arXiv subjects

B. Shiffman

Publications and source records attributed to B. Shiffman.

4 recordsLinked to original sources

arXiv2003

Random polynomials of high degree and Levy concentration of measure

We show that the L^p norms of random sequences {s_N} of L^2 normalized holomorphic sections of increasing powers of an ample line bundle on a compact Kahler manifold are almost surely bounded for 2<p< infinity, and are almost surely O((log N)^{1/2}) for p= infinity. This estimate also holds for almost-holomorphic sections of positive line bundles on symplectic manifolds (in the sense of math.SG/0212180) and we give almost sure bounds for the C^k norms. Our methods involve asymptotics of Bergman-Szego kernels and the concentration of measure phenomenon.

math.CV↗

arXiv2003

Harmonic Analysis on Toric Varieties

Harmonic analysis on a toric Kahler variety M refers to the orthonormal basis of eigenfunctions of the complex torus action on the spaces H^0(M, L^N) of holomorphic sections of powers of a positive line bundle L and the Fourier multipliers that act on them. Using this harmonic analysis, we give an exact formula for the Szego kernel as a Fourier multiplier applied to the pull back of the Szego kernel of projective space under a monomial embedding. The Fourier multiplier involves a partition function of the convex lattice polytope P associated to M. We further prove that this Fourier multiplier is a Toeplitz operator, and as a corollary we obtain an oscillatory integral formula for the characters χ_{NP} of the torus action on H^0(M, L^N).

math.CV↗

arXiv2002

Asymptotics of almost holomorphic sections on symplectic manifolds

We study the asymptotics of almost holomorphic sections $s \in H^0_J(M, ω)$ of an ample line bundle $L \to M$ over an almost complex symplectic manifold in the sense of Boutet de Monvel-Guillemin. Such sections are defined as the kernel of a complex which is analogous to the $\bar{\partial}$ complex for a positive line bundle over a complex manifold. Our main result is the scaling limit asymptotics of the Szego projectors $Π_N$ of powers $L^N$. The Kodaira embedding theorem and Tian almost isometry theorem are almost immediate consequences of the scaling limit. We also relate such almost holomorphic sections to the asymptotically holomorphic sections in the sense of Donaldson and Auroux.

math.SG↗

arXiv2002

Asymptotics of almost holomorphic sections of ample line bundles on symplectic manifolds: an addendum

We define a Gaussian measure on the space $H^0_J(M, L^N)$ of almost holomorphic sections of powers of an ample line bundle $L$ over a symplectic manifold $(M, ω)$, and calculate the joint probability densities of sections taking prescribed values and covariant derivatives at a finite number of points. We prove that they have a universal scaling limit as $N \to \infty$. This result completes our proof (with P. Bleher) that correlations between zeros of sections in the almost-holomorphic setting have the same universal scaling limit as in the complex case (see Universality and scaling of zeros on symplectic manifolds, Random matrix models and their applications, 31--69, Math. Sci. Res. Inst. Publ., 40)

math.SG↗