English

Discrepancy densities for planar and hyperbolic Zero Packing

Complex Variables 2016-05-30 v1

Abstract

We study the problem of geometric zero packing, recently introduced by Hedenmalm. There are two natural densities associated to this problem: the discrepancy density ρH\rho_{\mathbb{H}}, given by ρH=lim infr1inffD(0,r)((1z2)f(z)1)2dA(z)1z2D(0,r)dA(z)1z2 \rho_{\mathbb{H}} = \liminf_{r\to 1^-} \inf_{f} \frac{\int_{\mathbb{D}(0,r)} \left((1-\lvert z\rvert^2) \lvert f(z)\rvert-1\right)^2 \frac{dA(z)}{1-\lvert z\rvert^2}} {\int_{\mathbb{D}(0,r)} \frac{dA(z)}{1-\lvert z\rvert^2}} which measures the discrepancy in optimal approximation of (1z2)1(1-\lvert z\rvert^2)^{-1} with the modulus of polynomials ff, and it's relative, the tight discrepancy density ρH\rho_{\mathbb{H}}^*, which will trivially satisfy ρHρH\rho_{\mathbb{H}}\leq\rho_{\mathbb{H}}^*. These densities have deep connections to the boundary behaviour of conformal mappings with kk-quasiconformal extensions, which can be seen from the Hedenmalm's result that the universal asymptotic variance Σ2\Sigma^2 is related to ρH\rho_{\mathbb{H}}^* by Σ2=1ρH\Sigma^2=1-\rho_{\mathbb{H}}^*. Here we prove that in fact ρH=ρH\rho_{\mathbb{H}}=\rho_{\mathbb{H}}^*, resolving a conjecture by Hedenmalm in the positive. The natural planar analogues ρC\rho_{\mathbb{C}} and ρC\rho_{\mathbb{C}}^* to these densities make contact with work of Abrikosov on Bose-Einstein condensates. As a second result we prove that also ρC=ρC\rho_{\mathbb{C}}=\rho_{\mathbb{C}}^*. The methods are based on Ameur, Hedenmalm and Makarov's H\"ormander-type ˉ\bar\partial-estimates with polynomial growth control. As a consequence we obtain sufficiency results on the degrees of approximately optimal polynomials.

Cite

@article{arxiv.1605.08674,
  title  = {Discrepancy densities for planar and hyperbolic Zero Packing},
  author = {Aron Wennman},
  journal= {arXiv preprint arXiv:1605.08674},
  year   = {2016}
}

Comments

19 pages, 1 figure

R2 v1 2026-06-22T14:11:18.050Z