- With R. TODOR and I. CHIOSE

Morse Inequalities on covering manifolds

Nagoya Math. J.**163**, 2001, 145-165

We study the existence of ${L}^{2}$ holomorphic sections of invariant line bundles over Galois coverings. We show that the von Neumann dimension of the space of ${L}^{2}$ holomorphic sections is bounded below under weak curvature conditions. We also give criteria for a compact complex space with isolated singularities and some related strongly pseudoconcave manifolds to be Moishezon. As applications we prove the stability of the previous Moishezon pseudoconcave manifolds under perturbation of complex structures as well as weak Lefschetz theorems. - With R. TODOR and I. CHIOSE

On ${L}^{2}$ holomorphic sections of bundles over weakly pseudoconvex manifolds

Geom. Dedicata**91**, 2002, 23-43. - With X. MA

The ${\mathrm{spin}}^{c}$ Dirac operator on high tensor powers of line bundles.

Math. Z.**240**, 2002, 651-664

arXiv:0111138

We study the asymptotic of the spectrum of the spin-c Dirac operator on high tensor powers of a line bundle. As application, we get a simple proof of the main result of Guillemin-Uribe [Asymptotic Anal. 1 (1988), no. 2, 105-113] which was originally proved by using the analysis of Toeplitz operators of Boutet de Monvel and Guillemin. - On
Moishezon spaces with isolated singularities.

Ann. Mat. Pura Appl.**184**, 2005, no.1, 1-16. - With T. C. DINH

On compactification of hyperconcave ends and the theorems of Siu-Yau and Nadel

This is an expanded version of our paper which appeared in

Invent. Math.**164**(2006), no. 2, 233-248

announced in C. R. Math. Acad. Sci. Paris**342**(2006), no. 9, 675-680

arXiv:0210485We show that the `pseudoconcave holes' of some naturally arising class of manifolds,

called hyperconcave ends, can be filled in, including the case of complex dimension two.

As a consequence we obtain a stronger version of the compactification theorem of Siu-Yau

and extend Nadel's theorems to dimension two.If you don't have acces to the published versions from the journal web page, you could

download my local copies (Invent. Math. or CRAS) - Existence
of holomorphic sections and perturbation of positive line bundles over
q-concave manifolds

Bull. Inst. Math. Acad. Sin. (N.S.)**11**(2016), no. 1, 235-300

arXiv:0402041

By using holomorphic Morse inequalities we prove that sufficiently small deformations of a pseudoconcave domain in a projective manifold is Moishezon. - With N. YEGANEFAR

Embeddability of some strongly pseudoconvex manifolds

Trans. Amer. Math. Soc.**359**(2007), 4757-4771

arXiv:math.CV/0403044

We obtain an embedding theorem for compact strongly pseudoconvex CR manifolds which are bounadries of some complete Hermitian manifolds. We use this to compactify some negatively curved Kähler manifolds with compact strongly pseudoconvex boundary. An embedding theorem for Sasakian manifolds is also derived. - With X. MA

Generalized Bergman kernels on symplectic manifolds

Adv. Math.**217**(2008), no. 4, 1756--1815

announced in C. R. Acad. Sci.**339**(2004), 493-298

arXiv:math.DG/0411559

We establish the near diagonal asymptotic expansion of the generalized Bergman kernel of the renormalized Bochner-Laplacian (introduced by Guillemin-Uribe) on high tensor powers of a positive line bundle over acompact symplectic manifold. The Bergman kernel is the smooth kernel of the projection on the spectral space corresponding to small eigenvalues of the renormalized Bochner-Laplacian. We also discuss some applications (calculation of the density of states of the renormalized Bochner-Laplacian, a symplectic version of the convergence of the induced Fubini-Study metric and Kodaira embedding theorem, as well generalizations for non-compact or singular manifolds). - Habilitationsschrift

The Laplace Operator on High tensor Powers of a Line Bundle - With X. MA

The first coefficients of the asymptotic expansion of the Bergman kernel of the ${\mathrm{spin}}^{c}$ Dirac operator

Internat. J. Math.**17**(2006), no. 6, 737--759

arXiv:math.CV/0511395

We establish the existence of the asymptotic expansion of the Bergman kernel associated to the spin-c Dirac operators acting on high tensor powers of line bundles with non-degenarate mixed curvature (negative and positive eigenvalues) by extending the work of Dai, Liu, Ma [ J. Differential Geom. 72 (2006), no. 1, 1-41]. We compute the second coefficient ${b}_{1}$ in the asymptotic expansion using the method of our paper Generalized Bergman kernels on symplectic manifolds. - With X. MA

Holomorphic Morse Inequalities and Bergman Kernels

In the present book we give a self-contained and unified approach of the holomorphic Morse inequalities and the asymptotic expansion of the Bergman kernel by using the heat kernel, and we present also various applications. Our point of view is from the local index theory,especially from the analytic localization techniques developed by Bismut-Lebeau. Basically, the holomorphic Morse inequalities are a consequence of the small time asymptotic expansion of the heat kernel. The Bergman kernel corresponds to the limit of the heat kernel when time goes to infinity, and is more sophisticate. A simple principle in this book is that the existence of the spectral gap of the operators implies the existence of the asymptotic expansion of the corresponding Bergman kernel whether the manifold is compact or not, or singular, or with boundary. Moreover, we present a general and algorithmic way to compute the coefficients in the expansion.

The book was awarded the 2006 Ferran Sunyer i Balaguer Prize. It appeared in July 2007 in the series Progress in Mathematics (Birkhäuser Verlag).Before rushing to buy the book it is wise to have a look at the Contents and Introduction.

- With X. MA

Toeplitz operators on symplectic manifolds

J. Geom. Anal.**18**(2008), No. 2, 565-611

We study the Berezin-Toeplitz quantization on symplectic manifolds making use of the full off-diagonal asymptotic expansion of the Bergman kernel. We give also a characterization of Toeplitz operators in terms of their asymptotic expansion. The semi-classical limit properties of the Berezin-Toeplitz quantization for non-compact manifolds and orbifolds are also established. - With C.-Y. HSIAO

Szegö kernel asymptotics and Morse inequalities on CR manifolds

Math. Z.**271**(2012), 509–553

arXiv:1005.5471

We consider an abstract compact orientable Cauchy-Riemann manifold endowed with a Cauchy-Riemann complex line bundle. We assume that the manifold satisfies condition Y(q) everywhere. In this paper we obtain a scaling upper-bound for theSzegő kernel on (0, q)-forms with values in the high tensor powers of the line bundle. This gives after integration weak Morse inequalities, analogues of the holomorphic Morse inequalities of Demailly. By a refined spectral analysis we obtain also strong Morse inequalities which we apply to the embedding of some convex-concave manifolds. - With X. MA

Berezin-Toeplitz quantization on Kähler manifolds

J. Reine Angew. Math.,**662**(2012), 1-56

arXiv:1009.5405

We study Berezin-Toeplitz quantization on Kähler manifolds. We explain first how to compute various associated asymptotic expansions, then we compute explicitly the first terms of the expansion of the kernel of the Berezin-Toeplitz operators, and of the composition of two Berezin-Toeplitz operators. As an application, we estimate the norm of Donaldson's Q-operator. - With X. MA

Berezin-Toeplitz Quantization and its kernel expansion

Travaux Mathématiques. Special Issue: Geometry and Quantization. Lectures of the school GEOQUANT 2009 at the University of Luxembourg. Volume XIX, 2011, 125–166

arXiv:1203.4201.

We survey recent results about the asymptotic expansion of Toeplitz operators and their kernels, as well as Berezin-Toeplitz quantization. We deal in particular with calculation of the first coefficients of these expansions. - With T. C. DINH and
V. SCHMIDT

Equidistribution of zeros of holomorphic sections in the non compact setting

J. Stat. Phys.**148**(2012), no. 1, 113-136

arXiv:1106.5244.

We consider N-tensor powers of a positive Hermitian line bundle L over a non-compact complex manifold X. In the compact case, B. Shiffman and S. Zelditch proved that the zeros of random sections become asymptotically uniformly distributed with respect to the natural measure coming from the curvature of L, as N tends to infinity. Under certain boundedness assumptions on the curvature of the canonical line bundle of X and on the Chern form of L we prove a non-compact version of this result. We give various applications, including the limiting distribution of zeros of cusp forms with respect to the principal congruence subgroups of SL2(Z) and to the hyperbolic measure, the higher dimensional case of arithmetic quotients and the case of orthogonal polynomials with weights at infinity. We also give estimates for the speed of convergence of the currents of integration on the zero-divisors. - With D. COMAN

Equidistribution results for singular metrics on line bundles

Ann. Sci. Éc. Norm. Supér (4),**48**(2015), no. 3, 497-536

arXiv:1108.5163.

Let L be a holomorphic line bundle with a positively curved singular Hermitian metric over a complex manifold X. One can define naturally the sequence of Fubini-Study currents associated to the space of square integrable holomorphic sections of the p-th tensor powers of L. Assuming that the singular set of the metric is contained in a compact analytic subset of X and that the logarithm of the Bergman kernel function associated to the p-th tensor power of L (defined outside the singular set) grows like o(p) as p tends to infinity, we prove the following: 1) the k-th power of the Fubini-Study currents converge weakly on the whole X to the k-th power of the curvature current of L. 2) the expectations of the common zeros of a random k-tuple of square integrable holomorphic sections converge weakly in the sense of currents to to the k-th power of the curvature current of L. Here k is so that the codimension of the singular set of the metric is greater or equal as k. Our weak asymptotic condition on the Bergman kernel function is known to hold in many cases, as it is a consequence of its asymptotic expansion. We also prove it here in a quite general setting. We then show that many important geometric situations (singular metrics on big line bundles, Kaehler-Einstein metrics on Zariski-open sets, artihmetic quotients) fit into our framework. - With C.-Y. HSIAO

Asymptotics of spectral function of lower energy forms and Bergman kernel of semi-positive and big line bundles

Comm. Anal. Geom.**22**(2014), no. 1, 1–108

arXiv:1112.5464.

In this paper we study the asymptotic behaviour of the spectral function corresponding to the lower part of the spectrum of the Kodaira Laplacian on high tensor powers of a holomorphic line bundle. This implies a full asymptotic expansion of this function on the set where the curvature of the line bundle is non-degenerate. As application we obtain the Bergman kernel asymptotics for adjoint semi-positive line bundles over complete Kähler manifolds, on the set where the curvature is positive. We also prove the asymptotics for big line bundles endowed with singular Hermitian metrics with strictly positive curvature current. In this case the full asymptotics holds outside the singular locus of the metric. - With D. COMAN

Convergence of Fubini-Study currents for orbifold line bundles

Internat. J. Math.**24**(2013), No. 07, 1350051

arXiv:1210.5604.

We discuss positive closed currents and Fubini-Study currents on orbifolds, as well as Bergman kernels of singular Hermitian orbifold line bundles. We prove that the Fubini-Study currents associated to high powers of a semipositive singular line bundle converge weakly to the curvature current on the set where the curvature is strictly positive, generalizing a well-known theorem of Tian. We include applications to the asymptotic distribution of zeros of random holomorphic sections. - With D. COMAN

On the approximation of positive closed currents on compact Kähler manifolds

Math. Rep. (Bucur.)**15**(2013), No. 4, p. 373-386

arXiv:1302.0292.

Let L be a holomorphic line bundle with a positively curved singular Hermitian metric over compact Kähler manifold X of dimension n. In certain cases when the k-th power of the curvature current of L is a well defined current for some positive integer k (less or equal than n), we prove that it can be approximated by averages of currents of integration over the common zero sets of k-tuples of holomorphic sections over X of the high powers of L. In the second part of the paper we study the convergence of the Fubini-Study currents and the equidistribution of zeros of square integrable holomorphic n-forms with values in the high powers of L. As an application, we obtain an approximation theorem for the k-th power of the curvature current of L using currents of integration over the common zero sets of k-tuples of such n-forms. - With X. MA

Remark on the off-diagonal expansion of the Bergman kernel on compact Kähler manifolds

Commun. Math. Stat.**1**(2013), no. 1, 37-41

arXiv:1302.2346.

In this short note, we compare our previous works on the off-diagonal expansion of the Bergman kernel and the recent preprint of Lu-Shiffman (arxiv.1301.2166). In particular, we note that the vanishing of the coefficient of p^{-1/2} is implicitly contained in Dai-Liu-Ma's work (J. Differential Geom. 72 (2006), no. 1, 1-41) and was explicitly stated in our book (Holomorphic Morse inequalities and Bergman kernels, Progress in Math., vol. 254, Birkhäuser, 2007). - With T. BARRON and
X. MA and M. PINSONNAULT

Semi-classical properties of Berezin-Toeplitz operators with C^k symbol

J. Math. Phys.**55**, 042108 (2014)

arXiv:1310.3571.

We obtain the semi-classical expansion of the kernels and traces of Toeplitz operators with C^k symbol on a symplectic manifold. We also give a semi-classical estimate of the distance of a Toeplitz operator to the space of self-adjoint and multiplication operators. - With X. MA

Exponential estimate for the asymptotics of Bergman kernels

Math. Ann.**362**(2015), no. 3-4, 1327-1347

arXiv:1310.3776.

We prove an exponential estimate for the asymptotics of Bergman kernels of a positive line bundle under hypotheses of bounded geometry. Further, we give Bergman kernel proofs of complex geometry results, such as separation of points, existence of local coordinates and holomorphic convexity by sections of positive line bundles. - With X. MA and
S. ZELDITCH

Scaling asymptotics of heat kernels of line bundles

Analysis, Complex Geometry, and Mathematical Physics: In Honor of Duong H. Phong, 175-202,

Contemp. Math., 644, Amer. Math. Soc., Providence, RI, 2015.

arXiv:1406.0201

We consider a general Hermitian holomorphic line bundle L on a compact complex manifold M and the Kodaira Laplacian on (0,q) forms with values in L^p. The main result is a complete asymptotic expansion for the semi-classically scaled heat kernel along the diagonal. It is a generalization of the Bergman/Szegö kernel asymptotics in the case of a positive line bundle, but no positivity is assumed. We give two proofs, one based on the Hadamard parametrix for the heat kernel on a principal bundle and the second based on the analytic localization of the Dirac-Dolbeault operator. - With C.-Y. HSIAO

On the singularities of the Szegő projections on lower energy forms

J. Differential Geom.**107**(2017), no. 1 , 83-155

arXiv:1407.6305

Let X be an abstract not necessarily compact orientable CR manifold of dimension 2n-1, n>1. We show that the spectral function of the Kohn Laplacian on (0,q)-forms admits a full asymptotic expansion on the non-degenerate part of the Levi form. As a corollary, we deduce that if X is compact and the Levi form is non-degenerate of constant signature on X, then the spectrum of the Kohn Laplacian consists of point eigenvalues of finite multiplicity. Moreover, we show that a certain microlocal conjugation of the associated Szegő kernel admits an asymptotic expansion under a local closed range condition. As applications, we establish the Szegő kernel asymptotic expansions on some weakly pseudoconvex CR manifolds and on CR manifolds with transversal CR circle actions. By using these asymptotics, we establish some local embedding theorems on CR manifolds and we give an analytic proof of a theorem of Lempert asserting that a compact strictly pseudoconvex CR manifold of dimension three with a transversal CR circle action can be CR embedded into a complex Euclidean space. - With T.-C. DINH and
X. MA

Equdistribution and convergence speed for zeros of holomorphic sections of singular Hermitian line bundles

J. Funct. Anal.**271**(2016), no. 11, 3082-3110

arXiv:1411.4705

We establish the equidistribution of zeros of random holomorphic sections of powers of a semipositive singular Hermitian line bundle, with an estimate of the convergence speed. - With C.-Y. HSIAO

Berezin-Toeplitz quantization for lower energy forms

Comm. Partial Differential Equations,**42**(2017), no. 6, 895-942

arXiv:1411.6654

Let M be an arbitrary complex manifold and let L be a Hermitian holomorphic line bundle over M. We introduce the Berezin-Toeplitz quantization of the open set of M where the curvature on L is non-degenerate. The quantum spaces are the spectral spaces corresponding to [0,k^{-N}] (N>1 fixed), of the Kodaira Laplace operator acting on forms with values in tensor powers L^k. We establish the asymptotic expansion of associated Toeplitz operators and their composition as k goes to infinity and we define the corresponding star-product. If the Kodaira Laplace operator has a certain spectral gap this method yields quantization by means of harmonic forms. As applications, we obtain the Berezin-Toeplitz quantization for semi-positive and big line bundles. - With D. COMAN and
X. MA

Equidistribution for sequences of line bundles on normal Kähler spaces

Geom. Topol.**21**(2017), no. 2, 923-962

arXiv:1412.8184

We study the asymptotics of Fubini-Study currents and zeros of random holomorphic sections associated to a sequence of singular Hermitian line bundles on a compact normal Kähler complex space. - With C.-Y. HSIAO

Szegö kernel asymptotics and Kodaira embedding theorems of Levi-flat CR manifolds

Math. Res. Lett.**24**(2017), no. 5 ,1385-1451

arXiv:1502.01642

Let X be an orientable compact Levi-flat CR manifold and let L be a positive CR complex line bundle over X. We prove that certain microlocal conjugations of the associated Szegő kernel admit an asymptotic expansion with respect to high powers of L. As an application, we give a Szegő kernel proof of the Kodaira type embedding theorem on Levi-flat CR manifolds due to Ohsawa and Sibony. - With D. COMAN and
V.-A. NGUYEN

Hölder singular metrics on big line bundles and equidistribution

Int. Math. Res. Not. IMRN, Vol. 2016, No. 16, pp. 5048-5075

arXiv:1506.01727

We show that normalized currents of integration along the common zeros of random m-tuples of sections of powers of m singular Hermitian big line bundles on a compact Kähler manifold distribute asymptotically to the wedge product of the curvature currents of the metrics. If the Hermitian metrics are Hölder with singularities we also estimate the speed of convergence. - With S. KLEVTSOV and
X. MA and P. WIEGMANN

Quantum Hall effect and Quillen metric

Comm. Math. Phys.**349**(2017), Issue 3, 819–855

arXiv:1510.06720

Video of a talk of Paul Wiegmann on this topic at Simons Center.

We study the generating functional, the adiabatic curvature and the adiabatic phase for the integer quantum Hall effect (QHE) on a compact Riemann surface. For the generating functional we derive its asymptotic expansion for the large flux of the magnetic field, i.e., for the large degree k of the positive Hermitian line bundle L^k. The expansion consists of the anomalous and exact terms. The anomalous terms are the leading terms of the expansion. This part is responsible for the quantization of the adiabatic transport coefficients in QHE. We then identify the anomalous part of the expansion with the Quillen metric on the determinant line bundle, and the subleading exact part with the asymptotics of the regularized spectral determinant of the Laplacian for the line bundle L^k, at large k. Finally, we show how the generating functional of the integer QHE is related to the gauge and gravitational (2+1)d Chern-Simons functionals. We observe the relation between the Bismut-Gillet-Soulé curvature formula for the Quillen metric and the adiabatic curvature for the electromagnetic and geometric adiabatic transport of the integer Quantum Hall state. Then we relate the adiabatic phase in QHE to the eta invariant and show that the geometric part of the adiabatic phase is given by the Chern-Simons functional. - With D. COMAN

On the first order asymptotics of partial Bergman kernels

Ann. Fac. Sci. Toulouse Math.**26**(2017) no. 5, 1193-1210

arXiv:1601.00241

We show that under very general assumptions the partial Bergman kernel function of sections vanishing along an analytic hypersurface has exponential decay in a neighborhood of the vanishing locus. Considering an ample line bundle, we obtain a uniform estimate of the Bergman kernel function associated to a singular metric along the hypersurface. Finally, we study the asymptotics of the partial Bergman kernel function on a given compact set and near the vanishing locus. - With C.-Y. HSIAO
and X. LI

Equivariant Kodaira embedding of CR manifolds with circle action

arXiv:1603.08872

We consider a compact CR manifold with a transversal CR locally free circle action endowed with a rigid positive CR line bundle. We prove that a certain weighted Fourier-Szegő kernel of the CR sections in the high tensor powers admits a full asymptotic expansion. As a consequence, we establish an equivariant Kodaira embedding theorem. - With H. AUVRAY
and X. MA

Bergman kernels on punctured Riemann surfaces

C. R. Math. Acad. Sci. Paris**354**(2016), no. 10, 1018-1022

arXiv:1603.08872

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. One of the technical tools is a new weighted elliptic estimate near the punctures, which is uniform with respect to the tensor power. 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. This holds in particular for the Bergman kernel of cusp forms of high weight of non-cocompact geometrically finite Fuchsian groups of first kind without elliptic elements. - With C.-Y. HSIAO
and X. LI

On the stability of equivariant embedding of compact CR manifolds with circle action

Math. Z., no. 1-2,**289**(2018), 201-222

arXiv:1608.00893

We prove the stability of the equivariant embedding of compact strictly pseudoconvex CR manifolds with transversal CR circle action under circle invariant perturbations of the CR structures. - With D. COMAN
and S. KLEVTSOV

Bergman kernel asymptotics for singular metrics on punctured Riemann surfaces

to appear in Indiana Univ. Math. J.

arXiv:1612.09197

We consider singular metrics on a punctured Riemann surface and on a line bundle and study the behavior of the Bergman kernel in the neighbourhood of the punctures. The results have an interpretation in terms of the asymptotic profile of the density of states function of the lowest Landau level in quantum Hall effect. - With D. COMAN and
V.-A. NGUYEN

Approximation and equidistribution results for pseudo-effective line bundles

Journal de Mathématiques Pures et Appliquées,**115**(2018), 218-236

arXiv:1701.00120

We study the distribution of the common zero sets of m-tuples of holomorphic sections of powers of m singular Hermitian pseudo-effective line bundles on a compact Käahler manifold. As an application, we obtain sufficient conditions which ensure that the wedge product of the curvature currents of these line bundles can be approximated by analytic cycles. - With W. LU
and X. MA

Optimal convergence speed of Bergman metrics on symplectic manifolds

arXiv:1702.00974

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 metrics induced by these embeddings converge at speed rate 1/p^2 to the symplectic form. - With W. LU
and X. MA

Donaldson's Q-operators for symplectic manifolds

Sci. China Math.**60**(2017), no. 6, 1047–1056

arXiv:1703.05276

We prove an estimate for Donaldson's Q-operator on a prequantized compact symplectic manifold. This estimate is an ingredient in the recent result of Keller and Lejmi about a symplectic generalization of Donaldson's lower bound for the L^2-norm of the Hermitian scalar curvature. - With L. IOOS and
W. LU
and X. MA

Berezin-Toeplitz quantization for eigenstates of the Bochner-Laplacian on symplectic manifolds

J. Geom. Anal. (available online 8 January 2018)

arXiv:1703.06420

We study the Berezin-Toeplitz quantization using as quantum space the space of eigenstates of the renormalized Bochner Laplacian corresponding to eigenvalues localized near the origin on a symplectic manifold. We show that this quantization has the correct semiclassical behavior and construct the corresponding star-product. - With T. BAYRAKTAR and
D. COMAN

Universality results for zeros of random holomorphic sections

arXiv:1709.10346

In this work we prove an universality result regarding the equidistribution of zeros of random holomorphic sections associated to a sequence of singular Hermitian holomorphic line bundles on a compact Kähler complex space X. Namely, under mild moment assumptions, we show that the asymptotic distribution of zeros of random holomorphic sections is independent of the choice of the probability measure on the space of holomorphic sections. In the case when X is a compact Kähler manifold, we also prove an off-diagonal exponential decay estimate for the Bergman kernels of a sequence of positive line bundles on X.