https://doi.org/10.1140/epjc/s10052-019-6844-y
Regular Article - Theoretical Physics
Thermal contribution of unstable states
1
Institute of Theoretical Physics, University of Wroclaw, 50-204, Wrocław, Poland
2
Institute of Physics, Jan-Kochanowski University, 25-406, Kielce, Poland
* e-mail: pmlo@gsi.de
Received:
18
February
2019
Accepted:
2
April
2019
Published online:
13
April
2019
Within the framework of the Lee model, we analyze in detail the difference between the energy derivative of the phase shift and the standard spectral function of the unstable state. The fact that the model is exactly solvable allows us to demonstrate the construction of these observables from various exact Green functions. The connection to a formula due to Krein, Friedal, and Lloyd is also examined. We also directly demonstrate how the derivative of the phase shift correctly identifies the relevant interaction contributions for consistently including an unstable state in describing the thermodynamics.
© The Author(s), 2019
