This necessity arises because the existing
equation does not include the contribution from the kinetic energy of the particles in the
condensate. We have used two separate methods to obtain an expression for this energy,
one based on conservation of energy and the other on the requirements of the Heisenberg
uncertainty principle, and showed that both lead to the same value of∼kTB for the kinetic energy
per particle in the condensate. As we have already shown elsewhere [14], the modification
removes the several difficulties arising from London’s equation, including the infinite value
of the isothermal compressibility that is predicted for temperatures below TB