## Super-fluid 4He - (two domains)

Hi PF ,

I am making a review article which is mainly based on low temperature physics , upon going through my search I have stumbled across the famous " Lambda transition" of super liquid helium. Paraphrasing what some of the books said : " In the He II domain a percentage of atoms in same quantum state act as a single entity , while the rest of the percentage is made up of atoms which have different quantum states ( another book says normal , what do they mean by normal ? vector [position ?] , the overall density stays constant " .

I need bit of a clarification on the bold bit , also it's said that as the temperature is dropped to absolute zero , the number of atoms ( normal) decreases.

I know that in Q.M particles are said to obey einstein-bose statistics if they have an integer spin of zero , so in what way is He II similar to Bose- Einstein condensate.