In physics, X-waves are localized solutions of the wave equation that travel at a constant velocity in a given direction. X-waves can be sound, electromagnetic, or gravitational waves. They are built as a non-monochromatic superposition of Bessel beams. Ideal X-waves carry infinite energy, but finite-energy realizations have been observed in various frameworks. X-wave pulses can have superluminal phase and group velocity.
In optics, X-waves solution have been reported within a quantum mechanical formulation.
See also
Nonlinear X-wave
Droplet-shaped wave
References
J. Lu and J. F. Greenleaf, "Nondiffracting X waves: exact solutions to free-space scalar wave equation and their infinite realizations", IEEE Trans. Ultrasonic Ferroelectric Frequency. Control 39, 19–31 (1992). Erasmo Recami and Michel Zamboni-Rached and Hugo E. Hernandez-Figueroa, "Localized waves: A scientific and historical introduction" arxiv.org 0708.1655v2. Various authors in the book Localized Waves edited by Erasmo Recami, Michel Zamboni-Rached and Hugo E. Hernandez-Figueroa
External links
The Virtual Institute for Nonlinear Optics (VINO), a research collaboration devoted to the investigation of X-waves and conical waves in general Nolinear X-waves page at the nlo.phys.uniroma1.it website.