Friday, January 14, 2005

In Principle And In Practice

Recently, it became fashionable to claim string theory is not scientific because it makes no testable predictions. Let me not again get into the testable vs falsifyable discussion, I still think people who still insist on falsifyabilty should quickly patch their philosophy of science module to a more recent than the 1934 version (Karl Popper's "Logic of Scientific Discovery"). But I hope everybody would agree that a theory can only be scientific if it makes statements about empirical observations.

Now, many people claim that string theory does not fulfil this criterion for a good theory. This view is fed by string theorists speculation about landscapes of vacua of which the number has not error bars in the exponent (like some numbers in astronomy) but in the exponent of the exponent. It seems that if string theory has so many different low energy versions that we can never extract any unique features that are observable.

In addition people become more and more excited about LHC taking data in a foreseeable future and there are many many different versions of signatures of supersymmetry or even low scale quantum gravity being visible in the new detectors. And they all look very different and once again it seems string theory can fit more or less every possible experimental outcome.

However, I think that many sceptics confuse two things here: The property that something can be observed in principle and that it can be observed in practice (now or soon or with today's technology). If we had a Planck energy accelerator, nobody would have doubts that strings could be observed. As soon as you probe distance scales that so smaller than the compactification scale, string theory look effectively 10 (or 11) dimensional and has quite unique properties.

Unfortunately, it is very very unlikely that LHC energies are at least of the order of the fundamental Planck scale so it is save to assume that LHC will not speak the last word about string theory. And it is as save to believe that we will never come even close to 10^19GeV with accelerators before the sun blows up. So it is likely that in practice, we will not be able to confirm (or rule out) string theory unless some surprise happens (like somebody finds a way to link cosmological observations rather directly to string theory).

But claiming some theory is not scientific because current (or foreseeable future) observational technology in practice does not make definite statements is not appropriate. This question should be decided based on whether observation is possible in principle.

Atomic theory is still scientific if you currently have only optical light frequencies at your disposal and you cannot resolve atoms directly. In that situation you are even luckier as quantum mechanics make definitive statements about absorption spectra for observable frequencies, still you cannot directly observe the atoms.

And I can still make scientific statements about the contents of the office across the corridor although it is locked and I don't have the key. In practice, I cannot test my speculations but in principle I could.

Hackers and Cheter, dig your holes!

According to Heise news ticker (pointing to the original forum posting) some spokes person threatens people using the ego shooter program 'Americas Army' (published by the Pentagon) in creative ways that the army is angry "and we're coming for you." So, hackers and cheaters get ready, dig your holes so the army can track you down like the ace of spade! (Appearantly, this kind of cyber crime can bring you life long free housing...)

How to sum binomials

Could somebody please point out to me how to prove

I am not able to produce it with the usual tricks for manipulating binomials.

This arises in the following problem: In dimension D=2n, this shows that Fierzing works, that is that the product of two chiral Weyl spinors can be reexpressed as a linear combination of even dimensional forms. Maple gives me confidence that the above expression is correct, but how can I convince myself (and worse: students) that it holds?

Monday, January 10, 2005

Marken viel

I haven't blogged lately mainly due to time constraints (we've moved flats etc and starting Feb first, I'll be teaching something like "string theory for dummies") and lack of internet connectivity over the festive season. But at least for my German speakin readers, here is some fun with google translate when applied to a recipy for a vagan sheppard's pie.

Some of this sounds quite dangerous (bang the dishes in the oven...) plus that "degrees" here of course assumes Celsius rather than Fahrenheit so your oven might melt if you try to follow these instructions literally...

Pie-Chart Sheppards

Dieses ist Art einer Torsion auf dem Rindfleischeintopfgerichtrezept. Es fiel wirklich gut, altho aus, welches die Oberseite nicht goldenes Braun erhielt.

  • 3 - 4 gehackte potatos
  • 2 gehackte Karotten
  • 1 kann Bohnen oder das frische equilivent grünen
  • Sellerie mit 2 Stielen, gehackt
  • 1 Zwiebel, gehackt
  • Schalen mit 1 ½ Klumpen des Rindfleisches TVP
  • 3 Pakete brünieren Soßemischung
  • 6 - 8 Schalen stampften potatos (uns verwendeten Augenblick)

Setzen Sie alle gehackten veggies in einen grossen Topf mit gerade genügendem Wasser zur Abdeckung ein und fangen Sie an zu kochen. Während die veggies kochen, hydratisieren Sie das TVP wieder und fangen Sie an, die gestampften potatos vorzubereiten.

Wenn veggies fast erfolgt sind, drehen Sie weg Hitze und lassen Sie ab. Bilden Sie die Soße entweder mit dem Wasser von den veggies oder Süßwasser. Setzen Sie die veggies zurück in den Topf und addieren Sie die Soße und das TVP, Mischung throughly.

Mit 2 1 großem der Kasserolle Teller des smallish oder setzen Sie den Inhalt des Topfes (veggies und alle) in das Kasserolledish(s). Lassen Sie einen ungefähr Zoll oder so zwischen der Oberseite der veggiemischung und der Oberseite des Tellers. Fügen Sie potatos an der Oberseite der veggiemischung hinzu. Erhalten Sie einen guten Körper, Zoll denken Schicht auf die Oberseite. Wärmen Sie Ofen zu 350 Grad vor.

Knallen Sie dish(es) in den Ofen und backen Sie 30-45 Minuten, ist untill die Oberfläche Unternehmen und wenig brünierten. Bing! Sie werden getan!

Marken viel!

Long ago, we applied the translate function of babelfish to the daily hep-th listing. Our favourite was something along the lines "läutern Sie gegenwärtige Gipfelbedieneralgebren" which is something like "sublimate contemporary top user algebras". Well, originally the paper was about "affine current vertex operator algebras"...