Speaker
Description
Photon vortices caring orbital angular momentum (OAM) [1] with a wave function of Laguerre Gaussian (LG) wave or Bessel wave are one of the most interesting topics in various fields of physics. The interaction between a photon vortex and a material such nucleus may be different from that with standard photons because the photon vortex has non-zero orbital angular momentum parallel to the direction of the photon propagation. It is expected that photon vortices are created in astronomical systems such as black holes [2]. Gamma-ray bursts (GRBs) are one of the most energetic explosive phenomena in the universe, where highly linear (circular) polarization in the energy region of several hundred keV was observed. It may be generated by synchrotron radiations from relativistic electrons under strong magnetic fields.
In quantum theory, electron orbitals in a magnetic field are under Landau states. In the present work we have calculated the photon vortex production from a spiral moving electron under a uniform magnetic field with the strength of 10$^7$-10$^8$ T taking into account Landau quantization. We have theoretically presented that photon vortices are predominantly generated in astrophysical environments with strong magnetic fields such as magnetars or magnetized accretion disks around black holes [3]. This suggests that nucleosynthesis with photons should be changed from that with standard photons. A photon vortex is generated through a transition of an electron between two Landau levels and has a Bessel wave-function. We also calculate the decay widths from an electron in Landau levels and the energy spectra. The present result suggests a possibility that magnetic fields in neutron stars such as magnetar play an important role in the interpretation of many observed phenomena. Magnetars show properties different than normal neutron stars. Particularly large luminosity of photon and neutrino emission attract attention from many researchers.
By the way, this subject can be confirmed by experiments in the laborattory. However, the strength of the magnetic field that can be realized in the laboratory is up to 10 T, and when the Larmor radius is 10 mm, the number of Landau levels of an incident electron is huge, approximately 10$^5$. Recently, we have succeeded in developing a theoretical method to calculate photon vortex production from such a huge Landau level number. This will be presented in the paper.
[1] L. Allen, et al. Phys. Rev. A 45, 8185 (1992).
[2] F. Tamburini, et al. Nature Phys. 7, 195 (2011).
[3] T. Maruyama, et al. Phys. Lett. B826. 136779 (2022).
