- #1
Fra
- 4,105
- 607
There has been a few recent threads relating to the interpretation of QM, in particular the interpretation of probabilities and the RQM interpretations of Rovelli. I'd just like to highlight some from my point of view general constructing principles and ways of reasoning characterizing the relational interpretations but also (this is My main point) some differences in the various versions of this, and what status to assign to the SET of relations and their internal transformations (symmetries). And I will briefly argue that Rovelli's relational views, are only partly relational, and that this is related to a realist view of symmetry.
(Personally I would have chosen to place this thread in the beyond the standard model section, but since most of the related discussions has taken place here I'll put it here, and let the moderators move it if they wish.)
The general arguments here are also partly applicable to the discussion of background independence, where some argue for BI, but where there are different definitions or degrees of BI. It also applies by analogy to symmetry arguments. Symmetry, BI and relationality are closely related from the point of view of reasoning.
One of Rovelli's suggestions, in analogy with the classical theory of relativity is that information states are not objective, they are relative to the observer in direct analogy to the classical measurements are dependent upon the relative motion of the observer.
So far, it seems highly plausible.
But, one major difference is that at the time of classical theories there was a lot of realist thinking. In particular is there realist view of the transformations groups that RELATE the diversity of observations. This is poincare transformations in SR and also diffeomorphism transformationsin GR.
These transformations, seen as properties of nature, are not subject to measurement in the direct sense. This is fine in realist classical physics, which is somehow realistic from construction.
I have however serious doubts about this way of reasoning in the higher standard of modern physics. Rovelli partially carries over this realist view of physical symmetries into QM and QG. This is to me a major speculation, and I don't think it's right.
Rovelli considers QM to be relational, but IMHO he is treating the symmetries connecting the observers in a realist way. This breaks IMO the idea behind a measurement theory, because some majors elements are put in by hand, without critical analysis.
I am fully in agreement with Rovelli's relational ideas, if it wasn't for this realist view of symmetry, which is also very clearly expressed in this papers of what's observable in QM and QG, and his papers of partial observables.
So what is the alternative route within a relational interpretation? One alternative is where inference of symmetries are subject to the same constraints as all other physical interations. This leads almsot to a circularity, which can instead be interpreted as an evolutionary model. This is why I think this alernative reasoning points towards the ideas of Lee Smolin, which is also relational, but in a very different way than Rovelli. Smolins critique to eternal timeless laws and symmetries are also rgumetns in this.
I think Rovelli is aiming for something TOO complete, but fixing the structure in the hierarchy of relations of relations at some level, and consider them in a realist way to represent eternal strucutre of reality.
So I just wanted to highlight that there are several different relational interpretations, and where I personally consider rovelli to not be "relational enough".
Rovelli says that all measurements are relative to the observer. I wish he would also say that the set of relations for the set of observers are ALSO relative to the observer.
But this would lead to circularity. I think he wants to avoid this complication. But this circularity could evolution of laws Smolin is sniffing on. Where hte LAWS are the ultimate form of STATE, and even these are relative!
In this sense, I like rovelli's starting point, but he doesn't go all the way. And the point where he flips to realism seems ambigous to me.
/Fredrik
(Personally I would have chosen to place this thread in the beyond the standard model section, but since most of the related discussions has taken place here I'll put it here, and let the moderators move it if they wish.)
The general arguments here are also partly applicable to the discussion of background independence, where some argue for BI, but where there are different definitions or degrees of BI. It also applies by analogy to symmetry arguments. Symmetry, BI and relationality are closely related from the point of view of reasoning.
One of Rovelli's suggestions, in analogy with the classical theory of relativity is that information states are not objective, they are relative to the observer in direct analogy to the classical measurements are dependent upon the relative motion of the observer.
So far, it seems highly plausible.
But, one major difference is that at the time of classical theories there was a lot of realist thinking. In particular is there realist view of the transformations groups that RELATE the diversity of observations. This is poincare transformations in SR and also diffeomorphism transformationsin GR.
These transformations, seen as properties of nature, are not subject to measurement in the direct sense. This is fine in realist classical physics, which is somehow realistic from construction.
I have however serious doubts about this way of reasoning in the higher standard of modern physics. Rovelli partially carries over this realist view of physical symmetries into QM and QG. This is to me a major speculation, and I don't think it's right.
Rovelli considers QM to be relational, but IMHO he is treating the symmetries connecting the observers in a realist way. This breaks IMO the idea behind a measurement theory, because some majors elements are put in by hand, without critical analysis.
I am fully in agreement with Rovelli's relational ideas, if it wasn't for this realist view of symmetry, which is also very clearly expressed in this papers of what's observable in QM and QG, and his papers of partial observables.
So what is the alternative route within a relational interpretation? One alternative is where inference of symmetries are subject to the same constraints as all other physical interations. This leads almsot to a circularity, which can instead be interpreted as an evolutionary model. This is why I think this alernative reasoning points towards the ideas of Lee Smolin, which is also relational, but in a very different way than Rovelli. Smolins critique to eternal timeless laws and symmetries are also rgumetns in this.
I think Rovelli is aiming for something TOO complete, but fixing the structure in the hierarchy of relations of relations at some level, and consider them in a realist way to represent eternal strucutre of reality.
So I just wanted to highlight that there are several different relational interpretations, and where I personally consider rovelli to not be "relational enough".
Rovelli says that all measurements are relative to the observer. I wish he would also say that the set of relations for the set of observers are ALSO relative to the observer.
But this would lead to circularity. I think he wants to avoid this complication. But this circularity could evolution of laws Smolin is sniffing on. Where hte LAWS are the ultimate form of STATE, and even these are relative!
In this sense, I like rovelli's starting point, but he doesn't go all the way. And the point where he flips to realism seems ambigous to me.
/Fredrik