As you have rightly said absolute zero temp. is not possible - any wherein this world where we live. But it could be possible only in the black hole. That is because of two reasons.
1. The high gravity and compactness of matter in the black hole.
2. A normal stars emits light and energy. Due to neuclear rections mass gets converted to the Energy. A black hole absorbs the light and energy so reverse ( vice versa ) could be happening there, meaning the energy absorbed by it will convert to mass!
This is the reason that the black hole maintains its temp. at 0 deg. K.
I have done more work in the sub. You may read the same on my web page.
http://geocities.com/indumamtora
Things there are very diffict to digest and believe, but I have said what I thought is right!