<1>_{0, β_{K_X} - 3 β_2}^{X^{[2]}} = (-1)^{χ(\mathcal O_X)}$$ which is consistent with a well-known formula of Taubes [Tau]. In addition, for an arbitrary smooth projective surface X and $d \ge 1$, we verify that $$<1>_{1, dβ_2}^{X^{[2]}} = K_X^2/(12d).$$

math.AG↗
arXiv2013

The Cohomological Crepant Resolution Conjecture for the Hilbert-Chow morphisms

In this paper, we prove that Ruan's Cohomological Crepant Resolution Conjecture holds for the Hilbert-Chow morphisms. There are two main ideas in the proof. The first one is to use the representation theoretic approach proposed in [QW] which involves vertex operator techniques. The second is to prove certain universality structures about the 3-pointed genus-0 extremal Gromov-Witten invariants of the Hilbert schemes by using the indexing techniques from [LiJ], the product formula from [Beh2] and the co-section localization from [KL1, KL2, LL]. We then reduce Ruan's Conjecture from the case of an arbitrary surface to the case of smooth projective toric surfaces which has already been proved in [Che].

math.AG↗
arXiv2011

Mini-walls for Bridgeland stability conditions on the derived category of sheaves over surfaces

For the derived category of bounded complexes of sheaves on a smooth projective surface, Bridgeland and Arcara-Bertram constructed Bridgeland stability conditions $(Z_m, \mathcal P_m)$ parametrized by $m \in (0, +\infty)$. In this paper, we show that the set of mini-walls in $(0, +\infty)$ of a fixed numerical type is locally finite. In addition, we strengthen a result of Bayer by proving that the moduli of polynomial Bridgeland semistable objects of a fixed numerical type coincides with the moduli of $(Z_m, \mathcal P_m)$-semistable objects whenever $m$ is larger than a universal constant depending only on the numerical type. We further identify the moduli of polynomial Bridgeland semistable objects with the Gieseker/Simpson moduli spaces and the Uhlenbeck compactification spaces.

math.AG↗
arXiv2010

Donaldson-Thomas invariants of certain Calabi-Yau 3-folds

We compute the Donaldson-Thomas invariants for two types of Calabi-Yau 3-folds. These invariants are associated to the moduli spaces of rank-2 Gieseker semistable sheaves. None of the sheaves are locally free, and their double duals are locally free stable sheaves investigated earlier by Donaldson and Thomas, Li and Qin respectively. We show that these Gieseker moduli spaces are isomorphic to some Quot-schemes. We prove a formula for Behrend's functions when torus actions present with positive dimensional fixed point sets, and use it to obtain the generating series of the relevant Donaldson-Thomas invariants in terms of the McMahon function. Our results might shed some light on the wall-crossing phenomena of Donaldson-Thomas invariants.

math.AG↗
arXiv2009

1-point Gromov-Witten invariants of the moduli spaces of sheaves over the projective plane

The Gieseker-Uhlenbeck morphism maps the Gieseker moduli space of stable rank-2 sheaves on a smooth projective surface to the Uhlenbeck compactification, and is a generalization of the Hilbert-Chow morphism for Hilbert schemes of points. When the surface is the complex projective plane, we determine all the 1-point genus-0 Gromov-Witten invariants extremal with respect to the Gieseker-Uhlenbeck morphism. The main idea is to understand the virtual fundamental class of the moduli space of stable maps by studying the obstruction sheaf and using a meromorphic 2-form on the Gieseker moduli space.

math.AG↗
arXiv2008

Equivariant cohomology of incidence Hilbert schemes and loop algebras

Let $S$ be the affine plane $\C^2$ together with an appropriate $\mathbb T = \C^*$ action. Let $\hil{m,m+1}$ be the incidence Hilbert scheme. Parallel to \cite{LQ}, we construct an infinite dimensional Lie algebra that acts on the direct sum $$\Wft = \bigoplus_{m=0}^{+\infty}H^{2(m+1)}_{\mathbb T}(S^{[m,m+1]})$$ of the middle-degree equivariant cohomology group of $\hil{m,m+1}$. The algebra is related to the loop algebra of an infinite dimensional Heisenberg algebra. In addition, we study the transformations among three different linear bases of $\Wft$. Our results are applied to the ring structure of the ordinary cohomology of $\hil{m,m+1}$ and to the ring of symmetric functions in infinitely many variables.

math.AG↗
arXiv2006

Hilbert schemes of points on the minimal resolution and soliton equations

The equivariant and ordinary cohomology rings of Hilbert schemes of points on the minimal resolution C^2//G for cyclic G are studied using vertex operator technique, and connections between these rings and the class algebras of wreath products are explicitly established. We further show that certain generating functions of equivariant intersection numbers on the Hilbert schemes and related moduli spaces of sheaves on C^2//G are tau functions of 2-Toda hierarchies.

math.QA↗
arXiv2006

Incidence Hilbert schemes and infinite dimensional Lie algebras

Given a projetive surface $S$, using correspondences, we construct an infinite dimensional Lie algebra that acts on the direct sum $\Wfock$ of the cohomology groups of the incidence Hilbert schemes $S^{[n,n+1]}$ over all $n$. The algebra is related to an extension of an infinite dimensional Heisenberg algebra. The space $\Wfock$ is a highest weight representation of this algebra. Our result provides a representation-theoretic interpretation of Cheah's generating function of Betti numbers of the incidence Hilbert schemes. As a consequence, an additive basis of the cohomology group of the incidence Hilbert scheme is obtained.

math.AG↗
arXiv2006

The Gromov-Witten and Donaldson-Thomas correspondence for trivial elliptic fibrations

We study the Gromov-Witten and Donaldson-Thomas correspondence conjectured in [MNOP1, MNOP2], for trivial elliptic fibrations. In particular, we verify the Gromov-Witten and Donaldson-Thomas correspondence for primary fields when the threefold is $E \times S$ where $E$ is a smooth elliptic curve and $S$ is a smooth surface with numerically trivial canonical class.

math.AG↗
arXiv2005

On the Euler numbers of certain moduli spaces of curves and points

We determine the topological Euler number of certain moduli space of 1-dimensional closed subschemes in a smooth projective variety which admits a Zariski-locally trivial fibration with 1-dimensional fibers. The main approach is to use virtual Hodge polynomials and torus actions. The results might shed some light on the corresponding Donaldson-Thomas invariants.

math.AG↗
arXiv2005

On certain moduli spaces of ideal sheaves and Donaldson-Thomas invariants

We determine the structure of certain moduli spaces of ideal sheaves by generalizing an earlier result of the first author. As applications, we compute the (virtual) Hodge polynomials of these moduli space, and calculate the Donaldson-Thomas invariants of certain 3-folds with trivial canonical classes.

math.AG↗
arXiv2004

Integral operators and integral cohomology classes of Hilbert schemes

The methods of integral operators on the cohomology of Hilbert schemes of points on surfaces are developed. They are used to establish integral bases for the cohomology groups of Hilbert schemes of points on a class of surfaces (and conjecturally, for all simply connected surfaces).

math.AG↗