A particle in QM is described purely by a set of intrinsic quantum numbers, none of which have anything to do with space-time. Space-time enters the picture only when we attempt to describe the behavior of the particle in the observer's space-time frame. The difference with QFT is that the concept of a field has meaning only in a space-time context.There seems to be some -at least- conceptual difference between particles in QFT which is just a point -eventually- in the field AND the particle in QM which is described by a wavefunction which is extended in space. As if QFT somehow "collapses" the wavefunction.
the point I am trying to make is that the particle is a point in QFT in a particular place and that's that, and presumably they still have the same intrinsic quantum numbers.A particle in QM is described purely by a set of intrinsic quantum numbers, none of which have anything to do with space-time. Space-time enters the picture only when we attempt to describe the behavior of the particle in the observer's space-time frame. The difference with QFT is that the concept of a field has meaning only in a space-time context.
Where did you read this? This is not what field theory is about, nor quantum field theory.the point I am trying to make is that the particle is a point in QFT in a particular place and that's that
https://www.amazon.co.uk/Quantum-Particles-Strings-Frontiers-Physics/dp/0201360799Where did you read this? This is not what field theory is about, nor quantum field theory.
There are many types of particles in QFT. A particle is basically a quantized excitation of the field. There are many ways to describe field excitations, so there also correspondingly many types of particles in QFT. Some particles are localized, and others are spread out, like the eigenfunctions of the free particle of non-relativistic QM.There seems to be some -at least- conceptual difference between particles in QFT which is just a point -eventually- in the field AND the particle in QM which is described by a wavefunction which is extended in space. As if QFT somehow "collapses" the wavefunction.
but these are generally do not discussed in the established textbooks correct. I have most of those, they typically rehash the same things.spread out, like the eigenfunctions of the free particle of non-relativistic QM.
They are (among) the first quantum particles discussed in most QFT textbooks. For example, see https://books.google.com.sg/books?id=I-zHDWtQGRQC&vq=where&source=gbs_navlinks_s (Eq 2.68 and the paragraph after that).but these are generally do not discussed in the established textbooks correct. I have most of those, they typically rehash the same things.
To the contrary! In relativistic QT the QFT formulation is so much more approriate than the 1st-quantization approach, because you cannot localize particles in a more strict sense than already in non-relativistic QM. The reason is that to resolve a particles position you need other particles to scatter with sufficiently large momenta to have the wanted resolution in position. In relativistic QT an ever higher momentum to scatter particles to localize other particles doesn't lead to a better position resolution, because one creates new particles rather then get better position resolution.the point I am trying to make is that the particle is a point in QFT in a particular place and that's that, and presumably they still have the same intrinsic quantum numbers.