Little things can come together to make big things. And those big things can often be successfully described by an approximate theory that can be qualitatively different from the theory of the little things. We say that a macroscopic approximate theory has “emerged” from the microscopic one. But the concept of emergence is a bit more general than that, covering any case where some behavior of one theory is captured by another one even in the absence of complete information. An important and subtle example is (of course) how the classical world emerges from the quantum one.
And here is the Q&A video. Sorry, I hadn’t realized that comments were showing up here on the blog! I have a crack team rushing to get that fixed.
In the video I refer to a bunch of research papers, here they are:
Mad-Dog Everettianism: https://arxiv.org/abs/1801.08132
Locality from the Spectrum: https://arxiv.org/abs/1702.06142
Finite-Dimensional Hilbert Space: https://arxiv.org/abs/1704.00066
The Einstein Equation of State: https://arxiv.org/abs/gr-qc/9504004
Space from Hilbert Space: https://arxiv.org/abs/1606.08444
Einstein’s Equation from Entanglement: https://arxiv.org/abs/1712.02803
Quantum Mereology: https://arxiv.org/abs/2005.12938
I recently started watching your videos. This is fun! And.. You know exactly what I mean. {lol}
I’m all in Sean. The “Thought Experiment” is multi-faceted. There are hidden dimensions, hidden spacial localities, and variables in it, as well as with the obvious ones.
Sort of.. like.. hidden jokes. {lol} –
Einstein’s equation could use a little tweaking too.
Schrödinger’s Kat.
Sean, I would LOVE more videos about current research you and others are doing. There’s a giant gulf between “pop sci” science eye candy and über technical pre-prints we laypeople can’t parse. But you have such a unique gift to explain complicated ideas in understandable ways, filling that gap! Most of us who follow physics are more than well acquainted with “the canon” of ideas from decades and centuries ago. We’re so hungry for what’s fresh.
Comment To Video 21 Q&A at 1:11:00
Even if the Hamiltonian of the wave-function disappears as in the WDW equation, classical time can emerge in a simple way. This idea has been proposed about 10 years ago by Carlo Rovelli ( a proponent of LQG) and Alain Connes : “The Thermal Time Hypothesis” suggests that time emerges as a statistical effect. QM is reworked to make the concept of time unnecessary; so on the quantum scale time and the arrow of time do not exist, but emerge through a statistical averaging over the macro universe, analoguous to how the temperature of a thermodynamic system arises from averaging over the movements of the molecules of the system. – “Time is the effect of our ignorance” [about reality] (Rovelli).
However, critics of this approach have found that it runs into problems with conservation of Information.