Talk:Metastability

From Wikipedia, the free encyclopedia


Contents

[edit] Metastability vs hysteresis

I think that the article would gain from distinguishing between the words metastable equilibrium and hysteresis. A system at metastable equilibrium is well described by Statistical mechanics and the fluctuations obey the fluctuation dissipation theorem. On the other hand hysteresis refers to the fact that most physical systems do not reach equilibrium instantaneously.

EDIT: Perhaps it is better to write it the following way:

A metastable system can equilibrium system for all purposes. As an example the state of a metastable system is fully described by the value of temperature and pressure. (unsigned comment)

I added a "see also" link, but not an explanation of the difference between the two concepts. They both seem to have pretty clear definitions. If anyone feels the need to add this contrast, I would say it this way: hysteresis is the dependence of state on the history of the environment, not just the current environment (which may or may not imply equilibrium) and metastability is equilibrium (a stable state) outside the ground state. -- Beland (talk) 12:51, 6 June 2008 (UTC)

[edit] Explaining metastability

When I have to explain metastability, I always use the example of atomic nuclei. Iron is the only stable atomic nucleus. The rest of the atomic nuclei are only metastable. Nevertheless we can use statistical mechanics to describe chemical systems. The key feature here is separation of time scales. The timescale for atomic processes is much longer than the time scale of chemical reactions.

Actually chemical substances are another example of metastability. In quantum chemistry they have several methods for calculating the speed of a chemical reaction. All these methods rely on a crucial assumption that the vibration of the molecule is well described by a thermal equilibrium distribution. In other words they rely on an assumption of metastability. Once again the key assumption is separating time scales. The time needed to attain vibrational equilibrium is shorter than the inverse reaction rate.

[edit] Created two subarticles

I created two subarticles in order to be able to distinguish and specialize them.--Carl Hewitt 04:43, 21 July 2005 (UTC)

Additional note: Physics page no longer explains metastable. (unsigned comment)

I've merged several articles back into this one, so that the general scientific concept could be explained, and then applied to the various fields. Some subarticles remain. -- Beland (talk) 12:52, 6 June 2008 (UTC)

[edit] Dropped text

 This article or section is in need of attention from an expert on the subject.
Please help recruit one or improve this article yourself. See the talk page for details.
Please consider using {{Expert-subject}} to associate this request with a WikiProject

I dropped the following text during a merge:

Systems prone to metastable states tend to exhibit power law behavior when measured over time. This is because the interactions are scale invariant. For instance, adding a single grain to a sandpile can result in anything from a small local disturbance (common) to the collapse of almost the entire pile (rare).

I'm not sure this is correct, and it's unreferenced and rather sweeping in scope. References would be appreciated if this claim is defensible. -- Beland (talk) 01:40, 6 June 2008 (UTC)