Testing string theory

Compton scattering happens when a photon interacts with an electron - the photon leaves the interaction with a lower energy and the electron has a higher energy. The energies of the outgoing photon and electron along with the angle at which these two leave the interaction allow determination of the energy and direction of the original photon.

High energy particles have extremely small wavelengths and can probe subatomic distances: high energy particle accelerators serve as supermicroscopes:

http://hep.uchicago.edu/cdf/smaria/ms/aaas03_ms.pdf

If GLAST detects violations of lorentz invariance in the form of energy-dependent photons velocity, in agreement with theoretical calculations, such observations and such agreement would strongly support LQG. It would also represent a severe problem for string/m-theory, as string theory in its current formulation presupposes lorentz invariance is an exact symmetry of nature, valid at all scales.

So...
If the mass of a fermion is dependent of the frequency of vibrations of extended objects such as strings or membranes, etc, then wouldn't this frequency (and thus the mass) be subject to gravitational redshifting just as photons are? So shouldn't string/M-theory be just as easy to test as the gravitational redshifting of photons?

So from this deduction supplied in last quoted paragraph?

Nope. In 1905 Einstein taught us that small regions of spacetime respect Lorentz symmetry as exactly as they respect rotational invariance - and this statement is also verified experimentally - and all quantum field theories as well as string theory that were proposed later respected this
fact. There is no justification to give up Lorentz symmetry - the only reason might be an attempt to hide another problem showing that loop quantum gravity is inconsistent as a theory of spacetime.

LQG may make predictions that can be experimentally testable in the near future.

The path taken by a photon through a discrete spacetime geometry would be different from the path taken by the same photon through continuous spacetime. Normally, such differences should be insignificant, but Giovanni Amelino-Camelia points out that photons which have traveled from distant galaxies may reveal the structure of spacetime. LQG predicts that more energetic photons should travel ever so slightly faster than less energetic photons. This effect would be too small to observe within our galaxy. However, light reaching us from gamma ray bursts in other galaxies should manifest a varying spectral shift over time. In other words, distant gamma ray bursts should appear to start off more bluish and end more reddish. Alternatively, highly energetic photons from gamma ray bursts should arrive a split second sooner than less energetic photons. LQG physicists eagerly await results from space-based gamma-ray spectrometry experiments (GLAST).

2007 will see the launch of GLAST, and (hopefully) the completion and operation of LHC. The results of these experiments will profoundly develop the course of QG. These experiments may establish spontaneously broken supersymmetry, Higgs boson and the Higgs field, extra spatial dimensions, and/or violations of Lorentz invariance.

If GLAST detects violations of Lorentz invariance in the form of energy-dependent photon velocity, in agreement with theoretical calculations, such observations would strongly support LQG. However, string theory would not necessarily be disfavoured, since although it predicts an underlying exact Lorentz symmetry, it is possible that this may be spontaneously broken through a nonzero expectation value of tensor fields.

Other topics where observation may affect the future theoretical development of quantum gravity are dark matter and dark energy.

Wait... if particles are strings or other extended objects that "vibrate" with some frequency, then it should be affected by the time dilation of Special Relativity. So whatever characteristic of strings or membranes that are determined by the frequency of some vibration should change near speeds approaching the speed of light, right? That sounds like an easy confirmation of string theory, or M-theory. Right?

Wait... if particles are strings or other extended objects that "vibrate" with some frequency, then it should be affected by the time dilation of Special Relativity. So whatever characteristic of strings or membranes that are determined by the frequency of some vibration should change near speeds approaching the speed of light, right? That sounds like an easy confirmation of string theory, or M-theory. Right?

Wait... if particles are strings or other extended objects that "vibrate" with some frequency, then it should be affected by the time dilation of Special Relativity. So whatever characteristic of strings or membranes that are determined by the frequency of some vibration should change near speeds approaching the speed of light, right? That sounds like an easy confirmation of string theory, or M-theory. Right?