Related papers: Has superluminal light propagation been observed?
A number of general issues relating to superluminal photon propagation in gravitational fields are explored. The possibility of superluminal, yet causal, photon propagation arises because of Equivalence Principle violating interactions…
Superluminal tunneling of light through a barrier has attracted broad interest in the last several decades. Despite the observation of such phenomena in various systems, it has been under intensive debate whether the transmitted light truly…
The propagation of a weak probe field in a four-level N-type quantum system in the presence of spontaneously generated coherence (SGC) is theoretically investigated. The optical properties of the system are studied and it is shown that the…
Group velocity of electromagnetic waves in plasmas derived by standard relativistic resistive MHD (resistive RMHD) equations is superluminal. If we assume that the group velocity represents the propagation velocity of a signal, we have to…
The vacuum polarization in an external gravitational field due to one loop electron-positron pair and one loop millicharged fermion-antifermion pair is studied. Considering the propagation of electromagnetic (EM) radiation and gravitational…
General relativity provides an appropriate framework for addressing the issue of sub- or superluminality as an apparent effect. Even though a massless particle travels on the light cone, its average velocity over a finite path measured by…
In a recent theoretical article [Eur. Phys. J. D 70, 1 (2016)], Kazemi et al. claim to have demonstrated superluminal light transmission in an optomechanical system where a Bose-Einstein condensate serves as the mechanical oscillator. In…
Group delay for a reflected light pulse from a weakly absorbing dielectric slab is theoretically investigated, and large negative group delay is found for weak absorption near a resonance of the slab ($Re(kd)=m\pi$). The group delays for…
Experiments done in the early 1990's produced a surprising result: that single photons pass through a photonic tunnel barrier with a group velocity faster than the vacuum speed of light. Subsequent experiments with classical pulses have…
Though both theoretical and experimental investigations have revealed the superluminal behavior of evanescent electromagnetic waves, there are many disputes about the physical meaning and validity of such superluminal phenomenon, which is…
We present an easy way of observing superluminal group velocities using a birefringent optical fiber and other standard devices. In the theoretical analysis, we show that the optical properties of the setup can be described using the notion…
We have observed the propagation of an approximately 35 ns long light pulse with a negative group velocity through a laser-cooled 85Rb atomic medium. The anomalous dispersion results from linear atom-light interaction, and is unrelated to…
Contemporary observational and theoretical studies on the temporal nature of microscopic measurements renewed the discussion about the fundamental constants, leading to the possibility of light speed variation and superluminal pulse…
Based on boundary condition and dispersion relation, the superluminal group velocity in an anisotropic metamaterial (AMM) is investigated. The superluminal propagation is induced by the hyperbolic dispersion relation associated with the…
Superluminal behavior has been extensively studied in recent years, especially with regard to the topic of superluminality in the propagation of a signal. Particular interest has been devoted to Bessel-X waves propagation, since some…
We investigate the behavior of fast light pulse propagation in an N-type Doppler-broadened 4-level atomic system using double Raman gain processes. This system displays novel and interesting results of two controllable pairs of the double…
The propagation of a massless field in attractive and repulsive potentials is considered. It is shown that though the group velocity in such potentials can be larger than one, the wave front propagates with the speed of light. A…
A compact analysis of development and prospects in the study of the tunnelling evolution is given. A new systematization of various approaches to defining tunnelling times in the light of time as a quantum mechanical observable is proposed.…
We present a model for a vacuum-like effective medium composed of the absorbing and gain media under the special designed parameters. Within the linear response theory, we prove that any pulse signal (with or without a discontinuity)…
Experiments done with single photon in the early 1990's produced a surprising result: that single photon pass through a photon tunnel barrier with a group velocity faster than the vacuum speed of light. Recently, a series of experiments…