Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent.This fundamental tenet has remained experimentally challenging and is yet to be tested in the lab...Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent.This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory.A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence.This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime.Recently,the operation of the high-intensity Relativistic Laser at the X-ray Free Electron Laser provided by the Helmholtz International Beamline for Extreme Fields has been inaugurated at the High Energy Density scientific instrument of the European X-ray Free Electron Laser.We make the case that this worldwide unique combination of an X-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision X-ray polarimetry,refinements of prospective discovery scenarios and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity.展开更多
When exposed to intense electromagnetic fields, the quantum vacuum is expected to exhibit properties of a polarizable medium akin to a weakly nonlinear dielectric material. Various schemes have been proposed to measur...When exposed to intense electromagnetic fields, the quantum vacuum is expected to exhibit properties of a polarizable medium akin to a weakly nonlinear dielectric material. Various schemes have been proposed to measure such vacuum polarization effects using a combination of high- power lasers. Motivated by several planned experiments, we provide an overview of experimental signatures that have been suggested to confirm this prediction of quantum electrodynamics of real photon–photon scattering.展开更多
Experimental studies on full-scale straw-bale walls have demonstrated the adequacy of straw-bale wall systems for resisting lateral loads from wind or seismic actions.Critical to the performance of the wall system is ...Experimental studies on full-scale straw-bale walls have demonstrated the adequacy of straw-bale wall systems for resisting lateral loads from wind or seismic actions.Critical to the performance of the wall system is the anchorage of mesh reinforcement to the bottom plate and to the roof bearing assembly or top plate.Reported in this paper are the results of experiments examining mesh strength,anchorage strength,and failure mode for a variety of reinforcement meshes(steel,plastic,and hemp)and anchorage details.Because of the potential for new wood preservative pressure treatments to cause corrosion,stainless steel staples driven pneumatically into pressure-treated sill plates were tested in addition to electro-galvanized staples driven pneumatically into untreated sill plates and a heavier gauge staple driven manually into an untreated sill plate.Recommended anchorage details are identified,considering not only the test results but also the many other factors that must be considered in developing reliable,economical,and constructible details.展开更多
基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Grants Nos.392856280,416611371,416607684,416702141 and 416708866 within the Research Unit FOR2783/2 and Project-ID 278162697–SFB 1242.
文摘Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent.This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory.A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence.This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime.Recently,the operation of the high-intensity Relativistic Laser at the X-ray Free Electron Laser provided by the Helmholtz International Beamline for Extreme Fields has been inaugurated at the High Energy Density scientific instrument of the European X-ray Free Electron Laser.We make the case that this worldwide unique combination of an X-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision X-ray polarimetry,refinements of prospective discovery scenarios and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity.
文摘When exposed to intense electromagnetic fields, the quantum vacuum is expected to exhibit properties of a polarizable medium akin to a weakly nonlinear dielectric material. Various schemes have been proposed to measure such vacuum polarization effects using a combination of high- power lasers. Motivated by several planned experiments, we provide an overview of experimental signatures that have been suggested to confirm this prediction of quantum electrodynamics of real photon–photon scattering.
文摘Experimental studies on full-scale straw-bale walls have demonstrated the adequacy of straw-bale wall systems for resisting lateral loads from wind or seismic actions.Critical to the performance of the wall system is the anchorage of mesh reinforcement to the bottom plate and to the roof bearing assembly or top plate.Reported in this paper are the results of experiments examining mesh strength,anchorage strength,and failure mode for a variety of reinforcement meshes(steel,plastic,and hemp)and anchorage details.Because of the potential for new wood preservative pressure treatments to cause corrosion,stainless steel staples driven pneumatically into pressure-treated sill plates were tested in addition to electro-galvanized staples driven pneumatically into untreated sill plates and a heavier gauge staple driven manually into an untreated sill plate.Recommended anchorage details are identified,considering not only the test results but also the many other factors that must be considered in developing reliable,economical,and constructible details.
