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Dorin Ghisa

Publications and source records attributed to Dorin Ghisa.

10 recordsLinked to original sources
arXiv2016

The Geometry of the Mappings by General Dirichlet Series

We dealt in a series of previous publications with some geometric aspects of the mappings by functions obtained as analytic continuations to the whole complex plane of general Dirichlet series. Pictures illustrating those aspects contain a lot of other information which has been waiting for a rigorous proof. Such a task is partially fulfilled in this paper, where we succeeded among other things, to prove a theorem about general Dirichlet series having as corollary the Speiser's theorem. We have also proved that those functions do not possess multiple zeros of order higher than $2$ and the double zeros have very particular locations. Moreover, their derivatives have only simple zeros. With these results at hand, we revisited GRH for a simplified proof.

math.CV↗
arXiv2016

On the generalized Riemann hypothesis II

Some of my previous publications were incomplete in the sense that non trivial zeros belonging to a particular type of fundamental domain have been inadvertently ignored. Due to this fact, I was brought to believe that computations done by some authors in order to show counterexamples to RH were affected of approximation errors. In this paper I illustrate graphically the correctness of those computations and I fill the gaps in my publications.

math.CV↗
arXiv2015

Note on the Zeros of a Dirichlet Function

The existence of non trivial zeros off the critical line for a function obtained by analytic continuation of a particular Dirichlet series is studied. Contrary to what has been presumed for a long time, we prove that such zeros cannot exist.

math.CV↗
arXiv2013

On The Generalized Riemann Hypothesis

The study of the global mapping properties of arbitrary Dirichlet L-functions is undertaken. The results are applied to the proof of the Generalized Riemann Hypothesis.

math.CV↗
arXiv2012

Riemann Zeta Function

Global mapping properties of the Riemann Zeta function are used to investigate its non trivial zeros.

math.CV↗
arXiv2009

Fundamental Domains of Gamma and Zeta Functions

Branched covering Riemann surfaces $(\mathbb{C},f)$ are studied, where $f$ is the Euler Gamma function and the Riemann Zeta function. For both of them fundamental domains are found and the group of covering transformations is revealed. In order to find fundamental domains, pre-images of the real axis are taken and a thorough study of their geometry is performed. The technique of simultaneous continuation, introduced by the authors in previous papers, is used for this purpose. Color visualization of the conformal mapping of the complex plane by these functions is used for a better understanding of the theory. For the Riemann Zeta function the outstanding question of the multiplicity of its zeros, as well as of the zeros of its derivative is answered.

math.CV↗
arXiv2009

Geometry and Iteration of Dianalytic Transformation

This paper is a continuation of the paper [5] dealing with dynamics of dianalytic transformations of nonorientable Klein surfaces. We are examining mainly the transformations of the real projective plane $P^{2}, $ whose orientable double cover is the Riemann sphere $\overline{C}$ . It is shown that the automorphisms of $P^{2}$ are projections of the rotations of \ $\overline{C}$ and some of the other dianalytic transformations of $P^{2}$ are projections of Blaschke products.

math.CV↗
arXiv2009

Color Visualization of Blaschke Self-Mappings of the Real Projective Plan

The real projective plan $P^2$ can be endowed with a dianalytic structure making it into a non orientable Klein surface. Dianalytic self-mappings of that surface are projections of analytic self-mappings of the Riemann sphere $\widehat{\mathbb{C}}$. It is known that the only analytic bijective self-mappings of $\widehat{\mathbb{C}}$ are the Moebius transformations. The Blaschke products are obtained by multiplying particular Moebius transformations. They are no longer one-to-one mappings. However, some of these products can be projected on $P^2$ and they become dianalytic self-mappings of $P^2$. More exactly, they represent canonical projections of non orientable branched covering Klein surfaces over $P^2$. This article is devoted to color visualization of such mappings. The working tool is the technique of simultaneous continuation we introduced in previous papers.

math.CV↗
arXiv2008

Color Visualization of Blaschke Product Mappings

A visualization of Blaschke product mappings can be obtained by treating them as canonical projections of covering Riemann surfaces and finding fundamental domains and covering transformations corresponding to these surfaces. A working tool is the technique of simultaneous continuation we introduced in previous papers. Here, we are refining this technique for some particular types of Blaschke products for which coloring pre-images of annuli centered at the origin allow us to describe the mappings with a high degree of fidelity.

math.CV↗