Semiclassical and quantum description of an ideal Bose gas in a uniform gravitational field

• For a Bose gas the quantum and semiclassical isothermal compressibility and heat capacity concur.
• A 3d Bose system with uniform gravity has the same thermal properties as a 5d ideal Bose gas.
• Uniform gravity removes the divergence of the isothermal compressibility at TcTc of an ideal Bose gas.

We consider an ideal Bose gas contained in a cylinder in three spatial dimensions, subjected to a uniform gravitational field. It has been claimed by some authors that there is discrepancy between the semiclassical and quantum calculations in the thermal properties of such a system. To check this claim, we calculate the heat capacity and isothermal compressibility of this system semiclassically as well as from the quantum spectrum of the density of states. The quantum calculation is done for a finite number of particles. We find good agreement between the two calculations when the number of particles are taken to be large. We also find that this system has the same thermal properties as an ideal five dimensional Bose gas.