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Introduction To Online Text by Christopher Stubbs



Figure 4: Fermilab researchers.

While physicists have had remarkable successes in understanding the world in terms of its basic constituents and their fundamental interactions, physicists also now recognize that the reductionist approach has very real limitations. For example, even if we knew the inventory of all the objects that made up some physical system, and their initial configuration and interactions, there are both practical and intrinsic limitations to our ability to predict the system's behavior at all future times. Even the most powerful computers have a limitation to the resolution with which numbers can be represented, and eventually computational roundoff errors come into play, degrading our ability to replicate nature in a computer once we are dealing with more than a few dozen objects in a system for which the fundamental interactions are well-known.

As one of our authors, David Pines, writes:

An interesting and profound change in perspective is the issue of the emergent properties of matter. When we bring together the component parts of any system, be it people in a society or matter in bulk, the behavior of the whole is very different from that of its parts, and we call the resulting behavior emergent. Emergence is a bulk property. Thus matter in bulk acquires properties that are different from those of its fundamental constituents (electrons and nuclei) and we now recognize that a knowledge of their interactions does not make it possible to predict its properties, whether one is trying to determine whether a material becomes, say, an antiferromagnet or a novel superconductor, to say nothing of the behavior of a cell in living matter or the behavior of the neurons in the human brain. Feynman famously said: "life is nothing but the wiggling and jiggling of atoms," but this does not tell us how these gave rise to LUCA, the last universal ancestor that is the progenitor of living matter, to say nothing of its subsequent evolution. It follows that we need to rethink the role of reductionism in understanding emergent behavior in physics or biology.

Figure 5: Superconductor materials at Jenny Hoffman's Lab.

Understanding emergent behavior requires a change of focus. Instead of adopting the traditional reductionist approach that begins by identifying the individual constituents (quarks, electrons, atoms, individuals) and uses these as the basic building blocks for constructing a model that describes emergent behavior, we focus instead on identifying the collective organizing concepts and principles that lead to or characterize emergent behavior, and treat these as the basic building blocks of models of emergence.
Both the reductionist and the scientist with an emergent perspective focus on fundamentals. For the reductionist these are the individual constituents of the system, and the forces that couple them. For the scientist with an emergent perspective on matter in bulk, the fundamentals are the collective organizing principles that bring about the emergent behavior of the system as a whole, from the second law of thermodynamics to the mechanisms producing the novel coherent states of matter that emerge as a material seeks to reduce its entropy as its temperature is lowered.

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