Timeline for Where does matter come from?
Current License: CC BY-SA 2.5
27 events
| when toggle format | what | by | license | comment | |
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| Jan 5, 2011 at 21:32 | comment | added | user346 | @moshe - that is why I trust you, and others on this site, to intensively interrogate any statements I make! | |
| Jan 5, 2011 at 21:30 | history | edited | user346 | CC BY-SA 2.5 |
semantic change
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| Jan 5, 2011 at 21:25 | comment | added | user566 | We are both in the same boat, I am also enthusiastic about what I do, and have to control the natural urge to share that enthusiasm by overstating things. I just know from experience how fast this can degenerate into a discussion focused in its entirety on great sounding but half baked ideas. | |
| Jan 5, 2011 at 21:20 | comment | added | user346 | I say this in my answer about these approaches - "the viewpoint favored by approaches such as Non-Commutative Geometry, LQG ...". That is clearly not a statement of established fact, and is also more a statement of my personal opinion. In any case, I appreciate and understand your concerns and will try my best to keep them in mind. | |
| Jan 5, 2011 at 21:16 | comment | added | user566 | Both Lisi's and the braid models you mention (both of which I am actually quite familiar with) are works in progress which may or not pan out in the end. I have no problem with that, presenting them as an established fact is what I was having a problem with. | |
| Jan 5, 2011 at 21:08 | comment | added | user346 | @moshe - I did not mention Wheeler's geons in my answer. I was referring to far more recent models such as the braid model of Bilson-Thompson. On another note, I'll include whatever I feel is legitimate in an answer. You are free to disagree and down-vote, and if you wish to dismiss a viewpoint as out of bounds for discussion before you've even had a chance to look at the details is your prerogative. | |
| Jan 5, 2011 at 15:44 | comment | added | user566 | I was not referring to E8 which I could not care less about, just to your original answer. When a non-expert comes and ask a question, I'll let him know what is known with near certainty (the answer to this question has probably to do with reheating). I also like the idea of matter from geometry, and Wheeler's geons and all the rest, but the fact is that this idea currently plays no role in accepted mainstream theories, and in most research directions to extend them. That may change in the future, at which point it would be legitimate to include it in an answer. | |
| Jan 5, 2011 at 15:29 | comment | added | user346 | @moshe - only time will what is or is not the true value of "exotica". A quote by this guy named Gandhi comes to mind: "First they ignore you, then they ridicule you, then they fight you, then you win". We're at stage two right now in the E8 business, it seems. Only two more to go. Cheers! | |
| Jan 5, 2011 at 15:22 | comment | added | user566 | @ Matt: People promoting their favourite exotica instead of sticking to mainstream ideas is one of the failure modes of this type of effort (I am sure you could think about other such examples). Not sure what is the solution, but people more committed than myself should probably think about this. | |
| Jan 5, 2011 at 12:22 | comment | added | user346 | I have no problems with a theory being right or wrong. But dismissing a scientist, with a credible research history, simply because Jacques Distler or some other deity has proclaimed them to be a heretic is kind of Dark-Ages, don't you think? Besides you've finally given me motivation to get together everything I have on $E_8$. Oh, I can't wait. That rhymes! If only John Baez was on this site I wouldn't have to spend so much time defending Lisi. | |
| Jan 5, 2011 at 12:04 | comment | added | Marek | @space_cadet: I don't think this is right place to discuss Lisi but a note is in order: I don't know whether he is crackpot but his $E_8$ theory makes no sense and was criticized by many outstanding physicists. I don't like how you call Matt either chauvinistic or a censor. In science theory is either right (for the time being) or wrong. Some of the theories are just bound to be wrong and this is one of them. Why do you have problem with that? Of course, this comment box can't address Lisi's theory. Try asking a question, I'd be happy to provide an answer as to why his theory can't work ;-) | |
| Jan 5, 2011 at 7:14 | comment | added | user346 | Lastly coming back to your question as to "in what sense [do] either string theory or non-commutative geometry imply that matter is topological defects?". I'll let 't Hooft tackle this one. He does a much better job than I can :) Reference Of course, this work is somewhat hand-wavy in character but so was 't Hooft's 1992 paper on the Holographic Principle, and look how that one turned out! | |
| Jan 5, 2011 at 7:03 | comment | added | user346 | On the GUT issue ... ok, I'll happily abandon the word abandon in favor of something more neutral. GUTs do provide a nice picture and if you happen to have faith in them then I'm surprised that you find Lisi's work unappealing. I would think that $E_8$ being the largest exceptional lie group is a triumphant culmination of the GUT perspective. Or maybe I just don't know what I'm talking about :) | |
| Jan 5, 2011 at 6:58 | comment | added | user346 | "At any rate, I think this site should have answers involving accepted physics, of which GUTs are an example and whatever Lisi is doing isn't." - @Matt at best that sounds chauvinistic and at worst it sounds like censorship. Clearly you're speaking to someone who believes strongly in the general direction that Lisi's research is headed in. Given only his papers on arXiv (and ignoring his personal life) it would appear that he is a serious scientist. I've noticed this sentiment about Lisi's work expressed before on physics.se and it troubled me then and it troubles me now. | |
| Jan 5, 2011 at 6:10 | comment | added | Matt Reece | On the second point, I guess I was misreading you. But I still don't agree that GUTs are being abandoned. There's not a huge amount of active research on GUTs, because the underlying ideas have already been worked out. But unification of gauge couplings remains one of the most compelling reasons to hope that supersymmetry will be found at the TeV scale. Whether new physics can be fit into a GUT will definitely be something that people will be thinking about a lot when (let's hope) the LHC discovers new physics. | |
| Jan 5, 2011 at 6:06 | comment | added | Matt Reece | Your statement was about what GUTs attempt to do. They don't attempt to unify families. The fact that Garrett Lisi does is neither here nor there; I'm not going to argue about the definition of "crackpot," but his theory made little sense and rather than try to understand the obvious criticisms he seems to keep writing papers on the same thing. At any rate, I think this site should have answers involving accepted physics, of which GUTs are an example and whatever Lisi is doing isn't. | |
| Jan 5, 2011 at 5:36 | comment | added | user346 | Each one of your point being absolutely valid, my answer was directed at a less specialized audience. Now to your questions. 1. The hope behind Lisi's $E8% theory (no @marek Garrett Lisi is not a crackpot) was that it contained three copies (or "generations") of leptons and quarks. Apparently Jacques Distler has shown that this is not the case. But that is what is meant by "family unification". 2. I didn't say anything about abandoning field-theory ideas. I was speaking of the GUT approaches based on larger and larger groups. 3. This is too big to tackle in a comment. Maybe I'll add an edit. | |
| Jan 5, 2011 at 4:17 | comment | added | Matt Reece | I don't know what you mean by saying that bigger groups "contain all three families" of particles. The groups contain only gauge bosons; each generation of particles we know fits into some representation of these groups, but the generations are not unified. Also, I absolutely do not agree that research is "abandoning" field-theoretic ideas, which if nothing else are valid descriptions of low-energy physics. It's not at all clear to me in what sense either string theory or noncommutative geometry imply that matter is topological defects. | |
| Jan 5, 2011 at 2:34 | comment | added | yunone | @space_cadet, thanks for this answer, I appreciate the mathematical description you've given, as I'm more a math student than a physics one. | |
| Jan 4, 2011 at 15:38 | comment | added | user346 | "I don't believe anyone holds such a view or that it is in any way useful" ... but that's exactly my job @Marek :) I'm not saying that strings themselves are defects, but that when they wrap and coil up forming manifolds with various topologies, that those can be considered as defects with respect to a uniform background geometry. | |
| Jan 4, 2011 at 9:09 | comment | added | Marek | Regarding string theory: various particles are just excitations of the strings so your statement amounts to saying that strings are topological defects. Even if this view could somehow be made correct (e.g. by interpreting open string attached to a brane as topological torus) I don't believe anyone holds such a view or that it is in any way useful. | |
| Jan 4, 2011 at 5:16 | comment | added | user346 | Sure they do. I have nothing against them. They just defeat the purposes of discussion. | |
| Jan 4, 2011 at 4:32 | comment | added | dmckee --- ex-moderator kitten | @space_cadet: "Hit-n-run downvotes" has some currency. | |
| Jan 4, 2011 at 3:28 | comment | added | user346 | What do you call it when someone votes down without giving a reason? Downvote-and-run (as in hit-and-run)? | |
| Jan 4, 2011 at 2:19 | comment | added | user346 | Thanks @wsc. And yes, this perspective is completely in line with Wen's string-net paradigm. When Wen (pun intended) gave a talk some years back I remember thinking - "this guy's going to win the nobel prize". At the end of the day, I strongly believe, that dynamics of LQG will be understood only in the light of condensed matter. | |
| Jan 4, 2011 at 1:59 | comment | added | wsc | Up-voted. I don't really know how popular of a viewpoint this is, but it's one that I've always found strikingly beautiful. Also worth mention (though it's similar to the mechanism in LQG, it's more appealing to condensed matter folks) is the string-net condensate of Wen and Levin. | |
| Jan 4, 2011 at 1:38 | history | answered | user346 | CC BY-SA 2.5 |