Posted: Sep 21, 2011 7:07 pm
zaybu wrote:twistor59 wrote:zaybu wrote:
It's elementary in the sense that there hasn't been any new development in QM since the 1930's. Omitting the advancement in QFT from 1930 to 1970 would be like studying math without studying any math from calculus and on. Your grasp of the subject would be quite limited. How could you discuss renormalization, gauge invariance, higgs mechanism or Wilson loop? Yet these are the backbones of the subject matter.
(I'll split the responses to the previous post into separate posts, otherwise the paragraphs are going to be very hard to keep track of.)
But the issue under discussion, which is essentially something along the lines of "what does a photon look like - how should I think of it?" does not need the advances you describe (with the exception, perhaps, of the gauge idea, which has been around since Hermann Weyl, and which is important in identifying the fundamental degrees of freedom). Although you can get by without asking simplistic questions like the one I'm addressing, you cannot suppress the urge to try to answer such questions, and such questions are surprisingly difficult to answer.
QM deals with low energies. At those scales the wave model has validity. However, if you deal with smaller and smaller distances, meaning higher and higher energies, then QM is inadequate, and one must deal with QFT. At those higher scales of energies, the wave model is redundant. Take any textbook on QFT, and what you'll get is particles, particles, particles. Even a ''field'' is thought as an exchange of particles.
Now if you want to restrict the discussion to QM, I'm saying you're missing the point.
QM deals with scenarios where particles are not created or destroyed. That is the distinction between
The comment about QFT textbooks is not correct, it should read "take any textbook on QFT written with the main aim of teaching particle physicists to calculate scattering amplitudes .....". There is another massive domain of QFT - quantum optics - where the wave picture gives a better description of the behaviour of the quanta.
What exactly do you mean when you say that a field is thought of as the exchange of particles ?