Monday, December 4, 2023

Exploring Vacuum Polarization in Strong Field Emission Spectra

The concept of vacuum polarization has long been considered as an important aspect of quantum electrodynamics, particularly in the study of extreme astrophysical environments such as magnetars and black holes. The recent study conducted by M. Jirka and P. Bulanov has shed new light on the features of photon spectra that emerge due to the synergic emission of a charged particle in a polarized vacuum, providing a new way of exploring vacuum polarization.

The traditional approach to studying photon emission has been through the non-linear Compton scattering, where vacuum polarization effects are neglected. The new study by Jirka and Bulanov, however, has shown that the probability of photon emission of a charged particle in a strong field becomes modified if vacuum polarization is considered. The authors explore the features in photon spectra that emerge due to the synergic emission of a charged particle in a polarized vacuum, highlighting the differences from the traditional non-linear Compton scattering approach.

The new findings show that for today’s available 700 GeV (6.5 TeV) protons and the field provided by the generation of lasers, the emission spectra peak is enhanced by 30% due to vacuum polarization. This is an important discovery as it highlights the significance of vacuum polarization in quantum electrodynamics processes present in extreme astrophysical environments.

According to quantum theory, the vacuum behaves as a medium with a modified refractive index for a probe of electromagnetic radiation when under the action of a strong field. The vacuum polarization is characterized by an index of refraction n = 1 + ∆n, where |∆n| 1 is the change of refraction index due to vacuum polarization. The authors derive the formula for photon emission that includes the effect of the index of refraction and show that while for electrons characterized by χ 1 the effect of vacuum polarization on emission spectra peak is not expected, for today’s available 6.5 TeV (700 GeV) protons, the synergic nature of photon emission leads to suppression of emitted energy by tens of percent compared to a pure Compton process.

The study has also shown that a recoil experienced by the emitting particle, which has been considered negligible in the case of quantum Cherenkov radiation, plays an important role in the more general synergic processes, suppressing the effect of vacuum polarization on photon emission. The results of the study demonstrate that radiation from a charged particle traversing a strong field region provided by sources such as magnetars or ultra-intense lasers can be drastically enhanced or reduced once vacuum polarization is taken into account.

The synergic Compton-Cherenkov process enhances the peak of photon emission spectra by 30% in comparison to pure Compton radiation in which vacuum polarization is neglected. The results of the study are significant and provide a new perspective on the phenomenon of vacuum polarization in extreme astrophysical environments. The findings highlight the importance of considering vacuum polarization in the study of quantum electrodynamics processes and its impact on the emission of photons from charged particles in strong fields.



Source : Jirka, M., & Bulanov, P.S. (2023). Space quantum vacuum radiation 
in a laser-particle collision

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