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Zhijing Chen

Publications and source records attributed to Zhijing Chen.

7 recordsLinked to original sources
arXiv2022

Variational principles for topological pressures on subsets

In this paper, we investigate the relations between various types of topological pressures and different versions of measure-theoretical pressures. We extend Feng- Huang's variational principle for packing entropy to packing pressure and obtain two new variational principles for Pesin-Pitskel and packing pressures respectively. We show that various types of Katok pressures for an ergodic measure with respect to a potential function are equal to the sum of measure-theoretic entropy of this measure and the integral of the potential function. Moreover, we obtain Billingsley type theorem for packing pressure, which indicates that packing pressure can be determined by measure-theoretic upper local pressure of measures, and a variational principle for packing pressure of the set of generic points for any invariant ergodic Borel probability measure.

math.DS↗
arXiv2019

Thomson backscattering in combined two laser and magnetic field

The Thomson backscattering of an electron moving in combined fields is studied by a dynamically assisted mechanism. The combined fields are composed of two co-propagating laser fields and a magnetic field, where the first laser field is strong and low-frequency while the second is weak and high-frequency, relatively. The dependence of fundamental frequency of emission on the ratio of incident laser high-to-low frequency is presented and the spectrum of backscattering is obtained. It is found that, with a magnetic field, the peak of the spectrum and the corresponding radiation frequency are significantly larger in case of two-laser than that in case of only one laser. They are also improved obviously as the frequency of the weak laser field. Another finding is the nonlinear correlation between the emission intensity of the backscattering and the intensity of the weak laser field. These results provide a new possibility to adjust and control the spectrum by changing the ratios of frequency and intensity of the two laser fields.

physics.optics↗
arXiv2018

Angular Distributions of Thomson Scattering in Combined Laser and Magnetic fields

Angular distributions of Thomson scattering are researched in the combined fields with a circularly polarization of laser field and a strong uniform magnetic field. The trajectories of the electron and the dependence of it on the initial phase are also given. It is found that the angular distributions with respect to the azimuthal angle show twofold symmetry whatever the laser intensity, the order of harmonics, the resonance parameter, and the initial axial momentum are. On the other hand, the radiation with respect to the polar angle is mainly distributed in two regions which are roughly symmetric of the laser propagation. In addition, the larger the laser intensity, the resonance parameters, the initial axial momentum are, the closer radiation is to the laser propagation direction. Besides, a new possibility of X-ray production is indicated. That is to say, with appropriate choice of laser and electron parameters, the high frequency part of the Thomson scattering radiation can reach the frequency range of X-ray (10^17 Hz - 10^18 Hz).

physics.plasm-ph↗
arXiv2015

Point transitivity, $Δ$-transitivity and multi-minimality

Let $(X, f)$ be a topological dynamical system and $\mathcal {F}$ be a Furstenberg family (a collection of subsets of $\mathbb{N}$ with hereditary upward property). A point $x\in X$ is called an $\mathcal {F}$-transitive point if for every non-empty open subset $U$ of $X$ the entering time set of $x$ into $U$, $\{n\in \mathbb{N}: f^{n}(x) \in U\}$, is in $\mathcal {F}$; the system $(X,f)$ is called $\mathcal {F}$-point transitive if there exists some $\mathcal {F}$-transitive point. In this paper, we first discuss the connection between $\mathcal {F}$-point transitivity and $\mathcal {F}$-transitivity, and show that weakly mixing and strongly mixing systems can be characterized by $\mathcal {F}$-point transitivity, completing results in [Transitive points via Furstenberg family, Topology Appl. 158 (2011), 2221--2231]. We also show that multi-transitivity, $Δ$-transitivity and multi-minimality can also be characterized by $\mathcal {F}$-point transitivity, answering two questions proposed by Kwietniak and Oprocha [On weak mixing, minimality and weak disjointness of all iterates, Erg. Th. Dynam. Syst., 32 (2012), 1661--1672].

math.DS↗
arXiv2014

On multi-transitivity with respect to a vector

A topological dynamical system $(X,f)$ is said to be multi-transitive if for every $n\in\mathbb{N}$ the system $(X^{n}, f\times f^{2}\times \dotsb\times f^{n})$ is transitive. We introduce the concept of multi-transitivity with respect to a vector and show that multi-transitivity can be characterized by the hitting time sets of open sets, answering a question proposed by Kwietniak and Oprocha [On weak mixing, minimality and weak disjointness of all iterates, Erg. Th. Dynam. Syst., 32 (2012), 1661--1672]. We also show that multi-transitive systems are Li-Yorke chaotic.

math.DS↗