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Yingbo Han

Publications and source records attributed to Yingbo Han.

15 recordsLinked to original sources
arXiv2026

On the Hamilton-Tian Conjecture in a compact transverse Fano Sasakian $5$-manifold

In this paper, we first confirm the Hamilton-Tian conjecture for the Sasaki-Ricci flow in a compact transverse Fano quasi-regular Sasakian $5$-manifold with klt foliation singularities. Secondly, we derive the compactness theorem of Sasaki-Ricci solitons on transverse Fano quasi-regular Sasakian $5$-manifolds. Then,by the second Sasakian structure theorem, we confirm the Hamilton-Tian conjecture for a compact transverse Fano Sasakian $5$-manifold. With its applications, we show that the gradient Sasaki-Ricci soliton orbifold metric on a compact Sasakian $5$-manifold is Sasaki-Einstein if $M$ is transverse $K$-stable.

math.DG↗
arXiv2026

On the Sasakian Structure of Manifolds with Nonnegative Transverse Bisectional Curvature

In this paper, we concern with the Sasaki analogue of Yau uniformization conjecture in a complete noncompact Sasakian manifold with nonnegative transverse bisectional curvature. As a consequence, we confirm that any $5$-dimensional complete noncompact Sasakian manifold with positive transverse bisectional curvature and the maximal volume growth must be CR-biholomorphic to the standard Heisenberg group $\mathbb{H}_{2}$ which can be stated as the standard contact Euclidean $5$-space $\mathbb{R}^{5}$.

math.DG↗
arXiv2025

Geometry and Topology of Gradient Shrinking Sasaki-Ricci Solitons

In this paper, we study the geometry and topology of complete gradient shrinking Sasaki-Ricci solitons. We first prove that they must be connected at infinity. This is a Sasaki analogue of gradient shrinking K\"ahler-Ricci solitons. Secondly, with the positive sectional curvature or positive transverse holomorphic bisectional curvature, we show that they must be compact. All results are served as a generalization of Perelman in dimension three, of Naber in dimension four, and of Munteanu-Wang in all dimensions, respectively.

math.DG↗
arXiv2023

The geometry of $\Phi_{(3)}$-harmonic maps

In this paper, we motivate and extend the study of harmonic maps or $\Phi_{(1)}$-harmonic maps (cf [15], Remark 1.3 (iii)), $\Phi$-harmonic maps or $\Phi_{(2)}$-harmonic maps (cf. [24], Remark 1.3 (v)), and explore geometric properties of $\Phi_{(3)}$-harmonic maps by unified geometric analytic methods. We define the notion of $\Phi_{(3)}$-harmonic maps and obtain the first variation formula and the second variation formula of the $\Phi_{(3)}$-energy functional $E_{\Phi_{(3)}}$. By using a stress-energy tensor, the $\Phi_{(3)}$-conservation law, a monotonicity formula, and the asymptotic assumption of maps at infinity, we prove Liouville type results for $\Phi_{(3)}$-harmonic maps. We introduce the notion of $\Phi_{(3)}$-Superstrongly Unstable ($\Phi_{(3)}$-SSU) manifold and provide many interesting examples. By using an extrinsic average variational method in the calculus of variations (cf. [51, 49]), we find $\Phi_{(3)}$-SSU manifold and prove that for $i=1,2,3$, every compact $\Phi_{(i)}$-$\operatorname{SSU}$ manifold is $\Phi_{(i)}$-$\operatorname{SU}$, and hence is $\Phi_{(i)}$-$\operatorname{U}$ (cf. Theorem 9.3). As consequences, we obtain topological vanishing theorems and sphere theorems by employing a $\Phi_{(3)}$-harmoic map as a catalyst. This is in contrast to the approaches of utilizing a geodesic ([45]), minimal surface, stable rectifiable current ([34, 29, 50]), $p$-harmonic map (cf. [53]), etc., as catalysts. These mysterious phenomena are analogs of harmonic maps or $\Phi_{(1)}$-harmonic maps, $p$-harmonic maps, $\Phi_{S}$-harmonic maps, $\Phi_{S,p}$-harmonic maps, $\Phi_{(2)}$-harmonic maps, etc., (cf. [21, 40, 42, 41, 12, 13]).

math.DG↗
arXiv2023

Legendrian mean curvature flow in $\eta$-Einstein Sasakian manifolds

Recently, there are a great deal of work done which connects the Legendrian isotopic problem with contact invariants. The isotopic problem of Legendre curve in a contact 3-manifold was studies via the Legendrian curve shortening flow which was introduced and studied by K. Smoczyk. On the other hand, in the SYZ Conjecture, one can model a special Lagrangian singularity locally as the special Lagrangian cones in C^{3}. This can be characterized by its link which is a minimal Legendrian surface in the 5-sphere. Then in these points of view, in this paper we will focus on the existence of the long-time solution and asymptotic convergence along the Legendrian mean curvature flow in higher dimensional {\eta}-Einstein Sasakian (2n+1)-manifolds under the suitable stability condition due to the Thomas-Yau conjecture.

math.DG↗
arXiv2022

Gradient Shrinking Sasaki-Ricci Solitons on Sasakian Manifolds of Dimension Up to Seven

In this paper, we show that the uniform L^4-bound of the transverse Ricci curvature along the Sasaki-Ricci flow on a compact quasi-regular transverse Fano Sasakian (2n+1)-manifold M. When M is dimension up to seven and the space of leaves of the characteristic foliation is well-formed, we first show that any solution of the Sasaki-Ricci flow converges in the Cheeger-Gromov sense to the unique singular orbifold Sasaki-Ricci soliton on the limit space which is a S^1-orbibundle over the unique singular Kaehler-Ricci soliton on a normal projective variety with codimension two orbifold singularities. Secondly, for n=1, we show that there are only two nontrivial Sasaki-Ricci solitons on a compact quasi-regular Fano Sasakian three-sphere with its leave space a teardrop-like and football-like space, respectively. For n=2,3, we show that the Sasaki-Ricci soliton is trivial one if M is transverse K-stable.

math.DG↗
arXiv2022

Convergence of the Sasaki-Ricci flow on Sasakian 5-manifolds of general type

In this paper, we show that the uniform L^{4}-bound of the transverse Ricci curvature along the Sasaki-Ricci flow on a compact quasi-regular Sasakian (2n+1)-manifold M of general type. As an application, any solution of the normalized Sasaki-Ricci flow converges in the Cheeger-Gromov sense to the unique singular Sasaki {\eta}-Einstein metric on the transverse canonical model M_{can} of M if n is less than or equal to 3. In particular for n equal to 2, M_{can} is a S^{1}-orbibundle over the unique Keahler-Einstein orbifold surface (Z_{can},{\omega}_{KE}) with finite point orbifold singularities. The floating foliation (-2)-curves in M will be contracted to orbifold points by the Sasaki-Ricci flow as t goes to infinite.

math.DG↗
arXiv2019

Nonexistence of proper $p$-biharmonic maps and Liouville type theorems I: case of $p\geq2$

Let $u: (M, g)\to (N, h)$ be a map between Riemannian manifolds $(M, g)$ and $(N, h)$. The $p$-bienergy of $u$ is defined by $E_p(u)=\int_M|τ(u)|^pdν_g$, where $τ(u)$ is the tension field of $u$ and $p>1$. Critical points of $E_p(\cdot)$ are called $p$-biharmonic maps. In this paper we will prove nonexistence result of proper $p$-biharmonic maps when $p\geq2$. In particular when $M=\mathbb{R}^m$, we get Liouville type results under proper integral conditions , which extend the related results of Baird, Fardoun and Ouakkas \cite{BFO}.

math.DG↗
arXiv2019

$Φ$-Harmonic Maps and $Φ$-Superstrongly Unstable Manifolds

In this paper, we motivate and define $Φ$-energy density, $Φ$-energy, $Φ$-harmonic maps and stable $Φ$-harmonic maps. Whereas harmonic maps or $p$-harmonic maps can be viewed as critical points of the integral of $σ_1$ of a pull-back tensor, $Φ$-harmonic maps can be viewed as critical points of the integral of $σ_2$ of a pull-back tensor. By an extrinsic average variational method in the calculus of variations (cf. \cite{HW,WY,13,HaW}), we derive the average second variation formulas for $Φ$-energy functional, express them in orthogonal notation in terms of the differential matrix, and find $Φ$-superstrongly unstable $(Φ$-$\text{SSU})$ manifolds. We prove, in particular that every compact $Φ$-$\text{SSU}$ manifold must be $Φ$-strongly unstable $(Φ$-$\text{SU})$, i.e., $(a)$ A compact $Φ$-$\text{SSU}$ manifold cannot be the target of any nonconstant stable $Φ$-harmonic maps from any manifold, $\rm (b)$ The homotopic class of any map from any manifold into a compact $Φ$-$\text{SSU}$ manifold contains elements of arbitrarily small $Φ$-energy, $(\rm c)$ A compact $Φ$-$\text{SSU}$ manifold cannot be the domain of any nonconstant stable $Φ$-harmonic map into any manifold, and $(\rm d)$ The homotopic class of any map from a compact $Φ$-$\text{SSU}$ manifold into any manifold contains elements of arbitrarily small $Φ$-energy (cf. Theorem $1.1 (a),(b),(c)$, and $(d)$.) We also provide many examples of $Φ$-SSU manifolds, and establish a link of $Φ$-SSU manifold to $p$-SSU manifold and topology. The extrinsic average variational method in the calculus of variations that we have employed is in contrast to an average method in PDE that we applied in \cite {CW} to obtain sharp growth estimates for warping functions in multiply warped product manifolds.

math.DG↗
arXiv2019

Existence of nonconstant CR-holomorphic functions of polynomial growth in Sasakian Manifolds

In this paper, we show that there exists a nonconstant CR holomorphic function of polynomial growth in a complete noncompact Sasakian manifold of nonnegative pseudohermitian bisectional curvature with the CR maximal volume growth property. This is the very first step toward the CR analogue of Yau uniformization conjecture which states that any complete noncompact Sasakian manifold of positive pseudohermitian bisectional curvature is CR biholomorphic to the standard Heisenberg group.

math.DG↗
arXiv2018

On the sharp dimension estimate of CR holomorphic functions in Sasakian Manifolds

This is the very first paper to focus on the CR analogue of Yau's uniformization conjecture in a complete noncompact pseudohermitian $(2n+1)$-manifold of vanishing torsion (i.e. Sasakian manifold) which is an odd dimensional counterpart of Kähler geometry. In this paper, we mainly deal with the problem of the sharp dimension estimate of CR holomorphic functions in a complete noncompact pseudohermitian manifold of vanishing torsion with nonnegative pseudohermitian bisectional curvature.

math.DG↗
arXiv2018

On the CR Poincaré-Lelong equation, Yamabe steady solitons and structures of complete noncompact Sasakian manifolds

In this paper, we solve the so-called CR Poincaré-Lelong equation by solving the CR Poisson equation on a complete noncompact CR $(2n+1)$-manifold with nonegative pseudohermitian bisectional curvature tensors and vanishing torsion which is an odd dimensional counterpart of Kähler geometry. With applications of this solution plus the CR Liouvelle property, we study the structures of complete noncompact Sasakian manifolds and CR Yamabe steady solitons.

math.DG↗
arXiv2018

On the three-circle theorem and its applications in Sasakian manifolds

This paper mainly focuses on the CR analogue of the three-circle theorem in a complete noncompact pseudohermitian manifold of vanishing torsion being odd dimensional counterpart of Kähler geometry. In this paper, we show that the CR three-circle theorem holds if its pseudohermitian sectional curvature is nonnegative. As an application, we confirm the first CR Yau's uniformization conjecture and obtain the CR analogue of the sharp dimension estimate for CR holomorphic functions of polynomial growth and its rigidity when the pseudohermitian sectional curvature is nonnegative. This is also the first step toward second and third CR Yau's uniformization conjecture. Moreover, in the course of the proof of the CR three-circle theorem, we derive CR sub-Laplacian comparison theorem. Then Liouville theorem holds for positive pseudoharmonic functions in a complete noncompact pseudohermitian (2n+1)-manifold of vanishing torsion and nonnegative pseudohermitian Ricci curvature.

math.DG↗
arXiv2016

On the p-pseudoharmonic map heat flow

In this paper, we consider the heat flow for p-pseudoharmonic maps from a closed Sasakian manifold M into a compact Riemannian manifold N. We prove global existence and asymptotic convergence of the solution for the p-pseudoharmonic map heat flow, provided that the sectional curvature of the target manifold N is nonpositive. Moreover, without the curvature assumption on the target manifold, we obtain global existence and asymptotic convergence of the p-pseudoharmonic map heat flow as well when its initial p-energy is sufficiently small.

math.DG↗