Exploring Hidden Variables in Quantum Gravity: A Philosophical Perspective

[SimonA]

To move beyond the standard model, especially in terms of quantum gravity, I assume we need to make a decision on the existence of hidden variables in QM. It seems that a decision has been made against hidden variables, but I'm still confused as to why. It appears that the reasons are around the fact that;

1) No hidden variables theory has made any Popper like unique predictions
2) Finding an epistemology that explains quantum behaviour and its non-locality etc requires an intellectual leap in philosophical terms that challenges the highly specialised researchers in these areas.

But let's step back a bit. If string theory has anything going for it, and recent evidence suggests a tentative affirmation of that, then our natural three dimensional view of space (lets forget Einstein for now) is flawed. So suddenly non locality becomes a non issue (please say if I'm oversimplifying here). If you consider some of the non-rolled-up-into-a-cartesian-like-point views of dimensionality(Randall etc), that take us away from the graphs we drew at school, then non locality at the quantum level is no longer some kind of mystery. If particles really exist in all dimensions, and our (physical) equipment and senses filter out only three of those spatial dimensions, surely our focus should be on why 3D matter filters out the other dimensions ?

Once we understand the mechanism of that filtration process, then perhaps we will start to understand spatial dimensionality itself ?

Any thoughts on this line of thinking ?

Regards

Simon

 

[SimonA]

I posted three posts last night and this was the only one that didn't get a reply - and yet I think it was the most interesting one.

Has modern science completely abandoned trying to find any explanation for quantum reality that could be explained to a waitress ? Do we want to understand it or do we just want to invent increasingly complex ideas of spatial geometry, and ignore the simply fluidic dynamics we see in the universe ?

To me it seems we have become too specialised. Intelligent people who research whirlpools and tornadoes should be engaged in trying to understand why galaxies move too fast at the edges (according to Newton).

If they were also told that our best leading edge science suggests that at the smallest level other dimensions exist, they may be able to come up with models that explain dark matter in way that makes sense. Ones that actually contribute to the models we have developed around the seeding of galaxies (by "dark matter"), and the filament nature of matter in the universe etc.

Its Hydrogen that first appears on the ladder of particles we know. Have we ignored the possibility of pre-hydrogen particles ? Does the periodic table really start with hydrogen ? And could dimensionality have a part to play in the fact we fervently believe that Hydrogen is the first member of that table ?

 

[malawi_glenn]

I think this post only reflects your ignorance about physics as seen and understood by a physicists, you are too influenced by philosophy and obsession with truth, reality and existence.

Also you have this biased view on "understanding", it seems like you dismiss understanding through mathematics as valid understanding. "understood by a waitress", why be content with that biased group of humans? Why not extend the criterion so that it should be understood by a monkey or a 5year old child?

And define "ladder of particles we know", and "pre-hydrogen particles".. you are talking mumbo jumbo in terms of physics; the hydrogen atom is made up of electrons, quarks, gluon etc and so on, if you don't know anything about physics - don't try to make any speculations about ti.

And "making sense" is subjective, to me Dark Matter in terms of so far undiscovered massive particles makes perfectly sense, since the framework they require (super symmetry) has such a great impact and applicability on unified theory building and quantum gravity. What will "modified Newtonian gravity" solve with respect to those issues? This is how I think, but not all agree with me, so "makes sense" is subjective.

 

[Naty1]

So suddenly non locality becomes a non issue (please say if I'm oversimplifying here).

ok, you are oversimplfying

If you consider some of the non-rolled-up-into-a-cartesian-like-point views of dimensionality(Randall etc), that take us away from the graphs we drew at school, then non locality at the quantum level is no longer some kind of mystery. If particles really exist in all dimensions, and our (physical) equipment and senses filter out only three of those spatial dimensions, surely our focus should be on why 3D matter filters out the other dimensions ?

extra tiny dimensions don't negate non locality mysteries.

There is no experimental evidence nor theory I've read that says particles we have theorized or observed experimentally exist in hidden dimensions...the particles are just too big ( or the dimensions too small)...string theory DOES posit those extra dimensions affect the energy pattern vibrations of strings which reside in three "big" dimensions of space, thus influencing their characteristics.

 

[malawi_glenn]

There is no experimental evidence nor theory I've read that says particles we have theorized or observed experimentally exist in hidden dimensions...the particles are just too big ( or the dimensions too small)...s

Kaluza-Klein particles? ..

 

[Demystifier]

SimonA, here is a paper on a possible relation between stringy nonlocalities and hidden variables:
http://xxx.lanl.gov/abs/hep-th/0605250

 

[SimonA]

SimonA, here is a paper on a possible relation between stringy nonlocalities and hidden variables:
http://xxx.lanl.gov/abs/hep-th/0605250

Thanks Demystifier

I'd forgotten that Bells inequalities force hidden variables down one or two paths. I got somewhat lost but it looks like Bohms interpretation could still have some surprises...

 

[SimonA]

ok, you are oversimplfying

extra tiny dimensions don't negate non locality mysteries.

There is no experimental evidence nor theory I've read that says particles we have theorized or observed experimentally exist in hidden dimensions...the particles are just too big ( or the dimensions too small)...string theory DOES posit those extra dimensions affect the energy pattern vibrations of strings which reside in three "big" dimensions of space, thus influencing their characteristics.

Despite some efforts, I'm unable to understand why people are so confident about the spatial dimensions we 'observe' being "big" and the ones we don't being "small" or "rolled up". This seems to me to be one massive Cartesian-point-like assumption. Surely Lisa Randall and others have shown that this is not the only option, and from my perspective it seems like some kind of sensio-centric way of approaching the subject.

We've abstracted up, down, left right, back, forward etc, and created an idea of dimensionality. I'm not criticising that, I'm just suggesting that we don't really understand what we are doing in that. We have millions of years of evolution that have led us to a position where we know its useful, and we have millennia of mathematics and physics that have shown it to have a connection to reality. But we still don't really know the distinction in terms accurate enough that we can describe why time can be considered in the same context and produce the likes of general relativity!

All I'm suggesting is that rolled up "small" extra dimensions is a concept that's holding back progress.

 

[tom.stoer]

... but it looks like Bohms interpretation could still have some surprises...

Can you tell us how to extend Bohm's idea in order to incorporate results from relativistic quantum field theory?

 

[SimonA]

Can you tell us how to extend Bohm's idea in order to incorporate results from relativistic quantum field theory?

There are papers but my simplistic mind likes Wikipedia :)

See "Comparison with experimental data" here -> http://en.wikipedia.org/wiki/Bohm_interpretation"

Further, it should be noted that since relativistic quantum theories (such as quantum field theory) can always be expressed in terms of a local Lagrangian density, it follows that probability mass in such theories always flows locally through configuration space, and therefore that a classical configuration of the system's (field) variables can still be made to evolve locally in a way that simply tracks the flow of the conserved probability current in configuration space. Therefore, Bohm's interpretation can be extended to a relativistic version that works in such a way that it exactly duplicates the predictions of standard quantum field theory, so, in fact, there can be no experimental contradiction of Bohm's approach (if suitably generalized in this way) that does not also contradict the standard model.

 

[Demystifier]

Can you tell us how to extend Bohm's idea in order to incorporate results from relativistic quantum field theory?

That's how:
http://xxx.lanl.gov/abs/0904.2287

 

[SimonA]

That's how:
http://xxx.lanl.gov/abs/0904.2287

Interesting paper, promising even. I also use double "ll"s more than I should :)

To me symmetry is one of the most amazing things about maths and physics. The way an equals sign can be combined with algebra, and sentience, and pierce into the nature of things, is astounding.

But if we really live in a multi dimensional universe, as evidence suggests, then the symmetry used in the likes of such fundamental precepts as Gauge theory surely need to be re-evaluated ?

I'd like to propose that the standard model is so reliable only in the same way an island is "the world" to those that live on it. It's a bit like people who used to think that the sun goes around the world. They had great evidence for their theory - evidence that was proven again and again every day. What they lacked is a true understanding of the context of their evidence.

 

[Demystifier]

I also use double "ll"s more than I should :)

What is that supposed to mean?

 

[humanino]

Demystifier : I think your paper is very interesting. As you may remember, I was wondering about gauge theories in Bohmian mechanics, and specifically how to interpret scaling violations in deep inelastic scattering, or say jet production for instance. I need to pay more time to the reading of your paper, but in the meantime would you make a statement as to the status of unbroken gauge theories in your interpretation ? Do you think it is worth a separate publication ?

 

[Demystifier]

Demystifier : I think your paper is very interesting. As you may remember, I was wondering about gauge theories in Bohmian mechanics, and specifically how to interpret scaling violations in deep inelastic scattering, or say jet production for instance. I need to pay more time to the reading of your paper, but in the meantime would you make a statement as to the status of unbroken gauge theories in your interpretation ? Do you think it is worth a separate publication ?

Hi Humanino,

In the paper above I do not study in detail gauge symmetries. Instead, my main preoccupation is to make the general features of QFT's (relativity, interactions, indefinite number of particles, particle creation and destruction) compatible with Bohmian mechanics. In section 3.4 I briefly indicate how fields with additional labels (including indices in the gauge group) can be incorporated, but I do not study gauge field theories in detail.

Thus, concerning your question, I could superficially say that gauge theories also fit nice in the whole framework. However, such an answer would probably not satisfy you. In order to give a better answer, you would help me a lot if you could indicate why exactly do you expect that gauge field theories might cause problems. If it turns out that really is a problem (of which I am currently not aware) that cannot be solved in a trivial way, then a possible solution of such a problem would certainly deserve a separate publication.

Thank you for your constructive questions and remarks which are very stimulating to me!

 

[SimonA]

What is that supposed to mean?

Only that the double "l" misspellings in the article are similar to the misspellings I make. eg;

successfull
allways

Its always amusing to me that those who are millitant about spelling usually consider Shakespear (rightly) to be a genius. Hoisted on their own petard, as they say...

 

[humanino]

In order to give a better answer, you would help me a lot if you could indicate why exactly do you expect that gauge field theories might cause problems.

The problem is that there is not a unique wavefunction for quarks or gluons inside a hadron : there is evolution under the renormalisation group as the scale changes.

Usually, people write the wavefunctions in terms of transverse spatial coordinates and longitudinal momentum fraction. More precisely, it simplifies the hadrons to look at them on the light cone, from a referential with "infinite momentum". From here, one can compute evolution of the wavefunctions with the scale of observation. However, during the last few years, it became customary to simply add another dimension to models, defining them on a(n anti-)de Sitter space. There is no claim that the additional dimension is necessarily "out there", it may according to Maldacena, but mostly the additional dimension serves as a reference scale for the observation and the evolution is embedded in the wave equation. I do not know if it is trivial to interpret a single wavefunction for (say) u quarks in the proton under those circumstances. It is also possible that gluon radiation fits perfectly well within your calculations without the need for any new ingredient. In that case, you would need (for instance) a running mass to about 300 MeV for quarks at long distances, as well as for gluons, and gauge invariance becomes tricky to deal with, however any interpretation must be gauge invariant.

 

[Demystifier]

Thanks humanino!

I have already answered to you to this question, but let me rephrase my answer here.

First, in my opinion, the scale dependence associated with the renormalization group is not directly related to gauge symmetries. Such a phenomena may occur in non-gauge theories as well.

Second, a true wave function is unique, but it may evolve in a non-trivial way due to an interaction with a probe having this or that energy. At low energies a many-particle wave function may be well approximated by a single-particle wave function, which explains why 3 quarks may look like a single proton at low energies. Essentially, it is not much different from the fact that a nucleus looks like a single particle at sufficiently low energies, or that an atom looks like a single particle at sufficiently low energies, or even that a whole planet looks like a single particle at sufficiently low energies.

 

[SimonA]

Hi Demystifyer

Do you believe that EM radiation (aka light) travels through space (Minowski or not) as individual particles ? This "probe" phrase you use suggests to me something more like a field reaching out, and then getting absorbed wholely by whatever matter we use to 'measure' it.

I'm still SO curious about Young's slit experiment. I feel closer to Crammer and his transactional interpretation than I do to the current box we've relegated the experiment to ("the formalism is all that matters..."). Why can light not go backwards in time if we accept that it goes forward in time, considering that at c velocity there is no time! And I have a suspicion that Bohm was onto something - albeit supposedly challenged by Bell and EPR etc.

Surely these extra dimensions (that are becoming ever more obvious) hold the key to something in QM we consider essentially random-but-following-rules ?

Lets ignore extra spatial dimensions, and just assume a single extra time-like dimension. If EM radiation moved only in this time-like dimension, but was visible to normal-space-time, in much the same way that gravity appears to leak into extra dimensions according to the hierarchy issue (via a reflection even in "dark energy" dimensions), then its appearance as a wave and then a particle would surely be the self evident result ?

Am I missing something there ?

 

[Demystifier]

Do you believe that EM radiation (aka light) travels through space (Minowski or not) as individual particles ?

Yes I do.

Am I missing something there ?

Yes, you miss equations that would support your point of view. (Equations that support my point of view are given in the paper mentioned above.)