On Thu, Jul 09, 2009 at 09:11:28AM -0700, glen e. p. ropella wrote: > Thus spake russell standish circa 07/08/2009 05:33 PM: > > On Wed, Jul 08, 2009 at 10:16:55AM -0700, glen e. p. ropella wrote: > >> Well, since my post consisted of questions, I could hardly be wrong. ;-) > >> > >> The question was: Is there any identifiable property of a system that is > >> NOT an emergent property, regardless of how one defines "system"? If > >> anyone knows of one, please name it! > > > > Absolutely! The positions of the particles in a Newtonian n-body system > > are not emergent. Of course there are other properties of these > > systems that are emergent, but position & momenta of the particles are > > not amongst them, being part of the basic vocabulary of the model. > > Excellent! Thanks Russell. > > However, I claim that the positions and momenta (note the plural) of the > individual components are not properties of the _system_. Those are > properties of the individual components. A systemic property related to > those component properties might be a centroid or cumulative (averaged, > summed, etc.) momentum for the system as a whole.
Is not the vector of positions and momenta a systemic property? It precisely defines the state of the system. > > Of course, the position or momentum of an individual particle is a > systemic property of the system that constitutes that single particle (a > system of quarks, say). > > The question then becomes, is a centroid or cumulative measure of a > system of particles "emergent"? Or are the position and momentum of a > system of quarks "emergent"? > I would agree with you that the centre of mass, and the summed momenta are emergent properties, however - they are what Bedau calls "resultant emergent", the very weakest, and least interesting of emergent phenomena. WRT quarks - in the Standard Model, protons and neutrons _are_ emergent, and properties such as their positions and momenta are emergent. But in something like Bohr's hydrogen model, the nucleus is a point particle, so the position of the nucleus is not an emergent property. Maybe you're wondering why I keep banging on about models - the point is that emergence is always relative to a model. It has nothing to do with real systems (except in as much as the models are good descriptions of the system). In fact I would tend to go further an claim that the concept of a "real system" is actually flawed, but that is a whole other debate, as emergence has nothing to do with "real systems", whether or not real systems really exist. > -- > glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com > > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org -- ---------------------------------------------------------------------------- Prof Russell Standish Phone 0425 253119 (mobile) Mathematics UNSW SYDNEY 2052 [email protected] Australia http://www.hpcoders.com.au ---------------------------------------------------------------------------- ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org
