近日，加拿大麦吉尔大学的Hugo Scherer及其研究团队取得一项新进展。经过不懈努力，他们对相空间中全温区和全密度下的光子自能进行研究。相关研究成果已于2024年11月26日在国际知名学术期刊《高能物理杂志》上发表。

在这项工作中，研究人员证明了离壳自能与在壳情况在性质上存在显著差异。研究人员开发了在整个相空间中都准确的解析近似方法，特别是在经典等离子体和简并等离子体中。通过这些方法，研究人员在适当的极限条件下恢复了在壳表达式。此外，这一表达式还再现了固体物理学中纵模的著名林哈德响应函数。

据悉，在由自由电荷构成的各向同性背景中，光子的横模和纵模的色散关系会受到显著修正，这种修正由介质中的光子自能来描述。先前的研究已经开发出简单的近似方法，用于描述在不同温度和密度下的等离子体中，在壳（on-shell）光子的传播情况。然而，离壳（off-shell）激发也会受到介质引起的大幅修正，而为了捕捉这些效应，人们常常使用在壳近似方法。

附：英文原文

Title: Photon self-energy at all temperatures and densities in all of phase space

Author: Scherer, Hugo, Schutz, Katelin

Issue&Volume: 2024-11-26

Abstract: In an isotropic background comprised of free charges, the transverse and longitudinal modes of the photon acquire large corrections to their dispersion relations, described by the in-medium photon self-energy. Previous work has developed simple approximations that describe the propagation of on-shell photons in plasmas of varying temperatures and densities. However, off-shell excitations can also receive large medium-induced corrections, and the on-shell approximations have often been used in an effort to capture these effects. In this work we show that the off-shell self-energy can be qualitatively very different than the on-shell case. We develop analytic approximations that are accurate everywhere in phase space, especially in classical and degenerate plasmas. From these, we recover the on-shell expressions in the appropriate limit. Our expressions also reproduce the well-known Lindhard response function from solid-state physics for the longitudinal mode.

DOI: 10.1007/JHEP11(2024)139

Source: https://link.springer.com/article/10.1007/JHEP11(2024)139