Based on the invariance of the phase of waves, plane waves were shown to propagate with negative frequencies in a medium which moves at ’superluminal’ speed opposite to the propagation direction of the plane waves. The validity of the invariance of the phase of plane waves was then called into question. A radical change of the conventional concept of plane waves is recently proposed to solve the problem of negative frequency of waves.We will explicitly point out flaws in that proposal. Thus, the validity of the invariance of the phase of plane waves remains questionable
Based on the invariance of the phase of waves, plane waves were shown to propagate with negative frequencies in a medium which moves at ’superluminal’ speed opposite to the propagation direction of the plane waves. The validity of the invariance of the phase of plane waves was then called into question. A radical change of the conventional concept of plane waves is recently proposed to solve the problem of negative frequency of waves.We will explicitly point out flaws in that proposal. Thus, the validity of the invariance of the phase of plane waves remains questionable
In last decade,faster-than-light(superluminal) propagation of short waves,microwaves,light waves and THz waves has been studied experimentally in several countries.Many of the attempts to send pulses faster than the speed of light involved a phonomenon called negative-velocities wave propagation.In this paper,we give a bird-eye view of the theoretical and experimental research work on negative-velocities wave propagation.For example and experimentally,a light pulse propagating through the atomic vapor cell has its peak reaching the exit side before entering it,resulting in a negative transit time,and negative group velocity.So that the group velocity vg can be greater than the velocity of light c,can be infinite and even negative.In recent years,many superluminal phenomena of negative-velocities have been discovered in experiments and observations,so we say it is a new frontier in sciences research.
As we saw in the previous chapter, a sinusoidal wave of amplitude ψ0 > 0, wavenumber k > 0, and angular frequency ω > 0, propagating in the positive x-direction, can be represented in terms of a wavefunction of the form ψ(x, t) = ψ0 cos(ω t − k x). (7.1) This type of wave is conventionally termed a one-dimensional plane wave. It is onedimensional because its associated wavefunction depends on only a single Cartesian coordinate. Furthermore, it is a plane wave because the wave maxima, which are located at ω t − k x = j 2π, (7.2) where j is an integer, consist of a series of parallel planes, normal to the x-axis, that are equally spaced a distance λ = 2π/k apart and propagate along the x-axis at the fixed phase velocity ω/k = v, where v is the characteristic wave speed. These conclusions follow because Equation (7.2) can be rewritten in the form x = d, (7.3) where d = v t − j λ. Moreover, (7.3) is the equation of a plane, normal to the x-axis, whose distance of closest approach to the origin is d.
It is shown that there are no dispersing media with «subluminal only» or «superluminal only» real group velocity – if in some medium at some frequencies the real group velocity is subluminal, then in the same medium there are necessarily frequencies at which the real group velocity is superluminal. Conversely, if a medium has frequencies with a superluminal group velocity, then it necessarily has frequencies with a subluminal group velocity. In other words, there is a necessary connection between subluminal and superluminal group velocity – if any medium is capable of generating subluminal group velocity, then the same medium is capable of generating superluminal group velocity. Similarly, there are no media with «only positive» or «only negative» imaginary part of the complex group velocity – if at some frequencies the imaginary part of the group velocity is positive, then at other frequencies in the same medium it is negative and vice versa. This means that if there is a carrier frequency in the medium at which some linearly frequency-modulated signal propagates at a speed lower than the group speed, then in the same medium there is necessarily a carrier frequency at which the same signal will propagate at a speed higher than the group speed and vice versa.
A simple covariant derivation of the de Broglie relations breaks down when one considers propagation of light in an anisotropic medium. This breakdown results in two distasteful conclusions. The first is that the de Broglie relations are not completely universal and their covariance is restricted. The second is that wave-particle duality is not universal. In this paper a resolution of these problems is suggested, a resolution which is an extrapolation of ideas of de Broglie and Andrade e Silva. The relations are generalized for propagation in anisotropic media by defining a new phase wave with wave vector l in the direction of energy transport and distinct from the conventional electromagnetic wave. The introduction of l follows the method by which de Broglie associated a wave with an electron. The magnitude of l is omega u/c-squared where omega is the angular frequency and u the velocity of energy transport. The physical meaning of l and the covariance of physical laws in the presence of matter are discussed. An experiment is described which would test the existence of the phase wave associated with the new wave vector l. This experiment is essentially a Young two-slit experiment carried out within an anisotropic crystal. Keywords: Scattering; Anisotropic materials.
Much experimental evidence of superluminal phenomena has been available by electromagnetic wave propagation experiments, with the results showing that the phase time describes the barrier traversal time. Based on the extrapolated phase time approach and numerical methods, we show that, in contrast to the ordinary Bessel waves of real argument, the group velocities of modified Bessel waves are superluminal. We obtain the following results. The group velocities increase with the increase of propagation distance, which is similar to the evanescent plane-wave cases. For large wave numbers, the group velocities fall off as the wave numbers increase, which is similar to the evanescent plane-wave cases. For small wave numbers, the group velocities increase with the increase of wave numbers, this is different from the evanescent plane-wave cases.
Newton mechanics is great, Newton's contribution is indelible. But from Newton's classical mechanics, the definition of velocity (=) must mean that this physical parameter is a vector, so "negative velocity" only means the opposite direction of motion, no other meaning. It is difficult to understand negative velocity within the framework of classical mechanics. However, wave is a special form of material motion, wave mechanics has a unique method and meaning, and its concept and connotation are significantly different from classical mechanics. For example, wave velocity (whether phase velocity or group velocity) is a scalar quantity. "Negative wave velocity" does not mean that the direction of motion is reversed, but a special phenomenon that does not accord with causality from the surface view. In any case, research in recent decades has shown that negative wave velocity is not only theoretically possible, it has also been repeatedly shown to exist experimentally. Moreover, negative wave velocity is a special form of superluminal speed; The wave with negative velocity is the advanced wave. It corresponds to the leading solution of the basic equation of electromagnetic field and electromagnetic wave. The past practice (discarding the advanced solution) is wrong! As for causality, scientists have provided a new definition and interpretation. In short, both wave mechanics and quantum optics take a different approach from classical mechanics. This paper points out that it is unusual for the 2022 Nobel Prize in Physics to be awarded to Alain Aspect and two others, since Aspect's experiments on the Bell inequality were completed in 1982, Which still stands today as a crucial experiment that proved Einstein's EPR paper wrong and quantum mechanics (QM) correct. Aspect's award in 2022 showed that mainstream physical community had been forced to accept that quantum entanglement existed and that the "light-speed limit" theory of SR was a mistake. This paper discusses the proposition "negative characteristic motion of electromagnetic wave" put forward by the author in 2013, pointing out that it is an inherent physical phenomenon reflecting symmetry in nature. In this paper, the faster-than-light motion of waves found in the near-field of antennas is discussed. In addition, the realizability of "time travel" is also discussed.