The European Physical Journal B - Condensed Matter and Complex Systems

, Volume 7, Issue 4, pp 523–525

Evanescent modes are not necessarily Einstein causal

  • G. Nimtz
Rapid Note

DOI: 10.1007/s100510050643

Cite this article as:
Nimtz, G. Eur. Phys. J. B (1999) 7: 523. doi:10.1007/s100510050643


Previously, experiments with microwave signals have shown that evanescent modes can travel faster than light. Several theoretical investigations have proven that in the case of signals with unlimitedly high frequency components, such superluminal velocities do not violate Einstein causality, thus group, signal, and energy velocities are \(\)c where c is the vacuum velocity of light. In this letter I shall show that frequency band limitation is a fundamental property of signals and that such signals containing only evanescent modes can violate Einstein causality.

PACS. 03.65.-w Quantum mechanics - 03.50.De Maxwell theory: general mathematical aspects - 03.30.+p Special relativity

Copyright information

© EDP Sciences, Springer-Verlag 1999

Authors and Affiliations

  • G. Nimtz
    • 1
  1. 1.II. Physikalisches Institut, Universität Köln, Zülpicherstrasse 77, 50937 Köln, GermanyDE