Behavior of heat capacity of an attractive Bose-Einstein Condensate approaching collapse

We report calculation of heat capacity of an attractive Bose-Einstein condensate, with the number N of bosons increasing and eventually approaching the critical number Ncr for collapse, using the correlated potential harmonics (CPH) method. Boson pairs interact via the realistic van der Waals potential. It is found that the transition temperature Tc increases initially slowly, then rapidly as N becomes closer to Ncr . The peak value of heat capacity for a fixed N increases slowly with N, for N far away from Ncr . But after reaching a maximum, it starts decreasing when N approaches Ncr . The effective potential calculated by CPH method provides an insight into this strange behavior.