The asymptotic growth of equivariant sections of positive and big line bundles

If a finite group acts holomorphically on a pair (X,L), where X is a complex projective manifold and L a line bundle on it, for every k the space of holomorphic global section of the k-th power of L splits equivariantly according to the irreducible representations of G. We consider the asymptotic growth of these summands, under various positivity conditions on L. The methods apply also to the context of almost complex quantization

Local scaling asymptotics for the Gutzwiller trace formula in Berezin-T\"oplitz quantization

Under certain hypothesis on the underlying classical Hamiltonian flow, we produce local scaling asymptotics in the semiclassical regime for a Berezin-T\"oplitz version of the Gutzwiller trace formula on a quantizable compact K\"ahler manifold, in the spirit of the near-diagonal scaling asymptotics of Szeg\"o and T\"oplitz kernels. More precisely, we consider an analogue of the \lq Gutzwiller-T\"oplitz kernel\rq\, previously introduced in this setting by Borthwick, Paul and Uribe, and study how it asymptotically concentrates along the appropriate classical loci defined by the dynamics, with an explicit description of the exponential decay along normal directions. These local scaling asymptotics probe into the concentration behavior of the eigenfunctions of the quantized Hamiltonian flow. When globally integrated, they yield the analogue of the Gutzwiller trace formula.Comment: Corrected typos. Introduction extended with reference to the almost complex settin

Seshadri constants, gonality of space curves and restriction of stable bundles

We define the Seshadri constant of a space curve and consider ways to estimate it. We then show that it governs the gonality of the curve. We use an argument based on Bogomolov's instability theorem on a threefold. The same methods are then applied to the study of the behaviour of a stable vector bundle on P^3 under restriction to curves and surfaces.Comment: 36 pages, amslate

Local scaling asymptotics in phase space and time in Berezin-Toeplitz quantization

This paper deals with the local semiclassical asymptotics of a quantum evolution operator in the Berezin-Toeplitz scheme, when both time and phase space variables are subject to appropriate scalings in the neighborhood of the graph of the underlying classical dynamics. Global consequences are then drawn regarding the scaling asymptotics of the trace of the quantum evolution as a function of time

Szego kernels, Toeplitz operators, and equivariant fixed point formulae

Let $\gamma$ be an automorphism of a polarized complex projective manifold $(M,L)$. Then $\gamma$ induces an automorphism $\gamma_k$ of the space of global holomorphic sections of the $k$-th tensor power of $L$, for every $k=1,2,...$; for $k\gg 0$, the Lefschetz fixed point formula expresses the trace of $\gamma_k$ in terms of fixed point data. More generally, one may consider the composition of $\gamma_k$ with the Toeplitz operator associated to some smooth function on $M$. Still more generally, in the presence of the compatible action of a compact and connected Lie group preserving $(M,L,\gamma)$, one may consider induced linear maps on the equivariant summands associated to the irreducible representations of $G$. In this paper, under familiar assumptions in the theory of symplectic reductions, we show that the traces of these maps admit an asymptotic expansion as $k\to +\infty$, and compute its leading term.Comment: statement and proof simplified, exposition improved, references adde

A note on scaling asymptotics for Bohr-Sommerfeld Lagrangian submanifolds

An important problem in geometric quantization is that of quantizing certain classes of Lagrangian submanifolds, so-called Bohr-Sommerfeld Lagrangian submanifolds, equipped with a smooth half-density. A procedure for this in the complex projective setting is, roughly speaking, to apply the Szego kernel of the quantizing line bundle to a certain induced delta function supported on the submanifold. If the quantizing line bundle L is replaced by its k-th tensor power, and k tends to infinity, the resulting quantum states u_k concentrate asymptotically on the submanifold. This note deals with the scaling asymptotics of the u_k's along the submanifold; in particular, we point out a natural factorization in the corresponding asymptotic expansion, and provide some remainder estimates.Comment: exposition improve

Equivariant asymptotics for Toeplitz operators

In recent years, the Tian-Zelditch asymptotic expansion for the equivariant components of the Szeg\"{o} kernel of a polarized complex projective manifold, and its subsequent generalizations in terms of scaling limits, have played an important role in algebraic, symplectic, and differential geometry. A natural question is whether there exist generalizations in which the projector onto the spaces of holomorphic sections can be replaced by the projector onto more general (non-complete) linear series. One case that lends itself to such analysis, and which is natural from the point of view of geometric quantization, is given by the linear series determined by imposing spectral bounds on an invariant self-adjoint Toeplitz operator. In this paper we focus on the asymptotics of the spectral projectors associated to slowly shrinking spectral bands

Scaling limits for equivariant Szego kernels

Suppose that the compact and connected Lie group G acts holomorphically on the irreducible complex projective manifold M, and that the action linearizes to the Hermitian ample line bundle L on M. Assume that 0 is a regular value of the associated moment map. The spaces of global holomorphic sections of powers of L may be decomposed over the finite dimensional irreducible representations of G. In this paper, we study how the holomorphic sections in each equivariant piece asymptotically concentrate along the zero locus of the moment map. In the special case where G acts freely on the zero locus of the moment map, this relates the scaling limits of the Szego kernel of the quotient to the scaling limits of the invariant part of the Szego kernel of (M,L).Comment: exposition improved, examples and references adde

The Szego kernel of a symplectic quotient

Suppose a compact Lie group acts on a polarized complex projective manifold (M,L). Under favorable circumstances, the Hilbert-Mumford quotient for the action of the complexified group may be described as a symplectic quotient (or reduction). This paper addresses some metric questions arising from this identification, by analyzing the relationship between the Szego kernel of the pair (M,L) and that of the quotient.Comment: Typos corrected, some improvements in expositio

On the surjectivity of Wahl maps on a general curve

This paper explores the geometric meaning of the failure of certain kinds of Wahl maps to surject on a general curve. Sufficient conditions for surjectivity are given. An approach used by Voisin to study canonical Wahl maps is applied in this direction.Comment: 18 pages amste