Force on a moving object in an ideal quantum gas

Abstract

We consider a heavy external object moving in an ideal gas of light particles. Collisions with the gas particles transfer momentum to the object, leading to a force that is proportional to the object's velocity but in the opposite direction. In an ideal classical gas at temperature $T$, the force acting on the object is proportional to $\sqrt{T}$. Quantum statistics causes a deviation from the $\sqrt{T}$-dependence and shows that the force scales with $T^2$ at low temperatures. At $T=0$, the force vanishes in a Bose gas but is finite in a Fermi gas.Comment: 11 pages, 4 figures; This material has been submitted to/accepted by the American Journal of Physics. After it is published, it will be found at (https://pubs.aip.org/aapt/ajps