Variational Formulations for Electromagnetic Field and Charged-Particle Stream Configurations and Their Linearization

Two variational formulations for electromagnetic field and charged-particle stream configurations, in which both field and particles are described by the field-like variables suited for the problems of electrodynamics, are presented. One of them is directly obtained through slight modifications of Sturrock's original procedure but has a complicated form. The other is obtained through linearization of the preceding one and has a compact form. Both formulations lend themselves to straightforward derivation of the well-known energy-momentum tensor and/or its conservation law. Specifically the latter one is of academic interest because of its compact form. Moreover, as a proof of its practical usefulness the variational principle under the small-amplitude approximation is derived from it, which is known to provide a basis for the study of certain types of instability in plasmas. It is, however, hoped that it will find main applications in the electrodynamics problems concerned with large-amplitude behavior

Heterogeneous In-Band Full-Duplex System for Simultaneous SUN-FSK Transmission and SUN-OFDM Reception

This study proposes a heterogeneous in-band full-duplex system for the simultaneous transmission of the existing wireless smart ubiquitous network (Wi-SUN) using IEEE 802.15.4g-compliant frequency-shift keying for smart utility network (SUN-FSK) and reception of the next-generation Wi-SUN using IEEE 802.15.4-2020-compliant orthogonal frequency-division multiplexing for SUN (SUN-OFDM). In particular, we propose a digital self-interference (SI) cancellation scheme based on high-precision SI channel estimation using the moving average method, which can be used when the SI signal is a SUN-FSK signal and the desired signal is a SUN-OFDM signal. Furthermore, we propose a highly efficient SUN-OFDM demodulation technique that considers the effect of residual SI. We evaluate the proposed methods through computer simulations. The proposed methods can achieve 67 dB of SI cancellation in the digital domain when the SI signal power and desired signal power ratio in the digital domain is 50 dB. The results of this study enable more efficient coexistence of the existing and next-generation Wi-SUNs, which is expected to improve the throughput and responsiveness of next-generation Wi-SUN systems employing SUN-OFDM

Fractional topological charge in lattice Abelian gauge theory

We construct a non-trivial $U(1)/\mathbb{Z}_q$ principal bundle on~$T^4$ from the compact $U(1)$ lattice gauge field by generalizing L\"uscher's constriction so that the cocycle condition contains $\mathbb{Z}_q$ elements (the 't~Hooft flux). The construction requires an admissibility condition on lattice gauge field configurations. From the transition function so constructed, we have the fractional topological charge that is $\mathbb{Z}_q$ one-form gauge invariant and odd under the lattice time reversal transformation. Assuming a rescaling of the vacuum angle $\theta\to q\theta$ for the consistency with the Witten effect, our construction provides a lattice implementation of the mixed 't~Hooft anomaly between the $\mathbb{Z}_q$ one-form symmetry and the time reversal symmetry in the $U(1)$ gauge theory with matter fields of charge~$q\in2\mathbb{Z}$ when $\theta=\pi$.Comment: 17 pages. The way of identification of the 't Hooft flux and the $\mathbb{Z}_q$ two-form gauge field in v1 was inappropriate. The correction on this point changed the conclusion