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Coherent Collective Excitations in a Superfluid: Spontaneously Broken Symmetries and Fluctuations-Dissipation

S. J. Han
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Abstract

This paper presents an elementary theory of the phase-coherent collective excitations in both He II in the gravitational field and atomic Bose-Einstein condensation in a trap. The theory is based on the concept of off-diagonal long-range order by Penrose and Onsager and the quantum theory of Bohm, with emphasis on the broken symmetry in a Bose-Einstein gas with repulsive interactions. It is shown that a spontaneously broken symmetry that accompanies a phonon (Nambu-Goldstone mode) takes place at the surface layer of an inhomogeneous Bose system in the presence of an external field. The spontaneously broken symmetry in a Bose system is described and is shown to manifest itself in both He II and the Bose-Einstein condensation - a shell-like structure of Bose-Einstein condensation in a trap. The broken symmetry gives a coherent explanation for a number of long standing puzzles in He II.

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S. J. Han. 2009-03-29. Coherent Collective Excitations in a Superfluid: Spontaneously Broken Symmetries and Fluctuations-Dissipation. https://arxiv.org/abs/cond-mat/0607433

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