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Comment: Re:No, there is no evidence of BSM yet (Score 1) 97

The SM doesn't specify what the neutrino masses are; they're free parameters just like the quark masses. Some people might be surprised that they're nonzero, but I'm not one of them. Personally, I think some of those some people are feigning surprise so they can pretend nonzero neutrino masses count as BSM, which is a bit silly.

Comment: No, there is no evidence of BSM yet (Score 5, Interesting) 97

I am a particle physicist, and I have worked directly on this problem. The uncertainty in the hadronic contributions to the vacuum polarization and light-by-light scattering are large enough that the supposed BSM signal is not significant.

That is, you can do nice high-order paper-and-pencil calculations of Feynman diagrams when the particles involved are electrons and muons, but there are important cases where the particles contributing to this effect are composite: hadrons (which are made of quarks). Since you cannot do calculations on hadrons without considering how the hadron is composed of quarks, you can't avoid getting into strongly coupled quantum chromodynamics (QCD). See here for further discussion: Hadronic Light-by-Light.

That means you can't do your calculation on paper, you have to use a supercomputer and something called lattice QCD. Unfortunately, it's easier to crank out a thousand crappy model calculations of BSM that is supposedly showing up than to properly fund studies of the theory uncertainties. As a result, the precision of the theory values are not good enough to establish whether the muon magnetic moment is consistent with the Standard Model or not.

That said, it's still an interesting place to look, and somebody will work out all the uncertainties eventually. In a few years, there might be something to talk about seriously.

Comment: Random starting configuration, eh? (Score 1) 100

by Xerxes314 (#46862749) Attached to: The People Who Are Still Addicted To the Rubik's Cube
So the starting configurations for setting the Rubik's cube record are random. If I wait long enough, the starting configurations will randomly be the identity transformation, and I can solve the cube in 0 seconds. Therefore, in the infinite-time limit, I am the Rubik's cube champion with an unbeatable time. QED

Comment: At my university, our group ended chalkboard talks (Score 2) 181

by Xerxes314 (#46429257) Attached to: Physics Forum At Fermilab Bans Powerpoint

For our group meetings, we used to do chalkboard talks, and this year we ended them for all the same reasons. Without slides, the discussion tends to wander aimlessly, and the speaker does not get to talk about what she intended to talk about in the first place. It takes forever to sketch the simplest diagrams on a chalkboard, the resulting figure has little accuracy and the audience has to sit through a lot of pointless sketching where no information is being conveyed.

Most people still use LaTeX-Beamer rather than PowerPoint, but the latest versions of PPT actually have very good equation tools, so IMHO, there's little reason to favor one over the other. The days of academics trashing on PPT are long gone.

Comment: Re:Feynman tutored me in QM at Caltech (Score 1) 106

by Xerxes314 (#46389477) Attached to: Physicists Test Symmetry Principle With an Antimatter Beam

"MAYBE THERE'S JUST ONE ELECTRON!" Feynman once shouted.

Actually, that's basically right. Our current understanding (in quantum field theory) is that there's only one electron field, and all electrons and positrons are quantum excitations of that field. It's a bit more complicated, in that there are actually four electron fields, which cover left-handed/right-handed and electron/positron degrees of freedom. But if you think of those four fields as being the "one" electron, the idea works perfectly.

Comment: Re:Not so sure about the language... (Score 1) 216

by Xerxes314 (#46369557) Attached to: Wolfram Language Demo Impresses

b) it is opaque, in the sense that there is little control on what code is doing what data: many of the functions act actually as black boxes and it is not straightforward to see how to actually get in control of the system and/or understand what is actually being done in order to provide an answer.

You can usually twiddle all the options in a function; the documentation is pretty good for most of the standard libraries. Of course, the demo doesn't look as slick if you have to use 6 lines of optional parameters to get the exact thing you want. Typically, the default options do a pretty good job, and there's a lot less typing for those cases.

Of course, it's also a universal language. You don't have to use the standard libraries; feel free to roll your own. I'm sure an hour later, you'll have a bit more respect for how well the default stuff works.

+ - Mt Gox hacked. All coins gone. ->

Submitted by ch0ad
ch0ad (1127549) writes "Mt. Gox, once the world’s largest bitcoin exchange, has gone offline, apparently after losing hundreds of millions of dollars due to a years-long hacking effort that went unnoticed by the company.

The hacking attack is detailed in a leaked “crisis strategy draft” plan, apparently created by Gox and published Monday by Ryan Selkis, a bitcoin entrepreneur and blogger (see below). According to the document, the exchange is insolvent after losing 744,408 bitcoins — worth about $350 million at Monday’s trading prices."

Link to Original Source

+ - Apparent Theft at Mt. Gox Shakes Bitcoin World->

Submitted by Hugh Pickens DOT Com
Hugh Pickens DOT Com (2995471) writes "The most prominent Bitcoin exchange appeared to be on the verge of collapse late Monday, raising questions about the future of a volatile marketplace. On Monday night, a number of leading Bitcoin companies jointly announced that Mt. Gox, the largest exchange for most of Bitcoin’s existence, was planning to file for bankruptcy after months of technological problems and what appeared to have been a major theft. A document circulating widely in the Bitcoin world said the company had lost 744,000 Bitcoins in a theft that had gone unnoticed for years. That would be about 6 percent of the 12.4 million Bitcoins in circulation."
Link to Original Source

Comment: Re:Spin (Score 2) 150

by Xerxes314 (#46188761) Attached to: Quarks Know Their Left From Their Right

If the spin of the particle (electron in the summary) is germaine to the observed properties of the particle does that mean there are two different particles involved?

Yes! And there always has been. Left-handed particles are not the same as right-handed ones. Quarks in particular come in a dizzying amount of varieties. There are 6 flavors times 3 colors times 2 spins times 2 for regular/anti. So in total there are actually 72 kinds of quark!

But people find it easier to talk about there being fewer kinds and specifying the exact types only as necessary. That makes sense, because particles of one type can change into particles of another type pretty easily. For example, you could have a quark in a superposition of left- and right-handed states. Quarks are constantly changing their color as they exchange gluons with other quarks inside the proton. Flavor and regular/anti change the least, so you generally hear people talk about a "strange quark" or a "top antiquark". But all those other properties are always around.

Comment: Re:All three planets are probably tidally locked (Score 2) 203

by Xerxes314 (#44105833) Attached to: 3 Habitable-Zone Super-Earths Found Orbiting Nearby Star
Well, they're all much bigger and closer than Mercury, which would amplify the effects of tidal drag. Mercury avoids full locking by having a large eccentricity. None of the planets in the habitable zone (c,e,f) have substantial measured eccentricity, but the uncertainty is large enough that it might be possible for them to get into a 3:2 resonance. Even in a 3:2, the planet would still face the star for weeks at a time; the resulting temperature fluctuations might actually be more inhospitable than full locking.

Comment: All three planets are probably tidally locked (Score 3, Interesting) 203

by Xerxes314 (#44104863) Attached to: 3 Habitable-Zone Super-Earths Found Orbiting Nearby Star

I'm not sure what difference this makes to the actual habitability of the planets, but all of these are tidally locked. That is, the same part of the planet is always facing the star (and thus baked) while the same part faces empty space (and thus freezes). A thick atmosphere might transport heat and make things more uniform, but none of these are what one would naively think of as "habitable". In fact, all planets in the "habitable" zone of such small stars are going to be tidally locked. Wikipedia actually has a nice summary of the problem of tidal locking in small stars.

On the other hand, they might have very interesting moons.

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