Thanks, Roger. On Sat, Jun 13, 2015 at 9:46 AM Roger Critchlow <[email protected]> wrote:
> We have had discussions on this many times, and the usual result is that > everyone gets fed up with all the technical details that need to be kept > sorted out. There are equilibrium vs non-equilibrium systems, classical vs > statistical thermodynamics, closed vs open systems, statistical mechanics > vs information theory, and so on > > The MaxEnt that Simon is teaching is the only one usually abbreviated as > MaxEnt by its practitioners in an attempt to keep it from getting confused > with the other discussions. It's the practical procedure that grew out of > E T Jaynes observations about probability theory and physics. It > essentially says that if you repeatedly make observations of a system and > you correctly model the constraints on the system, then your observations > should follow a distribution with maximum entropy of the > statistical/information theory variety. The usual example is observing > dice throws which should equipartition themselves over the six possible > outcomes. If your observations converge to something other than this > MaxEnt equipartition, then you should conclude that the dice are loaded and > strive to improve your model. > > That non-equilibrium systems maximize entropy production is a conjecture > which can be defined and actually works for a very small proportion of > non-equilibrium systems. Basically, take the non-equilibrium systems that > are so close to equilibrium that they barely do anything at all, and you > can see this principle in action. Push the system a little further from > equilibrium and all hell breaks loose. What that means for everything else > in the world awaits an expansion of the theory which has been pending for > almost a century now. > > -- rec -- > > On Sat, Jun 13, 2015 at 12:28 AM, Russell Standish <[email protected]> > wrote: > >> On Sat, Jun 13, 2015 at 06:12:16AM +0000, Russ Abbott wrote: >> > Although I haven't gone through the MaxEnt tutorial I have a question if >> > anyone would be willing to think about it. >> > >> > As I understand it, one aspect of MaxEnt says that nature chooses that >> path >> > that maximizes entropy production -- and that satisfies whatever >> > constraints exist. (Or something like that. I don't claim to know enough >> > about it to say anything definitive.) Yet when I think about the earth >> and >> > the way it deals with the energy it gets from the sun, it seems to me >> that >> > the biosphere "does its best" to minimize the rate of entropy >> production. >> > >> > If there were no life on earth, all the sun's energy would be quickly >> > radiated back into space, mostly as heat and some as reflected light. >> That >> > seems like the fastest way to dissipate the sun's energy and produce >> > entropy. >> > >> > With life on earth the sun's energy is absorbed and "exploited" to the >> > maximum extent possible. That's what life does; it looks for and fills >> > unexploited energy niches. Eventually the remaining energy is radiated >> back >> > as heat. So that would seem to slow entropy production. >> > >> > Even more telling, much of the sun's energy is stored on earth as >> > energy-rich organic material left over biological organisms die. So >> some of >> > the sun's energy is never sent back to space -- until that stuff is >> burned. >> > So that would reduce the rate of entropy production even further. >> > >> > Is this a reasonable way of looking at what happens? Is this >> inconsistent >> > with the notion of MaxEnt? Or am I misunderstanding something? >> > >> > -- Russ >> >> It's been a decade or so since I read the MaxEnt literature, but from >> what I recall it is largely a physical principle, eg it describes >> things like the formation of Hadley cells to assist in the transport >> of energy between the equator and the poles. >> >> But it does seem plausible it ought to describe living systems too. In >> the fossil fuel example you allude to earlier, life is currently doing >> its darnedest to maximise the entropy after unlocking the excess >> negentropy locked up by geophysical processes. (ie burn, baby burn!). >> >> But I don't know of anyone who has succeeded in applying MaxEnt to >> information systems (such as biology) - I thought I'd try myself, but >> like with so many good intentions, life has intervened :). >> >> Cheers >> The other Rus. >> >> -- >> >> >> ---------------------------------------------------------------------------- >> Prof Russell Standish Phone 0425 253119 (mobile) >> Principal, High Performance Coders >> Visiting Professor of Mathematics [email protected] >> University of New South Wales http://www.hpcoders.com.au >> >> ---------------------------------------------------------------------------- >> >> ============================================================ >> FRIAM Applied Complexity Group listserv >> Meets Fridays 9a-11:30 at cafe at St. John's College >> to unsubscribe http://redfish.com/mailman/listinfo/friam_redfish.com >> > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > to unsubscribe http://redfish.com/mailman/listinfo/friam_redfish.com
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