|WikiProject Physics||(Rated Start-class, High-importance)|
|WikiProject Systems||(Rated Disambig-class, Mid-importance)|
-Ferromagnetic materials also present a metastable behavior. If one considers the presence of an external magnetic field, the equilibrium state is obtained when the material aligns its magnetization with the exterior field. But if the sample already presents a residual magnetization, which is in the opposite direction of a small exterior field, then the system becomes metastable. This situation has a very good description, what makes it even more interesting. —Preceding unsigned comment added by 220.127.116.11 (talk) 11:05, 17 July 2008 (UTC)
Is this wrong?
"It is analogous to being balanced precisely at the top of a round hill, rather than safely at the bottom of a valley" - -Wouldn't that be a definition of unstable (i.e. a small disturbance moves the system further and further away from the initial point) rather than metastable? Commutator (talk) 07:45, 13 June 2008 (UTC)
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)
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.
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)
|This topic is in need of attention from an expert on the subject.
The section or sections that need attention may be noted in a message below.
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).
Hello! I (wavepacket) added that text. I agree it is rather sweeping, but of course there is the usual author's tension between readable prose and mathematically precise terminology. I am not yet good at both at the same time. One reference might be Manfred Schroeder's "Fractals, Chaos, Power Laws" (1991, WH Freeman and Company). Chapter 4 (Power Laws: Endless Sources of Self-Similarity) notes that "scaling invariance results from the fact that homogeneous power laws lack natural scales...". In his references, Schroeder points to examples from RM May (Science 214 pg 1441), and a very cool power-law distribution of impact rates vs. particle size graph from Schoemaker, US Geological Survey.
Expert attention needed?
There's an expert attention needed tag in the article, but it's not particularly obvious why. (Obviously any Wikipedia article would be benefitted by having an expert view...) Unless someone suggests what specific issue should be looked at, I'll clear the tag. Djr32 (talk) 18:01, 1 August 2009 (UTC)
Metastability in electronics
There's a separate article about metastability in electronics - should add a link from this section to the article —Preceding unsigned comment added by 18.104.22.168 (talk) 20:44, 15 February 2010 (UTC)
Basic attention needed
You better believe this article is "start class". It is a simple concept at its heart that is impossible to understand based on this article unless, perhaps, you already know what it is. When dictionary.com is more informative, one has to wonder what planet you guys are on. I have entered a new article on metastability on simple.wikipedia.org which actually says what metastability is, a goal that apparently is out of reach on en.wikipedia.org. —Preceding unsigned comment added by 22.214.171.124 (talk), 24 May 2010 (UTC)
Lead section inadequate
I find that the lead section is absolutely unintelligible, with too many lucubrations and too few sound concepts. By reading it, I can understand metastability only because I already know what is metastability. So, I think it is to be completely rewritten. --GianniG46 (talk) 19:11, 17 October 2010 (UTC)
Electron systems in biochemistry
Section as it stands as of 14 February 2017: The evolution of a many-body quantum system between its characteristic set of states may be influenced by the following external actions:
- The environment may act chaotically on the system, adding uncertainty to all state energies (while decreasing their lifespans) – as in spectral line broadening.
- Resonant exterior actions may nudge the system into a lower cohesive energy state while making it release an intrinsic amount or quanta of its energy – as in stimulated emissions.
- Alternatively, external catalytic fields of forces may briefly flatten some of the barriers (ridges separating adjacent valleys) in the potential landscape of the system and help it tunnel through to lower energy states.
- Under the impact of thermal or directional external actions, some systems (see macromolecule complexes involving enzyme-cofactor association) may wander for extremely long periods of time among a certain sub-group of their states (all having distinct configurations but energy differences within the thermal fluctuation range). As such the enzymes will enter a biochemical reaction sequence with an initial configuration, perform the many steps of the sequence as catalysts while continuously contorting, and eventually leave that reaction sequence in the same configuration as they entered it, ready to perform again.
This section seems to be roughly on topic, but the concepts are not well-connected. The first three points do not seem to apply to biochemistry any more than they apply to many other fields of chemistry. If these points are of particular interest in biochemistry, more explanation is needed. The last bullet point is an example of why metastability is important to complex biological systems, but does not make the connection clear enough for those who are not already familiar with the concept(s).Elriana (talk) 02:01, 15 February 2017 (UTC)