'Emergence and Naturalness,' Professor David Wallace, University of Pittsburgh

"Emergence and Naturalness," David Wallace, Mellon Chair in Philosophy and History & Philosophy of Science, University of Pittsburgh

If we want to start with the physics of the very small - molecules, atoms, subatomic particles - and work out the physics of large-scale systems - dust grains, iron bars, planets – we need to assume more than the laws of the very small: we have to make an additional assumption, often called “naturalness.” Despite the name, this assumption is puzzling in many respects, and the puzzle deepens into paradox because in our best theories of fundamental physics it seems to fail in two very specific places – the mass of the Higgs boson, and the rate of expansion of the Universe. In the lecture, I’ll explain what the naturalness assumption is, why we need it in almost all of physics, and why its failure in particle physics and cosmology is one of the deepest problems in contemporary physics.

[Domisterwoozy]

I am bit confused about the expected outcome from turning on the LHC with regards to the Higgs. First he says that we were very confident in finding the Higgs at the mass where we found it. But then he goes on to say that Naturalness predicts a much larger Higgs mass. Why were we so confident to find it where we did then? Do other parts of the standard model already contradict the Naturalness arguments before we even turned on the LHC?

[CalendulaF]

Very interesting talk and in particular a straightforward, yet comprehensive way to systematize the problem of emergence. However, I think it is rather obvious that the macro-world, in the terminology of David Wallace, is "unnaturally emergent". Unless we drastically change our terminology and apprehension of the world, that is. But I strongly bet that you can never derive most macro-relations and categories from the underlying micro-states plus laws plus some smooth ("natural") probability distribution. Even if we take the proverbial "box of gas" there is a lot of strangeness and particularity in the initial condition of a "box" or being "boxed" (on a certain scale). Not to mention categories like "materials" (eg wood) or "DNA" (as a carrier of information) etc, let alone "cities", "societies" and what have you. I just don't see any probability measure over microstates that would straightforwardly yield even modestly familiar macro-states (except maybe for some very very simple cases). And that I think is just a brute matter of fact about reductionism. There is no box of gas in the micro. You loose that information when going to the micro and you have to smuggle it back in, when going to the macro.