My understanding of the "particle" concept in Quantum Field Theory is that it describes something
- infinite in extent in space (and also time?)
- having no concept of trajectory (in absolutely any sense)
- (possibly) effectively immutable or having no temporal extent, like mathematical concepts / global statements about a model / coordinates, or possibly a minimal existence, for example just binary existance or cardinality but certainly no properties at an individual particle level
In experimental physics, notably including areas dealing with the phenomena intimately tied to Q.F.T., there is a concept of a "particle" which follows conventional English usage, as nicely mentioned in an answer to this question.
- localised in space
- having a definite trajectory (under appropriate conditions)
- having definite properties (up to some uncertainty) that vary with time (position, momentum, energy etc.)
- observed in bubble tanks as a concrete example
I am not asking which of these definitions is "correct" usage of the word. I am also not trying to get a correct characterisation of either phenomenon; I'm sure I've misrepresented them in some ways, but that doesn't matter as long as you can understand what I'm referring to. What I'm interested in is do these correspond to the same thing.
I am aware of wave-particle duality in basic quantum mechanics but in this case it seems like people are simply talking about different things. Are these related the same way "fields" are in maths and physics (linguistically only)? Are they different perspectives of the same thing? Or are they maybe at opposite ends of a conceptual scale?