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The equation of state of dilute Bose gases, in which the energy only depends on the s-wave scattering length, is rather unknown beyond the universal limit. We have carried out a bunch of diffusion Monte Carlo calculations up to gas parameters of 10^-2 to explore how the departure from the universality emerges. Using different model potentials, we calculate the energies of the gas in an exact way, within some statistical noise, and report the results as a function of the three relevant scattering parameters: the s-wave scattering length a₀, the s-wave effective range r₀, and the p-wave scattering length a₁. If the effective range is not large we observe universality in terms of a₀ and r₀ up to gas parameters of 10^-2. If r₀ grows the regime of universality in these two parameters is reduced and effects of a₁ start to be observed. In the (a₀, r₀) universal regime we propose an analytical law that reproduces fairly well the exact energies.
Planasdemunt et al. (Thu,) studied this question.