

Quantum effects in a system of Boltzmann hard spheresInstitute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow, Russian Federation Quantum contribution to the energy of the `Boltzmann' gas consisting of hard spheres proves to be virtually constant up to very high temperatures where the thermal de Broglie wavelength only makes a small fraction of the solid sphere diameter. Consequently, the heat capacity of the system virtually does not differ from a classical value of (3/2)k_{B} everywhere except the lowest temperature region, where heat capacity as a function of temperature has the 'Debye' form but with a very low Debye temperature of the order of several degrees. The line of equilibrium between quantum crystal and liquid for the 'Boltzmann' system of hard spheres coincides with the classical one with the exception of a verylowtemperature region. Hightemperature quantum effects are revealed in the system under consideration in a kind of `bare' form, while in the case of more realistic systems or models they can be masked by a complex behavior of other components of the total energy. 

