Searcharxiv⌕ Search

arXiv subjects

Yonghang Ruan

Publications and source records attributed to Yonghang Ruan.

2 recordsLinked to original sources

Weighted orbits of hypercyclic vectors on F-spaces

We study $\mathcal{F}$-hypercyclicity of weighted orbits $λ_nT^nx$ for continuous linear operators $T$ on complex F-spaces, where $\mathcal{F}$ is a Furstenberg family with the cut--shift--and--paste (CuSP) property. We characterize the scalar sequences for which weighted hypercyclicity always implies ordinary hypercyclicity: their nonzero values must be bounded and bounded away from zero. The same condition removes weights for every such family. For the converse inclusion, we prove that a bounded scalar sequence preserves all $\mathcal{F}$-hypercyclic vectors if its backward-shift $ω$-limit system is distal and does not contain the zero sequence. For chaotic operators, minimality of this system suffices. In particular, every complex nilsequence which is not identically zero preserves $\mathcal{F}$-hypercyclicity, and equality holds when its nonzero values are bounded away from zero. We also obtain simultaneous weighted return results and stability under unimodular weights with asymptotically trivial multiplicative differences.

math.FA↗

Weak disjointness of hypercyclic operators

We study the weak disjointness of hypercyclic operators to refine the classifications of hypercyclic operators. We establish an analogue of the Weiss-Akin-Glasner Theorem from topological dynamics within the framework of linear dynamics, which gives a characterization of the weak disjointness of each class of mixing operators with respect to a given Furstenberg family. The key ingredient is an analogue of the Weiss-Akin-Glasner Lemma from topological dynamics, which gives a characterization of subsets of non-negative integers which can be realized by the return time sets of mixing operators with respect to a given Furstenberg family. We also provide several examples to distinguish some classes of hypercyclic operators and end with the characterization of the mixing property with respect to Furstenberg families of direct sums of backward shifts on Fréchet sequence spaces.

math.DS↗