Probing the Purcell effect without radiative decay: Lessons in the frequency and time domains

The effect of cavities or plates upon the electromagnetic quantum vacuum are considered in the context of electro-optic sampling, revealing how they can be directly studied. These modifications are at the heart of e.g. the Casimir force or the Purcell effect such that a link between electro-optic sampling of the quantum vacuum and environment-induced vacuum effects is forged. Furthermore, we discuss the microscopic processes underlying electro-optic sampling of quantum-vacuum fluctuations, leading to an interpretation of these experiments in terms of exchange of virtual photons. With this in mind it is shown how one can reveal the dynamics of vacuum fluctuations by resolving them in the frequency and time domains using electro-optic sampling experiments.

Superluminal velocity beyond the scope of application of relativity

People have carried on the extensive researches on the superluminal velocity in experiment and theory, but it is difficult to reach consensus. The biggest problem here is the theory of relativity, which shows that when a object (a matter with mass) reaches or exceeds the speed of light, whose relativistic factor will become infinite or imaginary numbers, so it is impossible to superluminal motion. In fact, although relativity is quite correct quantitative theory, but it has certain limitations. Relativistic effects are the vacuum effects, not the substantive effects. Relativistic physical quantities are only apparent physical quantities expressed through ether(physical vacuum). The substantive physical quantities of an objects are proper physical quantities, which will not vary with the velocity. Moreover the ether in superluminal velocity would lose superfluidity, and thus the superluminal velocity is beyond its scope of application of relativity. Therefore studying superluminal velocity need not scruple the restriction of relativity. Human superluminal activities will involve gravitational shielding, superluminal communication and other supertechnologies.

Detectable Optical Signatures of QED Vacuum Nonlinearities Using High-Intensity Laser Fields

Up to date, quantum electrodynamics (QED) is the most precisely tested quantum field theory. Nevertheless, particularly in the high-intensity regime it predicts various phenomena that so far have not directly been accessible in all-optical experiments, such as photon-photon scattering phenomena induced by quantum vacuum fluctuations. Here, we focus on all-optical signatures of quantum vacuum effects accessible in the high-intensity regime of electromagnetic fields. We present an experimental setup giving rise to signal photons distinguishable from the background. This configuration is based on two optical pulsed petawatt lasers: one generates a narrow but high-intensity scattering center to be probed by the other one. We calculate the differential number of signal photons attainable with this field configuration analytically and compare it with the background of the driving laser beams.

X-ray spectra and polarization from magnetar candidates

ABSTRACT Magnetars are believed to host the strongest magnetic fields in the present universe ($B\gtrsim 10^{14}$ G) and the study of their persistent emission in the X-ray band offers an unprecedented opportunity to gain insight into physical processes in the presence of ultra-strong magnetic fields. Up to now, most of our knowledge about magnetar sources came from spectral analysis, which allowed to test the resonant Compton scattering scenario and to probe the structure of the star magnetosphere. On the other hand, radiation emitted from magnetar surface is expected to be strongly polarized and its observed polarization pattern bears the imprint of both scatterings on to magnetospheric charges and quantum electro-dynamics (QED) effects as it propagates in the magnetized vacuum around the star. X-ray polarimeters scheduled to fly in the next years will finally allow to exploit the wealth of information stored in the polarization observables. Here we revisit the problem of assessing the spectro-polarimetric properties of magnetar persistent emission. At variance with previous investigations, proper account for more physical surface emission models is made by considering either a condensed surface or a magnetized atmosphere. Results are used to simulate polarimetric observations with the forthcoming Imaging X-ray Polarimetry Explorer. We find that X-ray polarimetry will allow to detect QED vacuum effects for all the emission models we considered and to discriminate among them.