Bremsstrahlung from relativistic electrons is considered under conditions when some transverse direction of momentum transfer is statistically preferred. It is shown that in the dipole approximation all the medium anisotropy effects can be accumulated into a special modulus-bound transverse vector, $\bm N$. To exemplify a target with $N^2\sim1$, we calculate radiation from electron incident at a small angle on an atomic row in oriented crystal. Radiation intensity and polarization dependence on the emission angle and frequency for constant $\bm N$ is investigated. Net polarization for the angle-integral cross-section is evaluated, which appears to be proportional to $N^2/2$, and decreases with the increase of the photon energy fraction. A prominent feature of the radiation angular distribution is the existence of an angle at which the radiation may be completely polarized, in spite of the target complete or partial isotropy -- that owes to existence of an origin-centered tangential circle for polarization in the fully differential radiation probability kernel. Possibilities for utilizing various properties of the polarized bremsstrahlung flux for preparation of polarized photon beams and for probing intrinsic anisotropy of the medium are analyzed.
Neutrino Bremsstrahlung in Neutron Matter from Effective Nuclear Interactions
我们重新讨论了中子-中子散射中中微子对韧致辐射的发射率，nn -> nn nu nubar，这是由Friman和Maxwell从包含关联效应的一π交换势计算的。从自由空间低动量核子-核子相互作用V_{low k}出发，考虑了张量、自旋轨道和二阶介质诱导的非中心效应对中子物质散射振幅的贡献。我们发现核子-核子相互作用的屏蔽降低了密度低于核物质密度的中微子韧致辐射的发射率。我们讨论了介质修改的影响，通过中微子发射冷却的中子星，考虑到最近的结果极化效应的中子超流性。
Local Spin Polarization in Anisotropic Gubser Flow: Suppression Mechanism and Formulation Dependence
The University of Tokyo（东京大学）；University of Science and Technology of China（中国科学技术大学）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
