Re: The time it takes to emit one photon

On 2005-09-02, Eugene Stefanovich <eugenev@xxxxxxxxxxxx> wrote:
> Igor Khavkine wrote:

>> Quantization of a regular field theory yields a bosonic quantum field
>> theory, whose excitations translate to identical particles with
>> symmetrized wave functions. Quantization of a Grassmann field theory
>> yields a fermionic quantum field theory, whose excitations translate to
>> identical particles with antisymmetrized wave functions.
>> Field approach: 1, particle approach: 0.
>
> You may be right here. The identity of electrons looks
> more natural in the field approach.
> But the QM postulate that two electrons are
> identical doesn't seem so unreasonable to me. Why in the world they
> should be different?

But why in the world should they be the same? The matter of fact is that
a particle theory can handle both possibilities. The identical particle
principle is empirically selected by fitting experiments (cf. Gibbs
paradox). The field formulation is more predictive, since it is only
consistent with a particle formulation supplemented by the identical
particle principle. If you dislike ad-hoc rules, then field theory is
coming out a clear winner.

>> False attack on QED. Its Hamiltonian is there to calculate for anyone
>> who cares/dares.
>
> This "anyone" would have a hard time calculating the time evolution of
> real particles using a Hamiltonian written in terms of bare particles
> and with infinite coefficients. Good luck!

Luck has nothing to do with this, and neither do infinite bare
coefficients. Let me supplement my earlier statement. "QED's Hamiltonian
is there to calculate for anyone competent who cares/dares."

Igor

.

Relevant Pages

  • Re: GR and quantum mechanics
    ... particles (a sector of interacting relativistic field theory). ... Are particles forbidden in string theory? ... In fact, if you pick a basis psi_k for the single particle subspace H_1, ...
    (sci.physics.research)
  • Re: The time it takes to emit one photon
    ... RQD is formulated in terms of particles, ... QFT is QM applied to field theory. ... >> time evolution, then so can QFT, and then so can QED. ... Effective Field Theory and the Fermi Surface ...
    (sci.physics.research)
  • Re: The time it takes to emit one photon
    ... >> field theory, QFT, many particle quantum mechanics, and classical ... > You may note that I dropped QFT from that picture. ... > after making the unitary transformation to dressed particles. ...
    (sci.physics.research)
  • Re: The role of exchange particles in force
    ... People from other disciplines sometimes bring into a discussion important ... >Are propagators the formal equivalent of exchange particles? ... they're used in classical field theory, heat flow problems, etc. ... fundamental level of quantum field theory is the field, ...
    (sci.physics)
  • Re: Article: A Century of Einstein
    ... in his book "Quantum Field Theory in Curved Spacetime and Black Hole ... > spacetimes, and particles are never needed. ...
    (sci.physics.relativity)
Quantcast