Saturday, December 31, 2005

Scattering Amplitudes

So where has "experimentation" taken us to today?

Stanford Encyclopedia of Philosophy
Under the Heading of Bell's Theorem


The quantum state is exactly that representation of our knowledge of the complete situation which enables the maximal set of (probabilistic) predictions of any possible future observation. What comes new in quantum mechanics is that, instead of just listing the various experimental possibilities with the individual probabilities, we have to represent our knowledge of the situation by the quantum state using complex amplitudes. If we accept that the quantum state is no more than a representation of the information we have, then the spontaneous change of the state upon observation, the so-called collapse or reduction of the wave packet, is just a very natural consequence of the fact that, upon observation, our information changes and therefore we have to change our representation of the information, that is, the quantum state. (1999, p. S291).

Of course tryng infiltrate this undertanding inthose who have progressed before is the way in which we are lead to other ideas and works in progress.

Lubos Motl:
In the Minkowski space and de Sitter space, we can safely define the energies according to the strategy above, and we may also determine the time evolution, but only from -infinity to +infinity. If these infinities really appear in the far past and the far future, we call the evolution operator "S-matrix". String theory allows us to calculate the S-matrix (another example that we do call an "observable") for all particles in the spectrum which includes the scattering of gravitons. We don't have to insert our knowledge about the problematic "bulk" observables: string theory automatically tells us not only the right answers but also the right questions. "It is the S-matrix you should calculate, silly," she says. It also tells us what are the corresponding evolution observables for anti de Sitter space.

Someone may therefore convince you that the S-matrix is the only meaningful observable that has any physical meaning in a quantum theory of gravity. This sentence is both deep, if an appropriate interpretation is adopted, as well as discouraging.


It is indeed a struggle for me to be clear in this regard, but hopefully, recogizing the requirements of the physicist and the theoretician, that such scholar attributes can be waivered for the commoner?

Scattering Amplitudes?

SLAC E158: Measuring the Electron's WEAK Charge

At SLAC and elsewhere in the 1990s, precision measurements probing quantum effects from physics at higher energy scales were very successful. Precision electroweak measurements accurately predicted the mass of the top quark before it was discovered at the Tevatron at Fermilab, and they were cited in the awarding of the 1999 Nobel Prize to Veltmann and t'Hooft, which recognized their work in developing powerful mathematical tools for calculating quantum corrections and demonstrating that the Standard Model was a renormalizable theory. The discovery and mass measurement of the top quark at Fermilab's Tevatron and the precise Z0 boson mass measurement from CERN experiments added to well established values for other Standard Model parameters, to allow predictions for the only Standard Model parameter not yet measured, the Higgs mass.


asymmetric insight by Heather Rock Woods

Marciano agrees that the experiment contributes to the coming frontier-energy physics. "Perhaps just as important as its final result, E158 provides a clear demonstration that this technique can be employed at the proposed ILC by scattering its high-energy polarized electron beam off a fixed target of electrons. With the higher energy and much larger effective luminosity provided by that facility, unprecedented precision studies of polarized electron-electron scattering will be possible. These studies will probe deeply for virtual particles that pop in and out of existence and other signs of new physics."

In revealing the character of the symmetry-defying weak force, E158 has provided tools and exposed dead ends for the coming climb to higher peaks.

1 comment:

  1. You should label the diagram with photon striking electron "Compton effect".

    It is key to Heisenberg's uncertainty principle.

    The claims of "quantum entanglement" take it for certain that somehow when you measure a PHOTON not an electron, the PHOTON's polarisation is changed by a similarly uncertain amount, and since the Bell-Aspect experiment starts with two identical photons, you then conclude that measuring the polarisation of one magically changes that of the other (the result shows correlation).

    However, how does a photon's state change when measured, as it is going at light speed?

    Are you certain that the Compton effect "uncertainty principle" applies to measuring polarisation of light? There is no evidence for this. It is guesswork, so the xperiment proves nothing about entanglement.

    I did a lot of undergraduate experiments on polarised light, and I've used photomultipliers to register individual quanta.

    Light is a very complex problem in physics! Maxwell's theory of light has a "displacement current" created by electric field in the vacuum which creates a magnetic field, which in turn creates another electric field.

    Nobody in modern physics, particularly string theorists, know anything about displacement current. Yet they have the cheek to be abusive to investigators who work in electronics on capacitors and investigate it.

    String theorists have no interest in the experiments on light and its electromagnetic basis which come from electronics, which is the very seat of electromagnetism.

    All these people want to do is to pontificate, suppress, and make rude patronising comments on subjects they by their own admission are proud to remain ignorant of.

    Before claiming that you know for certain that two photons metres apart are "entangled" don't you first think you should be certain where the conflict between Maxwell's wave theory of light and quantum theory arises?

    If you don't have a clue about the model of light in classical electromagnetism and how it relates to the Heaviside light-speed electric energy flow, then you may be building a mud castle in quicksand.

    I'll copy this comment to my own blog in case you wish to delete it. I'm interested in why the thinking of practical physicists can be so different from that of string theorists pretending to be "laymen" when convenient, as you do!

    Best wishes