B Superconductivity & Quantum Emergence

[star apple]

Hello,

Is Superconductivity an example of emergence where you can't predict it's occurence by just working with the Schroedinger Equation?

If Superconductivity is an emergence, what do you call those none emergence processes?
Perhaps some examples would enlighten. Thanks to all those who can offer some insights!

 

[f95toli]

It is quite hard to pin down what "emergence" actually means. Often it just means something along the line of non-trivial collective phenomena (e.g. phenomena in systems of many interacting particles) which surprises us when they occur because we would not expect them just by looking at the parts.

This does NOT mean that we can't predict them. Classical (low-Tc) superconductivity is actually a very good example of a solid-state phenomena that can be predicted by QM; and with extremely high accuracy. The theory for this (BCS theory) is also surprisingly simple and was developed way back in the 50s.

These days If you have a fast enough computer you can use first principle calculations to predict properties such as the transition temperature, i.e. the data "in" would only be the type of element and the crystal structure. This works well for all the elements as well as binary alloys/compounds (e.g. MgB2), but our computers are not fast enough to handle more complicated structures.
The BCS theory does not explain high temperature superconductivity (although there are many similarities) and the structure of all the high-Tc compounds is to complicated to simulate even on the best supercomputers. However, I don't think anyone believes that there is some fundamentally new physics at play here; the numerical problem is just too complicated to solve in a reasonable amount of time.

 

[star apple]

It is quite hard to pin down what "emergence" actually means. Often it just means something along the line of non-trivial collective phenomena (e.g. phenomena in systems of many interacting particles) which surprises us when they occur because we would not expect them just by looking at the parts.

This does NOT mean that we can't predict them. Classical (low-Tc) superconductivity is actually a very good example of a solid-state phenomena that can be predicted by QM; and with extremely high accuracy. The theory for this (BCS theory) is also surprisingly simple and was developed way back in the 50s.

These days If you have a fast enough computer you can use first principle calculations to predict properties such as the transition temperature, i.e. the data "in" would only be the type of element and the crystal structure. This works well for all the elements as well as binary alloys/compounds (e.g. MgB2), but our computers are not fast enough to handle more complicated structures.
The BCS theory does not explain high temperature superconductivity (although there are many similarities) and the structure of all the high-Tc compounds is to complicated to simulate even on the best supercomputers. However, I don't think anyone believes that there is some fundamentally new physics at play here; the numerical problem is just too complicated to solve in a reasonable amount of time.

In the last part of this video http://backreaction.blogspot.com/2017/10/what-could-we-learn-from-quantum.html posted October 11, 2017 Sabine Hossenfelder described: “10th, it might be to combine quantum theory with gravity, we do not have to update gravity, but quantum theory, and if that is so, the consequence would be far reaching because quantum theory underlies all electronic devices. If it has to be changed, it might open entirely new possibilities. Quantum gravity therefore is not such a remote theoretical idea as it seems, we all travel though all space time everyday, understanding it could change our lives.”

I wonder how one can change quantum theory without updating gravity to produce quantum gravity.. Did Sabine mean there was an emergence in complex object not predicted in the Schroedinger equation?

 

[_PJ_]

There's a number of accuracy problems with the animation. For example, the description that "space can turn into time" in strong gravity is a misinterpretation of the nomenclature of spacelike and timelike trajectories as affected in extreme curvature.

With regards to the quesitn of "how one can change quantum theory without updating gravity to produce quantum gravity?" it would be an improvement on the successfully predictive quantum models that is increased to incorporate gravity - GR would simply remain used as a more convenient solution for classical scales - similar to how Newtonian mechanics are used for most general purpose despite being arguably. By further developing the QFT to incorporate gravity in some sense, it would enable a more complete description of reality - there would be no need to change anything in GR to accommodate, since (ideally) it would all be in the mathematics of the quantum toolkit.