Re: why can't we erase information?
Unitary evolution preserves information. It is only through measurement by an observer that information can be created or destroyed. Usually, the second law is interpreted as the destruction of information (anyone observing a closed system will over time know less information about the system), so it puzzles me that you have the sign the other way. Because of the action of the second law, it actually takes a thermodynamic flux to preserve information - which is why you need to read your old backup tapes an make copies every few years if you want to retain access to your data. Cheers On Sun, Apr 09, 2006 at 12:11:52AM -0700, Wei Dai wrote: If we consider our observable universe as a computation, it's rather atypical in that it doesn't seem to make use of the erase operation (or other any operation that irreversibly erases information). The second law of thermodynamics is a consequence of this. In order to forget anything (decrease entropy), we have to put the information somewhere else (increase entropy of the environment), instead of just making it disappear. If this doesn't make sense to you, see Seth Lloyd's new book Programming the Universe : A Quantum Computer Scientist Takes On the Cosmos for a good explanation of the relationship between entropy, computation, and information. Has anyone thought about why this is the case? One possible answer is that if it were possible to erase information, life organisms would be able to construct internal perpetual motion machines to power their metabolism, instead of competing with each other for sources of negentropy, and perhaps intelligence would not be able to evolve in this kind of environment. If this is the case, perhaps there is reason to hope that our universe does contain mechanisms to erase information, but they are not easily accessible to life before the evolution of intelligence. It may be a good idea to look out for such mechanisms, for example in high energy particle reactions. However I'm not sure this answer is correct because there would still be competition for raw material (matter and energy) where intelligence can still be an advantage. Anyone have other ideas? -- A/Prof Russell Standish Phone 8308 3119 (mobile) Mathematics0425 253119 () UNSW SYDNEY 2052 [EMAIL PROTECTED] Australiahttp://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02 --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: why can't we erase information?
Russell Standish wrote: Unitary evolution preserves information. It is only through measurement by an observer that information can be created or destroyed. Usually, the second law is interpreted as the destruction of information (anyone observing a closed system will over time know less information about the system), so it puzzles me that you have the sign the other way. What? You're saying that if I observe a system, then I know less about it. You must be using some non-standard meaning of know. Brent Meeker --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: why can't we erase information?
On reversibility, there is the observation (I think acredittable to Tom Toffoli) that most/all irreversible systems have a reversible subsystem and the dynamics arrive in that subsystem after some (finite) time. Thus any system that we observe a while after it has started will, with high likelihood, be reversible. In some sense the irreversibility dissipates and leaves a reversible core. Tim On Apr 10, 2006, at 3:22 AM, Jesse Mazer wrote: Saibal Mitra wrote: How would an observer know he is living in a universe in which information is lost? Information loss means that time evolution can map two different initial states to the same final state. The observer in the final state thus cannot know that information really has been lost. If he is able to figure out the fundamental laws of physics of his universe, then he could see whether or not they have this property of it being possible to deduce past states from present ones (I think the name for this property might be 'reversible', although I can't remember the difference between 'reversible' and 'invertible' laws). For example, the rules of Conway's Game of Life cellular automaton are not reversible, but if it were possible for such a world to support intelligent beings I don't see why it wouldn't be in principle possible for them to deduce the underlying rules. As for the question of why we live in a universe that apparently has this property, I don't think there's an anthropic explanation for it, I'd see it as part of the larger question of why we live in a universe whose fundamental laws seem to be so elegant and posess so many symmetries, one of which is time-symmetry (or to be more accurate, CPT-symmetry, which means the laws of physics are unchanged if you switch particles with antiparticles and flip the 'parity' along with reversing which direction of time is labeled 'the future' and which is labeled 'the past'). Some TOEs that have been bandied about here say that we should expect to live in a universe whose laws are very compressible, so maybe this would be one possible way of answering the question. Jesse -Tim Boykett TIME'S UP::Research Department \ / Industriezeile 33b A-4020 Linz Austria X+43-732-787804(ph) +43-732-7878043(fx) / \ [EMAIL PROTECTED]http://www.timesup.org - http://www.timesup.org/fieldresearch/setups/index.html --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: The Riemann Zeta Pythagorean TOE
Le 07-avr.-06, à 22:52, John M a écrit : I went to see your points 1-8, as suggested. I started to read AT THE BEGINNING and got stupefait (perplexed?) by your sentences. Which one? (If you are interested in an explanation). First: I don't appreciate thought experiments: All proof based on a theory are thought experiments, of course not all thought experiments are proof. The only way to decide what is the case can consist in following the argument and judiging by oneself. they are artifacts to show something NOT TRUE and make 'the truth' shown by it (eg. EPR). People love them because it leads them into the world of HP. People like fairytales. I like the ones I found out. I got stuck with the term 'subastitution' especially when it became a 's'-level. My eyes got glazed as I read on and less and less of your words matgerialized into meaning. Then came a cute figure (1) reminding me of Star Trek. I loved it as an anusing fairy tale. Then less and less reading occurred with conceptual following and more and more 'scroll-down;. This was not the first time I looked at your text. This time I made up my mind that I want to stay with it: I could not. No problem. Is it the comp hypothesis which makes problem for you?? It is my working hypothesis. All what I claim is that IF comp is correct THEN matter is not primitive, and its appearances can be justified from numbers and number theoretical relations (UDA), and then (but only then) I show that logic can help to find an effective way to derive laws of matter from laws of number. I have no idea if comp is true or false, indeed all what I have done has been to show that comp can be made precise enough so that it becomes refutable (although it remains unprovable in case it is true). snip HOW DO YOU FORMULATE NON-NUMBER CONCEPTS using solely NUMBERS? By programming, or by Godel numbers, or by using some representation result. It is hard to be both clear and rigorous giving the subtleties involved in an intrinsic difficult subject. John, what is your opinion about comp? Would you accept a digital brain transplant? What about the weaker question: Would you accept your daughter or your son get married with some one having already said yes for a digital brain substitution? Bruno http://iridia.ulb.ac.be/~marchal/ --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Numbers
Le 07-avr.-06, à 17:46, 1Z a écrit : To be precise, there is no problem with a very basic, simple notion of bare substance being the substrate, the bearer, of phenomenal properties as well as physical properties. Are you aware of the mind body problem. Are you aware the problem is still open. if you assume comutationalism (as a I undertand it, not as you understand it) you are already assuming the existence of matter, since computers are material. ... You just tell me that you are the one assuming that computers are material, so your are begging the question. The slide from idealism to solipsis is inevitable. Pythagoras and Plato already showed counterexamples. If numbers generate a video-game sort of reality, the game could still a priori be sharable, unless you prove the contrary. If the existence of matter is not needed to explain my experiences, the existence of other experiencers with their own experiences is not neeed to explain my experience either. Possible, but not necessary. Other minds appears in comp through the notion of first person plural, (arising from the duplication of entire population of individuals) and this leads to a notion of arithmetical entanglement. Actually theory like Shmidhuber or Hal Finney UDIST, could probably justify the existence of genuine other minds, and this despite they are lacking the 1/3 distinction povs. They suppress nevertheless successfully the 3 person white rabbits, and this explains, I guess for them, the negligible probability that someone behaving like a human is a zombie. The 1/3 distinction needs a more detailed treatment and the question is obviously still open. Please follow your intuition if you believe you could find a contradiction in comp, as I understand it. I mean you could be right, but until now, you don't really argue in your posts. Bruno http://iridia.ulb.ac.be/~marchal/ --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re:why can't we erase information?
Wei Dai: If we consider our observable universe as a computation, it's rather atypical in that it doesn't seem to make use of the erase operation (or other any operation that irreversibly erases information). The second law of thermodynamics is a consequence of this. In order to forget anything (decrease entropy), we have to put the information somewhere else (increase entropy of the environment), instead of just making it disappear. ___ Not sure I get your point (and it is also possible you write 'erase' actually meaning 'delete', which is different, at least if you try to 'delete' quantum states.) Anyway it is (perhaps) possible to say that (according to Everett) the information content of the original universal state is going to be transformed into hidden information content of the correlations between the different 'branches'. It seems to me that this process is different from the (usual) entropy increase of the environment, since the 'environment' here is completely inaccessible. The increase of entropy of that inaccessible environment is, in part, balanced by the entropy decrease of our, actual, present 'branch', due to its growing specification, or decoherence, or selection (in turn due to all measurements performed untill now). --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re:why can't we erase information?
A few random thoughts: Not only can't you erase information, in the MWI I believe you can't create it either. The constancy of information is another way of expressing the QM principle of unitarity. I think it's also tied to time symmetry. Universes with time symmetry would be unable to create or destroy information. The MWI is time symmetric (that is, the Schrodinger equation is time symmetric). Wolfram investigated a variety of CA systems, some of which happened to be time symmetric. Generally I think those were more likely to create very regular patterns, while it was the time-asymmetric ones that were more likely to be chaotic and show interesting patterns. One advantage of being unable to destroy information is that it automatically makes learning and memory possible. These capabilities are probably necessary for the evolution of intelligence. It's not clear though that complete inability to destroy information is necessary for memory to work though. Perhaps if we favor simple universes, there is basically a choice between complete information preservation vs universes where it is not preserved well at all once you move above the Planck scale (e.g. information might be 0.999% preserved per Planck time step, which is not at all for our purposes). The idea of a universe where there are a few obscure loopholes that break the laws of physics is possible in this model, but somewhat unlikely. And there is no guarantee that the loopholes would be easy to find. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Do prime numbers have free will?
John M writes: Tom Caylor writes: 1) The reductionist definition that something is determined by the sum of atomic parts and rules. So how about this: EITHER something is determined by the sum of atomic parts and rules OR it is truly random. Sum of atomic parts? I am not sure about the figment based on primitive observations and on then applicable explanatory calculative conclusions within the narrow model of the ancient scientist's views, called atom. Then again the phrase restricts its validity to THAT (figmentious) bunch of allaged atoms, period. Nothing exists as a cut-off singularity without intereffects. I understood Tom's phrase atomic parts as meaning component parts rather than literally what scientists call atoms. RULES to the rescue! how far are you willing to accept the rules? Do they involve the ambience, all the way to the 'end' of the existing world with ALL its intereffectiveness? In that case a different wording would be more appropriate...(Not the closed model) The bigger thing is your OR (in caps, meaning that it is exclusive). You prescribe only TWO alternatives. That would be right if we are onmiscient and exclude any other ways of that interactive endless world - allowed to be followed. It was deliberately left vague: the rules are not necessarily the rules of present day science, but the rules of any possible future science, or, as you suggest, the rules known by an omniscient being. Truly random IMO means that we truly believe in our ignorance to detect some (so far undiscovered?) 'order' with 'rules' leading to those 'truly random' results. Yes, this is just what I meant: the truly random is beyond *any* rules, including ones not yet discovered. Otherwise, it would not be truly random. Same with chaos: we just did not (yet?) learn that kind of processes in the wide world existence that would result in our chaos- called process. (Like random.) I'm not sure what you mean here. In principle, a chaotic process could follow very simple and well-understood rules. The difficulty is that a future state of a chaotic system may be so sensitively dependent on initial conditions that it is impossible to measure these conditions to the requisite level of accuracy. The limitation is practical, not theoretical. Your following words underline this position: There are two mechanisms which make events seem random in ordinary life. One is the difficulty of actually making the required measurements, finding the appropriate rules and then doing the calculations. Amen (difficulty?) Classical chaos may make this practically impossible, but we still understand that the event (such as a coin toss) is fundamentally deterministic, and the randomness is only apparent. Amen again (we don't know.) The other mechanism is quantum randomness, for example in the case of radioctive decay. In a single world interpretation of QM this is, as far as I am aware, true randomness. In a no-collapse/ many worlds interpretation there is no true randomness because all outcomes occur deterministically according to the SWE. However, there is apparent randomness due to what Bruno calls the first person indeterminacy: the observer does not know which world he will end up in from a first person viewpoint, even though he knows that from a third person viewpoint he will end up in all of them. Sorry to agree both with QM and the new version of the classical MWI. The former is a 2nd tier (linear? -after Alwyn Scott) version of the model 'physical views', the latter is beyond the level I like to speculate on. I find the randomness resulting from first person indeterminacy in the MWI difficult to get my mind around. In the case of the chaotic coin toss one can imagine God being able to do the calculations and predict the outcome, but even God would not be able to tell me which world I will find myself in when a quantum event induces splitting. And yet, I am stuck thinking of quantum events in the MWI as fundamentally non-random. Make yourself a god that could figure it all out. But the point is that it is *impossible* even in theory - even for an omniscient being - to figure it out. If I undergo destructive teleportation and two exact copies emerge in two separate locations, A and B, can I expect to find myself at A or at B? From the symmetry of the situation, I *must* have a 1/2 chance of finding myself at one or other location post-teleportation, and not even God can change this without changing the initial experimental setup. Eric Cavalcanti, some time back, objected to the above using the example of a computer game: if a player is jacked in as the first person character who undergoes teleportation to A and B, the game designer from his godlike stance can *direct* that he experience ending up in either A or B every time. The problem with this is that the symmetry of the original example is
Re: why can't we erase information?
On Mon, Apr 10, 2006 at 12:03:47AM -0700, Brent Meeker wrote: Russell Standish wrote: Unitary evolution preserves information. It is only through measurement by an observer that information can be created or destroyed. Usually, the second law is interpreted as the destruction of information (anyone observing a closed system will over time know less information about the system), so it puzzles me that you have the sign the other way. What? You're saying that if I observe a system, then I know less about it. You must be using some non-standard meaning of know. Brent Meeker Yes - in the case of milk being stirred into coffee. Strange as it may seem, you know more information when the system is initially structured than after that initial structure has dispersed. And yes you need to observe it. Entropy is undefined without an observer. Cheers -- A/Prof Russell Standish Phone 8308 3119 (mobile) Mathematics0425 253119 () UNSW SYDNEY 2052 [EMAIL PROTECTED] Australiahttp://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02 --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: why can't we erase information?
From: Russell Standish [EMAIL PROTECTED] Reply-To: everything-list@googlegroups.com To: everything-list@googlegroups.com Subject: Re: why can't we erase information? Date: Mon, 10 Apr 2006 18:34:42 +1000 On Mon, Apr 10, 2006 at 12:03:47AM -0700, Brent Meeker wrote: Russell Standish wrote: Unitary evolution preserves information. It is only through measurement by an observer that information can be created or destroyed. Usually, the second law is interpreted as the destruction of information (anyone observing a closed system will over time know less information about the system), so it puzzles me that you have the sign the other way. What? You're saying that if I observe a system, then I know less about it. You must be using some non-standard meaning of know. Brent Meeker Yes - in the case of milk being stirred into coffee. Strange as it may seem, you know more information when the system is initially structured than after that initial structure has dispersed. And yes you need to observe it. Entropy is undefined without an observer. Cheers As I understand it, you don't need exactly need an observer, you just need to identify various macro-variables (like pressure and temperature) which can be used to coarse-grain the phase space of the system, with entropy being proportional to the logarithm of the number of possible detailed microstates (detailed descriptions of the positions and momenta of all the particles, within the limits of the uncertainty principle) compatible with a given macrostate (descriptions of the system which only tell you the value of the macro-variables). Once you have chosen your set of macro-variables, they should have well-defined values for any system, regardless of whether it's being observed by anyone or not. Of course, the choice of variables is based on what properties we human observers are actually capable of measuring in practice, so I don't necessarily disagree with your statement, but I think it needs a little clarification. Likewise, I think the second law is interpreted as the destruction of information needs a bit of clarification--as entropy increases, there are more and more microstates compatible with a given macrostate so the observer is losing information about the microstate, but information is not really being lost at a fundamental level, since *in principle* it would always be possible to measure a system's exact microstate. Jesse --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: why can't we erase information?
Russell Standish wrote: On Mon, Apr 10, 2006 at 12:03:47AM -0700, Brent Meeker wrote: Russell Standish wrote: Unitary evolution preserves information. It is only through measurement by an observer that information can be created or destroyed. Usually, the second law is interpreted as the destruction of information (anyone observing a closed system will over time know less information about the system), so it puzzles me that you have the sign the other way. What? You're saying that if I observe a system, then I know less about it. You must be using some non-standard meaning of know. Brent Meeker Yes - in the case of milk being stirred into coffee. Strange as it may seem, you know more information when the system is initially structured than after that initial structure has dispersed. What's that have to do with observing it? Stirring milk into coffee isn't observing it - and as you point out below, entropy depends on observation, i.e. on some coarse grained constraint. Your answer seems to consist of non-sequiturs. ISTM that my knowledge is increased when I observe something. Physically this corresponds to some small decrease in the entropy of a few neural connections in my brain. This is accompanied by a relative large increase in entropy of my body which I have to make up for by consuming some low entropy organic material. Whether the entropy the thing I observe is increased or decreased by the observation is a different question. Brent Meeker --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Everything List group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
