Photon emission in strong fields beyond the locally-constant field approximation
Photon emission in strong fields beyond the locally-constant field approximation
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DOI：
10.1103/physrevd.100.116003
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发表时间：
2019-09
影响因子：
5
通讯作者：
I. Aleksandrov;G. Plunien;V. Shabaev
中科院分区：
文献类型：
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作者：
I. Aleksandrov;G. Plunien;V. Shabaev
本文研究了强电磁场作用下真空光子发射的一个基本非线性过程，即：提供外场的时空不均匀性的精确处理。我们研究了由高强度激光脉冲形成的电磁驻波，并将近似预测与通过精确方法评估蝌蚪（可还原）和顶点（不可还原）贡献所获得的结果进行了比较。它表明，以前使用的近似方法可能无法正确地描述这两个术语的定量特征。在蝌蚪贡献的情况下，LCFA大大低估了足够高频率的外部场发射的光子数。顶点项预测了大量软光子的发射，其光谱与LCFA结果相比不再是各向同性的。光子产额之间的显着差异沿着不同的空间方向，这是没有捕获的LCFA，代表了一个重要的签名的光子发射过程的实验研究。由于这一特性只有在凯尔迪什参数远大于1时才会发生，因此它也可以用于间接观察施温格机制。
We investigate a fundamental nonlinear process of vacuum photon emission in the presence of strong electromagnetic fields going beyond the locally-constant field approximation (LCFA), i.e., providing the exact treatment of the spatio-temporal inhomogeneities of the external field. We examine a standing electromagnetic wave formed by high-intensity laser pulses and benchmark the approximate predictions against the results obtained by means of a precise approach evaluating both the tadpole (reducible) and vertex (irreducible) contributions. It is demonstrated that the previously-used approximate methods may fail to properly describe the quantitative characteristics of each of the two terms. In the case of the tadpole contribution, the LCFA considerably underestimates the number of photons emitted for sufficiently high frequency of the external field. The vertex term predicts emission of a great number of soft photons whose spectrum is no longer isotropic in contrast to the LCFA results. A notable difference among the photon yields along different spatial directions, which is not captured by the LCFA, represents an important signature for experimental studies of the photon emission process. Since this feature takes place unless the Keldysh parameter is much larger than unity, it can also be used in indirect observation of the Schwinger mechanism.