Temporal symmetry solves all quantum paradoxes?

[Careful]

To avoid difficult problems associated with consciousness and subjective human feel of the flow of time, let me put it this way: The thermodynamic arrow of time can explain why COMPUTERS remember the past and not the future. Would you agree with THAT?

No :-) I may give you a more elaborate answer if you tell me how you would construct such arrow of time from microscopic variables. And euh, why do you think computers wouldn't have a low form of consciousness?

 

[Demystifier]

All proofs so far in the context of the holographic principle contain loopholes and assumptions which may very well not be true.

Are you saying that there are attempts to explain the arrow of time from the holographic principle?
If so, can you give me a link?

 

[Careful]

Are you saying that there are attempts to explain the arrow of time from the holographic principle?
If so, can you give me a link?

Well sure, the whole point of the Bousso construction is to derive the second law for the combined gravity/matter system ASSUMING that it holds for ordinary matter (that is one loophole). See the paper of Wald, Marolf and Flanagan I referred to, but first I advise you to read to original Bousso paper (published around 2000 I believe).

 

[Demystifier]

I may give you a more elaborate answer if you tell me how you would construct such arrow of time from microscopic variables.

What exactly do you mean by "such"?

And euh, why do you think computers wouldn't have a low form of consciousness?

I never said that I do. But computers are better example than humans because we understand them much better than humans, and we do not NEED consciousness to understand how they work.

 

[Demystifier]

Well sure, the whole point of the Bousso construction is to derive the second law for the combined gravity/matter system ASSUMING that it holds for ordinary matter (that is one loophole).

It seems trivial to me, so that I am no longer interested in such a "derivation".

 

[Careful]

What exactly do you mean by "such"?

Well, give me one, and we can discuss scientifically.

I never said that I do. But computers are better example than humans because we understand them much better than humans, and we do not NEED consciousness to understand how they work.

Really? I could argue that it is precisely our consciouness which makes computers do whatever they do, but I believe computers are more self-supporting than that. Again, you think too classical here. A Schrodinger ''cat-like'' computer doesn't do sh*t.

 

[Careful]

It seems trivial to me, so that I am no longer interested in such a "derivation".

Really ? Then you really don't understand the nontrivial ideas which go into it. I mean someone like Wald is not going to write a paper about a trivial subject, is he?

For example, what does gravity do with entropy of matter ?

 

[Demystifier]

Really ? Then you really don't understand the nontrivial ideas which go into it. I mean someone like Wald is not going to write a paper about a trivial subject, is he?

I haven't seen the paper, my conclusion is based solely on your description.

 

[Demystifier]

Well, give me one, and we can discuss scientifically.

OK, macroscopic entropy defined through coarse graining of microscopic degrees of freedom. Do I need to explain?

 

[Careful]

OK, macroscopic entropy defined through coarse graining of microscopic degrees of freedom. Do I need to explain?

Well, if you could All these ideas run into deep sh*t with general covariance, but I guess this word is not so important in your dictionary Ok, suppose I am willing to accept that (which I am really not, since if you learn Bousso's paper you will see that gravitational entropy is attached to three dimensional null surfaces and not to some naive notion of space), then you can only apply this trick to the whole universe. All systems in nature are open, that is why WE exist, so what for God's sake would a global thermodynamic arrow of time tell you about the ''local'' functioning of the memory of a computer? The information in the computer might go up and it might go down, if I clean my hard disk the we would agree that by any reasonable definition of information, the latter would go down right? If I download the newest version of Windows Vista (if that still exists :-)) , then you know ''information'' would go up, right?

So, I repeat myself, the psychological arrow of time is much more fundamental - even for computers. For now, this discussion has been entirely classical, if we would repeat it quantum mechanically it would become even more evident that no entropical arrow of time can exists since entropy is and remains always zero whether you make measurements or not. So, unless gravity somehow destroys global unitarity, there is even no way to make sense of a global arrow of time in this context. But again, that would still not explain why computers observe only the past and not the future.

 

[Demystifier]

If I download the newest version of Windows Vista (if that still exists :-)) , then you know ''information'' would go up, right?

If you find Windows Vista on your computer, then you can be sure that it was downloaded in the PAST, but you cannot infer from that that it will be downloaded in the FUTURE. More generally, the CURRENT state in the computer memory tells you more about the past than about the future.

 

[Careful]

If you find Windows Vista on your computer, then you can be sure that it was downloaded in the PAST, but you cannot infer from that that it will be downloaded in the FUTURE. More generally, the CURRENT state in the computer memory tells you more about the past than about the future.

Sure, nobody objects that. The only thing I say is that a thermodynamic arrow of time is not explaining it. This is even so for humans, the local information in your brain may go down actually from time to time - a bottle of Vodka may assist you here Or in the worst case, you have a cerebrial bleeding and yeh many things are wiped out. So information *currents* cannot explain why time 'flows forwards' LOCALLY.

So yeh, I think someone like Carrol has a deep misunderstanding on this point.

 

[Demystifier]

The only thing I say is that a thermodynamic arrow of time is not explaining it.

I think it does, but I cannot explain it simply, and I don't have time to explain it in detail.

In relation to this, you might find this
http://lanl.arxiv.org/abs/gr-qc/0403001v2
interesting.

 

[Careful]

I haven't seen the paper, my conclusion is based solely on your description.

Then you don't understand why this is nontrivial, so my conclusion remains the same.

 

[Demystifier]

... general covariance, but I guess this word is not so important in your dictionary

General covariance is very important in my dictionary:
http://xxx.lanl.gov/abs/hep-th/0601027
http://xxx.lanl.gov/abs/hep-th/0202204
http://xxx.lanl.gov/abs/gr-qc/0111029

For a relation with the arrow of time. see also
http://xxx.lanl.gov/abs/gr-qc/0403121

 

[Careful]

I think it does, but I cannot explain it simply, and I don't have time to explain it in detail.

In relation to this, you might find this
http://lanl.arxiv.org/abs/gr-qc/0403001v2
interesting.

Sure not, because there is probably little to explain. Just give me a good common sense argument against my simple examples of Vodka and cerebrial bleeding and then I might look into it.

 

[Careful]

General covariance is very important in my dictionary:
http://xxx.lanl.gov/find/gr-qc/1/AND+au:+Nikolic_H+ti+AND+general+covariant/0/1/0/all/0/1

See also
http://xxx.lanl.gov/abs/gr-qc/0403121

Good, so I was not wrong in that respect then in getting to know each other thoughts on a better level So, then you also understand my joke and difficult challenge to give meaning to your words.

 

[Demystifier]

Just give me a good common sense argument against my simple examples of Vodka and cerebrial bleeding and then I might look into it.

Well, Vodka and cerebral bleeding also increase entropy in the brain, and certainly don't help to remember the future. So I don't see how this example contradicts my claims. To be clear, my claim is that thermodynamic time arrow is necessary, not sufficient, for remembering the past.

 

[Careful]

Well, Vodka and cerebral bleeding also increase entropy in the brain, and certainly don't help to remember the future. So I don't see how this example contradicts my claims. To be clear, my claim is that thermodynamic time arrow is necessary, not sufficient, for remembering the past.

That's not fair, you know I wasn't talking about decrease of entropy, I was talking about decrease of information. Now, I can actually learn many new things, so in general my information will go up (and entropy will go down). A refrigerator does the same thing, so if you want to take it backwards in this way, well yes here you have it. The same thing happens when a single egg cell fertilized by a spermatozoid grows to a full blown baby, information goes up and entropy goes down.

If you deny this, then you get in conflict with Darwinian evolution and precisely confirm what creationists hold against the second law of thermodynamics. Namely that God would be needed to create complex life forms.

 

[Demystifier]

That's not fair, you know I wasn't talking about increase of entropy, I was talking about decrease of information.

So we were not talking about the same thing, so we could not have been in conflict ...

 

[Careful]

So we were not talking about the same thing, so we could not have been in conflict ...

I corrected that sentence meanwhile. Small logical error by typing too fast. So I refer you back to post 54.

 

[Demystifier]

OK, here is a simple explanation of the fact that thermodynamic time arrow explains why do we remember the past and not the future.

The fact is that we actually don't remember anything. All we do is that we observe the state NOW. But from this state now, we try to CONCLUDE something about the future and about the past. Or more precisely, to CORRELATE the state now with the possible future and past states. However, owing to the second law, the correlations diminish towards the future. Thus, it is much easier to make the conclusions about the past. And it is such conclusions about the past that we call "remembering".

 

[Careful]

OK, here is a simple explanation of the fact that thermodynamic time arrow explains why do we remember the past and not the future.

The fact is that we actually don't remember anything. All we do is that we observe the state NOW. But from this state now, we try to CONCLUDE something about the future and about the past. Or more precisely, to CORRELATE the state now with the possible future and past states. However, owing to the second law, the correlations diminish towards the future. Thus, it is much easier to make the conclusions about the past. And it is such conclusions about the past that we call "remembering".

Well, but you really did not answer my objection since the second law does not always hold locally. I agree that what we know about the past is the ''information'' given to us by a measurement *NOW* of our brain state, but what I don't see is what the second law of thermodynamics has to do with this. For example, my guess is that those parts of our brain which deal with the long term memory are quasi stationary with respect to the full *local* hamiltonian of the brain... this would shield them against decay. There is no need to invoque any assymetry in the physics here. The short term memory on the other hand is much more turbulent and mixing of ''information'' can occur here. Of course, it remains to be seen what happens to some long term ''information'' when short term ''information'' becomes long term. But I genuinly think the brain is adaptive here and has the capacity for local entropy decrease.

How would you explain otherwise Darwinian evolution?

 

[Demystifier]

the second law does not always hold.

It holds ALMOST always, provided that you formulate it in a correct way: The system evolves from a less probable state towards a more probable state. (Note that I didn't mention entropy here.)

 

[Careful]

It holds ALMOST always, provided that you formulate it in a correct way: The system evolves from a less probable state towards a more probable state. (Note that I didn't mention entropy here.)

? But there is no such thing as a probability measure on the set of states! Suppose you had one, ok, then it must be invariant under the Poincare group right? So, it seems there does not exist such measure because the latter is not compact (and the ordinary Lebesgue measure does not exist). Again, you would get into severe troubles with Darwinian evolution where everyone intuitively knows that a higher life form is far less probable than a lower one. The only ''dynamical'' ''measure'' we are aware of is some fu***ng renormalized expression
e^{- a H}/ Tr e^{- aH} but yeah that one usually does not exist for interacting theories as far as I remember (and this is certainly not an integration measure over the unit sphere in Hilbert space). Moreover, the standard von Neumann entropy of a usual state is still zero.

You keep on reasoning from the classical perspective, but refuse to answer my very legitimate quantum objections. Not only are my classical objections very much to the point, the burden on you just increases in the quantum world. You would have to go over to these dynamical entropies I explained to you previously and that would get you into severe trouble with general covariance. Moreover, still then you would have to prove (!) that a localized second law holds.

Just out of curiosity, you admitted that sometimes localized entropy goes down. Would you say then that in that case we would turn around future and past ? :-)

 

[Careful]

I agree with you that Darwinian evolution appears to go slow but it really does not in my opinion. If you have children, you would notice for example that the average IQ per generation goes up : our brain functions just become more sophisticated with time (on average). The average length, age and so also increases and it is doubtful that this is merely due to an improvement of nutrition, a better lifestyle or more advanced medicine.

But more to the point is -like I said before- the birth of life, the formation of a child out of a spermatozoid and egg: I think you can hardly claim that a reasonable definition of information would lead to a more or less permanent decrease. That is, it would lead to a logical contradiction, since it would imply that a mother and father contain much more information than their offspring (irrespective of how many children they have) since the latter are only build from a few eggs and spermatozoids (then I don't count the number of times yet that you ''miss'' ). You might think that there is a logical loophole here and that is that somehow, the information of the father -say- would be approximately equal to the information contained in one spermatozoid, but still then information would need to increase once the spermatozoid left the father. I mean, it would be good for my spermatozoids :-)

It seems I am not the only one thinking that, but it is funny to see that a countryfellow of mine initiated the idea http://www.eoht.info/page/Local+entropy+decrease .

 

[Maui]

Just out of curiosity, you admitted that sometimes localized entropy goes down. Would you say then that in that case we would turn around future and past ? :-)

Ouch!

Reductio ad absurdum.

 

[Careful]

Ouch!

Reductio ad absurdum.

Let's try to stay serious here, plenty of respectable people have similar ''ideas'' to those of demystifier, so I appreciate it that we could make the logical excercise .

 

[Maui]

Let's try to stay serious here, plenty of respectable people have similar ''ideas'' to those of demystifier, so I appreciate it that we could make the logical excercise .

The argument ends in a reductio ad absurdum. That was a cool idea on your part.

 

[Careful]

The argument ends in a reductio ad absurdum. That was a cool idea on your part.

Well, if people do not want to listen to more reasonable arguments, you have to pull out the ultimate weapon

 

[nismaratwork]

Well, if people do not want to listen to more reasonable arguments, you have to pull out the ultimate weapon

It's not a weapon, it's a white flag.

 

[Careful]

It's not a weapon, it's a white flag.

English is not my natural language, but if you are suggesting here that this is not a legitimate reductio ad absurdum, then I don't know what does classify in your book like that. Perhaps you might want to comment on the specific arguments I have raised against demystifiers position (and there were plenty of them) instead of uttering a sentence which can just mean anything. I remember having invited you for a specific, technical discussion about the holographic principle. Up till now, I haven't seen any evidence that you do more than just repeating politically correct (but wrong) statements in physics (neither have shown yet to have any particular deep insights into this issue).

Actually, if demystifier feels he can reasonably surpass my objections, I would more than welcome his contributions. But until now, he has offered no evidence that he can (and that might even be an understatement). I am not insisting upon discussing the paper demystifier mentioned, arXiv:1011.4173v1, I just think that the authors are barking up the wrong three (and if someone cares, I could explain that in more detail, but I have no strong desire to do so).

 

[nismaratwork]

English is not my natural language, but if you are suggesting here that this is not a legitimate reductio ad absurdum, then I don't know what does classify in your book like that. Perhaps you might want to comment on the specific arguments I have raised against demystifiers position (and there were plenty of them) instead of uttering a sentence which can just mean anything. I remember having invited you for a specific, technical discussion about the holographic principle. Up till now, I haven't seen any evidence that you do more than just repeating politically correct (but wrong) statements in physics (neither have shown yet to have any particular deep insights into this issue).

Actually, if demystifier feels he can reasonably surpass my objections, I would more than welcome his contributions. But until now, he has offered no evidence that he can (and that might even be an understatement). I am not insisting upon discussing the paper demystifier mentioned, arXiv:1011.4173v1, I just think that the authors are barking up the wrong three (and if someone cares, I could explain that in more detail, but I have no strong desire to do so).

Flying a white flag is one of the universal symbols of surrender... does that clarify my original post?

 

[Careful]

Flying a white flag is one of the universal symbols of surrender... does that clarify my original post?

No, because you seem to imply that I surrender. Or you suggest that he made that error on purpose which I would find quite unlikely. I mean, he cites papers of a single author who has written about this issue, so I assume this author would have an answer to the simple objections I raise. I just glanced into this paper and looked for the argument why interacting systems with a different thermodynamic arrow of time shoud allign their time directions... hmmm the physical idea behind it is not quite ok, I would say, although the math looks superficially ok.

 

[ThomasT]

But if our common sense experience of the world is time asymmetric (I know we remember the past and wonder about the future) in the way we perceive causality, what sense does it make to talk about an objective reality where time is symmetric?

None, imho. I don't know of any compelling reason to think that the time asymmetry of our experience is not rooted in the fundamental dynamics of our universe, and in quantum level phenomena that aren't amenable to our sensory perception.

However, time asymmetry is a somewhat easy solution to some foundational problems. So, some philosopers and physicists adopt this approach.

The truth is, currently, anybody's guess. But it's good to keep in mind that the basic equations of motion of physics aren't correctly identified as time symmetric. Rather, they're time independent. They're equations of 'motion', not of 'time'. And insofar as they might describe a real 'time evolution', then that evolution proceeds in a particular 'direction' and is time asymmetric.

Everything that's actually known about the evolution of our universe suggests that its evolution is asymmetric (which would necessarily apply to the evolution of any of our universe's subsystems).