Interpretations of quantum mechanics

[Max Pain]

Hello,

I am currently writing on my diploma thesis on a topic of quantum mechanics. I think I am familiar enough with the formalism and how to apply it but the interpretation is something totally different. So I made a poll to see what you guys think about this. The options are from wikipedia where you can also find some information about them.

I for myself are more a mathematically inclined person and I feel inelegantly about interpretations containing some form of collapse of the wave function. Something along the lines of the many worlds interpretation would be more believable for me but I am not really determined.

Please do elaborate on your point of view if you like. I'm looking forward to a fruitful discussion .

Best regards,

Max

 

[boogabooga]

What poll?

When I took Modern Physics many years ago, the take home message I got on quantum mechanics was that it results from the solution to a partial differential equation, and that it can be very, very closely approximated by classical mechanics at the length scales that humans are familiar with. Period. It was a purely mathematical endeavor; these sorts of interpretive questions were actually frowned upon.

If you grew up in a universe in which you could travel from point to point without crossing the space between, or you could walk through a wall if you tried enough times, then that would be your sense of "normal" and you probably wouldn't question it to much.

Let me put it another way, why is mass-energy conserved? What interpretation could there be for this observation?

 

[Artlav]

Many worlds interpretation.
It takes the math on face value, and assumes that what is described is what is.
Wave functions are what exist, without any classic "compatibility mode".
Particles and classic objects are derived as you sum it all up and go up in scale, instead of trying to apply the quantum math to some sort of pre-existing "particles" and trying to explain why they are suddenly both waves or corpuscules.

The multitude of worlds are not any additional complexity or strange things to add.
I heard it called "macroscopic quantum superposition", and that name describes it best.
Think of the waves on water - two waves pass through each other without interacting, co-existing in the same medium.

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Also, that poll is quite overloaded with options.

 

[Urwumpe]

Also, I would have a hard time finding out what each of these options mean and how they differ, since I don't study this.

For me personally, as completely innocent person in that context, quantum mechanics are just applied statistics to me.

 

[Max Pain]

I am surprised that so far everyone chose many worlds interpretation. I hope it's not because it is in italics.

Maybe I throw in here that there are some problems with the many worlds interpretation like calculating the probabilities of events with an infinite number of alternate events.

It was a purely mathematical endeavor; these sorts of interpretive questions were actually frowned upon.

Some sort of interpretation is necessary because the evolution of the wave function is a deterministic one. However, if you do some experiment there is clearly a stochastic element. You need some minimal interpretation (like copenhagen interpretation) for merely applying the laws of quantum mechanics to real world experiments. Moreover, different interpretations can actually differ in their predicitons.

Also, that poll is quite overloaded with options.

I just wanted to make sure that everything is there, so I copied from wikipedia. Just skip through the ones you don't know.

For me personally, as completely innocent person in that context, quantum mechanics are just applied statistics to me.

Then you might want to choose the ensemble interpretation. It basically says that quantum mechanics is incomplete and therefore can make only statistical predictions about quantum systems (watch out for Bell's inequalities!).

 

[Urwumpe]

Then you might want to choose the ensemble interpretation. It basically says that quantum mechanics is incomplete and therefore can make only statistical predictions about quantum systems (watch out for Bell's inequalities!).

Thats true, but not the whole truth. A statistic is only as good as the model behind. Maybe describing it as a mixture between statistics and metrology... :lol:

After all: All our science is incomplete. Except mathematics.

 

[Face]

My personal approach to quantum mechanics is best described with the relational interpretation, I think. Well, maybe the standard Copenhagen is also close to it, according to Wikipedia's quote of Davies' "reality is in the observations, not the electron".

I think every aspect of the physical world depends on the point of view, and of course I also take the micro-cosmos into this view, too. I think many of the observed quantum effects could be interpreted in a similar way as e.g. magnetic induction can be interpreted as relativistic electrostatic effects.

 

[Artlav]

Maybe I throw in here that there are some problems with the many worlds interpretation like calculating the probabilities of events with an infinite number of alternate events.

Why is it infinite? Where does this problem come from, in precise formulation?

Some sort of interpretation is necessary because the evolution of the wave function is a deterministic one. However, if you do some experiment there is clearly a stochastic element.

If you take the equation literally, then you'd find that the outcomes are as deterministic as they look. The "observer" is as much a part of the system as the thing being observed.

So, in classic Schrodinger cat:
The atom decoheres into "split" and "not split", the detector decoheres into "detected split atom" and "not detected anything", the gun decoheres into "fired at the cat" and "not fired at the cat", and the human decoheres into "sees dead cat" and "sees living cat".
Entirely deterministic.
That is the beauty of MWI.

The probabilistic nature comes from the fact that the "observer" might find itself in the side that have a dead cat, or on the side that have the living cat, with probabilities related to the wave function.
This is known as the Born rule, and why it occurs is still an open question.

Moreover, different interpretations can actually differ in their predicitons.

There are the equations. How you interpret them only changes your scope of looking for evidence.

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I think every aspect of the physical world depends on the point of view

Define point of view please. It is a very each-hears-his-own expression.

 

[Face]

Define point of view please. It is a very each-hears-his-own expression.

Well, frame of reference would perhaps come close to what I mean, but it is often used only for mechanical or geometric aspects, therefore I tend to avoid it. I guess your philosophical "each-hears-his-own" might be even closer to it .

 

[Linguofreak]

I'm not entirely sure if it matches up with any of the other interpretations here, but what seems most plausible to me is a modified many-worlds in which there indeed is no wavefunction collapse, but in which the physical world we observe is the entire superposition of states of the universal wavefunction and not just one branch of it (so that there isn't actually any kind of multiverse).

 

[Max Pain]

My personal approach to quantum mechanics is best described with the relational interpretation, I think.

That's actually a very interesting concept but I have some problems unterstanding it.

Why is it infinite? Where does this problem come from, in precise formulation?

The formulation I used was probably wrong. The problem is more about giving propabilities, when every world is really existant. You may look into Brian Greenes Hidden Reality Chapter 8. Especially the footnote 9 is enlighting.

This is known as the Born rule, and why it occurs is still an open question.

Some interpretations can derive the Born rule (e.g. de Broglie Bohm theory).

There are the equations. How you interpret them only changes your scope of looking for evidence.

All of the interpretations have the same microscopic Schroedinger equation but sometimes only as a limiting case. Often it is possible to find an experiment to distinguish between them (look e.g. footnote 11 of chapter 8 of hidden reality, there is an experiment to distinguish between many worlds and copenhagen interpretation).

I'm not entirely sure if it matches up with any of the other interpretations here, but what seems most plausible to me is a modified many-worlds in which there indeed is no wavefunction collapse, but in which the physical world we observe is the entire superposition of states of the universal wavefunction and not just one branch of it (so that there isn't actually any kind of multiverse).

In the many worlds interpretation all branches do exist simultaniously. It is still just "one" universe, there are just a multitude of different versions of you running around at the same time without interacting together :lol:

Another serious problem I have with the many worlds interpretation is how it (artificially ?) emphasizes classicaly (local) basis states for the branching into different "worlds". I mean that there are different possibilities for splitting and we find ourselves always on classical ones. Probably there is some connection to the strong antropic principle.

 

[RGClark]

I like the de Broglie–Bohm theory myself. Note this a purely deterministic interpretation of quantum mechanics. It would require superluminal speeds but I happen to think a final theory will include superluminal speeds.

Bob Clark