In physics, geometrical symmetry is a fundamental property of importance since it is associated with physical conservation. Here, we reveal an exceptional form of symmetry for a family of knots that are both chiral and three-dimensional (3D) rotationally symmetric about every axis of a standard Cartesian coordinate system. We call these unique knotted structures chiral balls. Moreover, chirality can bring about polarization transformation in electromagnetic waves. As a consequence of their 3D rotational symmetry, we further expect the polarization transformation performance of chiral balls to exhibit ultra-wide angle-independent behavior. Such a remarkable property has not been previously reported on in…

🗺️ From the Green Book to Today’s Immigration Sanctuary Map 🌍 In the 20th century, the Negro Motorist Green Book helped Black Americans travel safely through a segregated United States. It offered more than travel tips — it was a lifeline, a guide to dignity, safety, and freedom of movement in an unjust world. Today, a new kind of map is quietly taking shape — one that shows sanctuary cities, counties, and states. These are places where local policies limit cooperation with federal immigration enforcement, also where local support and community networks might be more available. 🟤 How to Use…

This chapter is organized as follows. In Section 7.2, innovative work on the optimization-enabled GST metasurfaces for sophisticated beam switching and control is highlighted. In Section 7.3, recent developments in the field of temporal artificial media are first reviewed, and then recent work on the time-varying anisotropic materials for complete polarization conversion is summarized. Finally, in Section 7.4, conclusions and a scope for future research are provided. Read more Lei Kang, Sawyer Campbell, Yuhao Wu, Jingwei Xu, Wending Mai, Eric Whiting, and Douglas H. Werner

This work introduces a new equivalent circuit generation method which can compute an accurate equivalent circuit representation for the known/measured impedance characteristics of antennas, which may assist in matching circuit design, non-Foster matching network design, and deep-learning antenna design. The method utilizes a modified Drude-Lorentz resonator representation inspired by optical material dispersion modeling to create multiple sub-circuits based on determined resonances in the impedance spectrum. Each computed sub-circuit is necessarily composed of physically realizable resistors, capacitors, and inductors, and they are connected in series to accurately reconstruct the device’s corresponding impedance characteristics over a specified region of interest. The process…

Taking lessons from epidemic contact tracing, this communication proposes a method for boosting the efficiency of a full-wave electromagnetic solver by tracking its simulated energy distribution. When the energy within a subdomain of the problem is near zero, such areas can be safely ignored by the solver, reducing computational load with negligible impact on accuracy. We show that time-domain problems can be adaptively partitioned into energy-active (infections), energy-adjacent (exposed), and energy-null (unexposed) domains. To demonstrate the high efficiency and accuracy of this method, it is successfully applied to several computational electromagnetic problems. Due to its reliance on the causality principle…

System response analysis is a powerful method for analyzing linear time-invariant (LTI) systems. In this work, we have demonstrated that a system response approach can also be applied to analyze the so-called linear space-invariant (LSI) but time-varying problems, which represent a dual of the conventional LTI problems. In this proposed approach, we perform a Fourier transform of the electric field distribution on the space coordinate, rather than in time, and express it in the wave-number domain. Specifically, we express any input signal and its corresponding output in the wave-number domain. Then, the transfer function for the LSI time-varying system can…