Abstract We show that in a dilute gas the wave function’s spreading is limited by scattering off other particles. This shows that quantum mechanics can be consistent with the kinetic theory of gases.
We compute the viscosity spectral function of the dilute Fermi gas for different values of the s-wave scattering length a, including the unitarity limit a→∞. We perform the calculation in kinetic theory by studying the response to a non-trivial background metric. We find the expected structure consisting of a diffusive peak in the transverse shear channel and a sound peak in the longitudinal channel. At zero momentum the width of the diffusive peak is ω0≃(2ϵ)/(3η) where ϵ is the energy density and η is the shear viscosity. At finite momentum the spectral function approaches the collisionless limit and the width is of order ω0∼k(T/m)1/2.
We compute the viscosity spectral function of the dilute Fermi gas for different values of the s-wave scattering length a , including the unitarity limit a → ∞ . We perform the calculation in kinetic theory by studying the response to a non-trivial background metric. We find the expected structure consisting of a diffusive peak in the transverse shear channel and a sound peak in the longitudinal channel. At zero momentum the width of the diffusive peak is ω 0 ≃(2ε)/(3η) where ε is the energy density and η is the shear viscosity. At finite momentum the spectral function approaches the collisionless limit and the width is of the order of ω 0 ∼ k ( T / m ) 1/2 .