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## Main Question or Discussion Point

Now plasma represents collective wave-like motions of charged particles. In 3D, their frequency is well known to be almost a constant, ##\omega^{3D}_p \approx \sqrt{4\pi ne^2/m}## with n=charge density, m=particle mass. However, in 2D, one can show that it becomes ##\omega^{2D}_p \sim \sqrt{q}##, where q= wave number. It gets dispersion. The group velocity is then ##v^{2D}_g \sim 1/\sqrt{q}##, which diverges as q→0. How could this be possible ? How could ##v^{2D}_g## exceed the speed of light ? This sounds ridiculous !

Highly appreciate your attention !!

Highly appreciate your attention !!