Problem 1.4. For the less common isotope of helium 3He, the quantum phase transition occurs at a MUCH colder temperature of 0.002491 K. The only difference between 3He and 4He is the presence of a neutron. What key quantum mechanical property of the atom might explain why 3He is so reluctant to phase change? (Hint: is 4He a boson or a fermion? What about helium-3?)