Will the LHC Smash Supersymmetry? 196
gbrumfiel writes "The Large Hadron Collider is just getting ready for its next big science run. One thing researchers hope it will find is evidence for supersymmetry, a theory that could help to unify fundamental forces and explain mysterious dark matter. But as Nature reports this week, the LHC has shown no signs of supersymmetry in data from last year's run. If super particles don't appear by 2012, then physicists might give up on the theory for good."
Naive Question (Score:4, Interesting)
Suppose they prove super-symmetry and find the Higgs Boson, what are we going to be able to do with it. Other than completing the theory, is there any practical use for this new found knowledge?
Genuine question, physics isn't my forté.
Thanks,
To be precise... (Score:5, Interesting)
In fact Faraday's joke was better than that, It was the Prime Minister (in those days called the First Lord of the Treasury, hence your confusion), and the Government had recently introduced some unpopular taxes. So Faraday's actual reply, "I know not, but I wager one day your Government will tax it" was doubly apposite.
The other one of these Victorian quotes is the response of the inventor of the dynamo when asked what use it was: "What use is a new-born baby?"
Re:high enough energy? (Score:4, Interesting)
1: Pure phenomenology. No-one constructing inflationary models that I know of actually seriously believes that it's fundamental physics (at least, not after the second or third year of their PhD). What they *do* believe, frequently, is that the phenomenology can help guide a more fundamental theory. Personally I don't always agree with that; I think it can shroud a fundamental theory (in a similar vein to how cosmology is built on phenomenology that basically shrouds a very serious and neglected underlying issue).
Unless you're using the Higgs itself to drive inflation -- Guth's first model did this but it ran into problems with a graceful exit; it's recently been reawakened and re-examinded, though -- you're going to have a massive problem identifying an inflaton. We've not observed *any scalar fields whatsoever*. Even the Higgs remains elusive, though that might change in the near future. (Don't hold your breath.) So you immediately have a problem that what you're doing is specious. You can then either ground your inflaton in a well-reasoned model of high-energy physics or, and this is the standard approach, just invent a scalar field, call it the inflaton, and give it an arbitrary potential. So long as you make the potential flat enough that scalar field is an inflaton.
Basically it's phenomenology. But the people who do it are convinced it gives *suggestions* about what lies underneath, and in some ways they've got a point. Inflation works extremely well and it's standard to assume there was an inflationary epoch. You solve the horizon problem, the flatness problem and (if you believe in various GUTs) the monopole problem. (Basically -- why does the CMB look identical in opposite directions when the universe is too young for them to have ever interacted; why is the universe so fucking SMOOTH; and why do we not see any of these magnetic monopoles that GUTs produce in abundance?) Even more importantly, though, the quantum fluctuations of a scalar field coupled to gravity in the early universe produce tiny seeds that are basically exactly right. You can make models that get them exactly wrong but actually you have to work a bit; basic inflation made a prediction of those seeds, and when WMAP came along and looked at the CMB in unprecedented detail, it was dramatically confirmed. Basically those ripples had to be almost exactly Gaussian random, and "scale-invariant" meaning that the extremely large wavelengths were massively more powerful than the shorter wavelengths. That maps through to the formation of the CMB, when electrons condensed into protons to form hydrogen and light rays could suddenly free-stream carrying with them a photograph of the early universe. And it maps through even further, to the large-scale structure of galaxy clusters where we can look at those very same wavelengths. Much of a shift from those early imprints and that distribution is changed actually quite dramatically.
2: Dark matter is a big issue (well, duh). Basically "dark matter" is a catch-all term for whatever is causing rotation curves to deviate from the Newtonian prediction. I get irritated when people immediately assume it's a new exotic species of particle. I've put a couple of rants on this thread aimed at this kind of thing. My feeling is that dark matter in galaxies (and galaxy clusters) is made up of five or six different effects, *all* of which act as "dark matter", ie to flatten rotation curves: exotic particles perhaps, if supersymmetry is true; massive neutrinos since we now know that they are massive even if we don't know the mass, and neutrinos are so abundant that with *any* mass they form at least a dark matter even if it can't be the full dark matter (attributing the entire dark matter to massive neutrinos badly washes out structure on galaxy cluster scales); relativistic corrections coming from our naive assumptions that galaxies inhabit Minkowski (ie normal flat) space, since they don't, and that may -- *may* -- be able to account for up to roughly a tenth or more of spiral galaxies' dark matter; i