Superluminal, subluminal, and negative velocities in free-space electromagnetic propagation

TL;DR

This paper analyzes the local and instantaneous nature of superluminal, subluminal, and negative velocities in free-space electromagnetic pulses, clarifying their physical interpretation and compatibility with causality and relativity.

Contribution

It provides a detailed time-domain analysis and discusses recent simulations and measurements of anomalous velocities in electromagnetic fields.

Findings

Velocities are local and instantaneous.

They do not violate causality or relativity.

Effects are mainly near- and intermediate-field phenomena.

Abstract

In this Chapter the time-domain analysis of the velocity of the electromagnetic field pulses generated by a spatially compact source in free space is presented. Recent simulations and measurements of anomalous superluminal, subluminal, and negative velocities are discussed. It is shown that such velocities are local and instantaneous in nature and do not violate either causality or special relativity. Although these effects are mainly confined to the near- and intermediate-field zones, some of them seem paradoxical and still lack adequate physical interpretation.