Quantum-statistical mechanics of extended objects. II. Breathers in the sine-Gordon system

Abstract

The analysis of the solitons in paper I is extended to breathers in the sine-Gordon system. The breather energy, the inertial mass of the breather, and the breather density at finite temperatures have been calculated. It was shown that the quantized breathers behave like elementary particles at low temperatures. At high temperatures ($E_s>T\gg m$, where $E_s$ is the soliton energy and $m$ is the mass of radiation), the total breather density becomes comparable to that of radiation, implying that the breather degree of freedom is essential in the thermodynamics of the sine-Gordon system.