Many Worlds

[Neutral Observer]

It's not just a question just of the number of possible outcomes, but also of the probability of each outcome. The vast majority of ways the coin can land are metastable and will decay to head or tails. A tiny fraction of landings will be on the edge and stable, and in that tiny fraction, there is a wide variety of possible orientations.

That's sort of the conclusion that I was coming to, but as almost always happens, it leads to another question.

Originally I was thinking that I could just add up all the possible outcomes to get the probability of a coin ending up on its side as opposed to either heads or tails, but of course that results in there being more outcomes in which the coin ends up on its side. So I then decided that instead of adding up all of the possible outcomes I should add up all of the possible paths, even if they result in identical outcomes. Doing that ends up with a result that looks much more like what we experience in the real world, however it raises a puzzling question. Does every possible path result in a unique reality, even when its outcome is identical to the reality created by a different path? It would seem as if they each have to result in their own unique reality if the probabilities that we experience in our reality are to accurately reflect the underlying quantum realities.

There may be a way around this by simply postulating that distinguishable realities only arise when they decohere from each other. Therefore the probability of any particular outcome is determined by the number of paths that can result in that outcome, and until such time as they decohere from each other they are in essence one and the same reality even if they got there via a different path. However that seems like a matter of convenience, and exists only because we didn't measure the path at some point prior to the outcome. If we had measured them earlier they would have decohered, and the only reason that they didn't was because we didn't measure them.

Therefore I'm currently of the opinion that if you're going to have MWI then you're going to have to have many worlds that are for all intents and purposes identical. It explains probability, but it makes for a lot more worlds.

I realize that this is complete gibberish, but probably no more so than your equations are to me. We come from different backgrounds, so we approach problems differently. I really don't expect this to make sense to you, but writing this stuff helps it make sense to me, for whatever that's worth.

 

[sjastro]

Heh, I was just looking to see if there are more recent pilot wave experiments (which I'll do more later), and I see Hossenfelder offers her opinions, which might be interesting or provocative to watch ;-). Anyway, I'll look for more recent experiments and try to get more about where we are at if there are any useful updates, but it may take a while since I'm stealing time right now from a home improvement project I want to get done ideally before christmas.

I had a look at Sabine's video on Bohmian mechanics.
When it was came out in 1952 the reaction from various famous individuals was quite hostile.

 

[FrumiousBandersnatch]

That's sort of the conclusion that I was coming to, but as almost always happens, it leads to another question.

Originally I was thinking that I could just add up all the possible outcomes to get the probability of a coin ending up on its side as opposed to either heads or tails, but of course that results in there being more outcomes in which the coin ends up on its side. So I then decided that instead of adding up all of the possible outcomes I should add up all of the possible paths, even if they result in identical outcomes. Doing that ends up with a result that looks much more like what we experience in the real world, however it raises a puzzling question. Does every possible path result in a unique reality, even when its outcome is identical to the reality created by a different path? It would seem as if they each have to result in their own unique reality if the probabilities that we experience in our reality are to accurately reflect the underlying quantum realities.

AIUI, any given macrostate can have many possible histories & futures - you need the microstate information to distinguish them. so each different path that results in a common macrostate will have a unique future because of its unique microstate. IOW, macrostates (e.g. how the coin finishes up) are coarse-grainings that ignore a lot of information about the exact state of the system.

For example, a glass of water at room temperature could have started as a glass of hot water or a glass of ice-water. In particular cases, we can eliminate a class of initial states - for example, we can be pretty sure that a glass of water with ice in it didn't start out hotter (because of the Past Hypothesis that entropy was low in the past).

There may be a way around this by simply postulating that distinguishable realities only arise when they decohere from each other. Therefore the probability of any particular outcome is determined by the number of paths that can result in that outcome, and until such time as they decohere from each other they are in essence one and the same reality even if they got there via a different path. However that seems like a matter of convenience, and exists only because we didn't measure the path at some point prior to the outcome. If we had measured them earlier they would have decohered, and the only reason that they didn't was because we didn't measure them.

Therefore I'm currently of the opinion that if you're going to have MWI then you're going to have to have many worlds that are for all intents and purposes identical. It explains probability, but it makes for a lot more worlds.

I realize that this is complete gibberish, but probably no more so than your equations are to me. We come from different backgrounds, so we approach problems differently. I really don't expect this to make sense to you, but writing this stuff helps it make sense to me, for whatever that's worth.

Whether one 'reality' is distinguishable or not from another depends on the level of coarse-graining, i.e. how close you look.

But having a large number of macroscopically indistinguishable worlds isn't a problem for MW - apparently Hilbert space has plenty of room...

BTW, I'm not a physicist, I have only an interested layperson's knowledge & understanding of some of it. IOW, by and large the mathematics is beyond me, so what I say is gleaned from attempts by those who do understand it to explain to those that don't. I'm well aware that sometimes only the maths will do.

 

[FrumiousBandersnatch]

Dare I repost what they say in the introduction(?) .. @stevevw and pseudoscientists will love this!:

Firstly, I don't see how 'a rational agent' is in any way independent from their model of the 'environment'.
Secondly, the concept of a 'rational agent' quantifying beliefs, now somehow qualifies as 'objective' for the purpose of creating a so-called: 'correct(!?) Principle', in Carroll's view, eh?
I presume all this as being an untestable philosophical principle .. in order to keep MWI alive, then?

Sorry Sean .. can't see this as meeting Physics' standards for 'objective', or a 'physical principle'.

(Confession: I haven't progressed beyond the introduction yet) .

Other explanations are available : MW - Probability and the Born rule.

 

[SelfSim]

I had a look at Sabine's video on Bohmian mechanics.
When it was came out in 1952 the reaction from various famous individuals was quite hostile.

Not as hostile, (apparently), as those men who chase her with their 'Theories of Everything .. (please don't send them to me) ..'

A classic in the making!

 

[SelfSim]

Other explanations are available : MW - Probability and the Born rule.

Well .. maybe I was being a bit critical of Carroll (etal's) approach there(?)
Theirs looks like a more systematic framework than Everrett's, I suppose ..

 

[FrumiousBandersnatch]

Well .. maybe I was being a bit critical of Carroll (etal's) there(?)
His looks like a more systematic framework than Everrett's, I suppose ..

It ought to be, given the amount of time & effort spent on it since Everett's time!

 

[sjastro]

Not as hostile, (apparently), as those men who chase her with their 'Theories of Everything .. (please don't send them to me) ..'

A classic in the making!

What the.............???
I think Sabine should stick to denigrating physicists instead of singing.

​

I believe the Theory of Everything should be a bottom up approach.
Currently we are at the stage of a Standard Model of Cosmology and Particle Physics.
There are various electronuclear force theories or GUTs (Grand Unified Theories) none of which are even remotely testable as particle accelerators are nowhere near the centre of mass energies required.
The predicted amount of vacuum energy in the universe according in quantum field theory is around 10¹²⁰ X higher than the observed amount observed from cosmology.
Then there are the Feynman path integrals and sum over histories when applied to gravity by summing over the momenta from the initial state |I> to the final state |F> resulting in ridiculous calculations where there are an infinite number of momenta which have an infinite value.

We have a long way to go before even considering a Theory of Everything.

 

[sjastro]

Not as hostile, (apparently), as those men who chase her with their 'Theories of Everything .. (please don't send them to me) ..'

A classic in the making!

Here incidentally is the video that sparked Sabine's musical tirade.
Now she has gone too far physicist bashing is one thing, mathematics bashing is a far more serious matter.

 

[SelfSim]

Here incidentally is the video that sparked Sabine's musical tirade.
Now she has gone too far physicist bashing is one thing, mathematics bashing is a far more serious matter.

Can't disagree much with anything she says there ..(?)
I don't think she's bashing math .. she only has a go at extensive public funding being injected into reasearch into 'pretty' (or elegant) math, which is only believed to 'have some basis in nature'(?) Akin to: Pure mathematics has to be anchored in observations before it can become of practical use. If so, I can't really object with that ..

 

[Hans Blaster]

Now she has gone too far physicist bashing is one thing, mathematics bashing is a far more serious matter.

Mathematicians playing at physics. I can line up to bash that...

 

[sjastro]

Can't disagree much with anything she says there ..(?)
I don't think she's bashing math .. she only has a go at extensive public funding being injected into reasearch into 'pretty' (or elegant) math, which is only believed to 'have some basis in nature'(?) Akin to: Pure mathematics has to be anchored in observations before it can become of practical use. If so, I can't really object with that ..

I totally disagree with her premise theoretical physicists build theories around the mathematics because it is "pretty".
This is as bad as developing a theory around a conclusion like ID used to justify creationism.
Physicists may appreciate mathematical beauty such as the equation in my avatar which mathematicians consider the most beautiful (complete with a shovel because of the blasted snowstorm).

Feynman wrote of this equation.
Our “jewel" and "one of the most remarkable, almost astounding, formulas in all of mathematics.

Physicists are quite pragmatic when it comes to mathematics.
Feynman came up with the most accurate theory in physics quantum electrodynamics which being a quantum field theory is mathematically ugly and not rigorous.
By comparison general relativity is considered a “beautiful theory” for its mathematical simplicity based on non Euclidean geometry.
General relativity gave the mathematician David Hilbert (of Hilbert space fame in quantum mechanics) the confidence that physics could be axiomatized like pure mathematics.
Quantum field theories destroyed this idea because it is not mathematically rigorous as many of its ideas are based on physical not mathematical insights.
The mathematics is either developed or adopted from pure mathematics.

On rare occasions however the mathematics developed by physicists is so good it makes inroads into mathematics and led to Ed Witten a physicist winning the Fields Medal in mathematics.

 

[sjastro]

Mathematicians playing at physics. I can line up to bash that...

Lets not forget mathematicians have come to the rescue when the physicists are floundering.
Albert was very grateful to David Hilbert and Emmy Noether getting him out of a pickle over the conservation of energy law in general relativity.

 

[SelfSim]

I totally disagree with her premise theoretical physicists build theories around the mathematics because it is "pretty".
This is as bad as developing a theory around a conclusion like ID used to justify creationism.
Physicists may appreciate mathematical beauty such as the equation in my avatar which mathematicians consider the most beautiful (complete with a shovel because of the blasted snowstorm).

Feynman wrote of this equation.
Our “jewel" and "one of the most remarkable, almost astounding, formulas in all of mathematics.

Physicists are quite pragmatic when it comes to mathematics.
Feynman came up with the most accurate theory in physics quantum electrodynamics which being a quantum field theory is mathematically ugly and not rigorous.
By comparison general relativity is considered a “beautiful theory” for its mathematical simplicity based on non Euclidean geometry.
General relativity gave the mathematician David Hilbert (of Hilbert space fame in quantum mechanics) the confidence that physics could be axiomatized like pure mathematics.
Quantum field theories destroyed this idea because it is not mathematically rigorous as many of its ideas are based on physical not mathematical insights.
The mathematics is either developed or adopted from pure mathematics.

On rare occasions however the mathematics developed by physicists is so good it makes inroads into mathematics and led to Ed Witten a physicist winning the Fields Medal in mathematics.

Ok .. so I just rewatched Hossenfelder's vid there again. I think the point she's making, is that the unification theories: Lisi, Weinstein and Wolfram, (I know nuffin' about the specific details of these), which she more or less says, seek to align the universe with 'what seems logical', are her target. She says she doesn't have a problem with them working on those, however.

I still think I agree with that.
Logic is our way of reasoning out what we observe (or perceive).. but reasoning in the absence of an observation (or need), is just waffle, (IMO). I guess all theoretical physics research might seem to fall into that category .. but it doesn't really.

Having said that, I would also say that Hossenfelder certainly appears to have problems with men stating their opinions/gut feelings .. (One might even go so far as to say, she might even have a chip on her shoulder about that?)

 

[SelfSim]

Lets not forget mathematicians have come to the rescue when the physicists are floundering.
Albert was very grateful to David Hilbert and Emmy Noether getting him out of a pickle over the conservation of energy law in general relativity.

A symbiotic relationship built on mutual respect! ..
Sounds good to me!

 

[sjastro]

Ok .. so I just rewatched Hossenfelder's vid there again. I think the point she's making, is that the unification theories: Lisi, Weinstein and Wolfram, (I know nuffin' about the specific details of these), which she more or less says, seek to align the universe with 'what seems logical', are her target. She says she doesn't have a problem with them working on those, however.

I still think I agree with that.
Logic is our way of reasoning out what we observe (or perceive).. but reasoning in the absence of an observation (or need), is just waffle, (IMO). I guess all theoretical physics research might seem to fall into that category .. but it doesn't really.

Having said that, I would also say that Hossenfelder certainly appears to have problems with men stating their opinions/gut feelings .. (One might even go so far as to say, she might even have a chip on her shoulder about that?)

I think Sabine makes it clear she thinks beautiful maths is the objective for researchers.
Lets go back to my diagram.

Using the bottom up approach you have the symmetry groups U(1), SU(2) and SU(3) corresponding to the electromagnetic, weak and strong interactions respectively.
U(1) leads to the theory of quantum electrodynamics and SU(3) to quantum chromodynamics.
As you progress up the diagram the symmetries become more complex as does the corresponding mathematics.
I have never heard of quantum chromodynamics being simple and elegant making it a beautiful theory, the symmetries for GUTs and the TOE would be far more complex as one would also expect from the resulting mathematics.
So I'm not sure where Sabine gets this idea the aim of researchers is to have beautiful mathematics in their theories.

I found this video from Arvin Ash whom I have never heard of until now.
He does a brilliant in job explaining the U(1), SU(2) and SU(3) symmetries in layman terms.
Perhaps the thing of beauty is in the application of symmetry in physics not the specific maths itself.

 

[SelfSim]

I think Sabine makes it clear she thinks beautiful maths is the objective for researchers.
Lets go back to my diagram.

View attachment 325498​

Using the bottom up approach you have the symmetry groups U(1), SU(2) and SU(3) corresponding to the electromagnetic, weak and strong interactions respectively.
U(1) leads to the theory of quantum electrodynamics and SU(3) to quantum chromodynamics.
As you progress up the diagram the symmetries become more complex as does the corresponding mathematics.
I have never heard of quantum chromodynamics being simple and elegant making it a beautiful theory, the symmetries for GUTs and the TOE would be far more complex as one would also expect from the resulting mathematics.
So I'm not sure where Sabine gets this idea the aim of researchers is to have beautiful mathematics in their theories.

I think she mentioned that a violation of symmetry at the GUT level, would account for particle physics but she seem to didn't explain this.

I found this video from Arvin Ash whom I have never heard of until now.
He does a brilliant in job explaining the U(1), SU(2) and SU(3) symmetries in layman terms.

Yep .. good one .. thanks (again)!

Perhaps the thing of beauty is in the application of symmetry in physics not the specific maths itself.

Symmetry leads to conservation laws, eh .. interesting ..

 

[sjastro]

I think she mentioned that a violation of symmetry at the GUT level, would account for particle physics but she seem to didn't explain this.

She refers to the symmetry being broken not violated which is an important difference.
In 1983 particle physicists were able to recreate temperatures of the very early universe high enough to produce the electroweak force based on the SU(2) X UA(1) symmetry.
The symmetry was broken as the universe cooled SU(2) X UA(1) → SU(2) + UA(1) into the separate weak and electromagnetic forces.

Yep .. good one .. thanks (again)!

Symmetry leads to conservation laws, eh .. interesting ..

The video doesn't explain why the carrier of the electromagnetic force, the photon has zero mass while the carriers of the weak force the W and Z bosons do.
This is caused by spontaneous symmetry breaking.

Spontaneous symmetry breaking is difficult to explain without going into the mathematics, this video does a decent job while keeping the maths to a minimum.

 

[Halbhh]

I had a look at Sabine's video on Bohmian mechanics.
When it was came out in 1952 the reaction from various famous individuals was quite hostile.

It provoked an interesting idea. I'm kinda busy, but I have been thinking about how it's an artificial idea we impose that a particle is somehow distinct from a wave, wavelike distribution, field, etc. What I mean is: What is a particle? Of course, that's a basic question, so physicists like to think on such, and of course there are articles about that. Here's one I searched up that might be useful to help think on it. (e.g., is QFT really incompatible with ideas like pilotwave (which can be also just a...view which provokes or suggests other ideas). I like to read other viewpoints to help provoke ideas and add extra aspects, so I'm always happy to read what might seem old ground, because of course, we don't really know what a particle is very fully -- we just know a lot of aspects (we know a lot, but that's not knowing all)... (it's sorta the entire question in a way, or can be)

What Is a Particle?

It has been thought of as many things: a pointlike object, an excitation of a field, a speck of pure math that has cut into reality. But never has physicists’ conception of a particle changed more…

www.quantamagazine.org

 

[sjastro]

It provoked an interesting idea. I'm kinda busy, but I have been thinking about how it's an artificial idea we impose that a particle is somehow distinct from a wave, wavelike distribution, field, etc. What I mean is: What is a particle? Of course, that's a basic question, so physicists like to think on such, and of course there are articles about that. Here's one I searched up that might be useful to help think on it. (e.g., is QFT really incompatible with ideas like pilotwave (which can be also just a...view which provokes or suggests other ideas). I like to read other viewpoints to help provoke ideas and add extra aspects, so I'm always happy to read what might seem old ground, because of course, we don't really know what a particle is very fully -- we just know a lot of aspects (we know a lot, but that's not knowing all)... (it's sorta the entire question in a way, or can be)

What Is a Particle?

It has been thought of as many things: a pointlike object, an excitation of a field, a speck of pure math that has cut into reality. But never has physicists’ conception of a particle changed more…

www.quantamagazine.org

The problem with Bohmian mechanics is the concept of time.
Quantum field theories originated when physicists were able to combine special relativity where time is relative with quantum mechanics.
Bohmian mechanics relies on absolute time and Lorentzian relativity requiring the existence of an ether which was ruled out by the Michelson- Morley experiment.

On the subject of particles it was in classical physics where the point particle was introduced, where the mass and charge of a particle was concentrated into an infinitesimally small volume.
It made the mathematics considerably more simple.
For example the inverse square law for the gravitational force F between two objects is based on the equation F= Gm₁m₂/r² where m₁, m₂ are their point masses and F is a function of the distance variable r.
A more realistic equation is to consider the mass of the objects not their point masses expressed in terms of density ρ and volume v where m = ρv where the equation becomes F = Gρ₁v₁ρ₂v₂/r².
Problems arise for irregular sized objects where the volume v is not easily defined mathematically.

Ironically while point masses makes Newtonian gravity easier to handle, gravity messes up QFT which also assumes point masses.
A quantum theory of gravity is possible where particles are not point sized such as in String theory