Subluminal and superluminal velocities of free-space photons
Year: 2026
Type: article
Abstract: We consider rectilinear free-space propagation of electromagnetic wave packets using electromagnetic field theory, scalar wave-packet propagation, and quantum-mechanical formalism. We demonstrate that spatially localized wave packets are inherently characterized by a subluminal group velocity and a superluminal phase velocity, whose product equals c2. These velocities are also known as the “energy” and “momentum” velocities, introduced by K. Milton and J. Schwinger. We illustrate general conclusions by explicit calculations for Gaussian and higher-order beams and wave packets, and also highlight the subtleties of the quantum-mechanical description based on the “photon wavefunction”.
Source: Low Temperature Physics
DOI: 10.1063/10.0044812
Author: Konstantin Y. Bliokh
Institutions: Ikerbasque, Donostia International Physics Center
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7130718023
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