Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008, USA.
National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
Phys Rev Lett. 2018 Aug 24;121(8):082501. doi: 10.1103/PhysRevLett.121.082501.
Nuclear response theory beyond the one-loop approximation is formulated for the case of finite temperature. For this purpose, the time blocking approximation to the time-dependent part of the in-medium nucleon-nucleon interaction amplitude is adopted for the thermal (imaginary-time) Green's function formalism. We found that introducing a soft blocking, instead of a sharp blocking at zero temperature, brings the Bethe-Salpeter equation to a single-frequency variable equation also at finite temperatures. The method is implemented self-consistently in the framework of quantum hadrodynamics and designed to connect the high-energy scale of heavy mesons and the low-energy domain of nuclear medium polarization effects in a parameter-free way. In this framework, we investigate the temperature dependence of dipole spectra in the even-even nuclei ^{48}Ca and ^{100,120,132}Sn with a special focus on the giant dipole resonance's width problem and on the low-energy dipole strength distribution.
核反应理论超越了单圈近似，针对有限温度的情况进行了阐述。为此，采用了时相关的中性质子-质子相互作用振幅的时间阻塞近似，用于热（虚时间）格林函数形式。我们发现，在有限温度下，引入软阻塞而不是零温度下的硬阻塞，也可以将 Bethe-Salpeter 方程转换为单频变量方程。该方法在量子重子动力学的框架内自洽地实现，并设计用于以无参数的方式连接重介子的高能标度和核介质极化效应的低能域。在这个框架内，我们研究了偶偶核^{48}Ca 和^{100,120,132}Sn 中偶极子谱的温度依赖性，特别关注了巨偶极共振的宽度问题和低能偶极子强度分布。
