As said from string theory, one cannot predict anything. This irritatting point begins to be broadly admitted by most honest string theorists.
That experimental observation, if real, cannot be explained from string theory but, and this is my point, you can modify string theory for adapting it to that data once you know that data. Historically that was the way.
You appears rather confounded, I recommend to you The book “Hiding in the Mirror: The Mysterious Allure of Extra Dimensions,” to be published this year by Krauss.
Krauss, a leading expert on cosmic dark matter and dark energy, argues that string theorists have produced no satisfactory explanations for anything.
That is, basically, I said in April.
Berislav said:
Bosonic string theory is developed by at first leaving the number of dimensions unknown. One then (as I said before) because of unphysical (as you say, tachionic) residual terms in the commutation relation of the Lorentz boost and angular momentum operator imposes the 26 dimensionality. The residual terms are then zero. I don't see anything wrong with this. Maybe it isn't "elegant", but then again that is a subjective concept.
I will explain again. String theorists claimed to public that theory was elegant; all was fixed in the theory in a natural manner (still people believe that string theory contains a single parameter), and cannot be experimentally tested.
Reality is as follow. You begin from a 4D formulation (initially people did not leave dimensionality unknown) but quantizing the open bosonic string, you obtain the spectral decomposition for the first excited state.
<br />
m^2 = (2 \pi T_{0}) \left[1 - \frac{D-2}{24}\right]<br />
For D<26 you obtain violation of Lorentz invariance, and for D>26 you obtain negative square mass states and by Einstein mass formula
<br />
m = \frac{m_{0}}{\sqrt{1 - \frac{v^2}{c^2}}}<br />
tachionic behavior (v > c). Both behaviors are not observed in nature (the tachionic behavior of ground state is ignored now), therefore the result D=26 is the direct outcome of a
direct experimental test of string theory. String theory may be consistent with previous theories, which explain past and present experiments. E.g. choosing D=4, bosonic string theory cannot explain data that special relativity already explain.
Since 40 years ago, string theory has been experimentally tested and modified for adapting it to known data. This is the point that string theorists fail to adequately explain to people, young students, etc.
Berislav said:
Aha. So you dislike supesymmetry as well as string theory.
Physics is not about like or dislike. Physics may explain the world we know. The world that we know does not provide signs of multidimensional strings or supersymmetric states.
Until now, all our experience is about non-supersymmetric universe in 4D. A honest physicist would construct a theory for a non-supersymmetric universe in 4D and after if one day additional dimensions or supersimmetry are discovered then generalize the framework. But string theorists first developed a mathematical theory for 26D and then began the 40-years dark age.
Remember that supersimmetry was added to string theory for solving some of its consistency problems and violation of experimental data.
All of string theory is about add, and add, and add, and add until that one day you obtain a theory that nobody know, is not defined, it has so many conjectures, unproved beliefs and open questions that can say anything and the contrary of anything. For example, if supersymmetry is not observed in next accelerator generation, then string theoreticians will be invoke a new change of scale (as in the past) or will add some new mathematical device that “cancels” it. The “theory” (so say) is permanently in a safe state.
Berislav said:
I don't know about those approaches.
Ok, but people working in other fields knew it, and those true physicists developed those fantastic approaches without pompous claims such as that of Brian Greene and friends. String theorists, arrogant as they are, claimed that all was already known and explained by string theory: the most important theory! The Last formulation!
if I remember correctly, they discovered that traditional quantization is not sufficient 5 years ago, and now are adaptation previous old version of brane theory to new formalism as explained in article. Still today, they are working with the simplest version of formalism (developed 20 or 30 years ago by others) now we are working with new more general theories. Perhaps by 2015, some string theorist will say “hey guys, this is not rigorous, we may use this theory” (we are working today) for obtaining the 123th version of string theory.
Berislav said:
Contrary to "the ST popular claim of derivation of Einstein field equations". That is, that supersymmetry coupled with gravity isn't the low energy limit of superstring theory.
From ST one cannot derive GR.
Berislav said:
This sounds like a very important discovery! I thought that we couldn't reach the necessary energy to observe such radical changes in the laws of spacetime. Some references, please!
As said it is a rumor, there is not paper still, but is appears that result is solid.
It seems that deviations from Newton's gravitational law at distances slightly below 100 microns were detected at the "4 sigma" confidence level. Since assertion would be revolutionary an increase to "8 sigma" is being worked. Traditionally string theory has claimed for the contrary fact, (I even have seen the r^-7 corrections to Newtonian potential from Matrix theory) but don’t worry, if finally true, string theorists will invoke some new mathematical device for saving string theory again. That is will develop the 45th version of the “theory”.
Robert B. Laughlin said:
People have been changing string theory in wild ways because it has never worked.
