5 not so Easy Pieces

Most recent answer: 09/15/2009

Q:
1) A photon is a wave of ElectroMangetic (EM) field. What field is electron a wave of? Is it a more compact wave of EM field? 2) What field is mass (e.g., of electron) a wave of? Is electron two packets of waves: one the EM wave packet, and the other mass wave packet? Does electron have 3 natures: two wave natures and one particle nature. 3) Since we know that gravity is simply the curvature of space, why then confuse the subject with the concept of graviton; why need a particle concept where curvature of space does the job? 4) The probability wave packet of a photon (or electron) has several waves of differing amplitudes. Are the distance between these waves constant and equal to the wavelength of the photon. 5) Is the length of the wave packet of a moving electron definite or is it infinite with gradually diminishing wave amplitudes?
- Mehran
Miami, FL
A:

1. A photon isn't really a wave 'of' an EM field. It's a wave of some abstract field which doesn't directly correspond to anything classical. When you get a many-photon field, it can show the behavior we call a classical EM field.
An electron is a state of another abstract field. It's not a more compact version of a photon. It has properties (e.g. participation in the weak force) which photons lack.

2. It's rumored that the electron (like other particle fields) picks up its mass from interaction with the Higgs field. This is over my head. I'm not sure whether this fact, if true, would justify calling it a composite of two fields.

It is, to the best of our knowledge in current interpretations of quantum mechanics, entirely unnecessary to postulate a separate 'particle' nature to the electron or anything else. Whether or not it turns out to be necessary to postulate another process, beyond the standard wave equation, is open to some dispute. Even if the answer is yes, the output of that process is still describable in standard quantum wave language. The famous 'wave-particle duality' is a relic of early days when people struggled to picture the genuinely mysterious quantum behavior in classical terms.

3. Even the curvature of space should propagate in wavelike ways. If that curvature is not itself a quantum object, big problems arise because any classical particle or field in  principle could be used to violate the uncertainty relations, unraveling the logical consistency of quantum mechanics.*

Now we get to the easy questions.

4. The wave can't have a single well-defined wavelength, because then it would extend uniformly over all space.

5. There can't be sharp boundaries to the wave, because that would involve infinite energies. The wave trails off continuously for ever.

whew

Mike W.

*Now the BICEP2 collaboration has seen what looks like the leftover effects of the quantum zero-point spread of gravitational waves, left as tiny "B-mode" ripples in the polarization of the cosmic microwave background radiation. In other words, they've probably seen something that wouldn't be there unless gravitational waves were quantum mechanical, So in that sense, gravitons have now been seen! /Mike W.


(published on 09/15/2009)