Relativismo: How Gravity Creates Unique Events

[marcus]

Relatismo (my made up term for this emerging philosophy) says that two events are only different if they have different past lightcones, different past histories. Or as Smolin puts it, different VIEWS.

You and I are different people only if we come from different cities or neighborhoods and had different experiences with girls and saw different movies and so on. If every detail in our past is the same, even down to our record collections, then (sorry about this) we are the same individual.

As I see it, the central relatista message in "The Case for Background Independence" is on page 33, in a passage which is extracted here from context and quoted first in isolation.

--key passage in isolation--
Julian Barbour and I call a spacetime in which the view of each event is distinct a Leibniz spacetime. We note, with some wonder, that the fact that our universe is not completely in thermal equilibrium is due to the fact that gravitationally bound systems have negative specific heat, and therefore cannot evolve to unique equilibrium configurations. Furthermore, gravity causes small fluctuations to grow that would otherwise be damped. This is why the universe is filled with galaxies and stars. Thus, gravity, which as Einstein taught us is the force that necessarily exists due to the relational character of space and time, is at the same time the agent that keeps the world out of equilibrium and causes fluctuations to grow rather than to dissipate, which is a necessary condition for it to have a completely relational description.
--end quote--

I am not sure why one can say Einstein taught us gravity is the force that necessarily exists due to the relational character of space and time--it sounds like the germ of an idea and I guess it has to do with the equivalence principle. Maybe someone can explain it, or if I think some more about it I'll understand.

the business about negative specific heat is straightforward. Picture something like a globular cluster, even better a globular cluster of smallish iceball comets. Like a cloud of gnats, gravity-bound.

If you can inject energy into the cluster, so it swells out IT GETS COLDER because things move slower---the way outer planets move slow and Oort cloud comets move even slower----so pumping energy into the cloud makes it expand and cool (less kinetic energy = less temperturature).

Astronomers say "virial theorem" (Latin vis, viris, energy, strength) this knowledge of the NEGATIVE SPECIFIC HEAT of gravitybound systems is several centuries old which is why it has an old name.

If you can bleed energy out of the cluster somehow, it gets HOTTER in the sense of their moving faster. Indeed if you can bleed enough energy out of a cloud of cold comets they can even pile together in a heap at the bottom of their own well, and form a star, and get REALLY hot.

So gravity-bound systems work the OPPOSITE of systems we are used to where putting energy in makes the temperature rise and bleeding energy out makes the temperature fall---that is a positive specific heat and that is always what we expect.

a bunch of things with pos specific heat will get into equilibrium the hotter ones will radiate heat and cool off, and the colder ones will receive radiant energy and warm up, till everything is the same temperature.

gravity things don't come to equilibrium like that because the things that radiate away some of their energy get HOTTER as they lose
and the things receiving energy get colder as they gain

ACCIDENTAL INEQUALITIES TEND TO GET MAGNIFIED by gravity. minor kinks (instead of automatically smoothing out) become major.

At least until everything is in the form of black holes. I can't picture it beyond that.
Or else until everything is RADIATION and no longer gravitationally bound.

But that is looking too far into the future. The main thing is that the way things are now the gravitationally bound systems have negative specific heat and gravity does NOT CONDUCE TO UNIFORMITY and equilibrium and keeps everything in an uneven clumped and clustered very hot here very cold there disequilibrium.

and gravity is unusual this way. other kinds of systems are more likely to show positive specific heat and to come to ordinary evened-out equilibrium.

Now I think a relatista would say that it is this UNEVENNESS of the universe that allows so many different past lightcones or past histories and thus allows so many distinct spacetime events.

According to extreme relatismo, the reason that the universe can have so many distinct spacetime points, called "events", in it is that gravity does a very good job of making the universe LUMPY and uneven and totally un-symmetrical. The universe has no symmetries, whew! what a relief! thank your lucky stars it has no symmetries because otherwise things wouldn't have UNIQUE IDENTITY from having different relations to their surroundings and different causal past histories. Don't say thank goodness, say THANK GRAVITY.

this is a risky thin-ice idea. It hasnt really been figured out yet by anybody, I suspect. At any rate for me it is just the thin bare beginnings of an idea.
Like someone you pretend not to notice because you are both reading your books, but actually do notice.

I will quote the same passage now, but in context.

 

[marcus]

--quote smolin section 7, context of that key passage--

7 A relational approach to the problems of unification and determination of the standard model parameters

Let us then assume we agree on the need to formulate a unified theory in a background independent framework. Even without having a complete formulation of this kind in hand, it may be of interest to ask what would a background independent approach to the problem of unification look like? How would it address the problems raised in the last section? To approach these questions we return to the question of how we are to explain the properties of the elementary particles?

In a relational theory, as I explained earlier, the properties of the elementary entities can have only to do with relations they have to other elementary entities. Let us explore the implications of this.

The first implication is that any relational system with a large number of parts must be complex, in the sense of having no symmetries. The reason is Leibniz’s principle of the identity of the indiscernible: If two entities have the same relations to the rest, they are to be identified. Each individual entity must then have a unique set of relations to the rest.

The elementary entities in general relativity are the events. An event is characterized by the information coming to it, from the past. We may call the information received by an event in spacetime, the view of that event. It literally consists of what an observer at that event would see looking out their backwards light cone.

It follows that any two events in a spacetime must have different views. This implies that

1. There are no symmetries.

2. The spacetime is not completely in thermal equilibrium.

These are in fact true of our universe. The universe may be homogeneous above the enormous scale of 300Mpc, but on every smaller scale there is structure. Similarly, while the microwave background is in thermal equilibrium, numerous bodies and regions are out of equilibrium with each other.

Julian Barbour and I call a spacetime in which the view of each event is distinct a Leibniz spacetime. We note, with some wonder, that the fact that our universe is not completely in thermal equilibrium is due to the fact that gravitationally bound systems have negative specific heat, and therefore cannot evolve to unique equilibrium configurations. Furthermore, gravity causes small fluctuations to grow that would otherwise be damped. This is why the universe is filled with galaxies and stars. Thus, gravity, which as Einstein taught us is the force that necessarily exists due to the relational character of space and time, is at the same time the agent that keeps the world out of equilibrium and causes fluctuations to grow rather than to dissipate, which is a necessary condition for it to have a completely relational description.

There is a further consequence of taking the relational view seriously. In a relational theory, the relations that define the properties of elementary entities are not static, they evolve in time according to some law. This means that the properties by which we characterize the interaction of an elementary particle with the rest of the universe are likely to include some which are not fixed a priori by the theory, but depend on solutions to dynamical equations. We can expect that this applies to all of the basic properties that characterize particles such as masses and charges.
---end quote---

In this essay "The Case for Background Independence" Smolin says explicitly that he is using the term background independent sometimes to mean the same as "relational". He also is using a gradual SCALE of B-independence, or relationality. There is no TOTALLY background independent theory, but some theories can be more relational than others, or less background dependent.

So the title of the essay could be translated to "The Case for Relationalism"
or even "A Relationalist Manifesto".

but it also has some very sensible practical advice for string theorists, so you can kind of poke around in the essay and find what is right for you.

Personally I find the unbridled Relatismo of section 7 stimulating, but tastes may vary.

 

[Spin_Network]

So we know that you do not just post great links marcus..you actually tackle the contents! amazing after introducing the thread, and of course other amizin threads, I am often puzzled as to the lack of continueation, when thread go silent? I tend to think that readers of the forums do actually take the time to delve into, let's face it is an amazing array of talent within LQG.

You have rightly highlighted a very intruging passage, which can be traced to Julian Barbours efforts from about 4 yrs ago, to "do away with the concept of time", in relation with progressing into string theory for instance. I believe Smolin was instrumental in taking Barbour onto another 'road'?

Looking good marcus..looking good ! thanks again.

P.S, there is a neat little outcome that has its relevence to Specific Heat, and Singularities, it raises a number of questions, on What the Questions actually are?..as a quick example:Classic standard Cosmology(questions therein) has energy density?..the PRESENCE of matter means there are diverging singularities with equations(from certain type of questions)..but there are relationary Gravitational converging processes, that tend also to have Singularities, that CANNOT have Matter?
Certain Singularities are MATTER-FREE.

 

[selfAdjoint]

"Julian Barbour and I..". So Smolin not only channels Barbour in this essay, but comes right out and cites him! To me that's the big news.

One thing in this that puzzles me. "There are no symmetries". Then why does the assumption that there are work so DAMN well in predicting physical quantities?

 

[MeJennifer]

There is no TOTALLY background independent theory, but some theories can be more relational than others, or less background dependent.

True, perhaps we are in need of a paradigm shift from a particle ontology to one of interactions to find a true background independent theory.

What do you think?

 

[marcus]

...
What do you think?

What I think is...I am more a research news reporter and commenter. I watch what papers appear and try to fit the pieces, draw connections, and notice trends.

I need to be feeling kind of giddy before I will make a pronouncement about what should happen---and usually it is a bit tongue in cheek or humorously put.

So I can't answer this question about should there be a paradigm shift.

But I am glad you asked and I hope other people here WILL respond

 

[marcus]

To respond more fully to the question, I will give the link to the article quoted in the original post.

The article quoted was The Case for Background Independence
http://arxiv.org/abs/hep-th/0507235

Relatismo (my made up term for this emerging philosophy) says that two events are only different if they have different past lightcones, different past histories. Or as Smolin puts it, different VIEWS.

You and I are different people only if we come from different cities or neighborhoods and had different experiences with girls and saw different movies and so on. If every detail in our past is the same, even down to our record collections, then (sorry about this) we are the same individual.

As I see it, the central relatista message in "The Case for Background Independence" is on page 33, in a passage which is extracted here from context and quoted first in isolation.

--key passage in isolation--
Julian Barbour and I call a spacetime in which the view of each event is distinct a Leibniz spacetime. We note, with some wonder, that the fact that our universe is not completely in thermal equilibrium is due to the fact that gravitationally bound systems have negative specific heat, and therefore cannot evolve to unique equilibrium configurations. Furthermore, gravity causes small fluctuations to grow that would otherwise be damped. This is why the universe is filled with galaxies and stars. Thus, gravity, which as Einstein taught us is the force that necessarily exists due to the relational character of space and time, is at the same time the agent that keeps the world out of equilibrium and causes fluctuations to grow rather than to dissipate, which is a necessary condition for it to have a completely relational description.
--end quote--

I am not sure why one can say Einstein taught us gravity is the force that necessarily exists due to the relational character of space and time--it sounds like the germ of an idea and I guess it has to do with the equivalence principle. Maybe someone can explain it, or if I think some more about it I'll understand.
...

 

[Chronos]

You can't turn something into nothing, nor nothing into something, so the story goes. I guess that means our universe is illegitimate [which would explain its lumpiness]. Relationalism is an attractive ornament on top of the Ying-Yang tree. Just to be clear, I am addressing Smolin's assertions, not Marcus.

 

[MeJennifer]

You can't turn something into nothing, nor nothing into something, so the story goes. I guess that means our universe is illegitimate [which would explain its lumpiness]. Relationalism is an attractive ornament on top of the Ying-Yang tree. Just to be clear, I am addressing Smolin's assertions, not Marcus.

It might be interesting as to why you think that a relational theory is "turning something into nothing". Could you explain your position.

 

[Careful]

To respond more fully to the question, I will give the link to the article quoted in the original post.

The article quoted was The Case for Background Independence
http://arxiv.org/abs/hep-th/0507235

Just to avoid misinterpretation, do you actually say that :
(a) physical events are distinct iff they have different pasts (because that is just the past distinguishing condition in GR, no relational implications here)?
(b) physical events are distinct iff they have non-isometric pasts ?
If you mean case (b), then we can argue.

 

[Fra]

You can't turn something into nothing, nor nothing into something, so the story goes. I guess that means our universe is illegitimate [which would explain its lumpiness]. Relationalism is an attractive ornament on top of the Ying-Yang tree.

But we can turn whatever presented to us, the current knowledge of state of matters, into something better by an evolutionary mechanism, which is relational in the sense that it relates the future to present. If we can formalize this rule, then all we need is some chaos or ignorance to feed our evolutionary rule. I've been giving this a lot of pondering and IMO there are striking similiarities between physical interactions and supposed intelligent learning interactions. Learning is a kind of evolution, we all have hands on experience with.

Can we find the optimally inferred future, given the present, I think we will also find the laws of physics. At first thought this may seem like a human construction... but I think it can be generalized. After all the human brain is physical. A particle is not as intelligent, but a particle can also store information in it's states. Particle interactions IMO can be interpreted as an elementary crude processing. A particle subject to a force, is a state subject to a conflict, this conflict needs to be resolve. The rule of this is the rule of information updates or could be. At least that's one of the ideas of one of the relational approaches. I asked about in this thread.

Comments on that anyone else?
https://www.physicsforums.com/showthread.php?p=1320610#post1320610

Or do I even make sense?

/Fredrik