# WaveFunctions vs Spacetime

Quantum Gravity is the successful merging of the two.. Wave functions (or QM) and Spacetime. So it would be good to know how the two differs. They seem to have one thing in common.. they are both mathematical abstraction. But then someone said (Peterdonis):

"Tidal gravity is not "just a math model". It's a physical observable. It is true that one is not *forced* to model tidal gravity using a curved spacetime; one could use another model. But in the context of that model, "spacetime curvature" is simply another name for "tidal gravity", so if tidal gravity is real (which it is), then spacetime curvature is real."

Can we say the same thing to Wave Function? Can anyone give an example where or supply the analogy where:

Tidal Gravity is to Spacetime Curvature
XXX is to Wave function.

Give an example of the XXX. Is there any?

PeterDonis
Mentor
Quantum Gravity is the successful merging of the two.. Wave functions (or QM) and Spacetime. So it would be good to know how the two differs. They seem to have one thing in common.. they are both mathematical abstraction. But then someone said (Peterdonis):

"Tidal gravity is not "just a math model". It's a physical observable. It is true that one is not *forced* to model tidal gravity using a curved spacetime; one could use another model. But in the context of that model, "spacetime curvature" is simply another name for "tidal gravity", so if tidal gravity is real (which it is), then spacetime curvature is real."

Can we say the same thing to Wave Function? Can anyone give an example where or supply the analogy where:

Tidal Gravity is to Spacetime Curvature
XXX is to Wave function.

Give an example of the XXX. Is there any?

First, a quick comment; this question could just as well go in the Quantum Physics forum, since it applies to QM in general, not just to theories beyond the SM:

https://www.physicsforums.com/forumdisplay.php?f=62

In answer to the question, I'm not sure there's a physical observable that matches up with the wave function the way tidal gravity matches up with spacetime curvature. However, the *square* of the wave function gives probabilities, which are direct physical observables. One could ask why we need wave functions instead of just working with the probabilities directly, but experiments showing quantum interference, such as the double slit experiment, demonstrate that quantum probabilities do not follow the same rules as classical probabilities, so we need wave functions (or something equivalent) to capture the quantum rules. That "or something equivalent" means that we could construct other models that reproduced the quantum predictions without using wave functions; but in the model that is usually used, wave functions are what give rise to probabilities, so they are real to the extent that the probabilities are real.

First, a quick comment; this question could just as well go in the Quantum Physics forum, since it applies to QM in general, not just to theories beyond the SM:

https://www.physicsforums.com/forumdisplay.php?f=62

In answer to the question, I'm not sure there's a physical observable that matches up with the wave function the way tidal gravity matches up with spacetime curvature. However, the *square* of the wave function gives probabilities, which are direct physical observables. One could ask why we need wave functions instead of just working with the probabilities directly, but experiments showing quantum interference, such as the double slit experiment, demonstrate that quantum probabilities do not follow the same rules as classical probabilities, so we need wave functions (or something equivalent) to capture the quantum rules. That "or something equivalent" means that we could construct other models that reproduced the quantum predictions without using wave functions; but in the model that is usually used, wave functions are what give rise to probabilities, so they are real to the extent that the probabilities are real.

What I mean to say is. I just want to know how Spacetime and Wave Function differ to being models of reality... like where they differ and where they are alike. It seems our reality is simply the models we have. Now wave functions are just mathematical abstractions. I'm familiar with QM like Copenhagen, Many Worlds, Bohmian. Now is there a version or counterpart of them in Spacetime physics? Which one do you think is more real or as substantive as concept of say scattering atoms experiment.. wave function or spacetime? It appears to be space and time because we feel them. But wave functions. We don't feel things in Hilbert Space.

I'm looking for other models that can do Tidal Gravity without Spacetime GR. Any other candidate like we do QM Copenhagen, Many worlds?

The reason I'm asking all these is so we can see from all perspective in our search for the final theory of Quantum Gravity (the unification of QM wave functions and GR Space) beyond the Standard Model (this is why it's in this thread).

Do you think Gravity Aether partner is Pilot Wave model in QM... whereas if it's pure geometry, then we have Copenhagen where everything is literally equations.. maybe we are really output from a surface somewhere out there in the concept of Black Hole Beckenstein? Holographic Paradigm. I think knowing which is important in our search for Quantum Spacetime (quantum gravity).