http://www.scientificamerican.com/article.cfm?id=beautiful-theory-collides If SUSY is dead, and that looks likely, then does that also mean that dark energy/matter is also dead? And hence BB is in deep trouble again?
It does seem so, as an educated guess, but at least we can wait a few weeks or whatever it takes. If there was no big bang, then red shift has to represent an energy loss, with blue shift being a gain. How it is felt that SUSY failing has a bearing on the big bang? Anything to do with so-called undetected 'photinos' having to balance the photons as their supposed antiparticle?
For the math of inflationary theory to work dark e/m was proposed, but without dark e/m then inflation becomes problematic I believe.
So here's the deal: you've lost something and it can't be found, somewhere on the surface of the earth. You look in your living room and can't find it. Do you give up the search? The problem with the statement that "SUSY is dead" is it presupposes what "SUSY" means. Supersymmetry, as a framework, will _never be dead. Oversimplified, highly specific theories are dead. Large chunks of the observable parameter space, which only account for a very small percentage of the total parameter space, are dead. But SUSY, by itself, is very much alive and well.
No. SUSY is dead, and so is dark matter in the form of WIMPs. But dark energy isn't - space is dark, and we have good evidence that it's expanding and that vacuum energy is real. As for dark matter, energy has a mass-equivalence. So dark matter is a just a region of space where the energy density is higher than average. No WIMPs required.
John Ellis speaks... I mean writes. http://arxiv.org/abs/1102.4585 I don't see that Farsight speaks to the data at all.
Yeah yeah rpenner: "We present updated predictions for the gluino mass, m_gl, the light Higgs boson mass, M_h, BR(B_s to mu mu) and the spin-independent dark matter scattering cross section, sigma_SI. The CMS and ATLAS data make inroads into the CMSSM, NUHM1 and VCMSSM (but not mSUGRA) parameter spaces, thereby strengthening previous lower limits on sparticle masses..." Don't you get it yet? There's no evidence at all for "sparticles". And these guys, who don't understand the electron never mind the gluon, are running out of wriggle room. It ain't going to be pretty.
Well, this happens to be the exact area I am doing my PhD on, I do Bayesian studies of these kinds of SUSY models, and it turns out that the parameter space so far killed doesn't really contain very much probability. So it would be unwise to pay your bets out quite yet. Especially because, as was mentioned, these are highly constrained models of around 5ish parameters which are subsets of the MSSM (minimal supersymmetric standard model) which itself has around 100 parameters. A 100 parameter theory is impossible to study phenomenologically so we are forced to look at the simplified models. Then you can make things more complicated, i.e. the NMSSM (next-to-minimal supersymmetric standard model) which has less fine-tuning issues, and subsets of that which are fairly analogous to the MSSM ones you quoted there. And so on. It is as Ben says; SUSY isn't just one theory, so you can't kill it so easily. You have to kill each manifestation of it as theorists think of them. Which is what these papers are trying to do.
The big bang depends in no way on SUSY. However, a major constraint on SUSY theories is how much dark matter they predict, which is determined by considering the thermodynamics of the early universe. The interactions need to be tweaked so that you don't end up with too much and contradict the astrophysical observations. There is no such particle as a 'photino', the physics is supersymmetric somewhere above the electroweak symmetry breaking scale, when there was no photon, Z or W bosons, just the fundamental U(1) and SU(2) gauge bosons which mix together to make the low energy stuff we see. So you have superpartners for the gauge bosons (called gauginos, or specifically winos (SU(2) partners) and the bino (U(1) partner) which mix together with some higgs boson superpartners (higgsinos) into different things, called neutralinos and charginos. Neutralinos are the usual dark matter suspect, which is another constraint: if a neutralino isn't the lighest superparticle then you generally have a charged dark matter particle, which wouldn't be dark at all, so that's no good. That is the story in the MSSM anyway, which is what people are usually talking about when they mention supersymmetry. The NMSSM is pretty much the same though, although the higgs sector gets fiddled with a bit. edit: ok apparently some people call the lightest neutralino the 'photino', but I have never heard this before I googled it just now, and it seems like a very misleading name, so I am going to boycott it Please Register or Log in to view the hidden image!.
Err, you have to have something in said region of space for the energy density to be higher than average. The energy density of space isn't going to vary for no reason.
No. I've been busy of late, and it dropped off my radar. I'll take a look. Edit: but I've got to go now. Sorry.
Who put you up to that? I'm sorry, but Bayesian "studies" in this context is an attempt to drape a cloak of respectability over the lack of scientific evidence. Noted. But take care that you aren't left with a PhD thesis on something that's going out of favour. You could end up like Ben. Out of physics. A "quant". No you don't. Think about the self-energy of a gravitational field. In a gravitational field 100 miles above a planet the spatial energy density is higher than it is a billion miles away. There's nothing in this region causing it. What does cause it is a concentration of energy tied up as matter. And it's 100 miles away.
Do you know anything about probability theory? These are actually the ONLY ways to understand quantitatively what the scientific evidence tells you about a theory. My thesis is more about the probability theory than the SUSY so that isn't really a concern. Besides, there are much worse things than being a quant, he probably makes more money than I ever would if I stay in physics. Note that this still requires some non-gravitational energy somewhere. Also this self-energy is perfectly well described by the curvature of space around the masses involved, which has been shown to be insufficient to explain (for example) the observations of gravitational lensing around galaxy clusters without the addition of a lot more mass. This discussion is off-topic though, it has nothing to do with how "dead" SUSY is.
Isn't it a strong statement? In my limited understanding, such a statement can be backed up by only two reasons. One is as in "Newtonian mechanics will never be dead", which is that we know Newtonian mechanics works very accurately in everyday situations, so any new theory must in certain sense contain Newtonian mechanics. As far as I know, supersymmetry deos not qualify this reason. The other reason is as in "if it is at all possible for humans to know the all encompassing physical law, it must be expressible in terms of mathematical equations or relations", which is almost a tautology because anything logical that we can think of is by definition part of mathematics. As far as I understand, there has not been any derivation of the kind that replaces "mathematics" in the above statement by "supersymmetry". Obviously, supersymmetry as a mathematical theory will never be dead, but if you meant supersymmetry as a theory in physics as the general trend in this thread seems to be, I would be happy to be enlightened.
"Never" is probably a little strong, but it's hardness to kill totally is not unlike the hardness to kill string theory. The low energy versions that are being looked at now can be killed, and as we build bigger and better accelerators we will be able to kill it at higher and higher energies, but as I understand it (and I don't know much about higher energy SUSY) there is no intrinsic reason why it can't manifest at some ridiculously high energy where we'll never see it, similarly to string theory. I feel like these different versions should be discussed separately though; it should be emphasized that it is only weak-scale SUSY which is currently being probed, nothing more. Of course if we don't see it in the next few years that is going to just about rule it out as the answer to the Higgs fine-tuning issues, dark matter, etc, which is a pretty big deal.
Yes. Sorry kurros, but there is no evidence for SUSY. OK noted. Yes. But it's somewhere else. That's space-time curvature. It isn't curved space, it's inhomogeneous space. But OK if you think this is irrelevant to SUSY, let's leave it at that.
Yet another example of your dishonesty. You tried this one on me, remember? You asked if I'd got a job yet and then if it was in physics. Both of which I answered 'yes' to. Both replies you then promptly ignored because it didn't fit the narrative in your head about how string theory PhDs are worthless. The fact Ben isn't in physics any more doesn't automatically imply his PhD worthless or his ability lacking. How many people end up in jobs not directly related to their most recent academic qualification? The majority. Its clear they weren't all forced into such a situation due to poor qualifications or subject choice. As such you need to demonstrate that Ben wanted to continue in academia but couldn't precisely because his thesis area is unpopular. The fact there's one (at least) string theory research position open each year in most high energy physics departments in the US and UK shows such a view would be false. The fact he's taken a very academic subject and gotten a very sort after job (as have I) shows your view that string theory PhDs are somehow a black mark on a CV is just nonsense. Pull your head out of your ..... ahem little self made world... Farsight, your views on how physics, academia and science in general simply aren't supported by reality. I could stop there but let's hammer the point home again. Both Ben and I did string theory PhDs. Both of us got jobs within months (weeks even) of starting to look, not too bad in todays job climate. Both of us got work published in journals, reputable journals. Both of us got employed to teach physics like quantum mechanics or special relativity to undergraduates during our postgrad periods. Both of us have been held to a high standard expected in physics and both of us have meet that standard. Now let's consider you. All your work has been rejected by every forum you've put it on (and that's a LOT of forums), every journal you've submitted it to, every publisher you're sent it to. So much so you've resorted to vanity publishing, appearing on a batshit crazy TV show and taking out ads in physics magazines. None of that should be necessary if you had been even close to meeting said physics standard. Before you try to insult others for how they've sent the last few years of their lives and what they've accomplished you need to take a good long look in the mirror. Just try not to admit your biceps when you do so, we all know how good an arm wrestler you believe yourself to be......
