# I Hidden dimensions and quadratic term of a free field

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1. Dec 2, 2017

### victorvmotti

Consider a free real scalar field. The quadratic term in field of spacetime implies that a universe of these free particles is created, annihilated, recreated, and so on moment by moment.

In this video Susskind explains the quadratic term in the Lagrangian

youtu.be/D7yXoNAg3J8

(At minute 32:0)

How they "absorb and emit" an undisturbed particle at the same point or neighboring points of spacetime.

Yet we are under the false impression that the particles exist continuously in spacetime.

The question is does this observation alone imply the existence of some extra or hidden dimensions in which the particle exists when annihilated in the four dimensional universe?

2. Dec 2, 2017

### dextercioby

Do you exist continuously in spacetime? You are roughly the sum of 10^25 elementary particles which, you say, appear and disappear at any moment...

3. Dec 2, 2017

### victorvmotti

Apparently I do exist.

Here of course undisturbed means that the freely moving particle is not scattered. However, when the particle propagates from a point in spacetime to another neighboring point it is annihilated in the former point of spacetime and created in the latter and so on.

I am asking if after annihilated and before recreated at a neighboring point can we say that the particle might exist in some hidden dimensions?

4. Dec 4, 2017

### Fervent Freyja

Good idea, but from what I know, we currently have no way to precisely describe the "in-between" of cause and effect events, such as this scenario. Sometimes approximations work, but calling that which we cannot measure something like a hidden dimension or hidden variable (or dark) is hardly satisfactory.

Of course, this does suggest there is something about nature that we cannot fully describe (simple "hidden" would be most accurate), but I view all these itty-bitty concepts being inadequate to begin with... We cannot follow those events from beginning to end, so, alot of what you're asking is possibly going to be a dead end with the theoretical requirements.

Say you are right, what mathematical proof could be given that the particle would exist somewhere else, hidden? How could it transform in between the annihilation and generation? Could you prove that such an "in-between" or "dimension" could contain a particle form?

Plus, I don't think QM is intended to be used for such interpretations. More like a checklist or something?

5. Dec 6, 2017

### Staff: Mentor

Right at its very foundations standard QM is a theory about observations that occur here in a common-sense world. It is possible to have interpretations where such is not the case - so strictly speaking a person like say Dirac would not even assume that - only the math - but those kind of interpretations (ie consciousnesses causes collapse) are rather fringe these days so virtually everyone would accept what I said. Whats going on between those observations is anyone's guess - you can assume virtually anything you like - but the question has to be asked - to what gain? If you want to invoke disappearing to hidden dimensions - yes you can do that, but exactly why? Yo u can prove it. I know why for example those that hold to De-Broglie Bohm believe in the unobservable guiding pilot wave but things like disappearing into hidden dimensions beats me.

Thanks
Bill

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