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Xiaonan Ma

Publications and source records attributed to Xiaonan Ma.

At least 19 recordsLinked to original sources
arXiv2026

Berezin-Toeplitz Quantization of non-compact manifolds

We develop Berezin-Toeplitz quantization in a non-compact complex geometric setting. Let $(X,Θ)$ be a Hermitian manifold, $(L,h^L)$ a positive holomorphic line bundle, and $(E,h^E)$ a holomorphic Hermitian vector bundle. Assuming that the Kodaira Laplacian on $(0,1)$-forms with values in $L^p\!\otimes E$ has a spectral gap growing linearly in $p$, we prove that the Bergman projection onto the $L^2$-holomorphic space $H^0_{(2)}(X,L^p\!\otimes E)$ enjoys the usual off-diagonal decay and admits a full asymptotic expansion on compact subsets as $p\to\infty$. As a consequence, for every smooth symbol $f\in\mathcal{C}^\infty_{\mathrm{const}}(X,\operatorname{End}(E))$ (constant outside a compact set), the associated Toeplitz operators $T_{f,p}=P_p f P_p$ form a closed algebra and satisfy a complete composition expansion, yielding a star-product on $\mathcal C^\infty_{\mathrm{const}}(X,\operatorname{End}(E))$ and the expected semiclassical commutator formula. We also give intrinsic criteria characterizing Toeplitz families with compactly supported kernels. We then provide geometric conditions guaranteeing the spectral gap on large classes of non-compact manifolds, via fundamental $L^2$-estimates for $\bar\partial$ on complete Hermitian manifolds (including bounded-geometry complete Kähler manifolds, Kähler-Einstein manifolds, pseudoconvex/weakly $1$-complete, and quasi-projective manifolds). Finally, for compactly supported bounded symbols, we prove a Szegő-type theorem describing the eigenvalue distribution of the compact Toeplitz operators $T_{f,p}$ as $p\to\infty$.

math.DG↗
arXiv2026

Bergman kernels and Poincaré series

We show that the Bergman kernel of a finite-volume quotient of a Hermitian manifold $\widetilde{X}$ with bounded geometry by a discrete group $Γ$ of its isometries is the same as the averaging over $Γ$ of the Bergman kernel on $\widetilde{X}$. We then use these results when $\widetilde{X}$ is a Hermitian symmetric space to show that a large class of relative Poincaré series does not vanish. This extends the results of Borthwick-Paul-Uribe and Barron (formerly Foth) to the case of general locally symmetric spaces of finite volume.

math.DG↗
arXiv2026

$λ$-ring structure in differential K-theory

We establish the splitting principle for differential K-theory, a refinement of topological K-theory that incorporates geometric data via differential forms. Using this principle, we prove that the differential $K^0$-ring associated to closed smooth manifolds admits a $λ$-ring structure. This structure enables a concrete construction of the Adams operations in differential K-theory introduced by Bunke. At last, we extend all these results to an equivariant setting associated with a compact Lie group action.

math.KT↗
arXiv2025

Fubini-Study forms on punctured Riemann surfaces

In this paper we consider a punctured Riemann surface endowed with a Hermitian metric that equals the Poincaré metric near the punctures, and a holomorphic line bundle that polarizes the metric. We show that the quotient of the induced Fubini-Study forms by Kodaira maps of high tensor powers of the line bundle and the Poincaré form near the singularity grows polynomially uniformly on a neighborhood of the singularity as the tensor power tends to infinity, as an application of the method in [5].

math.CV↗
arXiv2024

Tian's theorem for Moishezon spaces

We prove that the Fubini-Study currents associated to a sequence of singular Hermitian holomorphic line bundles on a compact normal Moishezon space distribute asymptotically as the curvature currents of their metrics.

math.DG↗
arXiv2023

Multipiezo effect in altermagnetic V2SeTeO monolayer

Inspired by recent theoretical proposal on the interesting piezomagnetism and C-paired valley polarization in V2Se2O monolayer, we predict a stable antiferromagnetic Janus monolayer V2SeTeO with altermagnetic configuration using density functional theory calculations. It exhibits a novel multi-piezo effect combining piezoelectric, piezovalley and piezomagnetism. Most interestingly, the valley polarization and the net magnetization under strain in V2SeTeO exceed these in V2Se2O, along with the additional large piezoelectric coefficient of e31 (0.322*10-10 C m-1). The multi-piezo effect makes antiferromagnetic Janus monolayer V2SeTeO a tantalizing material for potential applications in nanoelectronics, optoelectronics, spintronics and valleytronics.

cond-mat.mtrl-sci↗
arXiv2022

Comparison of two equivariant $η$-forms

In this paper, we first define the equivariant infinitesimal $η$-form, then we compare it with the equivariant $η$-form, modulo exact forms, by a locally computable form. As a consequence, we obtain the singular behavior of the equivariant $η$-form, modulo exact forms, as a function on the acting Lie group. This result extends a result of Goette and it plays an important role in our recent work on the localization of $η$-invariants and on the differential $K$-theory.

math.DG↗
arXiv2021

Tunable vertical ferroelectricity and domain walls by interlayer sliding in $β$-ZrI$_{2}$

Vertical ferroelectricity where a net dipole moment appears as a result of in-plane ionic displacements has gained enormous attention following its discovery in transition metal dichalcogenides. Based on first-principles calculations, we report on the evidence of robust vertical ferroelectricity upon interlayer sliding in layered semiconducting $β$-ZrI$_{2}$, a sister material of polar semimetals MoTe$_{2}$ and WTe$_{2}$. The microscopic origin of ferroelectricity in ZrI$_{2}$ is attributed to asymmetric shifts of electronic charges within a trilayer, revealing a subtle interplay of rigid sliding displacements and charge redistribution down to ultrathin thicknesses. We further investigate the variety of ferroelectric domain boundaries and predict a stable charged domain wall with a quasi-two-dimensional electron gas and a high built-in electric field that can increase electron mobility and electromechanical response in multifunctional devices. Semiconducting behaviour and a small switching barrier of ZrI$_{2}$ hold promise for novel ferroelectric applications, and our results provide important insights for further development of slidetronics ferroelectricity.

cond-mat.mtrl-sci↗
arXiv2021

Bergman kernels on punctured Riemann surfaces

In this paper we consider a punctured Riemann surface endowed with a Hermitian metric which equals the Poincaré metric near the punctures and a holomorphic line bundle which polarizes the metric. We show that the Bergman kernel can be localized around the singularities and its local model is the Bergman kernel of the punctured unit disc endowed with the standard Poincaré metric. As a consequence, we obtain an optimal uniform estimate of the supremum norm of the Bergman kernel, involving a fractional growth order of the tensor power.

math.DG↗
arXiv2020

Bergman kernels and equidistribution for sequences of line bundles on Kähler manifolds

Given a sequence of positive Hermitian holomorphic line bundles $(L_p,h_p)$ on a Kähler manifold $X$, we establish the asymptotic expansion of the Bergman kernel of the space of global holomorphic sections of $L_p$, under a natural convergence assumption on the sequence of curvatures $c_1(L_p,h_p)$. We then apply this to study the asymptotic distribution of common zeros of random sequences of $m$-tuples of sections of $L_p$ as $p\to\infty$.

math.CV↗
arXiv2020

Optimal convergence speed of Bergman metrics on symplectic manifolds

It is known that a compact symplectic manifold endowed with a prequantum line bundle can be embedded in the projective space generated by the eigensections of low energy of the Bochner Laplacian acting on high $p$-tensor powers of the prequantum line bundle. We show that the Fubini-Study forms induced by these embeddings converge at speed rate $1/p^{2}$ to the symplectic form. This result implies the generalization to the almost-Kähler case of the lower bounds on the Calabi functional given by Donaldson for Kähler manifolds, as shown by Lejmi and Keller.

math.DG↗
arXiv2020

Geometric quantization on CR manifolds

Let $X$ be a compact connected orientable CR manifold with the action of a connected compact Lie group $G$. Under natural pseudoconvexity assumptions we show that the CR Guillemin-Strernberg map is Fredholm at the level of Sobolev spaces of CR functions. As application we study this map for holomorphic line bundles which are positive near the inverse image of $0$ by the momentum map. We also show that "quantization commutes with reduction" for Sasakian manifolds.

math.CV↗
arXiv2020

Differential K-theory and localization formula for $η$-invariants

In this paper, we obtain a localization formula in differential K-theory for $S^1$-action. Then by combining an extension of Goette's result on the comparison of two types of equivariant $η$-invariants, we establish a version of localization formula for equivariant $η$-invariants. An important step of our approach is to construct a pre-$λ$-ring structure in differential K-theory which is interesting in its own right.

math.DG↗
arXiv2020

Quotient of Bergman kernels on punctured Riemann surfaces

In this paper we consider a punctured Riemann surface endowed with a Hermitian metric that equals the Poincar{é} metric near the punctures, and a holomorphic line bundle that polarizes the metric. We show that the quotient of the Bergman kernel of high tensor powers of the line bundle and of the Bergman kernel of the Poincar{é} model near the singularity tends to one up to arbitrary negative powers of the tensor power.

math.CV↗
arXiv2019

Generalized Bergman kernels on symplectic manifolds of bounded geometry

We study the asymptotic behavior of the generalized Bergman kernel of the renormalized Bochner-Laplacian on high tensor powers of a positive line bundle on a symplectic manifold of bounded geometry. First, we establish the off-diagonal exponential estimate for the generalized Bergman kernel. As an application, we obtain the relation between the generalized Bergman kernel on a Galois covering of a compact symplectic manifold and the generalized Bergman kernel on the base. Then we state the full off-diagonal asymptotic expansion of the generalized Bergman kernel, improving the remainder estimate known in the compact case to an exponential decay. Finally, we establish the theory of Berezin-Toeplitz quantization on symplectic orbifolds associated with the renormalized Bochner-Laplacian.

math.DG↗
arXiv2019

Geometric hypoelliptic Laplacian and orbital integrals (after Bismut, Lebeau and Shen)

About 15 years ago, Bismut gave a natural construction of a Hodge theory for a hypoelliptic Laplacian acting on the total space of the cotangent bundle of a Riemannian manifold. This operator interpolates between the classical elliptic Laplacian on the base and the generator of the geodesic flow. We will describe recent developments of the theory of hypoelliptic Laplacians, in particular the explicit formula obtained by Bismut for orbital integrals and the recent solution by Shen of Fried's conjecture (dating back to 1986) for locally symmetric spaces. The conjecture predicts the equality of the analytic torsion and the value at 0 of the dynamic zeta function.

math.DG↗