1. 1 Introduction to Complex Systems: How to think like nature Russ Abbott Sr. Engr. Spec. Rotn to CCAE 310-336-1398 Russ.Abbott@Aero.org  1998-2007. The Aerospace Corporation. All Rights Reserved. Entities: what exists Presumptuous again?

2. 2 Is everything other than fundamental particles/ strings/whatever (if there is anything fundamental), (i.e., you, me, puppy dogs, etc.) epiphenomenal? –Even though they may have properties, which we can describe, is it all an illusion? –Are the mystics (and the reductionists) right? Entities are real. An entity is either –atomic: fundamental, no components, or –emergent: a region of reduced entropy persistent (static) or self-perpetuating (dynamic). The reality of higher-level entities (Slightly) more than epiphenomenal. Recall Shalizi

3. 3 Created in energy wells of various forces. –Atomic nuclei, atoms, molecules, crystal lattices, astronomical bodies and structures (planets, stars, solar systems, galaxies, etc.) (Negligibly) less mass than the sum of their parts. Supervenience works well. –Atomic nuclei, etc. are emergent from, epiphenomena of, and supervenient over their components. But even here, emergent functionality—e.g., the hardness of a diamond—is more than just its implementation. Defined only with respect to an external environment. Static emergence Entities at an energy equilibrium Somewhat more than slightly more than epiphenomenal.

4. 4 Self-perpetuating through their appropriation of energy from their environment. Typically biological and social entities. –Hurricanes, you, me, a corporation, a nation, Theseus’ ship. –Many have statically emergent “skeletons.” (Negligibly) more mass than the sum of their parts. –Since they are “in operation,” they include the energy that is flowing through them. A warm body has (negligibly) more mass than “the same body” if allowed to cool. Supervenience does not work well. Dynamic emergence“Far from equilibrium” Again, somewhat more than slightly more than epiphenomenal. Entities not at an energy equilibrium

5. 5 A hurricane is a far- from-equilibrium non-biological dynamic entity Has a “metabolism.” Generates heat internally — by condensation rather than combustion. –“Eats” warm moist surface air; “excretes” cooler drier air. –Energy produced powers its self-perpetuating processes. Design: one can talk about how it works. Fitness: persists (is self-perpetuating) only so long as its environment provides adequate resources. http://earthobservatory.nasa.gov/Library/Hurricanes/ No genetic code. Doesn’t reproduce or evolve.

6. 6 A glider supervenes only over the entire set of cells it traverses. A hurricane supervenes only over the air and water molecules that make it up over its lifetime. You and I supervene only over the entire set of particles that become us over our lifetimes. A corporation or social organization supervenes only over all the stuff that it ever owns plus the particles of all the people who comprise it over its lifetime. Theseus ship (and most systems) are similarly open. Most dynamic entities of interest supervene over historical accidents. When supervenience doesn’t help

7. 7 Modeling problems: the difficulty of looking downward Strict reductionism implies that it is impossible to find a non-arbitrary base level for models. –What are we leaving out that might matter? Use Morse code to transmit messages on encrypted lines. No good models of biological arms races. –Combatants exploit and/or disrupt or otherwise foil each other’s epiphenomena. Insects vs. plants: bark, bark boring, toxin, anti-toxin, …. Geckos use the Van der Waals “force” to climb. Models of computer security or terrorism will always be incomplete. Can only model unimaginative enemies. Nature is not segmented into a strictly layered hierarchy. epiphenomenal

8. 8 Don’t know how to build models that can notice emergent phenomena and characterize their interactions. We don’t know what we aren’t noticing. –We/they can use our commercial airline system to deliver mail/bombs. Model gravity as an agent-based system. –Ask system to find equation of earth’s orbit. –Once told what to look for, system can find ellipse. (GP) –But it won’t notice the yearly cycle of the seasons — even though it is similarly emergent. Modeling problems: the difficulty of looking upward Models of computer security or terrorism will always be incomplete. Can only model unimaginative enemies. Exploit an existing process.

9. 9 Higher level entities are real. –They have more structure than their surroundings. We exist only so long as we can hold it together. –They have more or less mass than their components. Interaction among entities is epiphenomenal. –A kiss is not really just a kiss. –The only real forces are elementary forces. Hence: epiphenomena do real work. Higher level entities are real. –They have more structure than their surroundings. We exist only so long as we can hold it together. –They have more or less mass than their components. Interaction among entities is epiphenomenal. –A kiss is not really just a kiss. –The only real forces are elementary forces. Simultaneous multi-scalar interactions. We need new mathematics for multi-scalar systems. Hence: epiphenomena do real work. Summary David Gross Physicists want an equation for everything. It won’t happen. No equation will map electron flows to software functionality.

10. 10 Complexity typically involves multiple autonomous components Poincare showed a century ago that the three-body gravitational problem has no general solution. Distributed software is the most difficult to write. Making effective use of multi-core computers will be the computing challenge of the next decade. Recall the ants and termites; the snake control authority and the snake farmers. All are multi-agent. Command and Control (or organization management) is still more art than science. All this contrasts with monolithic top-down control. Wikipedia commons When multiple autonomous entities interact within an environment, one often gets emergent results. Systems of that sort tend to be called complex. } Imagine having to program the Game of Life. Derogatory terms in the complex systems world Power to the edge!