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== Consciousness as vibrating strings ==
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:That sounds more BS than string theory. But perhaps only slightly. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/121.209.152.190|121.209.152.190]] ([[User talk:121.209.152.190|talk]]) 19:10, 2 January 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
== Exaggeration regarding testability and science ==
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Bhny, your comment reminds me of those that attacked Galileo's, Newton's, and Einstein's theories. - Brad Watson, Miami [[Special:Contributions/66.229.56.118|66.229.56.118]] ([[User talk:66.229.56.118|talk]]) 14:42, 16 September 2011 (UTC)
== How is the string theory scientific? ==
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<blockquote>Since string theory is widely believed[who?] to be a consistent theory of quantum gravity, many hope that it correctly describes our universe, making it a theory of everything.</blockquote>
Really? It widely believed to be consistant? Consistant with itself? That means no divergences or infinities? Did somebody prove that? Or it's widely believed that somebody has proved that, even though nobody has actually proven that? I suppose we need a cite that many people believe something that isn't true. [[User:Sbharris|<
:The phrase "consistent with itself" is a tautology. These questions are the subject of countless papers that you may read, and yes all conceivable kinds of self-consistency checks have been passed. In practice, establishing consistency means checking in detail that all rigorously derivable conclusions are consistent with one another, its much more difficult to prove that all possible logical inferences that may ever be drawn will all be consistent, but so far there is no consistency problem whatsoever. If you want to be precise, the consistency of quantum field theory isn't a rigorously derivable truth either, but that doesn't mean its inconsistent. In fact there's a huge amount of evidence that it is consistent. So you're "who" tag doesn't make much sense. – [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 06:47, 8 December 2011 (UTC)
::QFT (or more precisely, non-Abelian guage theories without anomalies) are renormalizable and free of infinities. This basically makes the entire standard model (all forces but gravity), renormalizable, as t'Hooft proved in 1971. [http://www.staff.science.uu.nl/~hooft101/lectures/erice00.pdf] No string theory that predicts fermions has been proven finite and free of divergences beyond the 3-loop case. So the idea that string theories that are candidates to be theories of everything are "consistent," is rather like claiming that Fermat's theorum has so far passed all consistancy checks because the integers 3, 4 and 5 have been checked! [http://math.ucr.edu/home/baez/week195.html]. (Yes, I know Fermat's theory was finally proven for all integers, but that's not what has happened to any string theory that has any chance of being a discription of nature). Smolin's paper on these problems, that later was expanded into a popular book ([[The Trouble With Physics]]) is available here: [http://xxx.lanl.gov/abs/hep-th/0303185]. Here's what is says about consistancy, and it quotes from the group that has actually computed terms. <blockquote>(from page 34) "As it does not appear to be widely appreciated that the '''consistency''' of string perturbation theory is still open [26], I quote here from a recent paper by experts in the field, which announced the proof of consistency at the two loop level: (quote follows) '''Despite great advances in superstring theory, multiloop amplitudes are still unavailable, almost twenty years after the derivation of the one-loop amplitudes by Green and Schwarz for Type II strings and by Gross et al. for heterotic strings. The main obstacle is the presence of supermoduli for world-sheets of non-trivial topology. Considerable efforts had been made by many authors in order to overcome this obstacle, and a chaotic situation ensued, with many competing prescriptions proposed in the literature. These prescriptions drew from a variety of fundamental principles such as BRST invariance and the picture-changing formalism, descent equations and Cechco homology, modular invariance, the light-cone gauge, the global geometry of the Teichmueller curve, the unitary gauge, the operator formalism, group theoretic methods, factorization, and algebraic supergeometry. However, the basic problem was that gauge-fixing required a local gauge slice, and the prescriptions ended up depending on the choice of such slices, violating gauge invariance. At the most pessimistic end, this raised the undesirable possibility that superstring amplitudes could be ambiguous, and that it may be necessary to consider other options, such as the Fischler-Susskind mechanism[131].'''</blockquote><p>As Smolin makes clear, the problem with the (infinite number of) string theories is not what they show, but what people THINK they show. No, Mandelstam did NOT show that any string theory is free of all infinities, or even that it is free to the extent of what t'Hooft did for guage theories. Smolin himself believed prior to his review what this colleagues had been telling him, that at least some versions of 3-D string theory that describe actual known particles, or are capable of it, were free of infinities (which means they might possibly be true). So far, none has actually been proven to be so. <p> So, string theory is DIFFERENT from guage theory QFTs describing the 3 non-gravity forces of the standard model. So, in what sense does your sentence make sense? <p> As a second problem, what is this stuff about "theories of everything"? Because all string theories are dependent on a Minkowski SR background which does not change in time, so far there are no quantum gravity theories that are free of infinities for even strong field gravity waves, which are the needed kind to deal with. After all, the flat-space-limit weak-field spin-2 gravity quantum was presented in 1930, and nobody needs strings to describe it-- you can read about weak field "gravitons" in Misner-Thorne-Wheeler. The "gravitons" in all string theories today are this same weak-field gravity quanta, so the fact these particular gravitons have no infinities, is not very interesting, since weak gravity waves are obviously not strong enough to have any contact with a "theory of everything," and certainly are not "quantum gravity" as we need it. Plain old general relativity describes gravitational waves far more powerful than this, but of course by that time, the field is not quantizable. Weak field gravitons never had any infinities before anybody had '''thought''' of string theories, but then, they also never had enough energy to need anything but a linearized GR field description anyway-- so what's the point? In other words, if string theories reduce to [[linearized gravity]] (as they all do), but not [[general relativity]] (which they most certainly by definition do NOT do, as Smolin points out), then what's the point? All that means, is these theories reduce to a field theory that isn't even as accurate as the field theory Einstein came up with, in 1915. Einstein's generalization has passed tests (linear gravity doesn't predict Mercury's precession). String theory (if you can call it a theory) has passed no tests, but if it reduces in the end to linear gravity, as all 10<sup>1500</sup> versions of it do, it can't be a candidate for a theory of everything (TOE), since it isn't even a candidate for describing the orbit of Mercury, let alone more interesting physics. So again, '''which''' people hope '''which''' string theory will be a theory of everything, and which theory is it, that they have hopes for? There are more string theories than particles in the universe by far, but the right one certainly cannot be any of the background dependent-ones. And if Smolin is right, all proposed classes of string theories are background dependent (they live in 4-d asymptotically flat space-time, even if they do have extra dimensions), which means NONE of them can possibly be candidates for TOEs. <p> To put this another way: You see those loops that are supposed to be the "gravitons" in string theories? Do you see them actually bending the space-time through which they move? No? That's right, you don't. And that's a HUGE problem. Since in any "Theory of Everything," they must. [[User:Sbharris|<
::: Despite your frequent use of the caps lock, almost every sentence you wrote is wrong. All string theories (or more precisely, all corners of string theory) possess [[general relativity]] as their low energy limits, not linearized gravity. This is a completely unambiguous, quantitative conclusion you can see worked out in detail in any string theory textbook. You should not be using a popular level book as you singular resource in order to dispute the most basic facts about what string theory implies, especially if its a book written by a person whose sole purpose is to reduce the stature of string theory and get more people to work on his own idea. String theories are fully diffeomorphism-invariant, i.e. they possess the same gauge symmetry as general relativity, and frequently this freedom is used to ''gauge fix'' to flat space in order to make calculation easier, but any suggestion that string theory is wedded to flat space is quite far removed from reality. If this was true, string theory would not have anything remotely approaching the interest and activity that it does. (and again its pretty hard not to notice if you step one inch into actually learning the subject)
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::::'''Polchinski also acknowledges the difference, when he says, “In string theory it has always been clear that the physics is background-independent even if the language being used is not, and the search for a more suitable language continues.” But this is not the most accurate way to put it. It would be more accurate to say, “Some string theorists believe that the formulations of perturbative string theories and dualities between them that they study concretely are approximations to a deeper, background independent formulation. This missing background independent formulation is not just a different t language for the theory, it is hoped to be the statement of the principles and laws that define the theory, from which everything studied so far would be derived as an approximation. Despite this belief, only a few concrete proposals have been made for the laws and principles of this conjectural background independent formulation of string theory and none has gained wide support.”''' [end of quote]
::::You can read the whole thing on the link. String theory is not wedded to flat space, but neither is it completely free of needing a space to back it. Indeed as you know, the various anti de Sitter spaces in [[AdS/CFT]] become more and more difficult to use in theories when the global universe they are supposed to explain is a manifestly de Sitter universe, with a positive cosmological constant. Something just being discovered by the Hubble Space Telescope as Maldacina made his first conjecture (alas). Which is still a conjecture. At least Ed Witten has admitted that string theories giving rise to de Sitter universes like ours, don't look like anything thought of, so far. [[User:Sbharris|<
::::: Again, Im not going to sort through all of your misconceptions and resolve them all for you, but what you say is wrong and ''demonstrably'' so. You can quote Smolin all day long, but these are quantitative questions that have been decided in ''papers'', not in popular-level books. The AdS/CFT is not in any way critical to these arguments and I didn't bring it up. The key point was that string theory possesses the same diffeomorphism symmetry as general relativity, and implies Einstein's equations as a low energy limit. Those are two unambiguous facts that are true of string theory as it exists today, not some dreamed about completion of it. They are pretty important things to know about it, and I cant guarantee I will continue conversing with someone who wont acknowledge these basic characteristics of the topic in question. Again, your wrong statements include your assertion that de Sitter space and moduli are "major unsolved problems". Does the actual literature written on these topics matter at all? I will leave a few recommended selections here. [http://arxiv.org/abs/hep-th/0701034v3] [http://arxiv.org/abs/hep-th/0610102] [http://arxiv.org/abs/hep-th/0503124v2] [http://arxiv.org/abs/hep-th/0505160] – [[User:Isocliff|Isocliff]] ([[User talk:Isocliff|talk]]) 05:06, 11 December 2011 (UTC)
== Popper and testability ==
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::::::::::: Wow, this still? Let me try to boil this down: String theory is not "shown" to be scientific in any particular place because it's status as a scientific theory is not seriously questioned in the scientific community (its correctness, on the other hand, is). If it were not science, there would not be O(1000) or more papers published in peer reviewed physics journals like Physical Review, MIT's course on string theory would be classified as math or something else instead of physics, and so on. Its quite easy to agree that ordinarily the claim that a given scientific theory is, in fact, science would not be noteworthy, but its obvious why this case is an exception: because there is a widely-selling popular-level physics book, as well as one of the most trafficked physics blogs on the internet, claiming otherwise. Im not opposed to having this book, as well as Smolin's, included in the article; since they surely have some significance (though not much in the way of rigorous content bearing on the scientific question itself). However, as long as the claim that string theory is not science is being presented, the article also deserves an explicit recitation of Popper's criterion, as well as the rigorously derivable properties of string theory that show unambiguously that it fits that criterion.
::::::::::: I noticed earlier that the phrase "de facto untestable" was criticized. Let me say that this was my phrase, and I basically chose it as a compromise with whatever was in there before – I dont remember exactly what the previous language was that I replaced, but it seemed too clearly wrong to stand. I choose this language because it does represent a claim about string theory that is not rigorous, and thus may take on varying shades of truth, depending on what a more detailed study of the landscape of phenomenologically viable solutions yields. That string theory is ''testable'' and that it is science according to Popper's criterion are empirical facts. That it may not be feasible to test ''in practice'' is more subtle, and thats what that language I chose was hoping to convey. I dont agree that string theory is de-facto untestable (or at least I think its too early to claim that), but this is at least a claim that is not rigorously ruled out, and I think it accurately captures what many of the more skeptical physicists think, yet it is distinct from the wrong statements that string theory fails to be science. <
:::::::::::: Isocliff, the dispute currently is not whether string theory is science. Personally, I consider string theory within the realm of science, for reasons like "it is done by science departments". Indeed, I think this issue is clear in the article. The first line is, after all: "String theory is an active research framework in particle physics..." No one is saying its Math or English.
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