36th Summer Topology Conference

July 18-22, 2022

University of Vienna, Department of Mathematics
Oskar-Morgenstern-Platz 1, 1090 Vienna, AUSTRIA

"Generating subgroups of the circle using a generalized class of density functions"

Das, Pratulananda

In this talk, we consider the generalized version $d^f_g$ of the natural density function where $g : \mathbb{N} \rightarrow [0,\infty)$ satisfies $g(n) \rightarrow \infty$ and $\frac{n}{g(n)} \nrightarrow 0$ whereas $f$ is an unbounded modulus function and generate versions of characterized subgroups of the circle group $\mathbb{T}$ using these density functions. We show that these subgroups have the same feature as the $s$-characterized subgroups [Dikranjan, Das, Bose, Fund. Math., 2020] and our results provide more general versions of the main results of that article. But at the same time the utility of this more general approach is justified by constructing new and nontrivial subgroups for suitable choice of $f$ and $g$. In several of our results we use properties of the ideal $\mathcal{Z}_g(f)$ which are first presented along with certain new observations about these ideals which were not there in [Bose, Das, Kwela, Indag. Math., 2018]

« back