4 ms·

What does "a critical point or phase transition [of the] electrodynamics of the cortex" mean? Electricity doesn't have "phases" AFAIK (well there's two/three-ph

What does "a critical point or phase transition [of the] electrodynamics of the cortex" mean? Electricity doesn't have "phases" AFAIK (well there's two/three-phase power but I don't think that's what they're talking about).

mlyle 5y ago
https://en.wikipedia.org/wiki/Phase_transition https://en.wikipedia.org/wiki/Phase_transition https://en.wikipedia.org/wiki/Critical_exponent https://en.wikipedia.org/wiki/Critical_exponent The concept of phase transition is broader than the phases of matter.
- ghostly_s 5y ago
  Interesting, though the only example I see listed in that article that's not a change in the physical properties of matter is the ferromagnetic<=>paramagnetic phases.
  - mlyle 5y ago
    Lots of the list are changes of physical properties of matter (e.g. breaking of physics symmetries in the cooling universe)... that are not conventional matter phase transitions between e.g. liquid and gas.
  - colechristensen 5y ago
    One that isn’t a matter it’s convection currents in a closed vessel between two plates of different temperatures. At low differentials there’s no convection just conduction, as you raise the temperature difference you get a stable single circulation loop which is well behaved, continue further and you get a tempest of circulations coming and going in an entirely unpredictable manner. There are distinct phase transitions between each of these states. Another one is a forced double pendulum. With just a little periodic force they swing gently back and forth, with a lot they do constant crazy unpredictable loops around each other.
  - tzs 5y ago
    Here's one you might enjoy. A phase transition that would destroy the universe as we know it: https://www.youtube.com/watch?v=gc4pxTjii9c https://www.youtube.com/watch?v=gc4pxTjii9c
colechristensen 5y ago
They're talking about the dynamics of the system's behavior not something physical about electrons.
alan-hn 5y ago
Its a transition between distinct operational phases of a dynamic system, iirc these can be described with a (my terminology may be a bit off here) topological phase diagram https://mitpress.mit.edu/books/dynamical-systems-neuroscience https://mitpress.mit.edu/books/dynamical-systems-neuroscienc...
ctchocula 5y ago
A link on HN yesterday that talks about critical points and phase transitions: * A mathematician explains what Foundation gets right about predicting the future (spoiler: critical points!): https://www.sciof.fi/a-mathematician-explains-psychohistory/ https://www.sciof.fi/a-mathematician-explains-psychohistory/ And if you're still interested, there's a more in-depth explanation with mathematical formulas and all. Even if I understood only 10-20% of what Ken Wilson was talking about, he gives a lucid motivation for why critical points are important and why they can be found in practice using renormalization groups, and not computer simulations: * Ken Wilson's Nobel Prize lecture: https://www.nobelprize.org/uploads/2018/06/wilson-lecture-2.pdf https://www.nobelprize.org/uploads/2018/06/wilson-lecture-2....

mlyle 5y ago

https://en.wikipedia.org/wiki/Phase_transition https://en.wikipedia.org/wiki/Phase_transition https://en.wikipedia.org/wiki/Critical_exponent https://en.wikipedia.org/wiki/Critical_exponent The concept of phase transition is broader than the phases of matter.

ghostly_s 5y ago
Interesting, though the only example I see listed in that article that's not a change in the physical properties of matter is the ferromagnetic<=>paramagnetic phases.
- mlyle 5y ago
  Lots of the list are changes of physical properties of matter (e.g. breaking of physics symmetries in the cooling universe)... that are not conventional matter phase transitions between e.g. liquid and gas.
- colechristensen 5y ago
  One that isn’t a matter it’s convection currents in a closed vessel between two plates of different temperatures. At low differentials there’s no convection just conduction, as you raise the temperature difference you get a stable single circulation loop which is well behaved, continue further and you get a tempest of circulations coming and going in an entirely unpredictable manner. There are distinct phase transitions between each of these states. Another one is a forced double pendulum. With just a little periodic force they swing gently back and forth, with a lot they do constant crazy unpredictable loops around each other.
- tzs 5y ago
  Here's one you might enjoy. A phase transition that would destroy the universe as we know it: https://www.youtube.com/watch?v=gc4pxTjii9c https://www.youtube.com/watch?v=gc4pxTjii9c

colechristensen 5y ago

They're talking about the dynamics of the system's behavior not something physical about electrons.

alan-hn 5y ago

Its a transition between distinct operational phases of a dynamic system, iirc these can be described with a (my terminology may be a bit off here) topological phase diagram https://mitpress.mit.edu/books/dynamical-systems-neuroscience https://mitpress.mit.edu/books/dynamical-systems-neuroscienc...

ctchocula 5y ago

A link on HN yesterday that talks about critical points and phase transitions: * A mathematician explains what Foundation gets right about predicting the future (spoiler: critical points!): https://www.sciof.fi/a-mathematician-explains-psychohistory/ https://www.sciof.fi/a-mathematician-explains-psychohistory/ And if you're still interested, there's a more in-depth explanation with mathematical formulas and all. Even if I understood only 10-20% of what Ken Wilson was talking about, he gives a lucid motivation for why critical points are important and why they can be found in practice using renormalization groups, and not computer simulations: * Ken Wilson's Nobel Prize lecture: https://www.nobelprize.org/uploads/2018/06/wilson-lecture-2.pdf https://www.nobelprize.org/uploads/2018/06/wilson-lecture-2....