Improved local-constant-field approximation for strong-field QED codes
Improved local-constant-field approximation for strong-field QED codes
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DOI：
10.1103/physreva.99.022125
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发表时间：
2018-11
影响因子：
2.9
通讯作者：
A. Piazza;M. Tamburini;S. Meuren;C. Keitel
中科院分区：
文献类型：
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作者：
A. Piazza;M. Tamburini;S. Meuren;C. Keitel
局域恒定场近似（LCFA）是研究具有复杂时空结构的背景电磁场中强场QED现象的重要理论工具。在我们以前的工作中[Phys. Rev. A 98，012134（2018）2469-992610.1103/PhysRevA.98.012134]，我们分析了背景平面波场情况下低发射光子能量下LCFA在非线性康普顿散射中的缺点。在这里，我们将这种分析推广到背景场，背景场可以具有几乎任意的时空结构。此外，我们提供了一个明确的和简单的实现的非线性康普顿散射微分概率的改进表达式，解决了在红外区域的标准LCFA的主要缺点，是适合于背景电磁场与任意时空结构，如发生在粒子细胞模拟。最后，我们进行了一个系统的程序来计算每单位的发射光子光锥能量的非线性康普顿散射和非线性Breit-Wheeler对生产每单位的正电子光锥能量超过LCFA在平面波背景场，这使我们能够确定这种近似的有效性的限制定量。
The local-constant-field approximation (LCFA) is an essential theoretical tool for investigating strong-field QED phenomena in background electromagnetic fields with complex spacetime structure. In our previous work [Phys. Rev. A 98, 012134 (2018)2469-992610.1103/PhysRevA.98.012134] we have analyzed the shortcomings of the LCFA in nonlinear Compton scattering at low emitted photon energies for the case of a background plane-wave field. Here, we generalize that analysis to background fields, which can feature a virtually arbitrary spacetime structure. In addition, we provide an explicit and simple implementation of an improved expression of the nonlinear Compton scattering differential probability that solves the main shortcomings of the standard LCFA in the infrared region and is suitable for background electromagnetic fields with arbitrary spacetime structure such as those occurring in particle-in-cell simulations. Finally, we carry out a systematic procedure to calculate the probability of nonlinear Compton scattering per unit of emitted photon light-cone energy and of nonlinear Breit-Wheeler pair production per unit of produced positron light-cone energy beyond the LCFA in a plane-wave background field, which allows us to identify the limits of validity of this approximation quantitatively.