🚀 go-pugleaf

In article <1992Apr9.233448.1@acad2.alaska.edu>, assib@acad2.alaska.edu writes:
|> The other day a friend of mine mentioned 'Virtual Particles...'
|> Could I get some more info on this?
|> 
|> If you have any feedback, send to:
|> ----------------------------------
|>       ASSIB@ACAD2.ALASKA.EDU

In Quantum Mechanics, you can compute transfer matrices from which
cross-sections come out, by doing a perturbation expansion about a
known solution.  That expansion looks sort of like a power series in
the perturbation Hamiltonian.  

In 'Second Quantization,' particles are treated like quantum
excitations in a field (ground state = vacuum, 1st excitation = 1
particle, 2nd excitation = 2 particles); the excitations obey
statistics (Fermi or Bose), and preserve the idea that particles have
no identity.  The formulation looks like raising and lowering operators
for the harmonic oscillator; particles can be 'created' or 'destroyed'
using the raising and lowering operator.  The Hamiltonian is written in
terms of the 'number' operator -- which is just the product of the
creation and destruction operators.

If you want to apply perturbation expansions to the scattering of
electrons from each other via the photon field, terms emerge that allow
the creation and destruction of electron-positron pairs from the
photonic interactions -- even if the energy isn't enough to create a
real pair, the terms do make contributions to the cross-section (sort
of a 2nd quantization version of tunneling -- very crudely).  Those
terms contribute to the self-energy, as well.  In a way, electrons are
never 'bare;' they are always in interaction with a photon field that
includes contributions from this kind of perturbation.  Reformulating
the effective mass and charge in terms of these contributions is called
renormalization; the effect is to 'dress' the 'bare' electron.


Dan