Wednesday, October 01, 2008

Codpiece topology

In this episode of "The Big Bang Theory" (a CBS sitcom aired in 30+ countries, see 3 parts of this episode at YouTube), string theorist Sheldon Cooper is literally kicked out of his apartment because his roommate and friend, experimental particle physicist Leonard Hofstadter, wants to date Leslie Winkle, an arrogant female subpar scientist who actually believes loop quantum gravity, a slanderous supervillain with an advanced degree who should have been filtered out by the graduate school.

Blonde beauty of average intelligence, Penny, a former potential girlfriend of Leonard, underestimates Sheldon's ability to solve these inappropriate situations. Incidentally, if you need to know the figure, Sheldon's IQ is 187 which turns out to be 60 IQ points above the "smart" category. Sheldon, after quitting Super Mario, enters his apartment and creates the right environment in which Ms Winkle can show her true colors.

She says a couple of very stupid things about physics - that may have been copied from Lee Smolin and that will be discussed separately - and even suggests that her and Leonard's children should be brainwashed to believe loop quantum gravity. Leonard of course knows that this theory is balderdash: he just wanted to be silent about it to have sex with Ms Winkle, which he only wanted because a new boyfriend of Penny has made him jealous, so he says a few neutral comments and eventually he breaks up with Ms Winkle. Well, she breaks up with him. Thank God: look how the bitch talked to Leonard in part 1 of the episode. ;-)

I am pretty sure that the producers of this silly sitcom - more precisely David Saltzberg, a physicist at UCLA who makes physics of these exchanges unusually accurate - had to read the physics blogosphere, especially TRF. Shouldn't they pay me royalties? :-) More seriously, I think that the sitcom shows quite faithfully how "ordinary people" look at important physics questions: they don't give a damn and they find it ludicrous if anyone does. And I have mixed feelings whether these caricatures improve or worsen the image of science (and scientists) held by the laymen.

The sitcom also correctly indicates that subpar subdisciplines of theoretical physics such as LQG are more often than usually investigated by women (because the main thing that supports these directions is affirmative action, not merit) and they are often arrogant and ugly bitches who love to backbite others. ;-)

If you like the sitcom, see e.g. Sheldon and Leonard showing their whiteboards to Penny: Talk Nerdy To Me, or 12 + 29 similar videos. Or see a 15-year old Korean bastard, Dennis Kim, parroting some Woitian propaganda about the landscape: Sheldon reacts highly irrationally here. ;-) Well, for a couple of minutes, until his friends decided to realize a sexy plan with Kim that Kim finally realized himself. :-)

Incidentally, Alyssa agrees with me that Penny has a genuine yet secret crush on Sheldon. I hope that the CBS guys will realize that! Sorry, Leonard. ;-)

Fridamonkey agrees with me that Leslie is obnoxious and should be eliminated from the show. ;-)

Refutation of Leslie's science

The producers of the sitcom obviously don't go deeply enough to science to become scientists and they say almost nothing about string theory. However, they say quite a lot about the loop quantum gravity talking points.

First, Leslie says that LQG offers more testable predictions than string theory. That's a favorite populist proclamation by its subpar proponents. (I love the "subpar" word that I wanted to use many times but couldn't find it - and I am thankful to Sheldon for improving my/our vocabulary.) The proposition is both irrelevant for the actual validity of the theory (because easy testability or falsifiability doesn't make a theory any more likely) as well as manifestly untrue, as shown below.

First of all, she follows Lee Smolin in claiming that the quantized character of the space leads to violations the Lorentz invariance: a different speed of light for different frequencies (or colors). That's of course nonsense. Violations of the Lorentz symmetry are both unnecessary as well as unjustified in a theory of quantum gravity and all promising models and theories of particle physics and quantum gravity still respect the Lorentz symmetry. Quite generally, Lorentz violations also make perpetuum mobile possible in the presence of black holes which is very bad for the consistency of any such theory.

So it's balderdash, as Sheldon correctly says, even though his subsequent rudimentary comment that matter is composed out of tiny strings seems to be directly unrelated to the question of Lorentz violation.

In her following exhibition, she claims that only loop quantum gravity calculates the entropy of black holes. Once again, Sheldon's snoring of derision is exactly the correct response here. String theory correctly reproduces the Bekenstein-Hawking entropy of huge classes of black holes, including infinitely many power-law corrections (OSV...) or objects as realistic as four-dimensional extremal Kerr black holes. It seems almost guaranteed that the result is always correct. These successes form a highly nontrivial set of consistency checks for a theory of quantum gravity that string theory passes beautifully.

On the other hand, as explained in the text about quasinormal modes and other texts, loop quantum gravity doesn't reproduce any of these successes. The very area proportionality law only holds if it is inserted at the very beginning - if the black hole interior is artificially "forgotten". And even if one does so (i.e. if one supplements the theory with an additional assumption about the character of black hole horizons that makes the proportionality manifest and trivial), the coefficient comes out incorrectly in the most obvious calculation. The multiplicative discrepancy is called the Barbero-Immirzi parameter and all specific hypotheses trying to justify the unnatural required value of this additional parameter, especially those based on the black hole quasinormal modes, have been proven incorrect.

This discussion is only academic because it seems very likely that loop quantum gravity cannot reproduce a modest yet essential concept of all of physics - a nearly smooth spacetime manifold - so it can't generate any black hole solutions, either. Strictly speaking, it makes all the discussions about black hole entropy meaningless. This final comment also applies to Leslie's (and Lee's) first statement about the modified dispersion relations. If they were more honest, they would say that their theory not only predicts the Lorentz symmetry to be broken but the space to be non-existent, too.

In fact, they realize that they make this prediction - that spacetime doesn't exist at all - but they try to obscure this lethal prediction by renaming the "non-existence of spacetime" by an intriguing phrase, "background independence".

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