Negative absolute temperature

[sandcastles]

I read wikipedia's article on Negative Absolute Temperature.  It has to do with the level of entropy decreasing after a certain point.  I thought the concept was bizarre and freaky enough for Orions Arm.  It does happen in things like lasers; I wondered if this is worth pursuing here.  What new uses would archailects find for it?  

https://en.wikipedia.org/wiki/Negative_temperature

[Cray]

Interesting idea. Negative temperature systems are ones where entropy decreases as energy is added. Are there situations, perhaps high energy plasmas, where decreased entropy is useful?