College Physics ›› 2021, Vol. 40 ›› Issue (2): 59-62.

### Generalized thermal wavelength: definition，significance and applications

LI Xin-yu，ZHANG Zi-yi，WANG Xin，LIU Quan-hui

1. School for Theoretical Physics，College of Physics and Electronics，Hunan University，Changsha，Hunan 410082，China
• Received:2020-04-15 Revised:2020-06-01 Online:2021-02-20 Published:2021-03-02

Abstract:

Photon gas and highly degenerate quantum gases are not classical ideal gas at all，and each of them has its own mean momentum from which a generalized thermal wave length can be thus defined，and the usual thermal wave length is an irrelevant concept.For a non-degenerate system，this wave length converges to the usual thermal one form a matter particle.For a degenerate system，the dimension of thermodynamic system must be larger than this generalized thermal wavelength，which leads to a criterion on the minimum dimension of the thermodynamic system.For some typical systems，we use the criterion to give their minimum dimensions.