English

On inversion of absolutely convergent weighted Dirichlet series in two variables

Functional Analysis 2024-07-30 v1

Abstract

Let 0<p10<p\leq 1, and let ω:N2[1,)\omega:\mathbb N^2 \to [1,\infty) be an almost monotone weight. Let H\mathbb H be the closed right half plane in the complex plane. Let a~\widetilde a be a complex valued function on H2\mathbb H^2 such that a~(s1,s2)=(m,n)N2a(m,n)ms1ns2\widetilde a(s_1,s_2)=\sum_{(m,n)\in \mathbb N^2}a(m,n)m^{-s_1}n^{-s_2} for all (s1,s2)H2(s_1,s_2)\in \mathbb H^2 with (m,n)N2a(m,n)pω(m,n)<\sum_{(m,n)\in \mathbb N^2} |a(m,n)|^p\omega(m,n)<\infty. If a~\widetilde a is bounded away from zero on H2\mathbb H^2, then there is an almost monotone weight ν\nu on N2\mathbb N^2 such that 1νω1\leq \nu\leq \omega, ν\nu is constant if and only if ω\omega is constant, ν\nu is admissible if and only if ω\omega is admissible, the reciprocal 1a~\frac{1}{\widetilde a} has the Dirichlet representation 1a~(s1,s2)=(m,n)N2b(m,n)ms1ns2\frac{1}{\widetilde a}(s_1,s_2)=\sum_{(m,n)\in \mathbb N^2}b(m,n)m^{-s_1}n^{-s_2} for all (s1,s2)H2(s_1,s_2)\in \mathbb H^2 and (m,n)N2b(m,n)pν(m,n)<\sum_{(m,n)\in \mathbb N^2}|b(m,n)|^p\nu(m,n)<\infty. If φ\varphi is holomorphic on a neighbourhood of the closure of range of a~\widetilde a, then there is an almost monotone weight ξ\xi on N2\mathbb N^2 such that 1ξω1\leq \xi\leq \omega, ξ\xi is constant if and only if ω\omega is constant, ξ\xi is admissible if and only if ω\omega is admissible, φa~\varphi \circ \widetilde a has the Dirichlet series representation (φa~)(s1,s2)=(m,n)N2c(m,n)ms1ns2  ((s1,s2)H2)(\varphi\circ \widetilde a)(s_1,s_2)=\sum_{(m,n)\in \mathbb N^2} c(m,n)m^{-s_1}n^{-s_2}\;((s_1,s_2)\in \mathbb H^2) and (m,n)N2c(m,n)pξ(m,n)<\sum_{(m,n)\in \mathbb N^2}|c(m,n)|^p\xi(m,n)<\infty. Let ω\omega be an admissible weight on N2\mathbb N^2, and let a~\widetilde a have pp-th power ω\omega- absolutely convergent Dirichlet series. Then it is shown that the reciprocal of a~\widetilde a has pp-th power ω\omega- absolutely convergent Dirichlet series if and only if a~\widetilde a is bounded away from zero.

Keywords

Cite

@article{arxiv.2407.19982,
  title  = {On inversion of absolutely convergent weighted Dirichlet series in two variables},
  author = {Prakash A. Dabhi},
  journal= {arXiv preprint arXiv:2407.19982},
  year   = {2024}
}