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Haibao Duan

Publications and source records attributed to Haibao Duan.

At least 19 recordsLinked to original sources
arXiv2026

A Classification of Self-Maps of Generalized Grassmannians

Generalized Grassmannians form a fundamental class of flag manifolds associated with Lie groups. The purpose of this paper is to classify self-maps of generalized Grassmannians of nonzero degree in terms of their induced actions on cohomology. We prove a rigidity theorem showing that, despite the rich and intricate structure of their cohomology rings, the induced cohomology endomorphisms fall into only two natural types: Adams operations determined by the degree and Dynkin symmetries arising from automorphisms of the Dynkin diagram. Combining the geometry of root and weight systems, the actions of Weyl and Dynkin symmetries on Schubert classes, and Bott--Samelson desingularizations of Schubert varieties, our approach applies uniformly to generalized Grassmannians of all Lie types.

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arXiv2026

On the degrees of equivariant maps from spheres to complex Stiefel manifolds

We study the set of degrees of $\mathbb{Z}/m$-equivariant maps from spheres to complex Stiefel manifolds, motivated by the work of Astey--Gitler--Micha--Pastor. Under a suitable arithmetic condition, this set is determined using results of James, Atiyah--Todd, and Adams--Walker. Our approach is homotopy-theoretic.

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arXiv2023

Schubert calculus in Lie groups

Let $G$ be a Lie group with a maximal torus $T$. Combining Schubert calculus in the flag manifold $G/T$ with the Serre spectral sequence of the fibration $G\rightarrow G/T$, we construct the integral cohomology ring $H^{\ast}(G)$ uniformly for all compact and simply connected Lie groups $G$.

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arXiv2022

Schubert calculus and Intersection theory of Flag manifolds

Hilbert's 15th problem called for a rigorous foundation of Schubert's calculus, in which a long standing and challenging part is Schubert's problem of characteristics. In the course of securing the foundation of algebraic geometry, Van der Waerden and André Weil attributed the problem to the determination of the intersection theory of flag manifolds. This article surveys the background, content, and resolution of the problem of characteristics. Our main results are a unified formula for the characteristics, and a system description for the intersection rings of flag manifolds. We illustrate the effectiveness of the formula and the algorithm via explicit examples.

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arXiv2022

Circle actions and Suspension operations on Smooth manifolds

Let $M$ be a smooth manifold with $\dim M\geq 3$ and a base point $x_{0}$. Surgeries along the oriented circle $S^{1}\times \{x_{0}\}$ on the product $ S^{1}\times M$ yields two manifolds $\Sigma _{0}M$ and $\Sigma _{1}M$, called the suspensions of $M$. The suspension operations $\Sigma _{i}$ play a basic role in the construction and classification of the smooth manifolds which admit free $ S^{1}$-actions. We illustrate this by a number of applications.

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arXiv2021

Estimate of number of simplices of triangulations of Lie groups

We present estimates of number of simplices of given dimension of classical compact Lie groups. As in the previous work \cite{GMP2} the approach is a combination of an estimate of number of vertices with a use of valuation of the covering type by cohomological argument of \cite{GMP} and application of the recent versions of the Lower Bound Theorem of combinatorial topology. For the case of exceptional Lie groups we made a complete calculation using the description of their cohomology rings given by the first and third author. For infinite increasing series of Lie groups of growing dimension $d$ the rate of growth of number of simplices of highest dimension is given which extends onto the case of simplices of (fixed) codimension $d-i$.

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arXiv2020

On Schubert's Problem of Characteristics

The Schubert varieties on a flag manifold G/P give rise to a cell decomposition on G/P whose Kronecker duals, known as the Schubert classes on G/P, form an additive base of the integral cohomology of G/P. The Schubert's problem of characteristics asks to express a monomial in the Schubert classes as a linear combination in the Schubert basis. We present a unified formula expressing the characteristics of a flag manifold G/P as polynomials in the Cartan numbers of the group G. As application we develop a direct approach to our recent works on the Schubert presentation of the cohomology rings of flag manifolds G/P.

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arXiv2020

String$\mathbf{^c}$ Structures and Modular Invariants

In this paper, we study some algebraic topology aspects of String$^c$ structures, more precisely, from the perspective of Whitehead tower and the perspective of the loop group of $Spin^c(n)$. We also extend the generalized Witten genera constructed for the first time in \cite{CHZ11} to correspond to String$^c$ structures of various levels and give vanishing results for them.

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arXiv2020

The multi-degree of coverings on Lie groups

We associate to each covering map of simple Lie groups a sequence of integers, called the multi-degree of the covering; extend Schubert calculus to evaluate the invariant; and apply the results to solve two outstanding topological problems arising from the studies of the Wess-Zumino-Witten models and the topological Gauge theories. The main tool in our approach is the Chow rings of Lie groups, introduced by Grothendieck in 1958.

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arXiv2019

The characteristic classes and Weyl invariants of Spinor groups

Based on a pair of cohomology operations on so called $δ-2$-formal spaces, we construct the integral cohomology rings of the classifying spaces of the Lie groups $Spin(n)$ and $Spin^{c}(n)$. As applications, we introduce characteristic classes for the reduced topological $K_{Spin}$ theory, determine the ring of integral Weyl invariants of the group $Spin(n)$, and demonstrate their usages in spin geometry.

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arXiv2017

The cohomology of projective unitary groups

The projective unitary group PU(n) is the quotient of the unitary group U(n) by its center. We compute the integral cohomology ring of PU(n) using explicit constructed generators.

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arXiv2017

On the Borel transgression in the fibration $G\rightarrow G/T$

Let $G$ be a semisimple Lie group with a maximal torus $T$. We present an explicit formula for the Borel transgression $τ:H^{1}(T)\rightarrow H^{2}(G/T)$ of the fibration $G\rightarrow G/T$. This formula corrects an error in the paper \cite{K}, and has been applied to construct the integral cohomology rings of compact Lie groups in the sequel works \cite{D,DZ2}.

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arXiv2017

Topology of unitary groups and the prime orders of binomial coefficients

Let $c:SU(n)\rightarrow PSU(n)=SU(n)/\mathbb{Z}_{n}$ be the quotient map of the special unitary group $SU(n)$ by its center subgroup $\mathbb{Z}_{n}$. We determine the induced homomorphism $c^{\ast}:$ $H^{\ast}(PSU(n))\rightarrow H^{\ast}(SU(n))$ on cohomologies by computing with the prime orders of binomial coefficients

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arXiv2016

Topology of Blow-ups and Enumerative Geometry

Let M be the blow--up of a manifold M along a submanifold X. In this paper we present closed formulae for the integral cohomology and the total Chern class of M. As applications we compute the cohomology of the varieties of complete conics and complete quadrices in 3--space, and justify two enumerative results due to Schubert.

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arXiv2016

Schubert calculus and cohomology of Lie groups. Part II. Compact Lie groups

Let $G$ be a compact Lie group with a maximal torus $T$. Based on a presentation of the integral cohomology ring $H^{\ast}(G/T)$ of the flag manifold $G/T$ in \cite{DZ1}we have presented in \cite{DZ2}an explicit and unified construction of the integral cohomology rings $H^{\ast}(G)$ for the $1$--connected Lie groups $G$. In this paper we extend this construction to all compact Lie groups.

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arXiv2015

Schubert presentation of the integral cohomology ring of the flag manifolds G/T

Let G be a compact connected Lie group with a maximal torus T\subsetG. In the context of Schubert calculus we obtain a canonical presentation for the integral cohomology ring H^{\ast}(G/T) of the complete flag manifold G/T. The result have been applied in [15] to construct the integral cohomology ring H^{\ast}(G) in terms of Schubert classes on G/T, and in [16] to determine the structure of the modp cohomology H^{\ast}(G;F_{p}) as a Hopf algebra over the Steenrod algebra.

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arXiv2013

The fixed set of the inverse involution on a Lie group

In [H. Duan and S. Liu, The isomorphism type of the centralizer of an element in a Lie group, Journal of algebra, 376(2013), 25-45], we have determined the isomorphism type of the centralizer of an element in a simpe Lie group. As a sequel to [H. Duan and S. Liu, The isomorphism type of the centralizer of an element in a Lie group, Journal of algebra, 376(2013), 25-45.] we present a general procedure to calculate the isomorphism type of the fixed set of the inverse involution on a Lie group.

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