ABSTRACT
The term "phase transition" is often used colloquially with the criterion that a phase transition occurs when incremental changes cause a sudden qualitative change in properties, instead of just having incremental effects. The idea that phase transitions can and do occur in the human brain, has also been pursued at more computable and measurable levels. Changes such as from being awake to sleep and from slow-sleep to Rapid Eye Movement sleep are being discussed as showing features of first order phase transitions. Phase transitions, consistent with this more rigorous usage of the term, are ubiquitous in nature. The most common phase changes are between liquid and solid phases and between liquid and gas phases. Phase transitions can also be caused by changes in the magnetic field. At phase transition, a physical property would change discontinuously, so it follows that some derivative of free energy should change discontinuously at phase transition.
