vincent

I think you mean "asymptotically free".

The above is really a result of a basic misunderstanding of the mass-energy equivalence you and martin seem to share. The mass-energy equivalence is not meant to apply in this way to individual elementary particles. Rather, it is a statement about the general interconvertability between mass and energy. The kind of statement the mass-energy equivalence does make about photons, again in the context of quantum electrodynamics, is that it’s energy can be converted to invariant-mass of electrically charged particles like the electron and vice versa. For further clarification, if you need any, you can consult any introductory text on the subject of special relativity. Whichever text you might choose, I am quite confident that you will find nowhere in it any statements along the lines of what you and martin are saying. Respectfully, Vince.

I pm'd you.

It appears that you have misjudged my intentions for intiating this thread. I'm not focussing on the idea that "energy is required to encode information". What I'm focussing on is the possible implication of the black hole area-entropy relation that energy and information are somehow interconvertible in the context of black hole physics, sort of analogous to the way that the mass-energy equivalence says that energy and invariant-mass are interconvertible. I'm sorry, but the idea of this thread was to refocuss the discussion on what in my opinion should have been the focus in the other thread. Merging the two threads not only makes no sense, but it would represent an abuse of authority on your part.

I’m initiating this thread because I don’t think people appreciated that this was the key part of Wheeler’s remarks. One of the main themes of the first thread was the obvious point that energy is needed to physically encode information. We don’t really need to examine the concepts of time or interpretive issues having to do with quantum mechanics to understand why this statement makes sense. But the question of the relation between information and energy takes it’s sharpest form in the case of black hole physics. This is because of the famous black hole area-entropy relation which says that the entropy of the event horizon is completely determined by the mass of the black hole. There is no analogous statement relating the energy of a system and the information encoded in it anywhere else in physics. This statement doesn’t just say that the entropy of a black hole is encoded in it’s mass. It suggests that somehow black hole entropy and black hole mass are the same thing! The question than is what does this say about the nature of the fundamental degrees of freedom of black holes? Is it possible that in some sense black hole degrees of freedom don't gravitate in any ordinary way? Is it possible that (as I believe someone suggested in the other thread) information can in some sense gravitate? Note that here we're discussing the entropy of a black hole and not the problem of how information encoded in matter that falls into a black hole is recovered. The problems associated with this latter subject are usually referred to as the black hole information problem.

Hi Martin, You didn't respond to my earlier post: What I pointed out there was that contrary to your above remark, there is nothing about the existence of massless particles that implies that the applicability of the mass-energy equivalence is somehow not universal. In fact, it is in terms of the mass-energy equivalence that we understand why there are processes in quantum electrodynamics in which photon energy is converted into electron and positron mass and vice versa! I'm just curious why you would believe that the mass-energy equivalence, which is perhaps the world's most famous equation, doesn't apply to massless particles?

Who do you think you are? You’re not a moderator and the posts have kept well within the posting guidelines. No one is forcing you to participate here.

What are you talking about!? There is nothing about the existence of massless particles that implies that the applicability of the mass-energy equivalence is somehow not universal. In fact, it is in terms of the mass-energy equivalence that we understand why there are processes in quantum electrodynamics in which photon energy is converted into electron and positron mass and vice versa. Okay, bye.

Where do you live?

This is the wrong forum for your question. You should have it reposted in the quantum theory forum.

Hi Mr Skeptic, I'm sorry but this is actually the wrong forum for this post. Try the classical physics forum. Hi Martin, This response is inappropriate. As a moderator you're responsibility was to tell Mr Skeptic what I just did and then move his post to a more appropriate forum.

No, when it comes to physics, Ben likes to think in terms of physics.

I disagree. The underlying reason for the absence of mixing of the charged leptons is that neutrinos are (very nearly) massless. Consider the neutrinos in the charged weak current for leptons in terms of mass eigenstates. Since the different neutrinos are massless, they are degenerate so that any unitary transformed neutrino states can be taken as mass eigenstates. The unitary transformation can thus be taken as the identity matrix. Therefore significant lepton mixing via the charged weak current can never show up in any physical process.

Only logically inconsistent theories can predict anything you want, and string theory has passed every one of the numerous self-consistency checks it has ever been subjected to. Given it's complexity and the fact that we still don't know what string theory is, this must be viewed as a highly nontrivial fact. Keep in mind that it took nearly two and a half millenia for the atomic hypothesis to be verified and that there were plenty of skeptics right up until it was. String theory on the other hand has been with us for less than fifty years. Given the fact that it is the only theory we have that appears to include the ingredients necessary for understanding all of the fundamental interactions in an absolutely natural, beautiful and coherent way, you'll understand why very nearly the entire physics community thinks it deserves a bit more time than you seem to think it does. By the way, where did you get this pearl of wisdom? I'm guessing not from studying string theory.

You shouldn’t have commented at all. I made it quite clear that this thread is for people who are interested in understanding string theory, and you've made it quite clear that you're not one of them. So please don`t further pollute this thread with your OT and unhelpful remarks.

Hi everybody, Let me be absolutely clear that by "strings physics only" I mean to not only exclude discussions of alternative theories, but also restrict discussion to technical and conceptual issues in string theory itself. If someone wants to discuss alternative theories in relation to discussions in this thread, they should initiate a new thread for that purpose. This thread is meant to help members (including myself!!!) deepen their understanding of string theory on it’s own merits and not in comparison to other ideas. To those members searching this statement for loopholes to exploit, I expect posters in this thread to also respect the spirit in which these remarks are intended, which should be quite clear to any half-way sentient creature posting in this forum.

It just seems to me that you`re searching for a way to evaluate string theory and it`s prospects without actually understanding string theory.

Precisely! Look fredrik, this sort of research cannot be done in the kind of organized way you`re promoting because we don`t know what's ahead and are constantly getting surprised. What we do know is that string theory has passed every one of the enormous number of tests of self-consistency it has ever been subjected to and is the only theory we have that appears to have all the ingredients necessary to solve all of the outstanding problems in this field of physics. As well, unlike virtually every other approach, string theory was not invented, it was discovered. This is why every other approach looks contrived in comparison. Some of these alternative ideas are interesting in certain respects, but none of them really stand comparison to string taken as a whole. This isn`t just a matter of how open an attitude one has. There are very good reasons why string theory dominates high energy theory and quantum gravity.

Hello again Martin! If you’re unsure what string people do mean, how can you be sure what they don’t mean? I already answered your questions with clarity and precision. In fact, what I posted was strings 101. I suggest you take a look at any of the by now numerous introductory textbooks on these topics. (Perhaps a look at some of the popular literature might make sense for you. I mean no offense by this). Unless you have any honest questions, I don’t know what else I can say to you.

One objective of quantum gravity is to obtain the correct Hilbert space of states of any given spacetime. If you like you can refer to these states as different quantum spacetime “geometries”, but the difference in usage of the term “geometry” among different groups of researchers is more cultural than anything else since we’re all after the same thing in the end: A quantum theory of gravity. It should be said though that the term quantum gravity may be a bit safer than quantum spacetime geometry since spacetime may turn out to be an emergent concept in a way that makes the term quantum spacetime geometry inappropriate. The object describing spacetime geometry in string theory is the same object that describes spacetime geometry in General Relativity which is the metric. This is because string theory contains General Relativity. In fact, General Relativity is encoded in string theory at the quantum level since the background fields in the world-sheet theory must satisfy the gravitational field equations of General Relativity if there is to be no quantum conformal anomaly. Quite remarkably, these equations turn out to be nothing less than the conditions on the beta functions that ensure conformal invariance beyond the classical level. These conditions also determine the number of spacetime dimensions. Such theories give us perturbative descriptions of "quantum spacetime geometry". There are nonperturbative approaches as well which include the theories that satisfy the so-called gauge/gravity correspondence. These theories are the only known complete and self-consistent quantum theories of gravity we have. The reason we know that these theories are complete and self-consistent is that the theories on the gravitational side of the correspondence are dual to various Super Yang-Mills theories which are well-understood. It’s quite amazing that theories that don’t involve gravity should be equivalent to theories whose degrees of freedom are purely gravitational.

Then why are you posting in this thread? Does the no hijacking rule not apply to moderators?

Hi iNow, I obviously posted in the wrong thread. Sorry about that. I added my response to your above post at the end of my original post which I've copied to the correct thread http://www.scienceforums.net/forum/showthread.php?p=358312#post358312

Right. It is a direct result of the basic principles of quantum mechanics that the narrower the probability distribution of one obervable is, the broader that of it’s conjugate will be. However the time-energy inequality is not on the same footing as the position-momentum uncertainty principle since there is no Hermitian operator corresponding to time. Yes, time is a dynamical quantity in that it varies with time, but in a trivial self-referential way and is really just a parameter on which other quantities depend. The actual meaning of ΔE and Δt in the time-energy inequality are respectively the spread in the energy distribution and the amount of time it takes for the wavefunction to changed appreciably. …therefore contradicting the tenets of quantum mechanics. Fine. But I would apply the term “on a much deeper level” instead to the relation between the uncertainty principle and the principle of complementarity. When due to the basic principles of quantum mechanics the use of one classical concept excludes the use of another, they are said to be complementary. The principle of complementarity says that the experimental arrangements that measure complementary properties are mutually exclusive and are both needed to demonstrate all of the physics of quantum mechanical systems. For example, consider wave-particle duality as applied to an electron which is the first form in which one usually encounters the concept of complementarity. Wave-particle duality is often erroneously described as meaning that the electron is simultaneously wave and particle. But this is impossible since particle and wavelike characteristics are strictly incompatible. What saves us is the uncertainty principle which says that there are no experiments one can perform in which the position of the electron, this being the particle aspect, and the momentum of the electron, this being the wave aspect, can be simultaneously measured to arbitrarly high precision. Thus the deeper meaning of the uncertainty principle is that it is the condition that ensures the logical consistency of quantum mechanics. A unitary quantum theory is one in which probability is conserved. Though they're pathological, one can imagine nonunitary theories in which the uncertainty principle formally still holds. All I can do is explain the role of the uncertainty principle in quantum mechanics. Do you believe that the uncertainty principle has a deeper role in quantum mechanics? Do you believe quantum mechanics to be incomplete?